Synch to Gnus 200310272146.

[elisp/gnus.git-] / texi / gnus.texi

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* Gnus: (gnus).         The newsreader Gnus.
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Copyright \copyright{} 1995, 1996, 1997, 1998, 1999, 2000, 2001,
2002, 2003
Free Software Foundation, Inc.


Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.1 or
any later version published by the Free Software Foundation; with no
Invariant Sections, with the Front-Cover texts being ``A GNU
Manual'', and with the Back-Cover Texts as in (a) below.  A copy of the
license is included in the section entitled ``GNU Free Documentation
License'' in the Emacs manual.

(a) The FSF's Back-Cover Text is: ``You have freedom to copy and modify
this GNU Manual, like GNU software.  Copies published by the Free
Software Foundation raise funds for GNU development.''

This document is part of a collection distributed under the GNU Free
Documentation License.  If you want to distribute this document
separately from the collection, you can do so by adding a copy of the
license to the document, as described in section 6 of the license.
\newpage
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@ifnottex

This file documents gnus, the GNU Emacs newsreader.

Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003
        Free Software Foundation, Inc.

Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.1 or
any later version published by the Free Software Foundation; with the
Invariant Sections being none, with the Front-Cover texts being ``A GNU
Manual'', and with the Back-Cover Texts as in (a) below.  A copy of the
license is included in the section entitled ``GNU Free Documentation
License'' in the Emacs manual.

(a) The FSF's Back-Cover Text is: ``You have freedom to copy and modify
this GNU Manual, like GNU software.  Copies published by the Free
Software Foundation raise funds for GNU development.''

This document is part of a collection distributed under the GNU Free
Documentation License.  If you want to distribute this document
separately from the collection, you can do so by adding a copy of the
license to the document, as described in section 6 of the license.
@end ifnottex

@tex

@titlepage
@title T-gnus 6.16 Manual

@author by Lars Magne Ingebrigtsen
@page

@vskip 0pt plus 1filll
Copyright @copyright{} 1995, 1996, 1997, 1998, 1999, 2000, 2001,
2002, 2003
        Free Software Foundation, Inc.

Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.1 or
any later version published by the Free Software Foundation; with no
Invariant Sections, with the Front-Cover texts being ``A GNU
Manual'', and with the Back-Cover Texts as in (a) below.  A copy of the
license is included in the section entitled ``GNU Free Documentation
License'' in the Emacs manual.

(a) The FSF's Back-Cover Text is: ``You have freedom to copy and modify
this GNU Manual, like GNU software.  Copies published by the Free
Software Foundation raise funds for GNU development.''

This document is part of a collection distributed under the GNU Free
Documentation License.  If you want to distribute this document
separately from the collection, you can do so by adding a copy of the
license to the document, as described in section 6 of the license.

@end titlepage
@page

@end tex


@node Top
@top The gnus Newsreader

@ifinfo

You can read news (and mail) from within Emacs by using T-gnus.  The news
can be gotten by any nefarious means you can think of---@acronym{NNTP}, local
spool or your mbox file.  All at the same time, if you want to push your
luck.

T-gnus provides @acronym{MIME} features based on @acronym{SEMI} API.  So
T-gnus supports your right to read strange messages including big images
or other various kinds of formats.  T-gnus also supports
internationalization/localization and multiscript features based on MULE
API.  So T-gnus does not discriminate various language communities.  Oh,
if you are a Klingon, please wait Unicode Next Generation.

This manual corresponds to T-gnus 6.16.

@end ifinfo

@iftex

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\gnuscleardoublepage
@end iflatex

Gnus is the advanced, self-documenting, customizable, extensible
unreal-time newsreader for GNU Emacs.

Oops.  That sounds oddly familiar, so let's start over again to avoid
being accused of plagiarism:

Gnus is a message-reading laboratory.  It will let you look at just
about anything as if it were a newsgroup.  You can read mail with it,
you can browse directories with it, you can @code{ftp} with it---you
can even read news with it!

Gnus tries to empower people who read news the same way Emacs empowers
people who edit text.  Gnus sets no limits to what the user should be
allowed to do.  Users are encouraged to extend gnus to make it behave
like they want it to behave.  A program should not control people;
people should be empowered to do what they want by using (or abusing)
the program.

@end iftex

@menu
* Starting Up::                 Finding news can be a pain.
* Group Buffer::                Selecting, subscribing and killing groups.
* Summary Buffer::              Reading, saving and posting articles.
* Article Buffer::              Displaying and handling articles.
* Composing Messages::          Information on sending mail and news.
* Select Methods::              Gnus reads all messages from various select methods.
* Scoring::                     Assigning values to articles.
* Various::                     General purpose settings.
* The End::                     Farewell and goodbye.
* Appendices::                  Terminology, Emacs intro, @acronym{FAQ}, History, Internals.
* Index::                       Variable, function and concept index.
* Key Index::                   Key Index.

Other related manuals

* Message:(message).            Composing messages.
* Emacs-MIME:(emacs-mime).      Composing messages; @acronym{MIME}-specific parts.
* Sieve:(sieve).                Managing Sieve scripts in Emacs.
* PGG:(pgg).                    @acronym{PGP/MIME} with Gnus.

@detailmenu
 --- The Detailed Node Listing ---

Starting Gnus

* Finding the News::            Choosing a method for getting news.
* The First Time::              What does Gnus do the first time you start it?
* The Server is Down::          How can I read my mail then?
* Slave Gnusae::                You can have more than one Gnus active at a time.
* Fetching a Group::            Starting Gnus just to read a group.
* New Groups::                  What is Gnus supposed to do with new groups?
* Changing Servers::            You may want to move from one server to another.
* Startup Files::               Those pesky startup files---@file{.newsrc}.
* Auto Save::                   Recovering from a crash.
* The Active File::             Reading the active file over a slow line Takes Time.
* Startup Variables::           Other variables you might change.

New Groups

* Checking New Groups::         Determining what groups are new.
* Subscription Methods::        What Gnus should do with new groups.
* Filtering New Groups::        Making Gnus ignore certain new groups.

Group Buffer

* Group Buffer Format::         Information listed and how you can change it.
* Group Maneuvering::           Commands for moving in the group buffer.
* Selecting a Group::           Actually reading news.
* Subscription Commands::       Unsubscribing, killing, subscribing.
* Group Data::                  Changing the info for a group.
* Group Levels::                Levels? What are those, then?
* Group Score::                 A mechanism for finding out what groups you like.
* Marking Groups::              You can mark groups for later processing.
* Foreign Groups::              Creating and editing groups.
* Group Parameters::            Each group may have different parameters set.
* Listing Groups::              Gnus can list various subsets of the groups.
* Sorting Groups::              Re-arrange the group order.
* Group Maintenance::           Maintaining a tidy @file{.newsrc} file.
* Browse Foreign Server::       You can browse a server.  See what it has to offer.
* Exiting Gnus::                Stop reading news and get some work done.
* Group Topics::                A folding group mode divided into topics.
* Misc Group Stuff::            Other stuff that you can to do.

Group Buffer Format

* Group Line Specification::    Deciding how the group buffer is to look.
* Group Mode Line Specification::  The group buffer mode line.
* Group Highlighting::          Having nice colors in the group buffer.

Group Topics

* Topic Commands::              Interactive E-Z commands.
* Topic Variables::             How to customize the topics the Lisp Way.
* Topic Sorting::               Sorting each topic individually.
* Topic Topology::              A map of the world.
* Topic Parameters::            Parameters that apply to all groups in a topic.

Misc Group Stuff

* Scanning New Messages::       Asking Gnus to see whether new messages have arrived.
* Group Information::           Information and help on groups and Gnus.
* Group Timestamp::             Making Gnus keep track of when you last read a group.
* File Commands::               Reading and writing the Gnus files.
* Sieve Commands::              Managing Sieve scripts.

Summary Buffer

* Summary Buffer Format::       Deciding how the summary buffer is to look.
* Summary Maneuvering::         Moving around the summary buffer.
* Choosing Articles::           Reading articles.
* Paging the Article::          Scrolling the current article.
* Reply Followup and Post::     Posting articles.
* Delayed Articles::            Send articles at a later time.
* Marking Articles::            Marking articles as read, expirable, etc.
* Limiting::                    You can limit the summary buffer.
* Threading::                   How threads are made.
* Sorting the Summary Buffer::  How articles and threads are sorted.
* Asynchronous Fetching::       Gnus might be able to pre-fetch articles.
* Article Caching::             You may store articles in a cache.
* Persistent Articles::         Making articles expiry-resistant.
* Article Backlog::             Having already read articles hang around.
* Saving Articles::             Ways of customizing article saving.
* Decoding Articles::           Gnus can treat series of (uu)encoded articles.
* Article Treatment::           The article buffer can be mangled at will.
* MIME Commands::               Doing MIMEy things with the articles.
* Charsets::                    Character set issues.
* Article Commands::            Doing various things with the article buffer.
* Summary Sorting::             Sorting the summary buffer in various ways.
* Finding the Parent::          No child support? Get the parent.
* Alternative Approaches::      Reading using non-default summaries.
* Tree Display::                A more visual display of threads.
* Mail Group Commands::         Some commands can only be used in mail groups.
* Various Summary Stuff::       What didn't fit anywhere else.
* Exiting the Summary Buffer::  Returning to the Group buffer,
                                or reselecting the current group.
* Crosspost Handling::          How crossposted articles are dealt with.
* Duplicate Suppression::       An alternative when crosspost handling fails.
* Security::                    Decrypt and Verify.
* Mailing List::                Mailing list minor mode.

Summary Buffer Format

* Summary Buffer Lines::        You can specify how summary lines should look.
* To From Newsgroups::          How to not display your own name.
* Summary Buffer Mode Line::    You can say how the mode line should look.
* Summary Highlighting::        Making the summary buffer all pretty and nice.

Choosing Articles

* Choosing Commands::           Commands for choosing articles.
* Choosing Variables::          Variables that influence these commands.

Reply, Followup and Post

* Summary Mail Commands::       Sending mail.
* Summary Post Commands::       Sending news.
* Summary Message Commands::    Other Message-related commands.
* Canceling and Superseding::

Marking Articles

* Unread Articles::             Marks for unread articles.
* Read Articles::               Marks for read articles.
* Other Marks::                 Marks that do not affect readedness.
* Setting Marks::               How to set and remove marks.
* Generic Marking Commands::    How to customize the marking.
* Setting Process Marks::       How to mark articles for later processing.

Threading

* Customizing Threading::       Variables you can change to affect the threading.
* Thread Commands::             Thread based commands in the summary buffer.

Customizing Threading

* Loose Threads::               How Gnus gathers loose threads into bigger threads.
* Filling In Threads::          Making the threads displayed look fuller.
* More Threading::              Even more variables for fiddling with threads.
* Low-Level Threading::         You thought it was over@dots{} but you were wrong!

Decoding Articles

* Uuencoded Articles::          Uudecode articles.
* Shell Archives::              Unshar articles.
* PostScript Files::            Split PostScript.
* Other Files::                 Plain save and binhex.
* Decoding Variables::          Variables for a happy decoding.
* Viewing Files::               You want to look at the result of the decoding?

Decoding Variables

* Rule Variables::              Variables that say how a file is to be viewed.
* Other Decode Variables::      Other decode variables.
* Uuencoding and Posting::      Variables for customizing uuencoding.

Article Treatment

* Article Highlighting::        You want to make the article look like fruit salad.
* Article Fontisizing::         Making emphasized text look nice.
* Article Hiding::              You also want to make certain info go away.
* Article Washing::             Lots of way-neat functions to make life better.
* Article Header::              Doing various header transformations.
* Article Buttons::             Click on URLs, Message-IDs, addresses and the like.
* Article Button Levels::       Controlling appearance of buttons.
* Article Date::                Grumble, UT!
* Article Display::             Display various stuff---X-Face, Picons, Smileys
* Article Signature::           What is a signature?
* Article Miscellanea::         Various other stuff.

Alternative Approaches

* Pick and Read::               First mark articles and then read them.
* Binary Groups::               Auto-decode all articles.

Various Summary Stuff

* Summary Group Information::   Information oriented commands.
* Searching for Articles::      Multiple article commands.
* Summary Generation Commands::
* Really Various Summary Commands::  Those pesky non-conformant commands.

Article Buffer

* Hiding Headers::              Deciding what headers should be displayed.
* Using MIME::                  Pushing articles through @acronym{MIME} before reading them.
* Customizing Articles::        Tailoring the look of the articles.
* Article Keymap::              Keystrokes available in the article buffer.
* Misc Article::                Other stuff.

Composing Messages

* Mail::                        Mailing and replying.
* Posting Server::              What server should you post and mail via?
* Mail and Post::               Mailing and posting at the same time.
* Archived Messages::           Where Gnus stores the messages you've sent.
* Posting Styles::              An easier way to specify who you are.
* Drafts::                      Postponing messages and rejected messages.
* Rejected Articles::           What happens if the server doesn't like your article?
* Signing and encrypting::      How to compose secure messages.

Select Methods

* Server Buffer::               Making and editing virtual servers.
* Getting News::                Reading USENET news with Gnus.
* Getting Mail::                Reading your personal mail with Gnus.
* Browsing the Web::            Getting messages from a plethora of Web sources.
* IMAP::                        Using Gnus as a @acronym{IMAP} client.
* Other Sources::               Reading directories, files, SOUP packets.
* Combined Groups::             Combining groups into one group.
* Gnus Unplugged::              Reading news and mail offline.

Server Buffer

* Server Buffer Format::        You can customize the look of this buffer.
* Server Commands::             Commands to manipulate servers.
* Example Methods::             Examples server specifications.
* Creating a Virtual Server::   An example session.
* Server Variables::            Which variables to set.
* Servers and Methods::         You can use server names as select methods.
* Unavailable Servers::         Some servers you try to contact may be down.

Getting News

* NNTP::                        Reading news from an @acronym{NNTP} server.
* News Spool::                  Reading news from the local spool.

@acronym{NNTP}

* Direct Functions::            Connecting directly to the server.
* Indirect Functions::          Connecting indirectly to the server.
* Common Variables::            Understood by several connection functions.

Getting Mail

* Mail in a Newsreader::        Important introductory notes.
* Getting Started Reading Mail::  A simple cookbook example.
* Splitting Mail::              How to create mail groups.
* Mail Sources::                How to tell Gnus where to get mail from.
* Mail Back End Variables::     Variables for customizing mail handling.
* Fancy Mail Splitting::        Gnus can do hairy splitting of incoming mail.
* Group Mail Splitting::        Use group customize to drive mail splitting.
* Incorporating Old Mail::      What about the old mail you have?
* Expiring Mail::               Getting rid of unwanted mail.
* Washing Mail::                Removing cruft from the mail you get.
* Duplicates::                  Dealing with duplicated mail.
* Not Reading Mail::            Using mail back ends for reading other files.
* Choosing a Mail Back End::    Gnus can read a variety of mail formats.

Mail Sources

* Mail Source Specifiers::      How to specify what a mail source is.
* Mail Source Customization::   Some variables that influence things.
* Fetching Mail::               Using the mail source specifiers.

Choosing a Mail Back End

* Unix Mail Box::               Using the (quite) standard Un*x mbox.
* Rmail Babyl::                 Emacs programs use the Rmail Babyl format.
* Mail Spool::                  Store your mail in a private spool?
* MH Spool::                    An mhspool-like back end.
* Maildir::                     Another one-file-per-message format.
* Mail Folders::                Having one file for each group.
* Comparing Mail Back Ends::    An in-depth looks at pros and cons.

Browsing the Web

* Archiving Mail::
* Web Searches::                Creating groups from articles that match a string.
* Slashdot::                    Reading the Slashdot comments.
* Ultimate::                    The Ultimate Bulletin Board systems.
* Web Archive::                 Reading mailing list archived on web.
* RSS::                         Reading RDF site summary.
* Customizing w3::              Doing stuff to Emacs/w3 from Gnus.

@acronym{IMAP}

* Splitting in IMAP::           Splitting mail with nnimap.
* Expiring in IMAP::            Expiring mail with nnimap.
* Editing IMAP ACLs::           Limiting/enabling other users access to a mailbox.
* Expunging mailboxes::         Equivalent of a ``compress mailbox'' button.
* A note on namespaces::        How to (not) use @acronym{IMAP} namespace in Gnus.

Other Sources

* Directory Groups::            You can read a directory as if it was a newsgroup.
* Anything Groups::             Dired?  Who needs dired?
* Document Groups::             Single files can be the basis of a group.
* SOUP::                        Reading @sc{soup} packets ``offline''.
* Mail-To-News Gateways::       Posting articles via mail-to-news gateways.

Document Groups

* Document Server Internals::   How to add your own document types.

SOUP

* SOUP Commands::               Commands for creating and sending @sc{soup} packets
* SOUP Groups::                 A back end for reading @sc{soup} packets.
* SOUP Replies::                How to enable @code{nnsoup} to take over mail and news.

Combined Groups

* Virtual Groups::              Combining articles from many groups.
* Kibozed Groups::              Looking through parts of the newsfeed for articles.

Gnus Unplugged

* Agent Basics::                How it all is supposed to work.
* Agent Categories::            How to tell the Gnus Agent what to download.
* Agent Commands::              New commands for all the buffers.
* Agent Visuals::               Ways that the agent may effect your summary buffer.
* Agent as Cache::              The Agent is a big cache too.
* Agent Expiry::                How to make old articles go away.
* Agent Regeneration::          How to recover from lost connections and other accidents.
* Agent and IMAP::              How to use the Agent with @acronym{IMAP}.
* Outgoing Messages::           What happens when you post/mail something?
* Agent Variables::             Customizing is fun.
* Example Setup::               An example @file{~/.gnus.el} file for offline people.
* Batching Agents::             How to fetch news from a @code{cron} job.
* Agent Caveats::               What you think it'll do and what it does.

Agent Categories

* Category Syntax::             What a category looks like.
* Category Buffer::             A buffer for maintaining categories.
* Category Variables::          Customize'r'Us.

Agent Commands

* Group Agent Commands::        Configure groups and fetch their contents.
* Summary Agent Commands::      Manually select then fetch specific articles.
* Server Agent Commands::       Select the servers that are supported by the agent.

Scoring

* Summary Score Commands::      Adding score entries for the current group.
* Group Score Commands::        General score commands.
* Score Variables::             Customize your scoring.  (My, what terminology).
* Score File Format::           What a score file may contain.
* Score File Editing::          You can edit score files by hand as well.
* Adaptive Scoring::            Big Sister Gnus knows what you read.
* Home Score File::             How to say where new score entries are to go.
* Followups To Yourself::       Having Gnus notice when people answer you.
* Scoring On Other Headers::    Scoring on non-standard headers.
* Scoring Tips::                How to score effectively.
* Reverse Scoring::             That problem child of old is not problem.
* Global Score Files::          Earth-spanning, ear-splitting score files.
* Kill Files::                  They are still here, but they can be ignored.
* Converting Kill Files::       Translating kill files to score files.
* GroupLens::                   Getting predictions on what you like to read.
* Advanced Scoring::            Using logical expressions to build score rules.
* Score Decays::                It can be useful to let scores wither away.

GroupLens

* Using GroupLens::             How to make Gnus use GroupLens.
* Rating Articles::             Letting GroupLens know how you rate articles.
* Displaying Predictions::      Displaying predictions given by GroupLens.
* GroupLens Variables::         Customizing GroupLens.

Advanced Scoring

* Advanced Scoring Syntax::     A definition.
* Advanced Scoring Examples::   What they look like.
* Advanced Scoring Tips::       Getting the most out of it.

Various

* Process/Prefix::              A convention used by many treatment commands.
* Interactive::                 Making Gnus ask you many questions.
* Symbolic Prefixes::           How to supply some Gnus functions with options.
* Formatting Variables::        You can specify what buffers should look like.
* Window Layout::               Configuring the Gnus buffer windows.
* Faces and Fonts::             How to change how faces look.
* Compilation::                 How to speed Gnus up.
* Mode Lines::                  Displaying information in the mode lines.
* Highlighting and Menus::      Making buffers look all nice and cozy.
* Buttons::                     Get tendinitis in ten easy steps!
* Daemons::                     Gnus can do things behind your back.
* NoCeM::                       How to avoid spam and other fatty foods.
* Undo::                        Some actions can be undone.
* Predicate Specifiers::        Specifying predicates.
* Moderation::                  What to do if you're a moderator.
* Image Enhancements::          Modern versions of Emacs/XEmacs can display images.
* Fuzzy Matching::              What's the big fuzz?
* Thwarting Email Spam::        A how-to on avoiding unsolicited commercial email.
* Various Various::             Things that are really various.

Formatting Variables

* Formatting Basics::           A formatting variable is basically a format string.
* Mode Line Formatting::        Some rules about mode line formatting variables.
* Advanced Formatting::         Modifying output in various ways.
* User-Defined Specs::          Having Gnus call your own functions.
* Formatting Fonts::            Making the formatting look colorful and nice.
* Positioning Point::           Moving point to a position after an operation.
* Tabulation::                  Tabulating your output.
* Wide Characters::             Dealing with wide characters.

Image Enhancements

* X-Face::                      Display a funky, teensy black-and-white image.
* Face::                        Display a funkier, teensier colored image.
* Smileys::                     Show all those happy faces the way they were meant to be shown.
* Picons::                      How to display pictures of what you're reading.
* XVarious::                    Other XEmacsy Gnusey variables.

Thwarting Email Spam

* The problem of spam::         Some background, and some solutions
* Anti-Spam Basics::            Simple steps to reduce the amount of spam.
* SpamAssassin::                How to use external anti-spam tools.
* Hashcash::                    Reduce spam by burning CPU time.
* Filtering Spam Using The Spam ELisp Package::
* Filtering Spam Using Statistics with spam-stat::

Filtering Spam Using The Spam ELisp Package

* Blacklists and Whitelists::
* BBDB Whitelists::
* Gmane Spam Reporting::
* Anti-spam Hashcash Payments::
* Blackholes::
* Regular Expressions Header Matching::
* Bogofilter::
* ifile spam filtering::
* spam-stat spam filtering::
* SpamOracle::
* Extending the spam elisp package::

Filtering Spam Using Statistics with spam-stat

* Creating a spam-stat dictionary::
* Splitting mail using spam-stat::
* Low-level interface to the spam-stat dictionary::

Appendices

* XEmacs::                      Requirements for installing under XEmacs.
* History::                     How Gnus got where it is today.
* On Writing Manuals::          Why this is not a beginner's guide.
* Terminology::                 We use really difficult, like, words here.
* Customization::               Tailoring Gnus to your needs.
* Troubleshooting::             What you might try if things do not work.
* Gnus Reference Guide::        Rilly, rilly technical stuff.
* Emacs for Heathens::          A short introduction to Emacsian terms.
* Frequently Asked Questions::  The Gnus FAQ.

History

* Gnus Versions::               What Gnus versions have been released.
* Other Gnus Versions::         Other Gnus versions that also have been released.
* Why?::                        What's the point of Gnus?
* Compatibility::               Just how compatible is Gnus with @sc{gnus}?
* Conformity::                  Gnus tries to conform to all standards.
* Emacsen::                     Gnus can be run on a few modern Emacsen.
* Gnus Development::            How Gnus is developed.
* Contributors::                Oodles of people.
* New Features::                Pointers to some of the new stuff in Gnus.

New Features

* ding Gnus::                   New things in Gnus 5.0/5.1, the first new Gnus.
* September Gnus::              The Thing Formally Known As Gnus 5.2/5.3.
* Red Gnus::                    Third time best---Gnus 5.4/5.5.
* Quassia Gnus::                Two times two is four, or Gnus 5.6/5.7.
* Pterodactyl Gnus::            Pentad also starts with P, AKA Gnus 5.8/5.9.
* Oort Gnus::                   It's big.  It's far out.  Gnus 5.10.

Customization

* Slow/Expensive Connection::   You run a local Emacs and get the news elsewhere.
* Slow Terminal Connection::    You run a remote Emacs.
* Little Disk Space::           You feel that having large setup files is icky.
* Slow Machine::                You feel like buying a faster machine.

Gnus Reference Guide

* Gnus Utility Functions::      Common functions and variable to use.
* Back End Interface::          How Gnus communicates with the servers.
* Score File Syntax::           A BNF definition of the score file standard.
* Headers::                     How Gnus stores headers internally.
* Ranges::                      A handy format for storing mucho numbers.
* Group Info::                  The group info format.
* Extended Interactive::        Symbolic prefixes and stuff.
* Emacs/XEmacs Code::           Gnus can be run under all modern Emacsen.
* Various File Formats::        Formats of files that Gnus use.

Back End Interface

* Required Back End Functions::  Functions that must be implemented.
* Optional Back End Functions::  Functions that need not be implemented.
* Error Messaging::             How to get messages and report errors.
* Writing New Back Ends::       Extending old back ends.
* Hooking New Back Ends Into Gnus::  What has to be done on the Gnus end.
* Mail-like Back Ends::         Some tips on mail back ends.

Various File Formats

* Active File Format::          Information on articles and groups available.
* Newsgroups File Format::      Group descriptions.

Emacs for Heathens

* Keystrokes::                  Entering text and executing commands.
* Emacs Lisp::                  The built-in Emacs programming language.

@end detailmenu
@end menu

@node Starting Up
@chapter Starting gnus
@cindex starting up

@kindex M-x gnus
@findex gnus
If your system administrator has set things up properly, starting gnus
and reading news is extremely easy---you just type @kbd{M-x gnus} in
your Emacs.

@findex gnus-other-frame
@kindex M-x gnus-other-frame
If you want to start gnus in a different frame, you can use the command
@kbd{M-x gnus-other-frame} instead.

If things do not go smoothly at startup, you have to twiddle some
variables in your @file{~/.gnus.el} file.  This file is similar to
@file{~/.emacs}, but is read when Gnus starts.

If you puzzle at any terms used in this manual, please refer to the
terminology section (@pxref{Terminology}).

@menu
* Finding the News::            Choosing a method for getting news.
* The First Time::              What does Gnus do the first time you start it?
* The Server is Down::          How can I read my mail then?
* Slave Gnusae::                You can have more than one Gnus active at a time.
* Fetching a Group::            Starting Gnus just to read a group.
* New Groups::                  What is Gnus supposed to do with new groups?
* Changing Servers::            You may want to move from one server to another.
* Startup Files::               Those pesky startup files---@file{.newsrc}.
* Auto Save::                   Recovering from a crash.
* The Active File::             Reading the active file over a slow line Takes Time.
* Startup Variables::           Other variables you might change.
@end menu


@node Finding the News
@section Finding the News
@cindex finding news

@vindex gnus-select-method
@c @head
The @code{gnus-select-method} variable says where gnus should look for
news.  This variable should be a list where the first element says
@dfn{how} and the second element says @dfn{where}.  This method is your
native method.  All groups not fetched with this method are
foreign groups.

For instance, if the @samp{news.somewhere.edu} @acronym{NNTP} server is where
you want to get your daily dosage of news from, you'd say:

@lisp
(setq gnus-select-method '(nntp "news.somewhere.edu"))
@end lisp

If you want to read directly from the local spool, say:

@lisp
(setq gnus-select-method '(nnspool ""))
@end lisp

If you can use a local spool, you probably should, as it will almost
certainly be much faster.  But do not use the local spool if your
server is running Leafnode; in this case, use @code{(nntp "localhost")}.

@vindex gnus-nntpserver-file
@cindex NNTPSERVER
@cindex @acronym{NNTP} server
If this variable is not set, gnus will take a look at the
@env{NNTPSERVER} environment variable.  If that variable isn't set,
gnus will see whether @code{gnus-nntpserver-file}
(@file{/etc/nntpserver} by default) has any opinions on the matter.
If that fails as well, gnus will try to use the machine running Emacs
as an @acronym{NNTP} server.  That's a long shot, though.

@vindex gnus-nntp-server
If @code{gnus-nntp-server} is set, this variable will override
@code{gnus-select-method}.  You should therefore set
@code{gnus-nntp-server} to @code{nil}, which is what it is by default.

@vindex gnus-secondary-servers
@vindex gnus-nntp-server
You can also make gnus prompt you interactively for the name of an
@acronym{NNTP} server.  If you give a non-numerical prefix to @code{gnus}
(i.e., @kbd{C-u M-x gnus}), gnus will let you choose between the servers
in the @code{gnus-secondary-servers} list (if any).  You can also just
type in the name of any server you feel like visiting.  (Note that this
will set @code{gnus-nntp-server}, which means that if you then @kbd{M-x
gnus} later in the same Emacs session, Gnus will contact the same
server.)

@findex gnus-group-browse-foreign-server
@kindex B (Group)
However, if you use one @acronym{NNTP} server regularly and are just
interested in a couple of groups from a different server, you would be
better served by using the @kbd{B} command in the group buffer.  It will
let you have a look at what groups are available, and you can subscribe
to any of the groups you want to.  This also makes @file{.newsrc}
maintenance much tidier.  @xref{Foreign Groups}.

@vindex gnus-secondary-select-methods
@c @head
A slightly different approach to foreign groups is to set the
@code{gnus-secondary-select-methods} variable.  The select methods
listed in this variable are in many ways just as native as the
@code{gnus-select-method} server.  They will also be queried for active
files during startup (if that's required), and new newsgroups that
appear on these servers will be subscribed (or not) just as native
groups are.

For instance, if you use the @code{nnmbox} back end to read your mail,
you would typically set this variable to

@lisp
(setq gnus-secondary-select-methods '((nnmbox "")))
@end lisp


@node The First Time
@section The First Time
@cindex first time usage

If no startup files exist, gnus will try to determine what groups should
be subscribed by default.

@vindex gnus-default-subscribed-newsgroups
If the variable @code{gnus-default-subscribed-newsgroups} is set, gnus
will subscribe you to just those groups in that list, leaving the rest
killed.  Your system administrator should have set this variable to
something useful.

Since she hasn't, gnus will just subscribe you to a few arbitrarily
picked groups (i.e., @samp{*.newusers}).  (@dfn{Arbitrary} is defined
here as @dfn{whatever Lars thinks you should read}.)

You'll also be subscribed to the gnus documentation group, which should
help you with most common problems.

If @code{gnus-default-subscribed-newsgroups} is @code{t}, gnus will just
use the normal functions for handling new groups, and not do anything
special.


@node The Server is Down
@section The Server is Down
@cindex server errors

If the default server is down, gnus will understandably have some
problems starting.  However, if you have some mail groups in addition to
the news groups, you may want to start gnus anyway.

Gnus, being the trusting sort of program, will ask whether to proceed
without a native select method if that server can't be contacted.  This
will happen whether the server doesn't actually exist (i.e., you have
given the wrong address) or the server has just momentarily taken ill
for some reason or other.  If you decide to continue and have no foreign
groups, you'll find it difficult to actually do anything in the group
buffer.  But, hey, that's your problem.  Blllrph!

@findex gnus-no-server
@kindex M-x gnus-no-server
@c @head
If you know that the server is definitely down, or you just want to read
your mail without bothering with the server at all, you can use the
@code{gnus-no-server} command to start gnus.  That might come in handy
if you're in a hurry as well.  This command will not attempt to contact
your primary server---instead, it will just activate all groups on level
1 and 2.  (You should preferably keep no native groups on those two
levels.) Also @pxref{Group Levels}.


@node Slave Gnusae
@section Slave Gnusae
@cindex slave

You might want to run more than one Emacs with more than one gnus at the
same time.  If you are using different @file{.newsrc} files (e.g., if you
are using the two different gnusae to read from two different servers),
that is no problem whatsoever.  You just do it.

The problem appears when you want to run two Gnusae that use the same
@file{.newsrc} file.

To work around that problem some, we here at the Think-Tank at the gnus
Towers have come up with a new concept: @dfn{Masters} and
@dfn{slaves}.  (We have applied for a patent on this concept, and have
taken out a copyright on those words.  If you wish to use those words in
conjunction with each other, you have to send $1 per usage instance to
me.  Usage of the patent (@dfn{Master/Slave Relationships In Computer
Applications}) will be much more expensive, of course.)

@findex gnus-slave
Anyway, you start one gnus up the normal way with @kbd{M-x gnus} (or
however you do it).  Each subsequent slave gnusae should be started with
@kbd{M-x gnus-slave}.  These slaves won't save normal @file{.newsrc}
files, but instead save @dfn{slave files} that contain information only
on what groups have been read in the slave session.  When a master gnus
starts, it will read (and delete) these slave files, incorporating all
information from them.  (The slave files will be read in the sequence
they were created, so the latest changes will have precedence.)

Information from the slave files has, of course, precedence over the
information in the normal (i.e., master) @file{.newsrc} file.

If the @file{.newsrc*} files have not been saved in the master when the
slave starts, you may be prompted as to whether to read an auto-save
file.  If you answer ``yes'', the unsaved changes to the master will be
incorporated into the slave.  If you answer ``no'', the slave may see some
messages as unread that have been read in the master.

@node Fetching a Group
@section Fetching a Group
@cindex fetching a group

@findex gnus-fetch-group
It is sometimes convenient to be able to just say ``I want to read this
group and I don't care whether gnus has been started or not''.  This is
perhaps more useful for people who write code than for users, but the
command @code{gnus-fetch-group} provides this functionality in any case.
It takes the group name as a parameter.


@node New Groups
@section New Groups
@cindex new groups
@cindex subscription

@vindex gnus-check-new-newsgroups
If you are satisfied that you really never want to see any new groups,
you can set @code{gnus-check-new-newsgroups} to @code{nil}.  This will
also save you some time at startup.  Even if this variable is
@code{nil}, you can always subscribe to the new groups just by pressing
@kbd{U} in the group buffer (@pxref{Group Maintenance}).  This variable
is @code{ask-server} by default.  If you set this variable to
@code{always}, then Gnus will query the back ends for new groups even
when you do the @kbd{g} command (@pxref{Scanning New Messages}).

@menu
* Checking New Groups::         Determining what groups are new.
* Subscription Methods::        What Gnus should do with new groups.
* Filtering New Groups::        Making Gnus ignore certain new groups.
@end menu


@node Checking New Groups
@subsection Checking New Groups

Gnus normally determines whether a group is new or not by comparing the
list of groups from the active file(s) with the lists of subscribed and
dead groups.  This isn't a particularly fast method.  If
@code{gnus-check-new-newsgroups} is @code{ask-server}, gnus will ask the
server for new groups since the last time.  This is both faster and
cheaper.  This also means that you can get rid of the list of killed
groups altogether, so you may set @code{gnus-save-killed-list} to
@code{nil}, which will save time both at startup, at exit, and all over.
Saves disk space, too.  Why isn't this the default, then?
Unfortunately, not all servers support this command.

I bet I know what you're thinking now: How do I find out whether my
server supports @code{ask-server}?  No?  Good, because I don't have a
fail-safe answer.  I would suggest just setting this variable to
@code{ask-server} and see whether any new groups appear within the next
few days.  If any do, then it works.  If none do, then it doesn't
work.  I could write a function to make gnus guess whether the server
supports @code{ask-server}, but it would just be a guess.  So I won't.
You could @code{telnet} to the server and say @code{HELP} and see
whether it lists @samp{NEWGROUPS} among the commands it understands.  If
it does, then it might work.  (But there are servers that lists
@samp{NEWGROUPS} without supporting the function properly.)

This variable can also be a list of select methods.  If so, gnus will
issue an @code{ask-server} command to each of the select methods, and
subscribe them (or not) using the normal methods.  This might be handy
if you are monitoring a few servers for new groups.  A side effect is
that startup will take much longer, so you can meditate while waiting.
Use the mantra ``dingnusdingnusdingnus'' to achieve permanent bliss.


@node Subscription Methods
@subsection Subscription Methods

@vindex gnus-subscribe-newsgroup-method
What gnus does when it encounters a new group is determined by the
@code{gnus-subscribe-newsgroup-method} variable.

This variable should contain a function.  This function will be called
with the name of the new group as the only parameter.

Some handy pre-fab functions are:

@table @code

@item gnus-subscribe-zombies
@vindex gnus-subscribe-zombies
Make all new groups zombies.  This is the default.  You can browse the
zombies later (with @kbd{A z}) and either kill them all off properly
(with @kbd{S z}), or subscribe to them (with @kbd{u}).

@item gnus-subscribe-randomly
@vindex gnus-subscribe-randomly
Subscribe all new groups in arbitrary order.  This really means that all
new groups will be added at ``the top'' of the group buffer.

@item gnus-subscribe-alphabetically
@vindex gnus-subscribe-alphabetically
Subscribe all new groups in alphabetical order.

@item gnus-subscribe-hierarchically
@vindex gnus-subscribe-hierarchically
Subscribe all new groups hierarchically.  The difference between this
function and @code{gnus-subscribe-alphabetically} is slight.
@code{gnus-subscribe-alphabetically} will subscribe new groups in a strictly
alphabetical fashion, while this function will enter groups into its
hierarchy.  So if you want to have the @samp{rec} hierarchy before the
@samp{comp} hierarchy, this function will not mess that configuration
up.  Or something like that.

@item gnus-subscribe-interactively
@vindex gnus-subscribe-interactively
Subscribe new groups interactively.  This means that gnus will ask
you about @strong{all} new groups.  The groups you choose to subscribe
to will be subscribed hierarchically.

@item gnus-subscribe-killed
@vindex gnus-subscribe-killed
Kill all new groups.

@item gnus-subscribe-topics
@vindex gnus-subscribe-topics
Put the groups into the topic that has a matching @code{subscribe} topic
parameter (@pxref{Topic Parameters}).  For instance, a @code{subscribe}
topic parameter that looks like

@example
"nnslashdot"
@end example

will mean that all groups that match that regex will be subscribed under
that topic.

If no topics match the groups, the groups will be subscribed in the
top-level topic.

@end table

@vindex gnus-subscribe-hierarchical-interactive
A closely related variable is
@code{gnus-subscribe-hierarchical-interactive}.  (That's quite a
mouthful.)  If this variable is non-@code{nil}, gnus will ask you in a
hierarchical fashion whether to subscribe to new groups or not.  Gnus
will ask you for each sub-hierarchy whether you want to descend the
hierarchy or not.

One common mistake is to set the variable a few paragraphs above
(@code{gnus-subscribe-newsgroup-method}) to
@code{gnus-subscribe-hierarchical-interactive}.  This is an error.  This
will not work.  This is ga-ga.  So don't do it.


@node Filtering New Groups
@subsection Filtering New Groups

A nice and portable way to control which new newsgroups should be
subscribed (or ignored) is to put an @dfn{options} line at the start of
the @file{.newsrc} file.  Here's an example:

@example
options -n !alt.all !rec.all sci.all
@end example

@vindex gnus-subscribe-options-newsgroup-method
This line obviously belongs to a serious-minded intellectual scientific
person (or she may just be plain old boring), because it says that all
groups that have names beginning with @samp{alt} and @samp{rec} should
be ignored, and all groups with names beginning with @samp{sci} should
be subscribed.  Gnus will not use the normal subscription method for
subscribing these groups.
@code{gnus-subscribe-options-newsgroup-method} is used instead.  This
variable defaults to @code{gnus-subscribe-alphabetically}.

@vindex gnus-options-not-subscribe
@vindex gnus-options-subscribe
If you don't want to mess with your @file{.newsrc} file, you can just
set the two variables @code{gnus-options-subscribe} and
@code{gnus-options-not-subscribe}.  These two variables do exactly the
same as the @file{.newsrc} @samp{options -n} trick.  Both are regexps,
and if the new group matches the former, it will be unconditionally
subscribed, and if it matches the latter, it will be ignored.

@vindex gnus-auto-subscribed-groups
Yet another variable that meddles here is
@code{gnus-auto-subscribed-groups}.  It works exactly like
@code{gnus-options-subscribe}, and is therefore really superfluous, but I
thought it would be nice to have two of these.  This variable is more
meant for setting some ground rules, while the other variable is used
more for user fiddling.  By default this variable makes all new groups
that come from mail back ends (@code{nnml}, @code{nnbabyl},
@code{nnfolder}, @code{nnmbox}, @code{nnmh}, and @code{nnmaildir})
subscribed.  If you don't like that, just set this variable to
@code{nil}.

New groups that match this regexp are subscribed using
@code{gnus-subscribe-options-newsgroup-method}.


@node Changing Servers
@section Changing Servers
@cindex changing servers

Sometimes it is necessary to move from one @acronym{NNTP} server to another.
This happens very rarely, but perhaps you change jobs, or one server is
very flaky and you want to use another.

Changing the server is pretty easy, right?  You just change
@code{gnus-select-method} to point to the new server?

@emph{Wrong!}

Article numbers are not (in any way) kept synchronized between different
@acronym{NNTP} servers, and the only way Gnus keeps track of what articles
you have read is by keeping track of article numbers.  So when you
change @code{gnus-select-method}, your @file{.newsrc} file becomes
worthless.

Gnus provides a few functions to attempt to translate a @file{.newsrc}
file from one server to another.  They all have one thing in
common---they take a looong time to run.  You don't want to use these
functions more than absolutely necessary.

@kindex M-x gnus-change-server
@findex gnus-change-server
If you have access to both servers, Gnus can request the headers for all
the articles you have read and compare @code{Message-ID}s and map the
article numbers of the read articles and article marks.  The @kbd{M-x
gnus-change-server} command will do this for all your native groups.  It
will prompt for the method you want to move to.

@kindex M-x gnus-group-move-group-to-server
@findex gnus-group-move-group-to-server
You can also move individual groups with the @kbd{M-x
gnus-group-move-group-to-server} command.  This is useful if you want to
move a (foreign) group from one server to another.

@kindex M-x gnus-group-clear-data-on-native-groups
@findex gnus-group-clear-data-on-native-groups
If you don't have access to both the old and new server, all your marks
and read ranges have become worthless.  You can use the @kbd{M-x
gnus-group-clear-data-on-native-groups} command to clear out all data
that you have on your native groups.  Use with caution.

@kindex M-x gnus-group-clear-data
@findex gnus-group-clear-data
Clear the data from the current group only---nix out marks and the
list of read articles (@code{gnus-group-clear-data}).

After changing servers, you @strong{must} move the cache hierarchy away,
since the cached articles will have wrong article numbers, which will
affect which articles Gnus thinks are read.
@code{gnus-group-clear-data-on-native-groups} will ask you if you want
to have it done automatically; for @code{gnus-group-clear-data}, you
can use @kbd{M-x gnus-cache-move-cache} (but beware, it will move the
cache for all groups).


@node Startup Files
@section Startup Files
@cindex startup files
@cindex .newsrc
@cindex .newsrc.el
@cindex .newsrc.eld

Now, you all know about the @file{.newsrc} file.  All subscription
information is traditionally stored in this file.

Things got a bit more complicated with @sc{gnus}.  In addition to
keeping the @file{.newsrc} file updated, it also used a file called
@file{.newsrc.el} for storing all the information that didn't fit into
the @file{.newsrc} file.  (Actually, it also duplicated everything in
the @file{.newsrc} file.)  @sc{gnus} would read whichever one of these
files was the most recently saved, which enabled people to swap between
@sc{gnus} and other newsreaders.

That was kinda silly, so Gnus went one better: In addition to the
@file{.newsrc} and @file{.newsrc.el} files, Gnus also has a file called
@file{.newsrc.eld}.  It will read whichever of these files that are most
recent, but it will never write a @file{.newsrc.el} file.  You should
never delete the @file{.newsrc.eld} file---it contains much information
not stored in the @file{.newsrc} file.

@vindex gnus-save-newsrc-file
@vindex gnus-read-newsrc-file
You can turn off writing the @file{.newsrc} file by setting
@code{gnus-save-newsrc-file} to @code{nil}, which means you can delete
the file and save some space, as well as exiting from gnus faster.
However, this will make it impossible to use other newsreaders than
gnus.  But hey, who would want to, right?  Similarly, setting
@code{gnus-read-newsrc-file} to @code{nil} makes gnus ignore the
@file{.newsrc} file and any @file{.newsrc-SERVER} files, which is
convenient if you have a tendency to use Netscape once in a while.

@vindex gnus-save-killed-list
If @code{gnus-save-killed-list} (default @code{t}) is @code{nil}, Gnus
will not save the list of killed groups to the startup file.  This will
save both time (when starting and quitting) and space (on disk).  It
will also mean that Gnus has no record of what groups are new or old,
so the automatic new groups subscription methods become meaningless.
You should always set @code{gnus-check-new-newsgroups} to @code{nil} or
@code{ask-server} if you set this variable to @code{nil} (@pxref{New
Groups}).  This variable can also be a regular expression.  If that's
the case, remove all groups that do not match this regexp before
saving.  This can be useful in certain obscure situations that involve
several servers where not all servers support @code{ask-server}.

@vindex gnus-startup-file
@vindex gnus-backup-startup-file
@vindex version-control
The @code{gnus-startup-file} variable says where the startup files are.
The default value is @file{~/.newsrc}, with the Gnus (El Dingo) startup
file being whatever that one is, with a @samp{.eld} appended.
If you want version control for this file, set
@code{gnus-backup-startup-file}.  It respects the same values as the
@code{version-control} variable.

@vindex gnus-save-newsrc-hook
@vindex gnus-save-quick-newsrc-hook
@vindex gnus-save-standard-newsrc-hook
@code{gnus-save-newsrc-hook} is called before saving any of the newsrc
files, while @code{gnus-save-quick-newsrc-hook} is called just before
saving the @file{.newsrc.eld} file, and
@code{gnus-save-standard-newsrc-hook} is called just before saving the
@file{.newsrc} file.  The latter two are commonly used to turn version
control on or off.  Version control is on by default when saving the
startup files.  If you want to turn backup creation off, say something like:

@lisp
(defun turn-off-backup ()
  (set (make-local-variable 'backup-inhibited) t))

(add-hook 'gnus-save-quick-newsrc-hook 'turn-off-backup)
(add-hook 'gnus-save-standard-newsrc-hook 'turn-off-backup)
@end lisp

@vindex gnus-init-file
@vindex gnus-site-init-file
When gnus starts, it will read the @code{gnus-site-init-file}
(@file{.../site-lisp/gnus} by default) and @code{gnus-init-file}
(@file{~/.gnus} by default) files.  These are normal Emacs Lisp files
and can be used to avoid cluttering your @file{~/.emacs} and
@file{site-init} files with gnus stuff.  Gnus will also check for files
with the same names as these, but with @file{.elc} and @file{.el}
suffixes.  In other words, if you have set @code{gnus-init-file} to
@file{~/.gnus}, it will look for @file{~/.gnus.elc}, @file{~/.gnus.el},
and finally @file{~/.gnus} (in this order).



@node Auto Save
@section Auto Save
@cindex dribble file
@cindex auto-save

Whenever you do something that changes the gnus data (reading articles,
catching up, killing/subscribing groups), the change is added to a
special @dfn{dribble buffer}.  This buffer is auto-saved the normal
Emacs way.  If your Emacs should crash before you have saved the
@file{.newsrc} files, all changes you have made can be recovered from
this file.

If gnus detects this file at startup, it will ask the user whether to
read it.  The auto save file is deleted whenever the real startup file is
saved.

@vindex gnus-use-dribble-file
If @code{gnus-use-dribble-file} is @code{nil}, gnus won't create and
maintain a dribble buffer.  The default is @code{t}.

@vindex gnus-dribble-directory
Gnus will put the dribble file(s) in @code{gnus-dribble-directory}.  If
this variable is @code{nil}, which it is by default, gnus will dribble
into the directory where the @file{.newsrc} file is located.  (This is
normally the user's home directory.)  The dribble file will get the same
file permissions as the @file{.newsrc} file.

@vindex gnus-always-read-dribble-file
If @code{gnus-always-read-dribble-file} is non-@code{nil}, Gnus will
read the dribble file on startup without querying the user.


@node The Active File
@section The Active File
@cindex active file
@cindex ignored groups

When gnus starts, or indeed whenever it tries to determine whether new
articles have arrived, it reads the active file.  This is a very large
file that lists all the active groups and articles on the server.

@vindex gnus-ignored-newsgroups
Before examining the active file, gnus deletes all lines that match the
regexp @code{gnus-ignored-newsgroups}.  This is done primarily to reject
any groups with bogus names, but you can use this variable to make gnus
ignore hierarchies you aren't ever interested in.  However, this is not
recommended.  In fact, it's highly discouraged.  Instead, @pxref{New
Groups} for an overview of other variables that can be used instead.

@c This variable is
@c @code{nil} by default, and will slow down active file handling somewhat
@c if you set it to anything else.

@vindex gnus-read-active-file
@c @head
The active file can be rather Huge, so if you have a slow network, you
can set @code{gnus-read-active-file} to @code{nil} to prevent gnus from
reading the active file.  This variable is @code{some} by default.

Gnus will try to make do by getting information just on the groups that
you actually subscribe to.

Note that if you subscribe to lots and lots of groups, setting this
variable to @code{nil} will probably make gnus slower, not faster.  At
present, having this variable @code{nil} will slow gnus down
considerably, unless you read news over a 2400 baud modem.

This variable can also have the value @code{some}.  Gnus will then
attempt to read active info only on the subscribed groups.  On some
servers this is quite fast (on sparkling, brand new INN servers that
support the @code{LIST ACTIVE group} command), on others this isn't fast
at all.  In any case, @code{some} should be faster than @code{nil}, and
is certainly faster than @code{t} over slow lines.

Some news servers (old versions of Leafnode and old versions of INN, for
instance) do not support the @code{LIST ACTIVE group}.  For these
servers, @code{nil} is probably the most efficient value for this
variable.

If this variable is @code{nil}, gnus will ask for group info in total
lock-step, which isn't very fast.  If it is @code{some} and you use an
@acronym{NNTP} server, gnus will pump out commands as fast as it can, and
read all the replies in one swoop.  This will normally result in better
performance, but if the server does not support the aforementioned
@code{LIST ACTIVE group} command, this isn't very nice to the server.

If you think that starting up Gnus takes too long, try all the three
different values for this variable and see what works best for you.

In any case, if you use @code{some} or @code{nil}, you should definitely
kill all groups that you aren't interested in to speed things up.

Note that this variable also affects active file retrieval from
secondary select methods.


@node Startup Variables
@section Startup Variables

@table @code

@item gnus-load-hook
@vindex gnus-load-hook
A hook run while gnus is being loaded.  Note that this hook will
normally be run just once in each Emacs session, no matter how many
times you start gnus.

@item gnus-before-startup-hook
@vindex gnus-before-startup-hook
A hook run after starting up gnus successfully.

@item gnus-startup-hook
@vindex gnus-startup-hook
A hook run as the very last thing after starting up gnus

@item gnus-started-hook
@vindex gnus-started-hook
A hook that is run as the very last thing after starting up gnus
successfully.

@item gnus-setup-news-hook
@vindex gnus-setup-news-hook
A hook that is run after reading the @file{.newsrc} file(s), but before
generating the group buffer.

@item gnus-check-bogus-newsgroups
@vindex gnus-check-bogus-newsgroups
If non-@code{nil}, gnus will check for and delete all bogus groups at
startup.  A @dfn{bogus group} is a group that you have in your
@file{.newsrc} file, but doesn't exist on the news server.  Checking for
bogus groups can take quite a while, so to save time and resources it's
best to leave this option off, and do the checking for bogus groups once
in a while from the group buffer instead (@pxref{Group Maintenance}).

@item gnus-inhibit-startup-message
@vindex gnus-inhibit-startup-message
If non-@code{nil}, the startup message won't be displayed.  That way,
your boss might not notice as easily that you are reading news instead
of doing your job.  Note that this variable is used before
@file{~/.gnus.el} is loaded, so it should be set in @file{.emacs} instead.

@item gnus-no-groups-message
@vindex gnus-no-groups-message
Message displayed by gnus when no groups are available.

@item gnus-play-startup-jingle
@vindex gnus-play-startup-jingle
If non-@code{nil}, play the gnus jingle at startup.

@item gnus-startup-jingle
@vindex gnus-startup-jingle
Jingle to be played if the above variable is non-@code{nil}.  The
default is @samp{Tuxedomoon.Jingle4.au}.

@end table


@node Group Buffer
@chapter Group Buffer
@cindex group buffer

@c Alex Schroeder suggests to rearrange this as follows:
@c
@c <kensanata> ok, just save it for reference.  I'll go to bed in a minute.
@c   1. Selecting a Group, 2. (new) Finding a Group, 3. Group Levels,
@c   4. Subscription Commands, 5. Group Maneuvering, 6. Group Data,
@c   7. Group Score, 8. Group Buffer Format
@c <kensanata> Group Levels should have more information on levels 5 to 9.  I
@c   suggest to split the 4th paragraph ("Gnus considers groups...") as follows:
@c <kensanata> First, "Gnus considers groups... (default 9)."
@c <kensanata> New, a table summarizing what levels 1 to 9 mean.
@c <kensanata> Third, "Gnus treats subscribed ... reasons of efficiency"
@c <kensanata> Then expand the next paragraph or add some more to it.
@c    This short one sentence explains levels 1 and 2, therefore I understand
@c    that I should keep important news at 3 and boring news at 4.
@c    Say so!  Then go on to explain why I should bother with levels 6 to 9.
@c    Maybe keep those that you don't want to read temporarily at 6,
@c    those that you never want to read at 8, those that offend your
@c    human rights at 9...


The @dfn{group buffer} lists all (or parts) of the available groups.  It
is the first buffer shown when gnus starts, and will never be killed as
long as gnus is active.

@iftex
@iflatex
\gnusfigure{The Group Buffer}{320}{
\put(75,50){\epsfig{figure=ps/group,height=9cm}}
\put(120,37){\makebox(0,0)[t]{Buffer name}}
\put(120,38){\vector(1,2){10}}
\put(40,60){\makebox(0,0)[r]{Mode line}}
\put(40,58){\vector(1,0){30}}
\put(200,28){\makebox(0,0)[t]{Native select method}}
\put(200,26){\vector(-1,2){15}}
}
@end iflatex
@end iftex

@menu
* Group Buffer Format::         Information listed and how you can change it.
* Group Maneuvering::           Commands for moving in the group buffer.
* Selecting a Group::           Actually reading news.
* Subscription Commands::       Unsubscribing, killing, subscribing.
* Group Data::                  Changing the info for a group.
* Group Levels::                Levels? What are those, then?
* Group Score::                 A mechanism for finding out what groups you like.
* Marking Groups::              You can mark groups for later processing.
* Foreign Groups::              Creating and editing groups.
* Group Parameters::            Each group may have different parameters set.
* Listing Groups::              Gnus can list various subsets of the groups.
* Sorting Groups::              Re-arrange the group order.
* Group Maintenance::           Maintaining a tidy @file{.newsrc} file.
* Browse Foreign Server::       You can browse a server.  See what it has to offer.
* Exiting Gnus::                Stop reading news and get some work done.
* Group Topics::                A folding group mode divided into topics.
* Misc Group Stuff::            Other stuff that you can to do.
@end menu


@node Group Buffer Format
@section Group Buffer Format

@menu
* Group Line Specification::    Deciding how the group buffer is to look.
* Group Mode Line Specification::  The group buffer mode line.
* Group Highlighting::          Having nice colors in the group buffer.
@end menu


@node Group Line Specification
@subsection Group Line Specification
@cindex group buffer format

The default format of the group buffer is nice and dull, but you can
make it as exciting and ugly as you feel like.

Here's a couple of example group lines:

@example
     25: news.announce.newusers
 *    0: alt.fan.andrea-dworkin
@end example

Quite simple, huh?

You can see that there are 25 unread articles in
@samp{news.announce.newusers}.  There are no unread articles, but some
ticked articles, in @samp{alt.fan.andrea-dworkin} (see that little
asterisk at the beginning of the line?).

@vindex gnus-group-line-format
You can change that format to whatever you want by fiddling with the
@code{gnus-group-line-format} variable.  This variable works along the
lines of a @code{format} specification, which is pretty much the same as
a @code{printf} specifications, for those of you who use (feh!) C.
@xref{Formatting Variables}.

@samp{%M%S%5y:%B%(%g%)\n} is the value that produced those lines above.

There should always be a colon on the line; the cursor always moves to
the colon after performing an operation.  @xref{Positioning
Point}.  Nothing else is required---not even the group name.  All
displayed text is just window dressing, and is never examined by Gnus.
Gnus stores all real information it needs using text properties.

(Note that if you make a really strange, wonderful, spreadsheet-like
layout, everybody will believe you are hard at work with the accounting
instead of wasting time reading news.)

Here's a list of all available format characters:

@table @samp

@item M
An asterisk if the group only has marked articles.

@item S
Whether the group is subscribed.

@item L
Level of subscribedness.

@item N
Number of unread articles.

@item I
Number of dormant articles.

@item T
Number of ticked articles.

@item R
Number of read articles.

@item U
Number of unseen articles.

@item t
Estimated total number of articles.  (This is really @var{max-number}
minus @var{min-number} plus 1.)

Gnus uses this estimation because the @acronym{NNTP} protocol provides
efficient access to @var{max-number} and @var{min-number} but getting
the true unread message count is not possible efficiently.  For
hysterical raisins, even the mail back ends, where the true number of
unread messages might be available efficiently, use the same limited
interface.  To remove this restriction from Gnus means that the back
end interface has to be changed, which is not an easy job.  If you
want to work on this, please contact the Gnus mailing list.

@item y
Number of unread, unticked, non-dormant articles.

@item i
Number of ticked and dormant articles.

@item g
Full group name.

@item G
Group name.

@item C
Group comment (@pxref{Group Parameters}) or group name if there is no
comment element in the group parameters.

@item D
Newsgroup description.  You need to read the group descriptions
before these will appear, and to do that, you either have to set
@code{gnus-read-active-file} or use the group buffer @kbd{M-d}
command.

@item o
@samp{m} if moderated.

@item O
@samp{(m)} if moderated.

@item s
Select method.

@item B
If the summary buffer for the group is open or not.

@item n
Select from where.

@item z
A string that looks like @samp{<%s:%n>} if a foreign select method is
used.

@item P
Indentation based on the level of the topic (@pxref{Group Topics}).

@item c
@vindex gnus-group-uncollapsed-levels
Short (collapsed) group name.  The @code{gnus-group-uncollapsed-levels}
variable says how many levels to leave at the end of the group name.
The default is 1---this will mean that group names like
@samp{gnu.emacs.gnus} will be shortened to @samp{g.e.gnus}.

@item m
@vindex gnus-new-mail-mark
@cindex %
@samp{%} (@code{gnus-new-mail-mark}) if there has arrived new mail to
the group lately.

@item p
@samp{#} (@code{gnus-process-mark}) if the group is process marked.

@item d
A string that says when you last read the group (@pxref{Group
Timestamp}).

@item u
User defined specifier.  The next character in the format string should
be a letter.  Gnus will call the function
@code{gnus-user-format-function-}@samp{X}, where @samp{X} is the letter
following @samp{%u}.  The function will be passed a single dummy
parameter as argument.  The function should return a string, which will
be inserted into the buffer just like information from any other
specifier.
@end table

@cindex *
All the ``number-of'' specs will be filled with an asterisk (@samp{*})
if no info is available---for instance, if it is a non-activated foreign
group, or a bogus native group.


@node Group Mode Line Specification
@subsection Group Mode Line Specification
@cindex group mode line

@vindex gnus-group-mode-line-format
The mode line can be changed by setting
@code{gnus-group-mode-line-format} (@pxref{Mode Line Formatting}).  It
doesn't understand that many format specifiers:

@table @samp
@item S
The native news server.
@item M
The native select method.
@end table


@node Group Highlighting
@subsection Group Highlighting
@cindex highlighting
@cindex group highlighting

@vindex gnus-group-highlight
Highlighting in the group buffer is controlled by the
@code{gnus-group-highlight} variable.  This is an alist with elements
that look like @code{(@var{form} . @var{face})}.  If @var{form} evaluates to
something non-@code{nil}, the @var{face} will be used on the line.

Here's an example value for this variable that might look nice if the
background is dark:

@lisp
(cond (window-system
       (setq custom-background-mode 'light)
       (defface my-group-face-1
         '((t (:foreground "Red" :bold t))) "First group face")
       (defface my-group-face-2
         '((t (:foreground "DarkSeaGreen4" :bold t)))
         "Second group face")
       (defface my-group-face-3
         '((t (:foreground "Green4" :bold t))) "Third group face")
       (defface my-group-face-4
         '((t (:foreground "SteelBlue" :bold t))) "Fourth group face")
       (defface my-group-face-5
         '((t (:foreground "Blue" :bold t))) "Fifth group face")))

(setq gnus-group-highlight
      '(((> unread 200) . my-group-face-1)
        ((and (< level 3) (zerop unread)) . my-group-face-2)
        ((< level 3) . my-group-face-3)
        ((zerop unread) . my-group-face-4)
        (t . my-group-face-5)))
@end lisp

Also @pxref{Faces and Fonts}.

Variables that are dynamically bound when the forms are evaluated
include:

@table @code
@item group
The group name.
@item unread
The number of unread articles in the group.
@item method
The select method.
@item mailp
Whether the group is a mail group.
@item level
The level of the group.
@item score
The score of the group.
@item ticked
The number of ticked articles in the group.
@item total
The total number of articles in the group.  Or rather,
@var{max-number} minus @var{min-number} plus one.
@item topic
When using the topic minor mode, this variable is bound to the current
topic being inserted.
@end table

When the forms are @code{eval}ed, point is at the beginning of the line
of the group in question, so you can use many of the normal gnus
functions for snarfing info on the group.

@vindex gnus-group-update-hook
@findex gnus-group-highlight-line
@code{gnus-group-update-hook} is called when a group line is changed.
It will not be called when @code{gnus-visual} is @code{nil}.  This hook
calls @code{gnus-group-highlight-line} by default.


@node Group Maneuvering
@section Group Maneuvering
@cindex group movement

All movement commands understand the numeric prefix and will behave as
expected, hopefully.

@table @kbd

@item n
@kindex n (Group)
@findex gnus-group-next-unread-group
Go to the next group that has unread articles
(@code{gnus-group-next-unread-group}).

@item p
@itemx DEL
@kindex DEL (Group)
@kindex p (Group)
@findex gnus-group-prev-unread-group
Go to the previous group that has unread articles
(@code{gnus-group-prev-unread-group}).

@item N
@kindex N (Group)
@findex gnus-group-next-group
Go to the next group (@code{gnus-group-next-group}).

@item P
@kindex P (Group)
@findex gnus-group-prev-group
Go to the previous group (@code{gnus-group-prev-group}).

@item M-n
@kindex M-n (Group)
@findex gnus-group-next-unread-group-same-level
Go to the next unread group on the same (or lower) level
(@code{gnus-group-next-unread-group-same-level}).

@item M-p
@kindex M-p (Group)
@findex gnus-group-prev-unread-group-same-level
Go to the previous unread group on the same (or lower) level
(@code{gnus-group-prev-unread-group-same-level}).
@end table

Three commands for jumping to groups:

@table @kbd

@item j
@kindex j (Group)
@findex gnus-group-jump-to-group
Jump to a group (and make it visible if it isn't already)
(@code{gnus-group-jump-to-group}).  Killed groups can be jumped to, just
like living groups.

@item ,
@kindex , (Group)
@findex gnus-group-best-unread-group
Jump to the unread group with the lowest level
(@code{gnus-group-best-unread-group}).

@item .
@kindex . (Group)
@findex gnus-group-first-unread-group
Jump to the first group with unread articles
(@code{gnus-group-first-unread-group}).
@end table

@vindex gnus-group-goto-unread
If @code{gnus-group-goto-unread} is @code{nil}, all the movement
commands will move to the next group, not the next unread group.  Even
the commands that say they move to the next unread group.  The default
is @code{t}.


@node Selecting a Group
@section Selecting a Group
@cindex group selection

@table @kbd

@item SPACE
@kindex SPACE (Group)
@findex gnus-group-read-group
Select the current group, switch to the summary buffer and display the
first unread article (@code{gnus-group-read-group}).  If there are no
unread articles in the group, or if you give a non-numerical prefix to
this command, gnus will offer to fetch all the old articles in this
group from the server.  If you give a numerical prefix @var{n}, @var{n}
determines the number of articles Gnus will fetch.  If @var{n} is
positive, Gnus fetches the @var{n} newest articles, if @var{n} is
negative, Gnus fetches the @code{abs(@var{n})} oldest articles.

Thus, @kbd{SPC} enters the group normally, @kbd{C-u SPC} offers old
articles, @kbd{C-u 4 2 SPC} fetches the 42 newest articles, and @kbd{C-u
- 4 2 SPC} fetches the 42 oldest ones.

When you are in the group (in the Summary buffer), you can type
@kbd{M-g} to fetch new articles, or @kbd{C-u M-g} to also show the old
ones.

@item RET
@kindex RET (Group)
@findex gnus-group-select-group
Select the current group and switch to the summary buffer
(@code{gnus-group-select-group}).  Takes the same arguments as
@code{gnus-group-read-group}---the only difference is that this command
does not display the first unread article automatically upon group
entry.

@item M-RET
@kindex M-RET (Group)
@findex gnus-group-quick-select-group
This does the same as the command above, but tries to do it with the
minimum amount of fuzz (@code{gnus-group-quick-select-group}).  No
scoring/killing will be performed, there will be no highlights and no
expunging.  This might be useful if you're in a real hurry and have to
enter some humongous group.  If you give a 0 prefix to this command
(i.e., @kbd{0 M-RET}), gnus won't even generate the summary buffer,
which is useful if you want to toggle threading before generating the
summary buffer (@pxref{Summary Generation Commands}).

@item M-SPACE
@kindex M-SPACE (Group)
@findex gnus-group-visible-select-group
This is yet one more command that does the same as the @kbd{RET}
command, but this one does it without expunging and hiding dormants
(@code{gnus-group-visible-select-group}).

@item C-M-RET
@kindex C-M-RET (Group)
@findex gnus-group-select-group-ephemerally
Finally, this command selects the current group ephemerally without
doing any processing of its contents
(@code{gnus-group-select-group-ephemerally}).  Even threading has been
turned off.  Everything you do in the group after selecting it in this
manner will have no permanent effects.

@end table

@vindex gnus-large-newsgroup
The @code{gnus-large-newsgroup} variable says what Gnus should
consider to be a big group.  If it is @code{nil}, no groups are
considered big.  The default value is 200.  If the group has more
(unread and/or ticked) articles than this, gnus will query the user
before entering the group.  The user can then specify how many
articles should be fetched from the server.  If the user specifies a
negative number (@var{-n}), the @var{n} oldest articles will be
fetched.  If it is positive, the @var{n} articles that have arrived
most recently will be fetched.

@vindex gnus-large-ephemeral-newsgroup
@code{gnus-large-ephemeral-newsgroup} is the same as
@code{gnus-large-newsgroup}, but is only used for ephemeral
newsgroups.

@vindex gnus-select-group-hook
@vindex gnus-auto-select-first
@vindex gnus-auto-select-subject
If @code{gnus-auto-select-first} is non-@code{nil}, select an article
automatically when entering a group with the @kbd{SPACE} command.
Which article this is is controlled by the
@code{gnus-auto-select-subject} variable.  Valid values for this
variable is:

@table @code

@item unread
Place point on the subject line of the first unread article.

@item first
Place point on the subject line of the first article.

@item unseen
Place point on the subject line of the first unseen article.

@item unseen-or-unread
Place point on the subject line of the first unseen article, and if
there is no such article, place point on the subject line of the first
unread article.

@item best
Place point on the subject line of the highest-scored unread article.

@end table

This variable can also be a function.  In that case, that function
will be called to place point on a subject line.

If you want to prevent automatic selection in some group (say, in a
binary group with Huge articles) you can set the
@code{gnus-auto-select-first} variable to @code{nil} in
@code{gnus-select-group-hook}, which is called when a group is
selected.


@node Subscription Commands
@section Subscription Commands
@cindex subscription

@table @kbd

@item S t
@itemx u
@kindex S t (Group)
@kindex u (Group)
@findex gnus-group-unsubscribe-current-group
@c @icon{gnus-group-unsubscribe}
Toggle subscription to the current group
(@code{gnus-group-unsubscribe-current-group}).

@item S s
@itemx U
@kindex S s (Group)
@kindex U (Group)
@findex gnus-group-unsubscribe-group
Prompt for a group to subscribe, and then subscribe it.  If it was
subscribed already, unsubscribe it instead
(@code{gnus-group-unsubscribe-group}).

@item S k
@itemx C-k
@kindex S k (Group)
@kindex C-k (Group)
@findex gnus-group-kill-group
@c @icon{gnus-group-kill-group}
Kill the current group (@code{gnus-group-kill-group}).

@item S y
@itemx C-y
@kindex S y (Group)
@kindex C-y (Group)
@findex gnus-group-yank-group
Yank the last killed group (@code{gnus-group-yank-group}).

@item C-x C-t
@kindex C-x C-t (Group)
@findex gnus-group-transpose-groups
Transpose two groups (@code{gnus-group-transpose-groups}).  This isn't
really a subscription command, but you can use it instead of a
kill-and-yank sequence sometimes.

@item S w
@itemx C-w
@kindex S w (Group)
@kindex C-w (Group)
@findex gnus-group-kill-region
Kill all groups in the region (@code{gnus-group-kill-region}).

@item S z
@kindex S z (Group)
@findex gnus-group-kill-all-zombies
Kill all zombie groups (@code{gnus-group-kill-all-zombies}).

@item S C-k
@kindex S C-k (Group)
@findex gnus-group-kill-level
Kill all groups on a certain level (@code{gnus-group-kill-level}).
These groups can't be yanked back after killing, so this command should
be used with some caution.  The only time where this command comes in
really handy is when you have a @file{.newsrc} with lots of unsubscribed
groups that you want to get rid off.  @kbd{S C-k} on level 7 will
kill off all unsubscribed groups that do not have message numbers in the
@file{.newsrc} file.

@end table

Also @pxref{Group Levels}.


@node Group Data
@section Group Data

@table @kbd

@item c
@kindex c (Group)
@findex gnus-group-catchup-current
@vindex gnus-group-catchup-group-hook
@c @icon{gnus-group-catchup-current}
Mark all unticked articles in this group as read
(@code{gnus-group-catchup-current}).
@code{gnus-group-catchup-group-hook} is called when catching up a group from
the group buffer.

@item C
@kindex C (Group)
@findex gnus-group-catchup-current-all
Mark all articles in this group, even the ticked ones, as read
(@code{gnus-group-catchup-current-all}).

@item M-c
@kindex M-c (Group)
@findex gnus-group-clear-data
Clear the data from the current group---nix out marks and the list of
read articles (@code{gnus-group-clear-data}).

@item M-x gnus-group-clear-data-on-native-groups
@kindex M-x gnus-group-clear-data-on-native-groups
@findex gnus-group-clear-data-on-native-groups
If you have switched from one @acronym{NNTP} server to another, all your marks
and read ranges have become worthless.  You can use this command to
clear out all data that you have on your native groups.  Use with
caution.

@end table


@node Group Levels
@section Group Levels
@cindex group level
@cindex level

All groups have a level of @dfn{subscribedness}.  For instance, if a
group is on level 2, it is more subscribed than a group on level 5.  You
can ask gnus to just list groups on a given level or lower
(@pxref{Listing Groups}), or to just check for new articles in groups on
a given level or lower (@pxref{Scanning New Messages}).

Remember:  The higher the level of the group, the less important it is.

@table @kbd

@item S l
@kindex S l (Group)
@findex gnus-group-set-current-level
Set the level of the current group.  If a numeric prefix is given, the
next @var{n} groups will have their levels set.  The user will be
prompted for a level.
@end table

@vindex gnus-level-killed
@vindex gnus-level-zombie
@vindex gnus-level-unsubscribed
@vindex gnus-level-subscribed
Gnus considers groups from levels 1 to
@code{gnus-level-subscribed} (inclusive) (default 5) to be subscribed,
@code{gnus-level-subscribed} (exclusive) and
@code{gnus-level-unsubscribed} (inclusive) (default 7) to be
unsubscribed, @code{gnus-level-zombie} to be zombies (walking dead)
(default 8) and @code{gnus-level-killed} to be killed (completely dead)
(default 9).  Gnus treats subscribed and unsubscribed groups exactly the
same, but zombie and killed groups have no information on what articles
you have read, etc, stored.  This distinction between dead and living
groups isn't done because it is nice or clever, it is done purely for
reasons of efficiency.

It is recommended that you keep all your mail groups (if any) on quite
low levels (e.g. 1 or 2).

Maybe the following description of the default behavior of Gnus helps to
understand what these levels are all about.  By default, Gnus shows you
subscribed nonempty groups, but by hitting @kbd{L} you can have it show
empty subscribed groups and unsubscribed groups, too.  Type @kbd{l} to
go back to showing nonempty subscribed groups again.  Thus, unsubscribed
groups are hidden, in a way.

Zombie and killed groups are similar to unsubscribed groups in that they
are hidden by default.  But they are different from subscribed and
unsubscribed groups in that Gnus doesn't ask the news server for
information (number of messages, number of unread messages) on zombie
and killed groups.  Normally, you use @kbd{C-k} to kill the groups you
aren't interested in.  If most groups are killed, Gnus is faster.

Why does Gnus distinguish between zombie and killed groups?  Well, when
a new group arrives on the server, Gnus by default makes it a zombie
group.  This means that you are normally not bothered with new groups,
but you can type @kbd{A z} to get a list of all new groups.  Subscribe
the ones you like and kill the ones you don't want.  (@kbd{A k} shows a
list of killed groups.)

If you want to play with the level variables, you should show some care.
Set them once, and don't touch them ever again.  Better yet, don't touch
them at all unless you know exactly what you're doing.

@vindex gnus-level-default-unsubscribed
@vindex gnus-level-default-subscribed
Two closely related variables are @code{gnus-level-default-subscribed}
(default 3) and @code{gnus-level-default-unsubscribed} (default 6),
which are the levels that new groups will be put on if they are
(un)subscribed.  These two variables should, of course, be inside the
relevant valid ranges.

@vindex gnus-keep-same-level
If @code{gnus-keep-same-level} is non-@code{nil}, some movement commands
will only move to groups of the same level (or lower).  In
particular, going from the last article in one group to the next group
will go to the next group of the same level (or lower).  This might be
handy if you want to read the most important groups before you read the
rest.

If this variable is @code{best}, Gnus will make the next newsgroup the
one with the best level.

@vindex gnus-group-default-list-level
All groups with a level less than or equal to
@code{gnus-group-default-list-level} will be listed in the group buffer
by default.

@vindex gnus-group-list-inactive-groups
If @code{gnus-group-list-inactive-groups} is non-@code{nil}, non-active
groups will be listed along with the unread groups.  This variable is
@code{t} by default.  If it is @code{nil}, inactive groups won't be
listed.

@vindex gnus-group-use-permanent-levels
If @code{gnus-group-use-permanent-levels} is non-@code{nil}, once you
give a level prefix to @kbd{g} or @kbd{l}, all subsequent commands will
use this level as the ``work'' level.

@vindex gnus-activate-level
Gnus will normally just activate (i. e., query the server about) groups
on level @code{gnus-activate-level} or less.  If you don't want to
activate unsubscribed groups, for instance, you might set this variable
to 5.  The default is 6.


@node Group Score
@section Group Score
@cindex group score
@cindex group rank
@cindex rank

You would normally keep important groups on high levels, but that scheme
is somewhat restrictive.  Don't you wish you could have Gnus sort the
group buffer according to how often you read groups, perhaps?  Within
reason?

This is what @dfn{group score} is for.  You can have Gnus assign a score
to each group through the mechanism described below.  You can then sort
the group buffer based on this score.  Alternatively, you can sort on
score and then level.  (Taken together, the level and the score is
called the @dfn{rank} of the group.  A group that is on level 4 and has
a score of 1 has a higher rank than a group on level 5 that has a score
of 300.  (The level is the most significant part and the score is the
least significant part.))

@findex gnus-summary-bubble-group
If you want groups you read often to get higher scores than groups you
read seldom you can add the @code{gnus-summary-bubble-group} function to
the @code{gnus-summary-exit-hook} hook.  This will result (after
sorting) in a bubbling sort of action.  If you want to see that in
action after each summary exit, you can add
@code{gnus-group-sort-groups-by-rank} or
@code{gnus-group-sort-groups-by-score} to the same hook, but that will
slow things down somewhat.


@node Marking Groups
@section Marking Groups
@cindex marking groups

If you want to perform some command on several groups, and they appear
subsequently in the group buffer, you would normally just give a
numerical prefix to the command.  Most group commands will then do your
bidding on those groups.

However, if the groups are not in sequential order, you can still
perform a command on several groups.  You simply mark the groups first
with the process mark and then execute the command.

@table @kbd

@item #
@kindex # (Group)
@itemx M m
@kindex M m (Group)
@findex gnus-group-mark-group
Set the mark on the current group (@code{gnus-group-mark-group}).

@item M-#
@kindex M-# (Group)
@itemx M u
@kindex M u (Group)
@findex gnus-group-unmark-group
Remove the mark from the current group
(@code{gnus-group-unmark-group}).

@item M U
@kindex M U (Group)
@findex gnus-group-unmark-all-groups
Remove the mark from all groups (@code{gnus-group-unmark-all-groups}).

@item M w
@kindex M w (Group)
@findex gnus-group-mark-region
Mark all groups between point and mark (@code{gnus-group-mark-region}).

@item M b
@kindex M b (Group)
@findex gnus-group-mark-buffer
Mark all groups in the buffer (@code{gnus-group-mark-buffer}).

@item M r
@kindex M r (Group)
@findex gnus-group-mark-regexp
Mark all groups that match some regular expression
(@code{gnus-group-mark-regexp}).
@end table

Also @pxref{Process/Prefix}.

@findex gnus-group-universal-argument
If you want to execute some command on all groups that have been marked
with the process mark, you can use the @kbd{M-&}
(@code{gnus-group-universal-argument}) command.  It will prompt you for
the command to be executed.


@node Foreign Groups
@section Foreign Groups
@cindex foreign groups

Below are some group mode commands for making and editing general foreign
groups, as well as commands to ease the creation of a few
special-purpose groups.  All these commands insert the newly created
groups under point---@code{gnus-subscribe-newsgroup-method} is not
consulted.

@table @kbd

@item G m
@kindex G m (Group)
@findex gnus-group-make-group
@cindex making groups
Make a new group (@code{gnus-group-make-group}).  Gnus will prompt you
for a name, a method and possibly an @dfn{address}.  For an easier way
to subscribe to @acronym{NNTP} groups (@pxref{Browse Foreign Server}).

@item G r
@kindex G r (Group)
@findex gnus-group-rename-group
@cindex renaming groups
Rename the current group to something else
(@code{gnus-group-rename-group}).  This is valid only on some
groups---mail groups mostly.  This command might very well be quite slow
on some back ends.

@item G c
@kindex G c (Group)
@cindex customizing
@findex gnus-group-customize
Customize the group parameters (@code{gnus-group-customize}).

@item G e
@kindex G e (Group)
@findex gnus-group-edit-group-method
@cindex renaming groups
Enter a buffer where you can edit the select method of the current
group (@code{gnus-group-edit-group-method}).

@item G p
@kindex G p (Group)
@findex gnus-group-edit-group-parameters
Enter a buffer where you can edit the group parameters
(@code{gnus-group-edit-group-parameters}).

@item G E
@kindex G E (Group)
@findex gnus-group-edit-group
Enter a buffer where you can edit the group info
(@code{gnus-group-edit-group}).

@item G d
@kindex G d (Group)
@findex gnus-group-make-directory-group
@cindex nndir
Make a directory group (@pxref{Directory Groups}).  You will be prompted
for a directory name (@code{gnus-group-make-directory-group}).

@item G h
@kindex G h (Group)
@cindex help group
@findex gnus-group-make-help-group
Make the gnus help group (@code{gnus-group-make-help-group}).

@item G a
@kindex G a (Group)
@cindex (ding) archive
@cindex archive group
@findex gnus-group-make-archive-group
@vindex gnus-group-archive-directory
@vindex gnus-group-recent-archive-directory
Make a gnus archive group (@code{gnus-group-make-archive-group}).  By
default a group pointing to the most recent articles will be created
(@code{gnus-group-recent-archive-directory}), but given a prefix, a full
group will be created from @code{gnus-group-archive-directory}.

@item G k
@kindex G k (Group)
@findex gnus-group-make-kiboze-group
@cindex nnkiboze
Make a kiboze group.  You will be prompted for a name, for a regexp to
match groups to be ``included'' in the kiboze group, and a series of
strings to match on headers (@code{gnus-group-make-kiboze-group}).
@xref{Kibozed Groups}.

@item G D
@kindex G D (Group)
@findex gnus-group-enter-directory
@cindex nneething
Read an arbitrary directory as if it were a newsgroup with the
@code{nneething} back end (@code{gnus-group-enter-directory}).
@xref{Anything Groups}.

@item G f
@kindex G f (Group)
@findex gnus-group-make-doc-group
@cindex ClariNet Briefs
@cindex nndoc
Make a group based on some file or other
(@code{gnus-group-make-doc-group}).  If you give a prefix to this
command, you will be prompted for a file name and a file type.
Currently supported types are @code{mbox}, @code{babyl},
@code{digest}, @code{news}, @code{rnews}, @code{mmdf}, @code{forward},
@code{rfc934}, @code{rfc822-forward}, @code{mime-parts},
@code{standard-digest}, @code{slack-digest}, @code{clari-briefs},
@code{nsmail}, @code{outlook}, @code{oe-dbx}, and @code{mailman}.  If
you run this command without a prefix, Gnus will guess at the file
type.  @xref{Document Groups}.

@item G u
@kindex G u (Group)
@vindex gnus-useful-groups
@findex gnus-group-make-useful-group
Create one of the groups mentioned in @code{gnus-useful-groups}
(@code{gnus-group-make-useful-group}).

@item G w
@kindex G w (Group)
@findex gnus-group-make-web-group
@cindex Google
@cindex nnweb
@cindex gmane
Make an ephemeral group based on a web search
(@code{gnus-group-make-web-group}).  If you give a prefix to this
command, make a solid group instead.  You will be prompted for the
search engine type and the search string.  Valid search engine types
include @code{google}, @code{dejanews}, and @code{gmane}.
@xref{Web Searches}.

If you use the @code{google} search engine, you can limit the search
to a particular group by using a match string like
@samp{shaving group:alt.sysadmin.recovery}.

@item G DEL
@kindex G DEL (Group)
@findex gnus-group-delete-group
This function will delete the current group
(@code{gnus-group-delete-group}).  If given a prefix, this function will
actually delete all the articles in the group, and forcibly remove the
group itself from the face of the Earth.  Use a prefix only if you are
absolutely sure of what you are doing.  This command can't be used on
read-only groups (like @code{nntp} group), though.

@item G V
@kindex G V (Group)
@findex gnus-group-make-empty-virtual
Make a new, fresh, empty @code{nnvirtual} group
(@code{gnus-group-make-empty-virtual}).  @xref{Virtual Groups}.

@item G v
@kindex G v (Group)
@findex gnus-group-add-to-virtual
Add the current group to an @code{nnvirtual} group
(@code{gnus-group-add-to-virtual}).  Uses the process/prefix convention.
@end table

@xref{Select Methods}, for more information on the various select
methods.

@vindex gnus-activate-foreign-newsgroups
If @code{gnus-activate-foreign-newsgroups} is a positive number,
gnus will check all foreign groups with this level or lower at startup.
This might take quite a while, especially if you subscribe to lots of
groups from different @acronym{NNTP} servers.  Also @pxref{Group Levels};
@code{gnus-activate-level} also affects activation of foreign
newsgroups.


@node Group Parameters
@section Group Parameters
@cindex group parameters

The group parameters store information local to a particular group.
Here's an example group parameter list:

@example
((to-address . "ding@@gnus.org")
 (auto-expire . t))
@end example

We see that each element consists of a ``dotted pair''---the thing before
the dot is the key, while the thing after the dot is the value.  All the
parameters have this form @emph{except} local variable specs, which are
not dotted pairs, but proper lists.

Some parameters have correspondent customizable variables, each of which
is an alist of regexps and values.

The following group parameters can be used:

@table @code
@item to-address
@cindex to-address
Address used by when doing followups and new posts.

@example
(to-address . "some@@where.com")
@end example

This is primarily useful in mail groups that represent closed mailing
lists---mailing lists where it's expected that everybody that writes to
the mailing list is subscribed to it.  Since using this parameter
ensures that the mail only goes to the mailing list itself, it means
that members won't receive two copies of your followups.

Using @code{to-address} will actually work whether the group is foreign
or not.  Let's say there's a group on the server that is called
@samp{fa.4ad-l}.  This is a real newsgroup, but the server has gotten
the articles from a mail-to-news gateway.  Posting directly to this
group is therefore impossible---you have to send mail to the mailing
list address instead.

See also @code{gnus-parameter-to-address-alist}.

@item to-list
@cindex to-list
Address used when doing @kbd{a} in that group.

@example
(to-list . "some@@where.com")
@end example

It is totally ignored
when doing a followup---except that if it is present in a news group,
you'll get mail group semantics when doing @kbd{f}.

If you do an @kbd{a} command in a mail group and you have neither a
@code{to-list} group parameter nor a @code{to-address} group parameter,
then a @code{to-list} group parameter will be added automatically upon
sending the message if @code{gnus-add-to-list} is set to @code{t}.
@vindex gnus-add-to-list

If you do an @kbd{a} command in a mail group and you don't have a
@code{to-list} group parameter, one will be added automatically upon
sending the message.

@findex gnus-mailing-list-mode
@cindex mail list groups
If this variable is set, @code{gnus-mailing-list-mode} is turned on when
entering summary buffer.

See also @code{gnus-parameter-to-list-alist}.

@anchor{subscribed}
@item subscribed
@cindex subscribed
@cindex Mail-Followup-To
If this parameter is set to @code{t}, Gnus will consider the
to-address and to-list parameters for this group as addresses of
mailing lists you are subscribed to.  Giving Gnus this information is
(only) a first step in getting it to generate correct Mail-Followup-To
headers for your posts to these lists.  @xref{Mailing Lists, ,Mailing
Lists, message, The Message Manual}, for a complete treatment of
available MFT support.

See also @code{gnus-find-subscribed-addresses}, the function that
directly uses this group parameter.

@item visible
@cindex visible
If the group parameter list has the element @code{(visible . t)},
that group will always be visible in the Group buffer, regardless
of whether it has any unread articles.

@item broken-reply-to
@cindex broken-reply-to
Elements like @code{(broken-reply-to . t)} signals that @code{Reply-To}
headers in this group are to be ignored, and for the header to be hidden
if @code{reply-to} is part of @code{gnus-boring-article-headers}.  This
can be useful if you're reading a mailing list group where the listserv
has inserted @code{Reply-To} headers that point back to the listserv
itself.  That is broken behavior.  So there!

@item to-group
@cindex to-group
Elements like @code{(to-group . "some.group.name")} means that all
posts in that group will be sent to @code{some.group.name}.

@item newsgroup
@cindex newsgroup
If you have @code{(newsgroup . t)} in the group parameter list, gnus
will treat all responses as if they were responses to news articles.
This can be useful if you have a mail group that's really a mirror of a
news group.

@item gcc-self
@cindex gcc-self
If @code{(gcc-self . t)} is present in the group parameter list, newly
composed messages will be @code{Gcc}'d to the current group.  If
@code{(gcc-self . none)} is present, no @code{Gcc:} header will be
generated, if @code{(gcc-self . "string")} is present, this string will
be inserted literally as a @code{gcc} header.  This parameter takes
precedence over any default @code{Gcc} rules as described later
(@pxref{Archived Messages}).

@strong{Caveat}: It yields an error putting @code{(gcc-self . t)} in
groups of an @code{nntp} server or so, because an @code{nntp} server
doesn't accept articles.

@item auto-expire
@cindex auto-expire
If the group parameter has an element that looks like @code{(auto-expire
. t)}, all articles read will be marked as expirable.  For an
alternative approach, @pxref{Expiring Mail}.

See also @code{gnus-auto-expirable-newsgroups}.

@item total-expire
@cindex total-expire
If the group parameter has an element that looks like
@code{(total-expire . t)}, all read articles will be put through the
expiry process, even if they are not marked as expirable.  Use with
caution.  Unread, ticked and dormant articles are not eligible for
expiry.

See also @code{gnus-total-expirable-newsgroups}.

@item expiry-wait
@cindex expiry-wait
@vindex nnmail-expiry-wait-function
If the group parameter has an element that looks like
@code{(expiry-wait . 10)}, this value will override any
@code{nnmail-expiry-wait} and @code{nnmail-expiry-wait-function}
(@pxref{Expiring Mail}) when expiring expirable messages.  The value
can either be a number of days (not necessarily an integer) or the
symbols @code{never} or @code{immediate}.

@item expiry-target
@cindex expiry-target
Where expired messages end up.  This parameter overrides
@code{nnmail-expiry-target}.

@item score-file
@cindex score file group parameter
Elements that look like @code{(score-file . "file")} will make
@file{file} into the current score file for the group in question.  All
interactive score entries will be put into this file.

@item adapt-file
@cindex adapt file group parameter
Elements that look like @code{(adapt-file . "file")} will make
@file{file} into the current adaptive file for the group in question.
All adaptive score entries will be put into this file.

@item admin-address
@cindex admin-address
When unsubscribing from a mailing list you should never send the
unsubscription notice to the mailing list itself.  Instead, you'd send
messages to the administrative address.  This parameter allows you to
put the admin address somewhere convenient.

@item display
@cindex display
Elements that look like @code{(display . MODE)} say which articles to
display on entering the group.  Valid values are:

@table @code
@item all
Display all articles, both read and unread.

@item an integer
Display the last @var{integer} articles in the group.  This is the same as
entering the group with @kbd{C-u @var{integer}}.

@item default
Display the default visible articles, which normally includes unread and
ticked articles.

@item an array
Display articles that satisfy a predicate.

Here are some examples:

@table @code
@item [unread]
Display only unread articles.

@item [not expire]
Display everything except expirable articles.

@item [and (not reply) (not expire)]
Display everything except expirable and articles you've already
responded to.
@end table

The available operators are @code{not}, @code{and} and @code{or}.
Predicates include @code{tick}, @code{unsend}, @code{undownload},
@code{unread}, @code{dormant}, @code{expire}, @code{reply},
@code{killed}, @code{bookmark}, @code{score}, @code{save},
@code{cache}, @code{forward}, @code{unseen} and @code{recent}.

@end table

The @code{display} parameter works by limiting the summary buffer to
the subset specified.  You can pop the limit by using the @kbd{/ w}
command (@pxref{Limiting}).

@item comment
@cindex comment
Elements that look like @code{(comment . "This is a comment")} are
arbitrary comments on the group.  You can display comments in the
group line (@pxref{Group Line Specification}).

@item charset
@cindex charset
Elements that look like @code{(charset . iso-8859-1)} will make
@code{iso-8859-1} the default charset; that is, the charset that will be
used for all articles that do not specify a charset.

See also @code{gnus-group-charset-alist}.

@item ignored-charsets
@cindex ignored-charset
Elements that look like @code{(ignored-charsets x-unknown iso-8859-1)}
will make @code{iso-8859-1} and @code{x-unknown} ignored; that is, the
default charset will be used for decoding articles.

See also @code{gnus-group-ignored-charsets-alist}.

@item posting-style
@cindex posting-style
You can store additional posting style information for this group
here (@pxref{Posting Styles}).  The format is that of an entry in the
@code{gnus-posting-styles} alist, except that there's no regexp matching
the group name (of course).  Style elements in this group parameter will
take precedence over the ones found in @code{gnus-posting-styles}.

For instance, if you want a funky name and signature in this group only,
instead of hacking @code{gnus-posting-styles}, you could put something
like this in the group parameters:

@example
(posting-style
  (name "Funky Name")
  ("X-My-Header" "Funky Value")
  (signature "Funky Signature"))
@end example

@item post-method
@cindex post-method
If it is set, the value is used as the method for posting message
instead of @code{gnus-post-method}.

@item banner
@cindex banner
An item like @code{(banner . @var{regexp})} causes any part of an article
that matches the regular expression @var{regexp} to be stripped.  Instead of
@var{regexp}, you can also use the symbol @code{signature} which strips the
last signature or any of the elements of the alist
@code{gnus-article-banner-alist}.

@item sieve
@cindex sieve
This parameter contains a Sieve test that should match incoming mail
that should be placed in this group.  From this group parameter, a
Sieve @samp{IF} control structure is generated, having the test as the
condition and @samp{fileinto "group.name";} as the body.

For example, if the @samp{INBOX.list.sieve} group has the @code{(sieve
address "sender" "sieve-admin@@extundo.com")} group parameter, when
translating the group parameter into a Sieve script (@pxref{Sieve
Commands}) the following Sieve code is generated:

@example
if address \"sender\" \"sieve-admin@@extundo.com\" @{
        fileinto \"INBOX.list.sieve\";
@}
@end example

The Sieve language is described in RFC 3028.  @xref{Top, Emacs Sieve,
Top, sieve, Emacs Sieve}.

@item (@var{variable} @var{form})
You can use the group parameters to set variables local to the group you
are entering.  If you want to turn threading off in @samp{news.answers},
you could put @code{(gnus-show-threads nil)} in the group parameters of
that group.  @code{gnus-show-threads} will be made into a local variable
in the summary buffer you enter, and the form @code{nil} will be
@code{eval}ed there.

Note that this feature sets the variable locally to the summary buffer.
But some variables are evaluated in the article buffer, or in the
message buffer (of a reply or followup or otherwise newly created
message).  As a workaround, it might help to add the variable in
question to @code{gnus-newsgroup-variables}.  @xref{Various Summary
Stuff}.  So if you want to set @code{message-from-style} via the group
parameters, then you may need the following statement elsewhere in your
@file{~/.gnus} file:

@lisp
(add-to-list 'gnus-newsgroup-variables 'message-from-style)
@end lisp

@vindex gnus-list-identifiers
A use for this feature is to remove a mailing list identifier tag in
the subject fields of articles.  E.g. if the news group

@example
nntp+news.gnus.org:gmane.text.docbook.apps
@end example

has the tag @samp{DOC-BOOK-APPS:} in the subject of all articles, this
tag can be removed from the article subjects in the summary buffer for
the group by putting @code{(gnus-list-identifiers "DOCBOOK-APPS:")}
into the group parameters for the group.

This can also be used as a group-specific hook function, if you'd like.
If you want to hear a beep when you enter a group, you could put
something like @code{(dummy-variable (ding))} in the parameters of that
group.  @code{dummy-variable} will be set to the result of the
@code{(ding)} form, but who cares?

@end table

Use the @kbd{G p} or the @kbd{G c} command to edit group parameters of a
group.  (@kbd{G p} presents you with a Lisp-based interface, @kbd{G c}
presents you with a Customize-like interface.  The latter helps avoid
silly Lisp errors.)  You might also be interested in reading about topic
parameters (@pxref{Topic Parameters}).

@vindex gnus-parameters
Group parameters can be set via the @code{gnus-parameters} variable too.
But some variables, such as @code{visible}, have no effect.  For
example:

@lisp
(setq gnus-parameters
      '(("mail\\..*"
         (gnus-show-threads nil)
         (gnus-use-scoring nil)
         (gnus-summary-line-format
          "%U%R%z%I%(%[%d:%ub%-23,23f%]%) %s\n")
         (gcc-self . t)
         (display . all))

        ("^nnimap:\\(foo.bar\\)$"
         (to-group . "\\1"))

        ("mail\\.me"
         (gnus-use-scoring  t))

        ("list\\..*"
         (total-expire . t)
         (broken-reply-to . t))))
@end lisp

String value of parameters will be subjected to regexp substitution, as
the @code{to-group} example shows.


@node Listing Groups
@section Listing Groups
@cindex group listing

These commands all list various slices of the groups available.

@table @kbd

@item l
@itemx A s
@kindex A s (Group)
@kindex l (Group)
@findex gnus-group-list-groups
List all groups that have unread articles
(@code{gnus-group-list-groups}).  If the numeric prefix is used, this
command will list only groups of level ARG and lower.  By default, it
only lists groups of level five (i.e.,
@code{gnus-group-default-list-level}) or lower (i.e., just subscribed
groups).

@item L
@itemx A u
@kindex A u (Group)
@kindex L (Group)
@findex gnus-group-list-all-groups
List all groups, whether they have unread articles or not
(@code{gnus-group-list-all-groups}).  If the numeric prefix is used,
this command will list only groups of level ARG and lower.  By default,
it lists groups of level seven or lower (i.e., just subscribed and
unsubscribed groups).

@item A l
@kindex A l (Group)
@findex gnus-group-list-level
List all unread groups on a specific level
(@code{gnus-group-list-level}).  If given a prefix, also list the groups
with no unread articles.

@item A k
@kindex A k (Group)
@findex gnus-group-list-killed
List all killed groups (@code{gnus-group-list-killed}).  If given a
prefix argument, really list all groups that are available, but aren't
currently (un)subscribed.  This could entail reading the active file
from the server.

@item A z
@kindex A z (Group)
@findex gnus-group-list-zombies
List all zombie groups (@code{gnus-group-list-zombies}).

@item A m
@kindex A m (Group)
@findex gnus-group-list-matching
List all unread, subscribed groups with names that match a regexp
(@code{gnus-group-list-matching}).

@item A M
@kindex A M (Group)
@findex gnus-group-list-all-matching
List groups that match a regexp (@code{gnus-group-list-all-matching}).

@item A A
@kindex A A (Group)
@findex gnus-group-list-active
List absolutely all groups in the active file(s) of the
server(s) you are connected to (@code{gnus-group-list-active}).  This
might very well take quite a while.  It might actually be a better idea
to do a @kbd{A M} to list all matching, and just give @samp{.} as the
thing to match on.  Also note that this command may list groups that
don't exist (yet)---these will be listed as if they were killed groups.
Take the output with some grains of salt.

@item A a
@kindex A a (Group)
@findex gnus-group-apropos
List all groups that have names that match a regexp
(@code{gnus-group-apropos}).

@item A d
@kindex A d (Group)
@findex gnus-group-description-apropos
List all groups that have names or descriptions that match a regexp
(@code{gnus-group-description-apropos}).

@item A c
@kindex A c (Group)
@findex gnus-group-list-cached
List all groups with cached articles (@code{gnus-group-list-cached}).

@item A ?
@kindex A ? (Group)
@findex gnus-group-list-dormant
List all groups with dormant articles (@code{gnus-group-list-dormant}).

@item A /
@kindex A / (Group)
@findex gnus-group-list-limit
List groups limited within the current selection
(@code{gnus-group-list-limit}).

@item A f
@kindex A f (Group)
@findex gnus-group-list-flush
Flush groups from the current selection (@code{gnus-group-list-flush}).

@item A p
@kindex A p (Group)
@findex gnus-group-list-plus
List groups plus the current selection (@code{gnus-group-list-plus}).

@end table

@vindex gnus-permanently-visible-groups
@cindex visible group parameter
Groups that match the @code{gnus-permanently-visible-groups} regexp will
always be shown, whether they have unread articles or not.  You can also
add the @code{visible} element to the group parameters in question to
get the same effect.

@vindex gnus-list-groups-with-ticked-articles
Groups that have just ticked articles in it are normally listed in the
group buffer.  If @code{gnus-list-groups-with-ticked-articles} is
@code{nil}, these groups will be treated just like totally empty
groups.  It is @code{t} by default.


@node Sorting Groups
@section Sorting Groups
@cindex sorting groups

@kindex C-c C-s (Group)
@findex gnus-group-sort-groups
@vindex gnus-group-sort-function
The @kbd{C-c C-s} (@code{gnus-group-sort-groups}) command sorts the
group buffer according to the function(s) given by the
@code{gnus-group-sort-function} variable.  Available sorting functions
include:

@table @code

@item gnus-group-sort-by-alphabet
@findex gnus-group-sort-by-alphabet
Sort the group names alphabetically.  This is the default.

@item gnus-group-sort-by-real-name
@findex gnus-group-sort-by-real-name
Sort the group alphabetically on the real (unprefixed) group names.

@item gnus-group-sort-by-level
@findex gnus-group-sort-by-level
Sort by group level.

@item gnus-group-sort-by-score
@findex gnus-group-sort-by-score
Sort by group score.  @xref{Group Score}.

@item gnus-group-sort-by-rank
@findex gnus-group-sort-by-rank
Sort by group score and then the group level.  The level and the score
are, when taken together, the group's @dfn{rank}.  @xref{Group Score}.

@item gnus-group-sort-by-unread
@findex gnus-group-sort-by-unread
Sort by number of unread articles.

@item gnus-group-sort-by-method
@findex gnus-group-sort-by-method
Sort alphabetically on the select method.

@item gnus-group-sort-by-server
@findex gnus-group-sort-by-server
Sort alphabetically on the Gnus server name.


@end table

@code{gnus-group-sort-function} can also be a list of sorting
functions.  In that case, the most significant sort key function must be
the last one.


There are also a number of commands for sorting directly according to
some sorting criteria:

@table @kbd
@item G S a
@kindex G S a (Group)
@findex gnus-group-sort-groups-by-alphabet
Sort the group buffer alphabetically by group name
(@code{gnus-group-sort-groups-by-alphabet}).

@item G S u
@kindex G S u (Group)
@findex gnus-group-sort-groups-by-unread
Sort the group buffer by the number of unread articles
(@code{gnus-group-sort-groups-by-unread}).

@item G S l
@kindex G S l (Group)
@findex gnus-group-sort-groups-by-level
Sort the group buffer by group level
(@code{gnus-group-sort-groups-by-level}).

@item G S v
@kindex G S v (Group)
@findex gnus-group-sort-groups-by-score
Sort the group buffer by group score
(@code{gnus-group-sort-groups-by-score}).  @xref{Group Score}.

@item G S r
@kindex G S r (Group)
@findex gnus-group-sort-groups-by-rank
Sort the group buffer by group rank
(@code{gnus-group-sort-groups-by-rank}).  @xref{Group Score}.

@item G S m
@kindex G S m (Group)
@findex gnus-group-sort-groups-by-method
Sort the group buffer alphabetically by back end name@*
(@code{gnus-group-sort-groups-by-method}).

@item G S n
@kindex G S n (Group)
@findex gnus-group-sort-groups-by-real-name
Sort the group buffer alphabetically by real (unprefixed) group name
(@code{gnus-group-sort-groups-by-real-name}).

@end table

All the commands below obey the process/prefix convention
(@pxref{Process/Prefix}).

When given a symbolic prefix (@pxref{Symbolic Prefixes}), all these
commands will sort in reverse order.

You can also sort a subset of the groups:

@table @kbd
@item G P a
@kindex G P a (Group)
@findex gnus-group-sort-selected-groups-by-alphabet
Sort the groups alphabetically by group name
(@code{gnus-group-sort-selected-groups-by-alphabet}).

@item G P u
@kindex G P u (Group)
@findex gnus-group-sort-selected-groups-by-unread
Sort the groups by the number of unread articles
(@code{gnus-group-sort-selected-groups-by-unread}).

@item G P l
@kindex G P l (Group)
@findex gnus-group-sort-selected-groups-by-level
Sort the groups by group level
(@code{gnus-group-sort-selected-groups-by-level}).

@item G P v
@kindex G P v (Group)
@findex gnus-group-sort-selected-groups-by-score
Sort the groups by group score
(@code{gnus-group-sort-selected-groups-by-score}).  @xref{Group Score}.

@item G P r
@kindex G P r (Group)
@findex gnus-group-sort-selected-groups-by-rank
Sort the groups by group rank
(@code{gnus-group-sort-selected-groups-by-rank}).  @xref{Group Score}.

@item G P m
@kindex G P m (Group)
@findex gnus-group-sort-selected-groups-by-method
Sort the groups alphabetically by back end name@*
(@code{gnus-group-sort-selected-groups-by-method}).

@item G P n
@kindex G P n (Group)
@findex gnus-group-sort-selected-groups-by-real-name
Sort the groups alphabetically by real (unprefixed) group name
(@code{gnus-group-sort-selected-groups-by-real-name}).

@item G P s
@kindex G P s (Group)
@findex gnus-group-sort-selected-groups
Sort the groups according to @code{gnus-group-sort-function}.

@end table

And finally, note that you can use @kbd{C-k} and @kbd{C-y} to manually
move groups around.


@node Group Maintenance
@section Group Maintenance
@cindex bogus groups

@table @kbd
@item b
@kindex b (Group)
@findex gnus-group-check-bogus-groups
Find bogus groups and delete them
(@code{gnus-group-check-bogus-groups}).

@item F
@kindex F (Group)
@findex gnus-group-find-new-groups
Find new groups and process them (@code{gnus-group-find-new-groups}).
With 1 @kbd{C-u}, use the @code{ask-server} method to query the server
for new groups.  With 2 @kbd{C-u}'s, use most complete method possible
to query the server for new groups, and subscribe the new groups as
zombies.

@item C-c C-x
@kindex C-c C-x (Group)
@findex gnus-group-expire-articles
Run all expirable articles in the current group through the expiry
process (if any) (@code{gnus-group-expire-articles}).  That is, delete
all expirable articles in the group that have been around for a while.
(@pxref{Expiring Mail}).

@item C-c C-M-x
@kindex C-c C-M-x (Group)
@findex gnus-group-expire-all-groups
Run all expirable articles in all groups through the expiry process
(@code{gnus-group-expire-all-groups}).

@end table


@node Browse Foreign Server
@section Browse Foreign Server
@cindex foreign servers
@cindex browsing servers

@table @kbd
@item B
@kindex B (Group)
@findex gnus-group-browse-foreign-server
You will be queried for a select method and a server name.  Gnus will
then attempt to contact this server and let you browse the groups there
(@code{gnus-group-browse-foreign-server}).
@end table

@findex gnus-browse-mode
A new buffer with a list of available groups will appear.  This buffer
will use the @code{gnus-browse-mode}.  This buffer looks a bit (well,
a lot) like a normal group buffer.

Here's a list of keystrokes available in the browse mode:

@table @kbd
@item n
@kindex n (Browse)
@findex gnus-group-next-group
Go to the next group (@code{gnus-group-next-group}).

@item p
@kindex p (Browse)
@findex gnus-group-prev-group
Go to the previous group (@code{gnus-group-prev-group}).

@item SPACE
@kindex SPACE (Browse)
@findex gnus-browse-read-group
Enter the current group and display the first article
(@code{gnus-browse-read-group}).

@item RET
@kindex RET (Browse)
@findex gnus-browse-select-group
Enter the current group (@code{gnus-browse-select-group}).

@item u
@kindex u (Browse)
@findex gnus-browse-unsubscribe-current-group
Unsubscribe to the current group, or, as will be the case here,
subscribe to it (@code{gnus-browse-unsubscribe-current-group}).

@item l
@itemx q
@kindex q (Browse)
@kindex l (Browse)
@findex gnus-browse-exit
Exit browse mode (@code{gnus-browse-exit}).

@item d
@kindex d (Browse)
@findex gnus-browse-describe-group
Describe the current group (@code{gnus-browse-describe-group}).

@item ?
@kindex ? (Browse)
@findex gnus-browse-describe-briefly
Describe browse mode briefly (well, there's not much to describe, is
there) (@code{gnus-browse-describe-briefly}).
@end table


@node Exiting Gnus
@section Exiting gnus
@cindex exiting gnus

Yes, gnus is ex(c)iting.

@table @kbd
@item z
@kindex z (Group)
@findex gnus-group-suspend
Suspend gnus (@code{gnus-group-suspend}).  This doesn't really exit gnus,
but it kills all buffers except the Group buffer.  I'm not sure why this
is a gain, but then who am I to judge?

@item q
@kindex q (Group)
@findex gnus-group-exit
@c @icon{gnus-group-exit}
Quit gnus (@code{gnus-group-exit}).

@item Q
@kindex Q (Group)
@findex gnus-group-quit
Quit gnus without saving the @file{.newsrc} files (@code{gnus-group-quit}).
The dribble file will be saved, though (@pxref{Auto Save}).
@end table

@vindex gnus-exit-gnus-hook
@vindex gnus-suspend-gnus-hook
@vindex gnus-after-exiting-gnus-hook
@code{gnus-suspend-gnus-hook} is called when you suspend gnus and
@code{gnus-exit-gnus-hook} is called when you quit gnus, while
@code{gnus-after-exiting-gnus-hook} is called as the final item when
exiting gnus.

Note:

@quotation
Miss Lisa Cannifax, while sitting in English class, felt her feet go
numbly heavy and herself fall into a hazy trance as the boy sitting
behind her drew repeated lines with his pencil across the back of her
plastic chair.
@end quotation


@node Group Topics
@section Group Topics
@cindex topics

If you read lots and lots of groups, it might be convenient to group
them hierarchically according to topics.  You put your Emacs groups over
here, your sex groups over there, and the rest (what, two groups or so?)
you put in some misc section that you never bother with anyway.  You can
even group the Emacs sex groups as a sub-topic to either the Emacs
groups or the sex groups---or both!  Go wild!

@iftex
@iflatex
\gnusfigure{Group Topics}{400}{
\put(75,50){\epsfig{figure=ps/group-topic,height=9cm}}
}
@end iflatex
@end iftex

Here's an example:

@example
Gnus
  Emacs -- I wuw it!
     3: comp.emacs
     2: alt.religion.emacs
    Naughty Emacs
     452: alt.sex.emacs
       0: comp.talk.emacs.recovery
  Misc
     8: comp.binaries.fractals
    13: comp.sources.unix
@end example

@findex gnus-topic-mode
@kindex t (Group)
To get this @emph{fab} functionality you simply turn on (ooh!) the
@code{gnus-topic} minor mode---type @kbd{t} in the group buffer.  (This
is a toggling command.)

Go ahead, just try it.  I'll still be here when you get back.  La de
dum@dots{} Nice tune, that@dots{} la la la@dots{} What, you're back?
Yes, and now press @kbd{l}.  There.  All your groups are now listed
under @samp{misc}.  Doesn't that make you feel all warm and fuzzy?
Hot and bothered?

If you want this permanently enabled, you should add that minor mode to
the hook for the group mode.  Put the following line in your
@file{~/.gnus.el} file:

@lisp
(add-hook 'gnus-group-mode-hook 'gnus-topic-mode)
@end lisp

@menu
* Topic Commands::              Interactive E-Z commands.
* Topic Variables::             How to customize the topics the Lisp Way.
* Topic Sorting::               Sorting each topic individually.
* Topic Topology::              A map of the world.
* Topic Parameters::            Parameters that apply to all groups in a topic.
@end menu


@node Topic Commands
@subsection Topic Commands
@cindex topic commands

When the topic minor mode is turned on, a new @kbd{T} submap will be
available.  In addition, a few of the standard keys change their
definitions slightly.

In general, the following kinds of operations are possible on topics.
First of all, you want to create topics.  Secondly, you want to put
groups in topics and to move them around until you have an order you
like.  The third kind of operation is to show/hide parts of the whole
shebang.  You might want to hide a topic including its subtopics and
groups, to get a better overview of the other groups.

Here is a list of the basic keys that you might need to set up topics
the way you like.

@table @kbd

@item T n
@kindex T n (Topic)
@findex gnus-topic-create-topic
Prompt for a new topic name and create it
(@code{gnus-topic-create-topic}).

@item T TAB
@itemx TAB
@kindex T TAB (Topic)
@kindex TAB (Topic)
@findex gnus-topic-indent
``Indent'' the current topic so that it becomes a sub-topic of the
previous topic (@code{gnus-topic-indent}).  If given a prefix,
``un-indent'' the topic instead.

@item M-TAB
@kindex M-TAB (Topic)
@findex gnus-topic-unindent
``Un-indent'' the current topic so that it becomes a sub-topic of the
parent of its current parent (@code{gnus-topic-unindent}).

@end table

The following two keys can be used to move groups and topics around.
They work like the well-known cut and paste.  @kbd{C-k} is like cut and
@kbd{C-y} is like paste.  Of course, this being Emacs, we use the terms
kill and yank rather than cut and paste.

@table @kbd

@item C-k
@kindex C-k (Topic)
@findex gnus-topic-kill-group
Kill a group or topic (@code{gnus-topic-kill-group}).  All groups in the
topic will be removed along with the topic.

@item C-y
@kindex C-y (Topic)
@findex gnus-topic-yank-group
Yank the previously killed group or topic
(@code{gnus-topic-yank-group}).  Note that all topics will be yanked
before all groups.

So, to move a topic to the beginning of the list of topics, just hit
@kbd{C-k} on it.  This is like the ``cut'' part of cut and paste.  Then,
move the cursor to the beginning of the buffer (just below the ``Gnus''
topic) and hit @kbd{C-y}.  This is like the ``paste'' part of cut and
paste.  Like I said -- E-Z.

You can use @kbd{C-k} and @kbd{C-y} on groups as well as on topics.  So
you can move topics around as well as groups.

@end table

After setting up the topics the way you like them, you might wish to
hide a topic, or to show it again.  That's why we have the following
key.

@table @kbd

@item RET
@kindex RET (Topic)
@findex gnus-topic-select-group
@itemx SPACE
Either select a group or fold a topic (@code{gnus-topic-select-group}).
When you perform this command on a group, you'll enter the group, as
usual.  When done on a topic line, the topic will be folded (if it was
visible) or unfolded (if it was folded already).  So it's basically a
toggling command on topics.  In addition, if you give a numerical
prefix, group on that level (and lower) will be displayed.

@end table

Now for a list of other commands, in no particular order.

@table @kbd

@item T m
@kindex T m (Topic)
@findex gnus-topic-move-group
Move the current group to some other topic
(@code{gnus-topic-move-group}).  This command uses the process/prefix
convention (@pxref{Process/Prefix}).

@item T j
@kindex T j (Topic)
@findex gnus-topic-jump-to-topic
Go to a topic (@code{gnus-topic-jump-to-topic}).

@item T c
@kindex T c (Topic)
@findex gnus-topic-copy-group
Copy the current group to some other topic
(@code{gnus-topic-copy-group}).  This command uses the process/prefix
convention (@pxref{Process/Prefix}).

@item T h
@kindex T h (Topic)
@findex gnus-topic-hide-topic
Hide the current topic (@code{gnus-topic-hide-topic}).  If given
a prefix, hide the topic permanently.

@item T s
@kindex T s (Topic)
@findex gnus-topic-show-topic
Show the current topic (@code{gnus-topic-show-topic}).  If given
a prefix, show the topic permanently.

@item T D
@kindex T D (Topic)
@findex gnus-topic-remove-group
Remove a group from the current topic (@code{gnus-topic-remove-group}).
This command is mainly useful if you have the same group in several
topics and wish to remove it from one of the topics.  You may also
remove a group from all topics, but in that case, Gnus will add it to
the root topic the next time you start Gnus.  In fact, all new groups
(which, naturally, don't belong to any topic) will show up in the root
topic.

This command uses the process/prefix convention
(@pxref{Process/Prefix}).

@item T M
@kindex T M (Topic)
@findex gnus-topic-move-matching
Move all groups that match some regular expression to a topic
(@code{gnus-topic-move-matching}).

@item T C
@kindex T C (Topic)
@findex gnus-topic-copy-matching
Copy all groups that match some regular expression to a topic
(@code{gnus-topic-copy-matching}).

@item T H
@kindex T H (Topic)
@findex gnus-topic-toggle-display-empty-topics
Toggle hiding empty topics
(@code{gnus-topic-toggle-display-empty-topics}).

@item T #
@kindex T # (Topic)
@findex gnus-topic-mark-topic
Mark all groups in the current topic with the process mark
(@code{gnus-topic-mark-topic}).  This command works recursively on
sub-topics unless given a prefix.

@item T M-#
@kindex T M-# (Topic)
@findex gnus-topic-unmark-topic
Remove the process mark from all groups in the current topic
(@code{gnus-topic-unmark-topic}).  This command works recursively on
sub-topics unless given a prefix.

@item C-c C-x
@kindex C-c C-x (Topic)
@findex gnus-topic-expire-articles
Run all expirable articles in the current group or topic through the
expiry process (if any)
(@code{gnus-topic-expire-articles}).  (@pxref{Expiring Mail}).

@item T r
@kindex T r (Topic)
@findex gnus-topic-rename
Rename a topic (@code{gnus-topic-rename}).

@item T DEL
@kindex T DEL (Topic)
@findex gnus-topic-delete
Delete an empty topic (@code{gnus-topic-delete}).

@item A T
@kindex A T (Topic)
@findex gnus-topic-list-active
List all groups that gnus knows about in a topics-ified way
(@code{gnus-topic-list-active}).

@item T M-n
@kindex T M-n (Topic)
@findex gnus-topic-goto-next-topic
Go to the next topic (@code{gnus-topic-goto-next-topic}).

@item T M-p
@kindex T M-p (Topic)
@findex gnus-topic-goto-previous-topic
Go to the next topic (@code{gnus-topic-goto-previous-topic}).

@item G p
@kindex G p (Topic)
@findex gnus-topic-edit-parameters
@cindex group parameters
@cindex topic parameters
@cindex parameters
Edit the topic parameters (@code{gnus-topic-edit-parameters}).
@xref{Topic Parameters}.

@end table


@node Topic Variables
@subsection Topic Variables
@cindex topic variables

The previous section told you how to tell Gnus which topics to display.
This section explains how to tell Gnus what to display about each topic.

@vindex gnus-topic-line-format
The topic lines themselves are created according to the
@code{gnus-topic-line-format} variable (@pxref{Formatting Variables}).
Valid elements are:

@table @samp
@item i
Indentation.
@item n
Topic name.
@item v
Visibility.
@item l
Level.
@item g
Number of groups in the topic.
@item a
Number of unread articles in the topic.
@item A
Number of unread articles in the topic and all its subtopics.
@end table

@vindex gnus-topic-indent-level
Each sub-topic (and the groups in the sub-topics) will be indented with
@code{gnus-topic-indent-level} times the topic level number of spaces.
The default is 2.

@vindex gnus-topic-mode-hook
@code{gnus-topic-mode-hook} is called in topic minor mode buffers.

@vindex gnus-topic-display-empty-topics
The @code{gnus-topic-display-empty-topics} says whether to display even
topics that have no unread articles in them.  The default is @code{t}.


@node Topic Sorting
@subsection Topic Sorting
@cindex topic sorting

You can sort the groups in each topic individually with the following
commands:


@table @kbd
@item T S a
@kindex T S a (Topic)
@findex gnus-topic-sort-groups-by-alphabet
Sort the current topic alphabetically by group name
(@code{gnus-topic-sort-groups-by-alphabet}).

@item T S u
@kindex T S u (Topic)
@findex gnus-topic-sort-groups-by-unread
Sort the current topic by the number of unread articles
(@code{gnus-topic-sort-groups-by-unread}).

@item T S l
@kindex T S l (Topic)
@findex gnus-topic-sort-groups-by-level
Sort the current topic by group level
(@code{gnus-topic-sort-groups-by-level}).

@item T S v
@kindex T S v (Topic)
@findex gnus-topic-sort-groups-by-score
Sort the current topic by group score
(@code{gnus-topic-sort-groups-by-score}).  @xref{Group Score}.

@item T S r
@kindex T S r (Topic)
@findex gnus-topic-sort-groups-by-rank
Sort the current topic by group rank
(@code{gnus-topic-sort-groups-by-rank}).  @xref{Group Score}.

@item T S m
@kindex T S m (Topic)
@findex gnus-topic-sort-groups-by-method
Sort the current topic alphabetically by back end name
(@code{gnus-topic-sort-groups-by-method}).

@item T S e
@kindex T S e (Topic)
@findex gnus-topic-sort-groups-by-server
Sort the current topic alphabetically by server name
(@code{gnus-topic-sort-groups-by-server}).

@item T S s
@kindex T S s
@findex gnus-topic-sort-groups
Sort the current topic according to the function(s) given by the
@code{gnus-group-sort-function} variable
(@code{gnus-topic-sort-groups}).

@end table

When given a prefix argument, all these commands will sort in reverse
order.  @xref{Sorting Groups}, for more information about group
sorting.


@node Topic Topology
@subsection Topic Topology
@cindex topic topology
@cindex topology

So, let's have a look at an example group buffer:

@example
@group
Gnus
  Emacs -- I wuw it!
     3: comp.emacs
     2: alt.religion.emacs
    Naughty Emacs
     452: alt.sex.emacs
       0: comp.talk.emacs.recovery
  Misc
     8: comp.binaries.fractals
    13: comp.sources.unix
@end group
@end example

So, here we have one top-level topic (@samp{Gnus}), two topics under
that, and one sub-topic under one of the sub-topics.  (There is always
just one (1) top-level topic).  This topology can be expressed as
follows:

@lisp
(("Gnus" visible)
 (("Emacs -- I wuw it!" visible)
  (("Naughty Emacs" visible)))
 (("Misc" visible)))
@end lisp

@vindex gnus-topic-topology
This is in fact how the variable @code{gnus-topic-topology} would look
for the display above.  That variable is saved in the @file{.newsrc.eld}
file, and shouldn't be messed with manually---unless you really want
to.  Since this variable is read from the @file{.newsrc.eld} file,
setting it in any other startup files will have no effect.

This topology shows what topics are sub-topics of what topics (right),
and which topics are visible.  Two settings are currently
allowed---@code{visible} and @code{invisible}.


@node Topic Parameters
@subsection Topic Parameters
@cindex topic parameters

All groups in a topic will inherit group parameters from the parent (and
ancestor) topic parameters.  All valid group parameters are valid topic
parameters (@pxref{Group Parameters}).

In addition, the following parameters are only valid as topic
parameters:

@table @code
@item subscribe
When subscribing new groups by topic (@pxref{Subscription Methods}), the
@code{subscribe} topic parameter says what groups go in what topic.  Its
value should be a regexp to match the groups that should go in that
topic.

@item subscribe-level
When subscribing new groups by topic (see the @code{subscribe} parameter),
the group will be subscribed with the level specified in the
@code{subscribe-level} instead of @code{gnus-level-default-subscribed}.

@end table

Group parameters (of course) override topic parameters, and topic
parameters in sub-topics override topic parameters in super-topics.  You
know.  Normal inheritance rules.  (@dfn{Rules} is here a noun, not a
verb, although you may feel free to disagree with me here.)

@example
Gnus
  Emacs
     3: comp.emacs
     2: alt.religion.emacs
   452: alt.sex.emacs
    Relief
     452: alt.sex.emacs
       0: comp.talk.emacs.recovery
  Misc
     8: comp.binaries.fractals
    13: comp.sources.unix
   452: alt.sex.emacs
@end example

The @samp{Emacs} topic has the topic parameter @code{(score-file
. "emacs.SCORE")}; the @samp{Relief} topic has the topic parameter
@code{(score-file . "relief.SCORE")}; and the @samp{Misc} topic has the
topic parameter @code{(score-file . "emacs.SCORE")}.  In addition,
@* @samp{alt.religion.emacs} has the group parameter @code{(score-file
. "religion.SCORE")}.

Now, when you enter @samp{alt.sex.emacs} in the @samp{Relief} topic, you
will get the @file{relief.SCORE} home score file.  If you enter the same
group in the @samp{Emacs} topic, you'll get the @file{emacs.SCORE} home
score file.  If you enter the group @samp{alt.religion.emacs}, you'll
get the @file{religion.SCORE} home score file.

This seems rather simple and self-evident, doesn't it?  Well, yes.  But
there are some problems, especially with the @code{total-expiry}
parameter.  Say you have a mail group in two topics; one with
@code{total-expiry} and one without.  What happens when you do @kbd{M-x
gnus-expire-all-expirable-groups}?  Gnus has no way of telling which one
of these topics you mean to expire articles from, so anything may
happen.  In fact, I hereby declare that it is @dfn{undefined} what
happens.  You just have to be careful if you do stuff like that.


@node Misc Group Stuff
@section Misc Group Stuff

@menu
* Scanning New Messages::       Asking Gnus to see whether new messages have arrived.
* Group Information::           Information and help on groups and Gnus.
* Group Timestamp::             Making Gnus keep track of when you last read a group.
* File Commands::               Reading and writing the Gnus files.
* Sieve Commands::              Managing Sieve scripts.
@end menu

@table @kbd

@item ^
@kindex ^ (Group)
@findex gnus-group-enter-server-mode
Enter the server buffer (@code{gnus-group-enter-server-mode}).
@xref{Server Buffer}.

@item a
@kindex a (Group)
@findex gnus-group-post-news
Start composing a message (a news by default)
(@code{gnus-group-post-news}).  If given a prefix, post to the group
under the point.  If the prefix is 1, prompt for a group to post to.
Contrary to what the name of this function suggests, the prepared
article might be a mail instead of a news, if a mail group is specified
with the prefix argument.  @xref{Composing Messages}.

@item m
@kindex m (Group)
@findex gnus-group-mail
Mail a message somewhere (@code{gnus-group-mail}).  If given a prefix,
use the posting style of the group under the point.  If the prefix is 1,
prompt for a group name to find the posting style.
@xref{Composing Messages}.

@item i
@kindex i (Group)
@findex gnus-group-news
Start composing a news (@code{gnus-group-news}).  If given a prefix,
post to the group under the point.  If the prefix is 1, prompt
for group to post to.  @xref{Composing Messages}.

This function actually prepares a news even when using mail groups.
This is useful for ``posting'' messages to mail groups without actually
sending them over the network: they're just saved directly to the group
in question.  The corresponding back end must have a request-post method
for this to work though.

@end table

Variables for the group buffer:

@table @code

@item gnus-group-mode-hook
@vindex gnus-group-mode-hook
is called after the group buffer has been
created.

@item gnus-group-prepare-hook
@vindex gnus-group-prepare-hook
is called after the group buffer is
generated.  It may be used to modify the buffer in some strange,
unnatural way.

@item gnus-group-prepared-hook
@vindex gnus-group-prepare-hook
is called as the very last thing after the group buffer has been
generated.  It may be used to move point around, for instance.

@item gnus-permanently-visible-groups
@vindex gnus-permanently-visible-groups
Groups matching this regexp will always be listed in the group buffer,
whether they are empty or not.

@item gnus-group-name-charset-method-alist
@vindex gnus-group-name-charset-method-alist
An alist of method and the charset for group names.  It is used to show
non-@acronym{ASCII} group names.

For example:
@lisp
(setq gnus-group-name-charset-method-alist
    '(((nntp "news.com.cn") . cn-gb-2312)))
@end lisp

@item gnus-group-name-charset-group-alist
@cindex UTF-8 group names
@vindex gnus-group-name-charset-group-alist
An alist of regexp of group name and the charset for group names.  It
is used to show non-@acronym{ASCII} group names.  @code{((".*"
utf-8))} is the default value if UTF-8 is supported, otherwise the
default is @code{nil}.

For example:
@lisp
(setq gnus-group-name-charset-group-alist
    '(("\\.com\\.cn:" . cn-gb-2312)))
@end lisp

@end table

@node Scanning New Messages
@subsection Scanning New Messages
@cindex new messages
@cindex scanning new news

@table @kbd

@item g
@kindex g (Group)
@findex gnus-group-get-new-news
@c @icon{gnus-group-get-new-news}
Check the server(s) for new articles.  If the numerical prefix is used,
this command will check only groups of level @var{arg} and lower
(@code{gnus-group-get-new-news}).  If given a non-numerical prefix, this
command will force a total re-reading of the active file(s) from the
back end(s).

@item M-g
@kindex M-g (Group)
@findex gnus-group-get-new-news-this-group
@vindex gnus-goto-next-group-when-activating
@c @icon{gnus-group-get-new-news-this-group}
Check whether new articles have arrived in the current group
(@code{gnus-group-get-new-news-this-group}).
@code{gnus-goto-next-group-when-activating} says whether this command is
to move point to the next group or not.  It is @code{t} by default.

@findex gnus-activate-all-groups
@cindex activating groups
@item C-c M-g
@kindex C-c M-g (Group)
Activate absolutely all groups (@code{gnus-activate-all-groups}).

@item R
@kindex R (Group)
@cindex restarting
@findex gnus-group-restart
Restart gnus (@code{gnus-group-restart}).  This saves the @file{.newsrc}
file(s), closes the connection to all servers, clears up all run-time
gnus variables, and then starts gnus all over again.

@end table

@vindex gnus-get-new-news-hook
@code{gnus-get-new-news-hook} is run just before checking for new news.

@vindex gnus-after-getting-new-news-hook
@code{gnus-after-getting-new-news-hook} is run after checking for new
news.


@node Group Information
@subsection Group Information
@cindex group information
@cindex information on groups

@table @kbd


@item H f
@kindex H f (Group)
@findex gnus-group-fetch-faq
@vindex gnus-group-faq-directory
@cindex FAQ
@cindex ange-ftp
Try to fetch the @acronym{FAQ} for the current group
(@code{gnus-group-fetch-faq}).  Gnus will try to get the @acronym{FAQ}
from @code{gnus-group-faq-directory}, which is usually a directory on
a remote machine.  This variable can also be a list of directories.
In that case, giving a prefix to this command will allow you to choose
between the various sites.  @code{ange-ftp} (or @code{efs}) will be
used for fetching the file.

If fetching from the first site is unsuccessful, gnus will attempt to go
through @code{gnus-group-faq-directory} and try to open them one by one.

@item H c
@kindex H c (Group)
@findex gnus-group-fetch-charter
@vindex gnus-group-charter-alist
@cindex charter
Try to open the charter for the current group in a web browser
(@code{gnus-group-fetch-charter}).  Query for a group if given a
prefix argument.

Gnus will use @code{gnus-group-charter-alist} to find the location of
the charter.  If no location is known, Gnus will fetch the control
messages for the group, which in some cases includes the charter.

@item H C
@kindex H C (Group)
@findex gnus-group-fetch-control
@vindex gnus-group-fetch-control-use-browse-url
@cindex control message
Fetch the control messages for the group from the archive at
@code{ftp.isc.org} (@code{gnus-group-fetch-control}).  Query for a
group if given a prefix argument.

If @code{gnus-group-fetch-control-use-browse-url} is non-@code{nil},
Gnus will open the control messages in a browser using
@code{browse-url}.  Otherwise they are fetched using @code{ange-ftp}
and displayed in an ephemeral group.

Note that the control messages are compressed.  To use this command
you need to turn on @code{auto-compression-mode} (@pxref{Compressed
Files, ,Compressed Files, emacs, The Emacs Manual}).

@item H d
@itemx C-c C-d
@c @icon{gnus-group-describe-group}
@kindex H d (Group)
@kindex C-c C-d (Group)
@cindex describing groups
@cindex group description
@findex gnus-group-describe-group
Describe the current group (@code{gnus-group-describe-group}).  If given
a prefix, force Gnus to re-read the description from the server.

@item M-d
@kindex M-d (Group)
@findex gnus-group-describe-all-groups
Describe all groups (@code{gnus-group-describe-all-groups}).  If given a
prefix, force gnus to re-read the description file from the server.

@item H v
@itemx V
@kindex V (Group)
@kindex H v (Group)
@cindex version
@findex gnus-version
Display current gnus version numbers (@code{gnus-version}).

@item ?
@kindex ? (Group)
@findex gnus-group-describe-briefly
Give a very short help message (@code{gnus-group-describe-briefly}).

@item C-c C-i
@kindex C-c C-i (Group)
@cindex info
@cindex manual
@findex gnus-info-find-node
Go to the gnus info node (@code{gnus-info-find-node}).
@end table


@node Group Timestamp
@subsection Group Timestamp
@cindex timestamps
@cindex group timestamps

It can be convenient to let gnus keep track of when you last read a
group.  To set the ball rolling, you should add
@code{gnus-group-set-timestamp} to @code{gnus-select-group-hook}:

@lisp
(add-hook 'gnus-select-group-hook 'gnus-group-set-timestamp)
@end lisp

After doing this, each time you enter a group, it'll be recorded.

This information can be displayed in various ways---the easiest is to
use the @samp{%d} spec in the group line format:

@lisp
(setq gnus-group-line-format
      "%M\%S\%p\%P\%5y: %(%-40,40g%) %d\n")
@end lisp

This will result in lines looking like:

@example
*        0: mail.ding                                19961002T012943
         0: custom                                   19961002T012713
@end example

As you can see, the date is displayed in compact ISO 8601 format.  This
may be a bit too much, so to just display the date, you could say
something like:

@lisp
(setq gnus-group-line-format
      "%M\%S\%p\%P\%5y: %(%-40,40g%) %6,6~(cut 2)d\n")
@end lisp

If you would like greater control of the time format, you can use a
user-defined format spec.  Something like the following should do the
trick:

@lisp
(setq gnus-group-line-format
      "%M\%S\%p\%P\%5y: %(%-40,40g%) %ud\n")
(defun gnus-user-format-function-d (headers)
  (let ((time (gnus-group-timestamp gnus-tmp-group)))
    (if time
        (format-time-string "%b %d  %H:%M" time)
      "")))
@end lisp


@node File Commands
@subsection File Commands
@cindex file commands

@table @kbd

@item r
@kindex r (Group)
@findex gnus-group-read-init-file
@vindex gnus-init-file
@cindex reading init file
Re-read the init file (@code{gnus-init-file}, which defaults to
@file{~/.gnus.el}) (@code{gnus-group-read-init-file}).

@item s
@kindex s (Group)
@findex gnus-group-save-newsrc
@cindex saving .newsrc
Save the @file{.newsrc.eld} file (and @file{.newsrc} if wanted)
(@code{gnus-group-save-newsrc}).  If given a prefix, force saving the
file(s) whether Gnus thinks it is necessary or not.

@c @item Z
@c @kindex Z (Group)
@c @findex gnus-group-clear-dribble
@c Clear the dribble buffer (@code{gnus-group-clear-dribble}).

@end table


@node Sieve Commands
@subsection Sieve Commands
@cindex group sieve commands

Sieve is a server-side mail filtering language.  In Gnus you can use
the @code{sieve} group parameter (@pxref{Group Parameters}) to specify
sieve rules that should apply to each group.  Gnus provides two
commands to translate all these group parameters into a proper Sieve
script that can be transfered to the server somehow.

@vindex gnus-sieve-file
@vindex gnus-sieve-region-start
@vindex gnus-sieve-region-end
The generated Sieve script is placed in @code{gnus-sieve-file} (by
default @file{~/.sieve}).  The Sieve code that Gnus generate is placed
between two delimiters, @code{gnus-sieve-region-start} and
@code{gnus-sieve-region-end}, so you may write additional Sieve code
outside these delimiters that will not be removed the next time you
regenerate the Sieve script.

@vindex gnus-sieve-crosspost
The variable @code{gnus-sieve-crosspost} controls how the Sieve script
is generated.  If it is non-@code{nil} (the default) articles is
placed in all groups that have matching rules, otherwise the article
is only placed in the group with the first matching rule.  For
example, the group parameter @samp{(sieve address "sender"
"owner-ding@@hpc.uh.edu")} will generate the following piece of Sieve
code if @code{gnus-sieve-crosspost} is @code{nil}.  (When
@code{gnus-sieve-crosspost} is non-@code{nil}, it looks the same
except that the line containing the call to @code{stop} is removed.)

@example
if address "sender" "owner-ding@@hpc.uh.edu" @{
        fileinto "INBOX.ding";
        stop;
@}
@end example

@xref{Top, Emacs Sieve, Top, sieve, Emacs Sieve}.

@table @kbd

@item D g
@kindex D g (Group)
@findex gnus-sieve-generate
@vindex gnus-sieve-file
@cindex generating sieve script
Regenerate a Sieve script from the @code{sieve} group parameters and
put you into the @code{gnus-sieve-file} without saving it.

@item D u
@kindex D u (Group)
@findex gnus-sieve-update
@vindex gnus-sieve-file
@cindex updating sieve script
Regenerates the Gnus managed part of @code{gnus-sieve-file} using the
@code{sieve} group parameters, save the file and upload it to the
server using the @code{sieveshell} program.

@end table


@node Summary Buffer
@chapter Summary Buffer
@cindex summary buffer

A line for each article is displayed in the summary buffer.  You can
move around, read articles, post articles and reply to articles.

The most common way to a summary buffer is to select a group from the
group buffer (@pxref{Selecting a Group}).

You can have as many summary buffers open as you wish.

@menu
* Summary Buffer Format::       Deciding how the summary buffer is to look.
* Summary Maneuvering::         Moving around the summary buffer.
* Choosing Articles::           Reading articles.
* Paging the Article::          Scrolling the current article.
* Reply Followup and Post::     Posting articles.
* Delayed Articles::            Send articles at a later time.
* Marking Articles::            Marking articles as read, expirable, etc.
* Limiting::                    You can limit the summary buffer.
* Threading::                   How threads are made.
* Sorting the Summary Buffer::  How articles and threads are sorted.
* Asynchronous Fetching::       Gnus might be able to pre-fetch articles.
* Article Caching::             You may store articles in a cache.
* Persistent Articles::         Making articles expiry-resistant.
* Article Backlog::             Having already read articles hang around.
* Saving Articles::             Ways of customizing article saving.
* Decoding Articles::           Gnus can treat series of (uu)encoded articles.
* Article Treatment::           The article buffer can be mangled at will.
* MIME Commands::               Doing MIMEy things with the articles.
* Charsets::                    Character set issues.
* Article Commands::            Doing various things with the article buffer.
* Summary Sorting::             Sorting the summary buffer in various ways.
* Finding the Parent::          No child support? Get the parent.
* Alternative Approaches::      Reading using non-default summaries.
* Tree Display::                A more visual display of threads.
* Mail Group Commands::         Some commands can only be used in mail groups.
* Various Summary Stuff::       What didn't fit anywhere else.
* Exiting the Summary Buffer::  Returning to the Group buffer,
                                or reselecting the current group.
* Crosspost Handling::          How crossposted articles are dealt with.
* Duplicate Suppression::       An alternative when crosspost handling fails.
* Security::                    Decrypt and Verify.
* Mailing List::                Mailing list minor mode.
@end menu


@node Summary Buffer Format
@section Summary Buffer Format
@cindex summary buffer format

@iftex
@iflatex
\gnusfigure{The Summary Buffer}{180}{
\put(0,0){\epsfig{figure=ps/summary,width=7.5cm}}
\put(445,0){\makebox(0,0)[br]{\epsfig{figure=ps/summary-article,width=7.5cm}}}
}
@end iflatex
@end iftex

@menu
* Summary Buffer Lines::        You can specify how summary lines should look.
* To From Newsgroups::          How to not display your own name.
* Summary Buffer Mode Line::    You can say how the mode line should look.
* Summary Highlighting::        Making the summary buffer all pretty and nice.
@end menu

@findex mail-extract-address-components
@findex gnus-extract-address-components
@vindex gnus-extract-address-components
Gnus will use the value of the @code{gnus-extract-address-components}
variable as a function for getting the name and address parts of a
@code{From} header.  Three pre-defined functions exist:
@code{gnus-extract-address-components}, which is the default, quite
fast, and too simplistic solution;
@code{mail-extract-address-components}, which works nicely, but is
slower; and @code{std11-extract-address-components}, which works very
nicely, but is slower.  The default function will return the wrong
answer in 5% of the cases.  If this is unacceptable to you, use the
other function instead:

@lisp
(setq gnus-extract-address-components
      'mail-extract-address-components)
@end lisp

@vindex gnus-summary-same-subject
@code{gnus-summary-same-subject} is a string indicating that the current
article has the same subject as the previous.  This string will be used
with those specs that require it.  The default is @code{""}.


@node Summary Buffer Lines
@subsection Summary Buffer Lines

@vindex gnus-summary-line-format
You can change the format of the lines in the summary buffer by changing
the @code{gnus-summary-line-format} variable.  It works along the same
lines as a normal @code{format} string, with some extensions
(@pxref{Formatting Variables}).

There should always be a colon or a point position marker on the line;
the cursor always moves to the point position marker or the colon after
performing an operation.  (Of course, Gnus wouldn't be Gnus if it wasn't
possible to change this.  Just write a new function
@code{gnus-goto-colon} which does whatever you like with the cursor.)
@xref{Positioning Point}.

The default string is @samp{%U%R%z%I%(%[%4L: %-23,23f%]%) %s\n}.

The following format specification characters and extended format
specification(s) are understood:

@table @samp
@item N
Article number.
@item S
Subject string.  List identifiers stripped,
@code{gnus-list-identifies}.  @xref{Article Hiding}.
@item s
Subject if the article is the root of the thread or the previous article
had a different subject, @code{gnus-summary-same-subject} otherwise.
(@code{gnus-summary-same-subject} defaults to @code{""}.)
@item F
Full @code{From} header.
@item n
The name (from the @code{From} header).
@item f
The name, @code{To} header or the @code{Newsgroups} header (@pxref{To
From Newsgroups}).
@item a
The name (from the @code{From} header).  This differs from the @code{n}
spec in that it uses the function designated by the
@code{gnus-extract-address-components} variable, which is slower, but
may be more thorough.
@item A
The address (from the @code{From} header).  This works the same way as
the @code{a} spec.
@item L
Number of lines in the article.
@item c
Number of characters in the article.  This specifier is not supported
in some methods (like nnfolder).
@item k
Pretty-printed version of the number of characters in the article;
for example, @samp{1.2k} or @samp{0.4M}.
@item I
Indentation based on thread level (@pxref{Customizing Threading}).
@item B
A complex trn-style thread tree, showing response-connecting trace
lines.  A thread could be drawn like this:

@example
>
+->
| +->
| | \->
| |   \->
| \->
+->
\->
@end example

You can customize the appearance with the following options.  Note
that it is possible to make the thread display look really neat by
replacing the default @acronym{ASCII} characters with graphic
line-drawing glyphs.
@table @code
@item gnus-sum-thread-tree-root
@vindex gnus-sum-thread-tree-root
Used for the root of a thread.  If @code{nil}, use subject
instead.  The default is @samp{> }.

@item gnus-sum-thread-tree-false-root
@vindex gnus-sum-thread-tree-false-root
Used for the false root of a thread (@pxref{Loose Threads}).  If
@code{nil}, use subject instead.  The default is @samp{> }.

@item gnus-sum-thread-tree-single-indent
@vindex gnus-sum-thread-tree-single-indent
Used for a thread with just one message.  If @code{nil}, use subject
instead.  The default is @samp{}.

@item gnus-sum-thread-tree-vertical
@vindex gnus-sum-thread-tree-vertical
Used for drawing a vertical line.  The default is @samp{| }.

@item gnus-sum-thread-tree-indent
@vindex gnus-sum-thread-tree-indent
Used for indenting.  The default is @samp{  }.

@item gnus-sum-thread-tree-leaf-with-other
@vindex gnus-sum-thread-tree-leaf-with-other
Used for a leaf with brothers.  The default is @samp{+-> }.

@item gnus-sum-thread-tree-single-leaf
@vindex gnus-sum-thread-tree-single-leaf
Used for a leaf without brothers.  The default is @samp{\-> }

@end table

@item T
Nothing if the article is a root and lots of spaces if it isn't (it
pushes everything after it off the screen).
@item [
Opening bracket, which is normally @samp{[}, but can also be @samp{<}
for adopted articles (@pxref{Customizing Threading}).
@item ]
Closing bracket, which is normally @samp{]}, but can also be @samp{>}
for adopted articles.
@item >
One space for each thread level.
@item <
Twenty minus thread level spaces.
@item U
Unread.  @xref{Read Articles}.

@item R
This misleadingly named specifier is the @dfn{secondary mark}.  This
mark will say whether the article has been replied to, has been cached,
or has been saved.  @xref{Other Marks}.

@item i
Score as a number (@pxref{Scoring}).
@item z
@vindex gnus-summary-zcore-fuzz
Zcore, @samp{+} if above the default level and @samp{-} if below the
default level.  If the difference between
@code{gnus-summary-default-score} and the score is less than
@code{gnus-summary-zcore-fuzz}, this spec will not be used.
@item V
Total thread score.
@item x
@code{Xref}.
@item D
@code{Date}.
@item d
The @code{Date} in @code{DD-MMM} format.
@item o
The @code{Date} in @var{YYYYMMDD}@code{T}@var{HHMMSS} format.
@item M
@code{Message-ID}.
@item r
@code{References}.
@item t
Number of articles in the current sub-thread.  Using this spec will slow
down summary buffer generation somewhat.
@item e
An @samp{=} (@code{gnus-not-empty-thread-mark}) will be displayed if the
article has any children.
@item P
The line number.
@item O
Download mark.
@item &user-date;
Age sensitive date format.  Various date format is defined in
@code{gnus-user-date-format-alist}.
@item u
User defined specifier.  The next character in the format string should
be a letter.  Gnus will call the function
@code{gnus-user-format-function-@var{x}}, where @var{x} is the letter
following @samp{%u}.  The function will be passed the current header as
argument.  The function should return a string, which will be inserted
into the summary just like information from any other summary specifier.
@end table

Text between @samp{%(} and @samp{%)} will be highlighted with
@code{gnus-mouse-face} when the mouse point is placed inside the area.
There can only be one such area.

The @samp{%U} (status), @samp{%R} (replied) and @samp{%z} (zcore) specs
have to be handled with care.  For reasons of efficiency, gnus will
compute what column these characters will end up in, and ``hard-code''
that.  This means that it is invalid to have these specs after a
variable-length spec.  Well, you might not be arrested, but your summary
buffer will look strange, which is bad enough.

The smart choice is to have these specs as far to the left as possible.
(Isn't that the case with everything, though?  But I digress.)

This restriction may disappear in later versions of gnus.


@node To From Newsgroups
@subsection To From Newsgroups
@cindex To
@cindex Newsgroups

In some groups (particularly in archive groups), the @code{From} header
isn't very interesting, since all the articles there are written by
you.  To display the information in the @code{To} or @code{Newsgroups}
headers instead, you need to decide three things: What information to
gather; where to display it; and when to display it.

@enumerate
@item
@vindex gnus-extra-headers
The reading of extra header information is controlled by the
@code{gnus-extra-headers}.  This is a list of header symbols.  For
instance:

@lisp
(setq gnus-extra-headers
      '(To Newsgroups X-Newsreader))
@end lisp

This will result in Gnus trying to obtain these three headers, and
storing it in header structures for later easy retrieval.

@item
@findex gnus-extra-header
The value of these extra headers can be accessed via the
@code{gnus-extra-header} function.  Here's a format line spec that will
access the @code{X-Newsreader} header:

@example
"%~(form (gnus-extra-header 'X-Newsreader))@@"
@end example

@item
@vindex gnus-ignored-from-addresses
The @code{gnus-ignored-from-addresses} variable says when the @samp{%f}
summary line spec returns the @code{To}, @code{Newsreader} or
@code{From} header.  If this regexp matches the contents of the
@code{From} header, the value of the @code{To} or @code{Newsreader}
headers are used instead.

@end enumerate

@vindex nnmail-extra-headers
A related variable is @code{nnmail-extra-headers}, which controls when
to include extra headers when generating overview (@acronym{NOV}) files.
If you have old overview files, you should regenerate them after
changing this variable, by entering the server buffer using @kbd{^},
and then @kbd{g} on the appropriate mail server (e.g. nnml) to cause
regeneration.

@vindex gnus-summary-line-format
You also have to instruct Gnus to display the data by changing the
@code{%n} spec to the @code{%f} spec in the
@code{gnus-summary-line-format} variable.

In summary, you'd typically put something like the following in
@file{~/.gnus.el}:

@lisp
(setq gnus-extra-headers
      '(To Newsgroups))
(setq nnmail-extra-headers gnus-extra-headers)
(setq gnus-summary-line-format
      "%U%R%z%I%(%[%4L: %-23,23f%]%) %s\n")
(setq gnus-ignored-from-addresses
      "Your Name Here")
@end lisp

(The values listed above are the default values in Gnus.  Alter them
to fit your needs.)

A note for news server administrators, or for users who wish to try to
convince their news server administrator to provide some additional
support:

The above is mostly useful for mail groups, where you have control over
the @acronym{NOV} files that are created.  However, if you can persuade your
nntp admin to add (in the usual implementation, notably INN):

@example
Newsgroups:full
@end example

to the end of her @file{overview.fmt} file, then you can use that just
as you would the extra headers from the mail groups.


@node Summary Buffer Mode Line
@subsection Summary Buffer Mode Line

@vindex gnus-summary-mode-line-format
You can also change the format of the summary mode bar (@pxref{Mode Line
Formatting}).  Set @code{gnus-summary-mode-line-format} to whatever you
like.  The default is @samp{Gnus: %%b [%A] %Z}.

Here are the elements you can play with:

@table @samp
@item G
Group name.
@item p
Unprefixed group name.
@item A
Current article number.
@item z
Current article score.
@item V
Gnus version.
@item U
Number of unread articles in this group.
@item e
Number of unread articles in this group that aren't displayed in the
summary buffer.
@item Z
A string with the number of unread and unselected articles represented
either as @samp{<%U(+%e) more>} if there are both unread and unselected
articles, and just as @samp{<%U more>} if there are just unread articles
and no unselected ones.
@item g
Shortish group name.  For instance, @samp{rec.arts.anime} will be
shortened to @samp{r.a.anime}.
@item S
Subject of the current article.
@item u
User-defined spec (@pxref{User-Defined Specs}).
@item s
Name of the current score file (@pxref{Scoring}).
@item d
Number of dormant articles (@pxref{Unread Articles}).
@item t
Number of ticked articles (@pxref{Unread Articles}).
@item r
Number of articles that have been marked as read in this session.
@item E
Number of articles expunged by the score files.
@end table


@node Summary Highlighting
@subsection Summary Highlighting

@table @code

@item gnus-visual-mark-article-hook
@vindex gnus-visual-mark-article-hook
This hook is run after selecting an article.  It is meant to be used for
highlighting the article in some way.  It is not run if
@code{gnus-visual} is @code{nil}.

@item gnus-summary-update-hook
@vindex gnus-summary-update-hook
This hook is called when a summary line is changed.  It is not run if
@code{gnus-visual} is @code{nil}.

@item gnus-summary-selected-face
@vindex gnus-summary-selected-face
This is the face (or @dfn{font} as some people call it) used to
highlight the current article in the summary buffer.

@item gnus-summary-highlight
@vindex gnus-summary-highlight
Summary lines are highlighted according to this variable, which is a
list where the elements are of the format @code{(@var{form}
. @var{face})}.  If you would, for instance, like ticked articles to be
italic and high-scored articles to be bold, you could set this variable
to something like
@lisp
(((eq mark gnus-ticked-mark) . italic)
 ((> score default) . bold))
@end lisp
As you may have guessed, if @var{form} returns a non-@code{nil} value,
@var{face} will be applied to the line.
@end table


@node Summary Maneuvering
@section Summary Maneuvering
@cindex summary movement

All the straight movement commands understand the numeric prefix and
behave pretty much as you'd expect.

None of these commands select articles.

@table @kbd
@item G M-n
@itemx M-n
@kindex M-n (Summary)
@kindex G M-n (Summary)
@findex gnus-summary-next-unread-subject
Go to the next summary line of an unread article
(@code{gnus-summary-next-unread-subject}).

@item G M-p
@itemx M-p
@kindex M-p (Summary)
@kindex G M-p (Summary)
@findex gnus-summary-prev-unread-subject
Go to the previous summary line of an unread article
(@code{gnus-summary-prev-unread-subject}).

@item G g
@kindex G g (Summary)
@findex gnus-summary-goto-subject
Ask for an article number and then go to the summary line of that article
without displaying the article (@code{gnus-summary-goto-subject}).
@end table

If gnus asks you to press a key to confirm going to the next group, you
can use the @kbd{C-n} and @kbd{C-p} keys to move around the group
buffer, searching for the next group to read without actually returning
to the group buffer.

Variables related to summary movement:

@table @code

@vindex gnus-auto-select-next
@item gnus-auto-select-next
If you issue one of the movement commands (like @kbd{n}) and there are
no more unread articles after the current one, gnus will offer to go to
the next group.  If this variable is @code{t} and the next group is
empty, gnus will exit summary mode and return to the group buffer.  If
this variable is neither @code{t} nor @code{nil}, gnus will select the
next group with unread articles.  As a special case, if this variable
is @code{quietly}, Gnus will select the next group without asking for
confirmation.  If this variable is @code{almost-quietly}, the same
will happen only if you are located on the last article in the group.
Finally, if this variable is @code{slightly-quietly}, the @kbd{Z n}
command will go to the next group without confirmation.  Also
@pxref{Group Levels}.

@item gnus-auto-select-same
@vindex gnus-auto-select-same
If non-@code{nil}, all the movement commands will try to go to the next
article with the same subject as the current.  (@dfn{Same} here might
mean @dfn{roughly equal}.  See @code{gnus-summary-gather-subject-limit}
for details (@pxref{Customizing Threading}).)  If there are no more
articles with the same subject, go to the first unread article.

This variable is not particularly useful if you use a threaded display.

@item gnus-summary-check-current
@vindex gnus-summary-check-current
If non-@code{nil}, all the ``unread'' movement commands will not proceed
to the next (or previous) article if the current article is unread.
Instead, they will choose the current article.

@item gnus-auto-center-summary
@vindex gnus-auto-center-summary
If non-@code{nil}, gnus will keep the point in the summary buffer
centered at all times.  This makes things quite tidy, but if you have a
slow network connection, or simply do not like this un-Emacsism, you can
set this variable to @code{nil} to get the normal Emacs scrolling
action.  This will also inhibit horizontal re-centering of the summary
buffer, which might make it more inconvenient to read extremely long
threads.

This variable can also be a number.  In that case, center the window at
the given number of lines from the top.

@end table


@node Choosing Articles
@section Choosing Articles
@cindex selecting articles

@menu
* Choosing Commands::           Commands for choosing articles.
* Choosing Variables::          Variables that influence these commands.
@end menu


@node Choosing Commands
@subsection Choosing Commands

None of the following movement commands understand the numeric prefix,
and they all select and display an article.

If you want to fetch new articles or redisplay the group, see
@ref{Exiting the Summary Buffer}.

@table @kbd
@item SPACE
@kindex SPACE (Summary)
@findex gnus-summary-next-page
Select the current article, or, if that one's read already, the next
unread article (@code{gnus-summary-next-page}).

If you have an article window open already and you press @kbd{SPACE}
again, the article will be scrolled.  This lets you conveniently
@kbd{SPACE} through an entire newsgroup.  @xref{Paging the Article}.

@item G n
@itemx n
@kindex n (Summary)
@kindex G n (Summary)
@findex gnus-summary-next-unread-article
@c @icon{gnus-summary-next-unread}
Go to next unread article (@code{gnus-summary-next-unread-article}).

@item G p
@itemx p
@kindex p (Summary)
@findex gnus-summary-prev-unread-article
@c @icon{gnus-summary-prev-unread}
Go to previous unread article (@code{gnus-summary-prev-unread-article}).

@item G N
@itemx N
@kindex N (Summary)
@kindex G N (Summary)
@findex gnus-summary-next-article
Go to the next article (@code{gnus-summary-next-article}).

@item G P
@itemx P
@kindex P (Summary)
@kindex G P (Summary)
@findex gnus-summary-prev-article
Go to the previous article (@code{gnus-summary-prev-article}).

@item G C-n
@kindex G C-n (Summary)
@findex gnus-summary-next-same-subject
Go to the next article with the same subject
(@code{gnus-summary-next-same-subject}).

@item G C-p
@kindex G C-p (Summary)
@findex gnus-summary-prev-same-subject
Go to the previous article with the same subject
(@code{gnus-summary-prev-same-subject}).

@item G f
@itemx .
@kindex G f  (Summary)
@kindex .  (Summary)
@findex gnus-summary-first-unread-article
Go to the first unread article
(@code{gnus-summary-first-unread-article}).

@item G b
@itemx ,
@kindex G b (Summary)
@kindex , (Summary)
@findex gnus-summary-best-unread-article
Go to the unread article with the highest score
(@code{gnus-summary-best-unread-article}).  If given a prefix argument,
go to the first unread article that has a score over the default score.

@item G l
@itemx l
@kindex l (Summary)
@kindex G l (Summary)
@findex gnus-summary-goto-last-article
Go to the previous article read (@code{gnus-summary-goto-last-article}).

@item G o
@kindex G o (Summary)
@findex gnus-summary-pop-article
@cindex history
@cindex article history
Pop an article off the summary history and go to this article
(@code{gnus-summary-pop-article}).  This command differs from the
command above in that you can pop as many previous articles off the
history as you like, while @kbd{l} toggles the two last read articles.
For a somewhat related issue (if you use these commands a lot),
@pxref{Article Backlog}.

@item G j
@itemx j
@kindex j (Summary)
@kindex G j (Summary)
@findex gnus-summary-goto-article
Ask for an article number or @code{Message-ID}, and then go to that
article (@code{gnus-summary-goto-article}).

@end table


@node Choosing Variables
@subsection Choosing Variables

Some variables relevant for moving and selecting articles:

@table @code
@item gnus-auto-extend-newsgroup
@vindex gnus-auto-extend-newsgroup
All the movement commands will try to go to the previous (or next)
article, even if that article isn't displayed in the Summary buffer if
this variable is non-@code{nil}.  Gnus will then fetch the article from
the server and display it in the article buffer.

@item gnus-select-article-hook
@vindex gnus-select-article-hook
This hook is called whenever an article is selected.  By default it
exposes any threads hidden under the selected article.  If you would
like each article to be saved in the Agent as you read it, putting
@code{gnus-agent-fetch-selected-article} on this hook will do so.

@item gnus-mark-article-hook
@vindex gnus-mark-article-hook
@findex gnus-summary-mark-unread-as-read
@findex gnus-summary-mark-read-and-unread-as-read
@findex gnus-unread-mark
This hook is called whenever an article is selected.  It is intended to
be used for marking articles as read.  The default value is
@code{gnus-summary-mark-read-and-unread-as-read}, and will change the
mark of almost any article you read to @code{gnus-unread-mark}.  The
only articles not affected by this function are ticked, dormant, and
expirable articles.  If you'd instead like to just have unread articles
marked as read, you can use @code{gnus-summary-mark-unread-as-read}
instead.  It will leave marks like @code{gnus-low-score-mark},
@code{gnus-del-mark} (and so on) alone.

@end table


@node Paging the Article
@section Scrolling the Article
@cindex article scrolling

@table @kbd

@item SPACE
@kindex SPACE (Summary)
@findex gnus-summary-next-page
Pressing @kbd{SPACE} will scroll the current article forward one page,
or, if you have come to the end of the current article, will choose the
next article (@code{gnus-summary-next-page}).

@vindex gnus-article-boring-faces
@vindex gnus-article-skip-boring
If @code{gnus-article-skip-boring} is non-@code{nil} and the rest of
the article consists only of citations and signature, then it will be
skipped; the next article will be shown instead.  You can customize
what is considered uninteresting with
@code{gnus-article-boring-faces}.  You can manually view the article's
pages, no matter how boring, using @kbd{C-M-v}.

@item DEL
@kindex DEL (Summary)
@findex gnus-summary-prev-page
Scroll the current article back one page (@code{gnus-summary-prev-page}).

@item RET
@kindex RET (Summary)
@findex gnus-summary-scroll-up
Scroll the current article one line forward
(@code{gnus-summary-scroll-up}).

@item M-RET
@kindex M-RET (Summary)
@findex gnus-summary-scroll-down
Scroll the current article one line backward
(@code{gnus-summary-scroll-down}).

@item A g
@itemx g
@kindex A g (Summary)
@kindex g (Summary)
@findex gnus-summary-show-article
@vindex gnus-summary-show-article-charset-alist
(Re)fetch the current article (@code{gnus-summary-show-article}).  If
given a prefix, fetch the current article, but don't run any of the
article treatment functions.  This will give you a ``raw'' article, just
the way it came from the server.

If given a numerical prefix, you can do semi-manual charset stuff.
@kbd{C-u 0 g cn-gb-2312 RET} will decode the message as if it were
encoded in the @code{cn-gb-2312} charset.  If you have

@lisp
(setq gnus-summary-show-article-charset-alist
      '((1 . cn-gb-2312)
        (2 . big5)))
@end lisp

then you can say @kbd{C-u 1 g} to get the same effect.

@item A <
@itemx <
@kindex < (Summary)
@kindex A < (Summary)
@findex gnus-summary-beginning-of-article
Scroll to the beginning of the article
(@code{gnus-summary-beginning-of-article}).

@item A >
@itemx >
@kindex > (Summary)
@kindex A > (Summary)
@findex gnus-summary-end-of-article
Scroll to the end of the article (@code{gnus-summary-end-of-article}).

@item A s
@itemx s
@kindex A s (Summary)
@kindex s (Summary)
@findex gnus-summary-isearch-article
Perform an isearch in the article buffer
(@code{gnus-summary-isearch-article}).

@item h
@kindex h (Summary)
@findex gnus-summary-select-article-buffer
Select the article buffer (@code{gnus-summary-select-article-buffer}).

@end table


@node Reply Followup and Post
@section Reply, Followup and Post

@menu
* Summary Mail Commands::       Sending mail.
* Summary Post Commands::       Sending news.
* Summary Message Commands::    Other Message-related commands.
* Canceling and Superseding::
@end menu


@node Summary Mail Commands
@subsection Summary Mail Commands
@cindex mail
@cindex composing mail

Commands for composing a mail message:

@table @kbd

@item S r
@itemx r
@kindex S r (Summary)
@kindex r (Summary)
@findex gnus-summary-reply
@c @icon{gnus-summary-mail-reply}
@c @icon{gnus-summary-reply}
Mail a reply to the author of the current article
(@code{gnus-summary-reply}).

@item S R
@itemx R
@kindex R (Summary)
@kindex S R (Summary)
@findex gnus-summary-reply-with-original
@c @icon{gnus-summary-reply-with-original}
Mail a reply to the author of the current article and include the
original message (@code{gnus-summary-reply-with-original}).  This
command uses the process/prefix convention.

@item S w
@kindex S w (Summary)
@findex gnus-summary-wide-reply
Mail a wide reply to the author of the current article
(@code{gnus-summary-wide-reply}).  A @dfn{wide reply} is a reply that
goes out to all people listed in the @code{To}, @code{From} (or
@code{Reply-to}) and @code{Cc} headers.  If @code{Mail-Followup-To} is
present, that's used instead.

@item S W
@kindex S W (Summary)
@findex gnus-summary-wide-reply-with-original
Mail a wide reply to the current article and include the original
message (@code{gnus-summary-wide-reply-with-original}).  This command uses
the process/prefix convention.

@item S v
@kindex S v (Summary)
@findex gnus-summary-very-wide-reply
Mail a very wide reply to the author of the current article
(@code{gnus-summary-wide-reply}).  A @dfn{very wide reply} is a reply
that goes out to all people listed in the @code{To}, @code{From} (or
@code{Reply-to}) and @code{Cc} headers in all the process/prefixed
articles.  This command uses the process/prefix convention.

@item S V
@kindex S V (Summary)
@findex gnus-summary-very-wide-reply-with-original
Mail a very wide reply to the author of the current article and include the
original message (@code{gnus-summary-very-wide-reply-with-original}).  This
command uses the process/prefix convention.

@item S B r
@kindex S B r (Summary)
@findex gnus-summary-reply-broken-reply-to
Mail a reply to the author of the current article but ignore the
@code{Reply-To} field (@code{gnus-summary-reply-broken-reply-to}).
If you need this because a mailing list incorrectly sets a
@code{Reply-To} header pointing to the list, you probably want to set
the @code{broken-reply-to} group parameter instead, so things will work
correctly.  @xref{Group Parameters}.

@item S B R
@kindex S B R (Summary)
@findex gnus-summary-reply-broken-reply-to-with-original
Mail a reply to the author of the current article and include the
original message but ignore the @code{Reply-To} field
(@code{gnus-summary-reply-broken-reply-to-with-original}).

@item S o m
@itemx C-c C-f
@kindex S o m (Summary)
@kindex C-c C-f (Summary)
@findex gnus-summary-mail-forward
@c @icon{gnus-summary-mail-forward}
Forward the current article to some other person
(@code{gnus-summary-mail-forward}).  If given a prefix, include the full
headers of the forwarded article.

@item S m
@itemx m
@kindex m (Summary)
@kindex S m (Summary)
@findex gnus-summary-mail-other-window
@c @icon{gnus-summary-mail-originate}
Prepare a mail (@code{gnus-summary-mail-other-window}).  By default, use
the posting style of the current group.  If given a prefix, disable that.
If the prefix is 1, prompt for a group name to find the posting style.

@item S i
@itemx i
@kindex i (Summary)
@kindex S i (Summary)
@findex gnus-summary-news-other-window
Prepare a news (@code{gnus-summary-news-other-window}).  By default,
post to the current group.  If given a prefix, disable that.  If the
prefix is 1, prompt for a group to post to.

This function actually prepares a news even when using mail groups.
This is useful for ``posting'' messages to mail groups without actually
sending them over the network: they're just saved directly to the group
in question.  The corresponding back end must have a request-post method
for this to work though.

@item S D b
@kindex S D b (Summary)
@findex gnus-summary-resend-bounced-mail
@cindex bouncing mail
If you have sent a mail, but the mail was bounced back to you for some
reason (wrong address, transient failure), you can use this command to
resend that bounced mail (@code{gnus-summary-resend-bounced-mail}).  You
will be popped into a mail buffer where you can edit the headers before
sending the mail off again.  If you give a prefix to this command, and
the bounced mail is a reply to some other mail, gnus will try to fetch
that mail and display it for easy perusal of its headers.  This might
very well fail, though.

@item S D r
@kindex S D r (Summary)
@findex gnus-summary-resend-message
Not to be confused with the previous command,
@code{gnus-summary-resend-message} will prompt you for an address to
send the current message off to, and then send it to that place.  The
headers of the message won't be altered---but lots of headers that say
@code{Resent-To}, @code{Resent-From} and so on will be added.  This
means that you actually send a mail to someone that has a @code{To}
header that (probably) points to yourself.  This will confuse people.
So, natcherly you'll only do that if you're really eVIl.

This command is mainly used if you have several accounts and want to
ship a mail to a different account of yours.  (If you're both
@code{root} and @code{postmaster} and get a mail for @code{postmaster}
to the @code{root} account, you may want to resend it to
@code{postmaster}.  Ordnung muss sein!

This command understands the process/prefix convention
(@pxref{Process/Prefix}).

@item S O m
@kindex S O m (Summary)
@findex gnus-summary-digest-mail-forward
Digest the current series (@pxref{Decoding Articles}) and forward the
result using mail (@code{gnus-summary-digest-mail-forward}).  This
command uses the process/prefix convention (@pxref{Process/Prefix}).

@item S M-c
@kindex S M-c (Summary)
@findex gnus-summary-mail-crosspost-complaint
@cindex crossposting
@cindex excessive crossposting
Send a complaint about excessive crossposting to the author of the
current article (@code{gnus-summary-mail-crosspost-complaint}).

@findex gnus-crosspost-complaint
This command is provided as a way to fight back against the current
crossposting pandemic that's sweeping Usenet.  It will compose a reply
using the @code{gnus-crosspost-complaint} variable as a preamble.  This
command understands the process/prefix convention
(@pxref{Process/Prefix}) and will prompt you before sending each mail.

@end table

Also @xref{Header Commands, ,Header Commands, message, The Message
Manual}, for more information.


@node Summary Post Commands
@subsection Summary Post Commands
@cindex post
@cindex composing news

Commands for posting a news article:

@table @kbd
@item S p
@itemx a
@kindex a (Summary)
@kindex S p (Summary)
@findex gnus-summary-post-news
@c @icon{gnus-summary-post-news}
Prepare for posting an article (@code{gnus-summary-post-news}).  By
default, post to the current group.  If given a prefix, disable that.
If the prefix is 1, prompt for another group instead.

@item S f
@itemx f
@kindex f (Summary)
@kindex S f (Summary)
@findex gnus-summary-followup
@c @icon{gnus-summary-followup}
Post a followup to the current article (@code{gnus-summary-followup}).

@item S F
@itemx F
@kindex S F (Summary)
@kindex F (Summary)
@c @icon{gnus-summary-followup-with-original}
@findex gnus-summary-followup-with-original
Post a followup to the current article and include the original message
(@code{gnus-summary-followup-with-original}).  This command uses the
process/prefix convention.

@item S n
@kindex S n (Summary)
@findex gnus-summary-followup-to-mail
Post a followup to the current article via news, even if you got the
message through mail (@code{gnus-summary-followup-to-mail}).

@item S N
@kindex S N (Summary)
@findex gnus-summary-followup-to-mail-with-original
Post a followup to the current article via news, even if you got the
message through mail and include the original message
(@code{gnus-summary-followup-to-mail-with-original}).  This command uses
the process/prefix convention.

@item S o p
@kindex S o p (Summary)
@findex gnus-summary-post-forward
Forward the current article to a newsgroup
(@code{gnus-summary-post-forward}).  If given a prefix, include the full
headers of the forwarded article.

@item S O p
@kindex S O p (Summary)
@findex gnus-summary-digest-post-forward
@cindex digests
@cindex making digests
Digest the current series and forward the result to a newsgroup
(@code{gnus-summary-digest-post-forward}).  This command uses the
process/prefix convention.

@item S u
@kindex S u (Summary)
@findex gnus-uu-post-news
@c @icon{gnus-uu-post-news}
Uuencode a file, split it into parts, and post it as a series
(@code{gnus-uu-post-news}).  (@pxref{Uuencoding and Posting}).
@end table

Also @xref{Header Commands, ,Header Commands, message, The Message
Manual}, for more information.


@node Summary Message Commands
@subsection Summary Message Commands

@table @kbd
@item S y
@kindex S y (Summary)
@findex gnus-summary-yank-message
Yank the current article into an already existing Message composition
buffer (@code{gnus-summary-yank-message}).  This command prompts for
what message buffer you want to yank into, and understands the
process/prefix convention (@pxref{Process/Prefix}).

@end table


@node Canceling and Superseding
@subsection Canceling Articles
@cindex canceling articles
@cindex superseding articles

Have you ever written something, and then decided that you really,
really, really wish you hadn't posted that?

Well, you can't cancel mail, but you can cancel posts.

@findex gnus-summary-cancel-article
@kindex C (Summary)
@c @icon{gnus-summary-cancel-article}
Find the article you wish to cancel (you can only cancel your own
articles, so don't try any funny stuff).  Then press @kbd{C} or @kbd{S
c} (@code{gnus-summary-cancel-article}).  Your article will be
canceled---machines all over the world will be deleting your article.
This command uses the process/prefix convention (@pxref{Process/Prefix}).

Be aware, however, that not all sites honor cancels, so your article may
live on here and there, while most sites will delete the article in
question.

Gnus will use the ``current'' select method when canceling.  If you
want to use the standard posting method, use the @samp{a} symbolic
prefix (@pxref{Symbolic Prefixes}).

If you discover that you have made some mistakes and want to do some
corrections, you can post a @dfn{superseding} article that will replace
your original article.

@findex gnus-summary-supersede-article
@kindex S (Summary)
Go to the original article and press @kbd{S s}
(@code{gnus-summary-supersede-article}).  You will be put in a buffer
where you can edit the article all you want before sending it off the
usual way.

The same goes for superseding as for canceling, only more so: Some
sites do not honor superseding.  On those sites, it will appear that you
have posted almost the same article twice.

If you have just posted the article, and change your mind right away,
there is a trick you can use to cancel/supersede the article without
waiting for the article to appear on your site first.  You simply return
to the post buffer (which is called @code{*sent ...*}).  There you will
find the article you just posted, with all the headers intact.  Change
the @code{Message-ID} header to a @code{Cancel} or @code{Supersedes}
header by substituting one of those words for the word
@code{Message-ID}.  Then just press @kbd{C-c C-c} to send the article as
you would do normally.  The previous article will be
canceled/superseded.

Just remember, kids: There is no 'c' in 'supersede'.

@node Delayed Articles
@section Delayed Articles
@cindex delayed sending
@cindex send delayed

Sometimes, you might wish to delay the sending of a message.  For
example, you might wish to arrange for a message to turn up just in time
to remind your about the birthday of your Significant Other.  For this,
there is the @code{gnus-delay} package.  Setup is simple:

@lisp
(gnus-delay-initialize)
@end lisp

@findex gnus-delay-article
Normally, to send a message you use the @kbd{C-c C-c} command from
Message mode.  To delay a message, use @kbd{C-c C-j}
(@code{gnus-delay-article}) instead.  This will ask you for how long the
message should be delayed.  Possible answers are:

@itemize @bullet
@item
A time span.  Consists of an integer and a letter.  For example,
@code{42d} means to delay for 42 days.  Available letters are @code{m}
(minutes), @code{h} (hours), @code{d} (days), @code{w} (weeks), @code{M}
(months) and @code{Y} (years).

@item
A specific date.  Looks like @code{YYYY-MM-DD}.  The message will be
delayed until that day, at a specific time (eight o'clock by default).
See also @code{gnus-delay-default-hour}.

@item
A specific time of day.  Given in @code{hh:mm} format, 24h, no am/pm
stuff.  The deadline will be at that time today, except if that time has
already passed, then it's at the given time tomorrow.  So if it's ten
o'clock in the morning and you specify @code{11:15}, then the deadline
is one hour and fifteen minutes hence.  But if you specify @code{9:20},
that means a time tomorrow.
@end itemize

The action of the @code{gnus-delay-article} command is influenced by a
couple of variables:

@table @code
@item gnus-delay-default-hour
@vindex gnus-delay-default-hour
When you specify a specific date, the message will be due on that hour
on the given date.  Possible values are integers 0 through 23.

@item gnus-delay-default-delay
@vindex gnus-delay-default-delay
This is a string and gives the default delay.  It can be of any of the
formats described above.

@item gnus-delay-group
@vindex gnus-delay-group
Delayed articles will be kept in this group on the drafts server until
they are due.  You probably don't need to change this.  The default
value is @code{"delayed"}.

@item gnus-delay-header
@vindex gnus-delay-header
The deadline for each article will be stored in a header.  This variable
is a string and gives the header name.  You probably don't need to
change this.  The default value is @code{"X-Gnus-Delayed"}.
@end table

The way delaying works is like this: when you use the
@code{gnus-delay-article} command, you give a certain delay.  Gnus
calculates the deadline of the message and stores it in the
@code{X-Gnus-Delayed} header and puts the message in the
@code{nndraft:delayed} group.

@findex gnus-delay-send-queue
And whenever you get new news, Gnus looks through the group for articles
which are due and sends them.  It uses the @code{gnus-delay-send-queue}
function for this.  By default, this function is added to the hook
@code{gnus-get-new-news-hook}.  But of course, you can change this.
Maybe you want to use the demon to send drafts?  Just tell the demon to
execute the @code{gnus-delay-send-queue} function.

@table @code
@item gnus-delay-initialize
@findex gnus-delay-initialize

By default, this function installs @code{gnus-delay-send-queue} in
@code{gnus-get-new-news-hook}.  But it accepts the optional second
argument @code{no-check}.  If it is non-@code{nil},
@code{gnus-get-new-news-hook} is not changed.  The optional first
argument is ignored.

For example, @code{(gnus-delay-initialize nil t)} means to do nothing.
Presumably, you want to use the demon for sending due delayed articles.
Just don't forget to set that up :-)
@end table


@node Marking Articles
@section Marking Articles
@cindex article marking
@cindex article ticking
@cindex marks

There are several marks you can set on an article.

You have marks that decide the @dfn{readedness} (whoo, neato-keano
neologism ohoy!) of the article.  Alphabetic marks generally mean
@dfn{read}, while non-alphabetic characters generally mean @dfn{unread}.

In addition, you also have marks that do not affect readedness.

@menu
* Unread Articles::             Marks for unread articles.
* Read Articles::               Marks for read articles.
* Other Marks::                 Marks that do not affect readedness.
@end menu

@ifinfo
There's a plethora of commands for manipulating these marks:
@end ifinfo

@menu
* Setting Marks::             How to set and remove marks.
* Generic Marking Commands::  How to customize the marking.
* Setting Process Marks::     How to mark articles for later processing.
@end menu


@node Unread Articles
@subsection Unread Articles

The following marks mark articles as (kinda) unread, in one form or
other.

@table @samp
@item !
@vindex gnus-ticked-mark
Marked as ticked (@code{gnus-ticked-mark}).

@dfn{Ticked articles} are articles that will remain visible always.  If
you see an article that you find interesting, or you want to put off
reading it, or replying to it, until sometime later, you'd typically
tick it.  However, articles can be expired (from news servers by the
news server software, Gnus itself never expires ticked messages), so if
you want to keep an article forever, you'll have to make it persistent
(@pxref{Persistent Articles}).

@item ?
@vindex gnus-dormant-mark
Marked as dormant (@code{gnus-dormant-mark}).

@dfn{Dormant articles} will only appear in the summary buffer if there
are followups to it.  If you want to see them even if they don't have
followups, you can use the @kbd{/ D} command (@pxref{Limiting}).
Otherwise (except for the visibility issue), they are just like ticked
messages.

@item SPACE
@vindex gnus-unread-mark
Marked as unread (@code{gnus-unread-mark}).

@dfn{Unread articles} are articles that haven't been read at all yet.
@end table


@node Read Articles
@subsection Read Articles
@cindex expirable mark

All the following marks mark articles as read.

@table @samp

@item r
@vindex gnus-del-mark
These are articles that the user has marked as read with the @kbd{d}
command manually, more or less (@code{gnus-del-mark}).

@item R
@vindex gnus-read-mark
Articles that have actually been read (@code{gnus-read-mark}).

@item O
@vindex gnus-ancient-mark
Articles that were marked as read in previous sessions and are now
@dfn{old} (@code{gnus-ancient-mark}).

@item K
@vindex gnus-killed-mark
Marked as killed (@code{gnus-killed-mark}).

@item X
@vindex gnus-kill-file-mark
Marked as killed by kill files (@code{gnus-kill-file-mark}).

@item Y
@vindex gnus-low-score-mark
Marked as read by having too low a score (@code{gnus-low-score-mark}).

@item C
@vindex gnus-catchup-mark
Marked as read by a catchup (@code{gnus-catchup-mark}).

@item G
@vindex gnus-canceled-mark
Canceled article (@code{gnus-canceled-mark})

@item F
@vindex gnus-souped-mark
@sc{soup}ed article (@code{gnus-souped-mark}).  @xref{SOUP}.

@item Q
@vindex gnus-sparse-mark
Sparsely reffed article (@code{gnus-sparse-mark}).  @xref{Customizing
Threading}.

@item M
@vindex gnus-duplicate-mark
Article marked as read by duplicate suppression
(@code{gnus-duplicate-mark}).  @xref{Duplicate Suppression}.

@end table

All these marks just mean that the article is marked as read, really.
They are interpreted differently when doing adaptive scoring, though.

One more special mark, though:

@table @samp
@item E
@vindex gnus-expirable-mark
Marked as expirable (@code{gnus-expirable-mark}).

Marking articles as @dfn{expirable} (or have them marked as such
automatically) doesn't make much sense in normal groups---a user doesn't
control expiring of news articles, but in mail groups, for instance,
articles marked as @dfn{expirable} can be deleted by gnus at
any time.
@end table


@node Other Marks
@subsection Other Marks
@cindex process mark
@cindex bookmarks

There are some marks that have nothing to do with whether the article is
read or not.

@itemize @bullet

@item
You can set a bookmark in the current article.  Say you are reading a
long thesis on cats' urinary tracts, and have to go home for dinner
before you've finished reading the thesis.  You can then set a bookmark
in the article, and gnus will jump to this bookmark the next time it
encounters the article.  @xref{Setting Marks}.

@item
@vindex gnus-replied-mark
All articles that you have replied to or made a followup to (i.e., have
answered) will be marked with an @samp{A} in the second column
(@code{gnus-replied-mark}).

@item
@vindex gnus-forwarded-mark
All articles that you have forwarded will be marked with an @samp{F} in
the second column (@code{gnus-forwarded-mark}).

@item
@vindex gnus-cached-mark
Articles stored in the article cache will be marked with an @samp{*} in
the second column (@code{gnus-cached-mark}).  @xref{Article Caching}.

@item
@vindex gnus-saved-mark
Articles ``saved'' (in some manner or other; not necessarily
religiously) are marked with an @samp{S} in the second column
(@code{gnus-saved-mark}).

@item
@vindex gnus-recent-mark
Articles that according to the server haven't been shown to the user
before are marked with a @samp{N} in the second column
(@code{gnus-recent-mark}).  Note that not all servers support this
mark, in which case it simply never appears.  Compare with
@code{gnus-unseen-mark}.

@item
@vindex gnus-unseen-mark
Articles that haven't been seen before in Gnus by the user are marked
with a @samp{.} in the second column (@code{gnus-unseen-mark}).
Compare with @code{gnus-recent-mark}.

@item
@vindex gnus-downloaded-mark
When using the Gnus agent (@pxref{Agent Basics}), articles may be
downloaded for unplugged (offline) viewing.  If you are using the
@samp{%O} spec, these articles get the @samp{+} mark in that spec.
(The variable @code{gnus-downloaded-mark} controls which character to
use.)

@item
@vindex gnus-undownloaded-mark
When using the Gnus agent (@pxref{Agent Basics}), some articles might
not have been downloaded.  Such articles cannot be viewed while you
are unplugged (offline).  If you are using the @samp{%O} spec, these
articles get the @samp{-} mark in that spec.  (The variable
@code{gnus-undownloaded-mark} controls which character to use.)

@item
@vindex gnus-downloadable-mark
The Gnus agent (@pxref{Agent Basics}) downloads some articles
automatically, but it is also possible to explicitly mark articles for
download, even if they would not be downloaded automatically.  Such
explicitly-marked articles get the @samp{%} mark in the first column.
(The variable @code{gnus-downloadable-mark} controls which character to
use.)

@item
@vindex gnus-not-empty-thread-mark
@vindex gnus-empty-thread-mark
If the @samp{%e} spec is used, the presence of threads or not will be
marked with @code{gnus-not-empty-thread-mark} and
@code{gnus-empty-thread-mark} in the third column, respectively.

@item
@vindex gnus-process-mark
Finally we have the @dfn{process mark} (@code{gnus-process-mark}).  A
variety of commands react to the presence of the process mark.  For
instance, @kbd{X u} (@code{gnus-uu-decode-uu}) will uudecode and view
all articles that have been marked with the process mark.  Articles
marked with the process mark have a @samp{#} in the second column.

@end itemize

You might have noticed that most of these ``non-readedness'' marks
appear in the second column by default.  So if you have a cached, saved,
replied article that you have process-marked, what will that look like?

Nothing much.  The precedence rules go as follows: process -> cache ->
replied -> saved.  So if the article is in the cache and is replied,
you'll only see the cache mark and not the replied mark.


@node Setting Marks
@subsection Setting Marks
@cindex setting marks

All the marking commands understand the numeric prefix.

@table @kbd
@item M c
@itemx M-u
@kindex M c (Summary)
@kindex M-u (Summary)
@findex gnus-summary-clear-mark-forward
@cindex mark as unread
Clear all readedness-marks from the current article
(@code{gnus-summary-clear-mark-forward}).  In other words, mark the
article as unread.

@item M t
@itemx !
@kindex ! (Summary)
@kindex M t (Summary)
@findex gnus-summary-tick-article-forward
Tick the current article (@code{gnus-summary-tick-article-forward}).
@xref{Article Caching}.

@item M ?
@itemx ?
@kindex ? (Summary)
@kindex M ? (Summary)
@findex gnus-summary-mark-as-dormant
Mark the current article as dormant
(@code{gnus-summary-mark-as-dormant}).  @xref{Article Caching}.

@item M d
@itemx d
@kindex M d (Summary)
@kindex d (Summary)
@findex gnus-summary-mark-as-read-forward
Mark the current article as read
(@code{gnus-summary-mark-as-read-forward}).

@item D
@kindex D (Summary)
@findex gnus-summary-mark-as-read-backward
Mark the current article as read and move point to the previous line
(@code{gnus-summary-mark-as-read-backward}).

@item M k
@itemx k
@kindex k (Summary)
@kindex M k (Summary)
@findex gnus-summary-kill-same-subject-and-select
Mark all articles that have the same subject as the current one as read,
and then select the next unread article
(@code{gnus-summary-kill-same-subject-and-select}).

@item M K
@itemx C-k
@kindex M K (Summary)
@kindex C-k (Summary)
@findex gnus-summary-kill-same-subject
Mark all articles that have the same subject as the current one as read
(@code{gnus-summary-kill-same-subject}).

@item M C
@kindex M C (Summary)
@findex gnus-summary-catchup
@c @icon{gnus-summary-catchup}
Mark all unread articles as read (@code{gnus-summary-catchup}).

@item M C-c
@kindex M C-c (Summary)
@findex gnus-summary-catchup-all
Mark all articles in the group as read---even the ticked and dormant
articles (@code{gnus-summary-catchup-all}).

@item M H
@kindex M H (Summary)
@findex gnus-summary-catchup-to-here
Catchup the current group to point (before the point)
(@code{gnus-summary-catchup-to-here}).

@item M h
@kindex M h (Summary)
@findex gnus-summary-catchup-from-here
Catchup the current group from point (after the point)
(@code{gnus-summary-catchup-from-here}).

@item C-w
@kindex C-w (Summary)
@findex gnus-summary-mark-region-as-read
Mark all articles between point and mark as read
(@code{gnus-summary-mark-region-as-read}).

@item M V k
@kindex M V k (Summary)
@findex gnus-summary-kill-below
Kill all articles with scores below the default score (or below the
numeric prefix) (@code{gnus-summary-kill-below}).

@item M e
@itemx E
@kindex M e (Summary)
@kindex E (Summary)
@findex gnus-summary-mark-as-expirable
Mark the current article as expirable
(@code{gnus-summary-mark-as-expirable}).

@item M b
@kindex M b (Summary)
@findex gnus-summary-set-bookmark
Set a bookmark in the current article
(@code{gnus-summary-set-bookmark}).

@item M B
@kindex M B (Summary)
@findex gnus-summary-remove-bookmark
Remove the bookmark from the current article
(@code{gnus-summary-remove-bookmark}).

@item M V c
@kindex M V c (Summary)
@findex gnus-summary-clear-above
Clear all marks from articles with scores over the default score (or
over the numeric prefix) (@code{gnus-summary-clear-above}).

@item M V u
@kindex M V u (Summary)
@findex gnus-summary-tick-above
Tick all articles with scores over the default score (or over the
numeric prefix) (@code{gnus-summary-tick-above}).

@item M V m
@kindex M V m (Summary)
@findex gnus-summary-mark-above
Prompt for a mark, and mark all articles with scores over the default
score (or over the numeric prefix) with this mark
(@code{gnus-summary-clear-above}).
@end table

@vindex gnus-summary-goto-unread
The @code{gnus-summary-goto-unread} variable controls what action should
be taken after setting a mark.  If non-@code{nil}, point will move to
the next/previous unread article.  If @code{nil}, point will just move
one line up or down.  As a special case, if this variable is
@code{never}, all the marking commands as well as other commands (like
@kbd{SPACE}) will move to the next article, whether it is unread or not.
The default is @code{t}.


@node Generic Marking Commands
@subsection Generic Marking Commands

Some people would like the command that ticks an article (@kbd{!}) go to
the next article.  Others would like it to go to the next unread
article.  Yet others would like it to stay on the current article.  And
even though I haven't heard of anybody wanting it to go to the
previous (unread) article, I'm sure there are people that want that as
well.

Multiply these five behaviors with five different marking commands, and
you get a potentially complex set of variable to control what each
command should do.

To sidestep that mess, Gnus provides commands that do all these
different things.  They can be found on the @kbd{M M} map in the summary
buffer.  Type @kbd{M M C-h} to see them all---there are too many of them
to list in this manual.

While you can use these commands directly, most users would prefer
altering the summary mode keymap.  For instance, if you would like the
@kbd{!} command to go to the next article instead of the next unread
article, you could say something like:

@lisp
@group
(add-hook 'gnus-summary-mode-hook 'my-alter-summary-map)
(defun my-alter-summary-map ()
  (local-set-key "!" 'gnus-summary-put-mark-as-ticked-next))
@end group
@end lisp

@noindent
or

@lisp
(defun my-alter-summary-map ()
  (local-set-key "!" "MM!n"))
@end lisp


@node Setting Process Marks
@subsection Setting Process Marks
@cindex setting process marks

Process marks are displayed as @code{#} in the summary buffer, and are
used for marking articles in such a way that other commands will
process these articles.  For instance, if you process mark four
articles and then use the @kbd{*} command, Gnus will enter these four
commands into the cache.  For more information,
@pxref{Process/Prefix}.

@table @kbd

@item M P p
@itemx #
@kindex # (Summary)
@kindex M P p (Summary)
@findex gnus-summary-mark-as-processable
Mark the current article with the process mark
(@code{gnus-summary-mark-as-processable}).
@findex gnus-summary-unmark-as-processable

@item M P u
@itemx M-#
@kindex M P u (Summary)
@kindex M-# (Summary)
Remove the process mark, if any, from the current article
(@code{gnus-summary-unmark-as-processable}).

@item M P U
@kindex M P U (Summary)
@findex gnus-summary-unmark-all-processable
Remove the process mark from all articles
(@code{gnus-summary-unmark-all-processable}).

@item M P i
@kindex M P i (Summary)
@findex gnus-uu-invert-processable
Invert the list of process marked articles
(@code{gnus-uu-invert-processable}).

@item M P R
@kindex M P R (Summary)
@findex gnus-uu-mark-by-regexp
Mark articles that have a @code{Subject} header that matches a regular
expression (@code{gnus-uu-mark-by-regexp}).

@item M P G
@kindex M P G (Summary)
@findex gnus-uu-unmark-by-regexp
Unmark articles that have a @code{Subject} header that matches a regular
expression (@code{gnus-uu-unmark-by-regexp}).

@item M P r
@kindex M P r (Summary)
@findex gnus-uu-mark-region
Mark articles in region (@code{gnus-uu-mark-region}).

@item M P g
@kindex M P g
@findex gnus-uu-unmark-region
Unmark articles in region (@code{gnus-uu-unmark-region}).

@item M P t
@kindex M P t (Summary)
@findex gnus-uu-mark-thread
Mark all articles in the current (sub)thread
(@code{gnus-uu-mark-thread}).

@item M P T
@kindex M P T (Summary)
@findex gnus-uu-unmark-thread
Unmark all articles in the current (sub)thread
(@code{gnus-uu-unmark-thread}).

@item M P v
@kindex M P v (Summary)
@findex gnus-uu-mark-over
Mark all articles that have a score above the prefix argument
(@code{gnus-uu-mark-over}).

@item M P s
@kindex M P s (Summary)
@findex gnus-uu-mark-series
Mark all articles in the current series (@code{gnus-uu-mark-series}).

@item M P S
@kindex M P S (Summary)
@findex gnus-uu-mark-sparse
Mark all series that have already had some articles marked
(@code{gnus-uu-mark-sparse}).

@item M P a
@kindex M P a (Summary)
@findex gnus-uu-mark-all
Mark all articles in series order (@code{gnus-uu-mark-series}).

@item M P b
@kindex M P b (Summary)
@findex gnus-uu-mark-buffer
Mark all articles in the buffer in the order they appear
(@code{gnus-uu-mark-buffer}).

@item M P k
@kindex M P k (Summary)
@findex gnus-summary-kill-process-mark
Push the current process mark set onto the stack and unmark all articles
(@code{gnus-summary-kill-process-mark}).

@item M P y
@kindex M P y (Summary)
@findex gnus-summary-yank-process-mark
Pop the previous process mark set from the stack and restore it
(@code{gnus-summary-yank-process-mark}).

@item M P w
@kindex M P w (Summary)
@findex gnus-summary-save-process-mark
Push the current process mark set onto the stack
(@code{gnus-summary-save-process-mark}).

@end table

Also see the @kbd{&} command in @ref{Searching for Articles}, for how to
set process marks based on article body contents.


@node Limiting
@section Limiting
@cindex limiting

It can be convenient to limit the summary buffer to just show some
subset of the articles currently in the group.  The effect most limit
commands have is to remove a few (or many) articles from the summary
buffer.

All limiting commands work on subsets of the articles already fetched
from the servers.  None of these commands query the server for
additional articles.

@table @kbd

@item / /
@itemx / s
@kindex / / (Summary)
@findex gnus-summary-limit-to-subject
Limit the summary buffer to articles that match some subject
(@code{gnus-summary-limit-to-subject}).  If given a prefix, exclude
matching articles.

@item / a
@kindex / a (Summary)
@findex gnus-summary-limit-to-author
Limit the summary buffer to articles that match some author
(@code{gnus-summary-limit-to-author}).  If given a prefix, exclude
matching articles.

@item / x
@kindex / x (Summary)
@findex gnus-summary-limit-to-extra
Limit the summary buffer to articles that match one of the ``extra''
headers (@pxref{To From Newsgroups})
(@code{gnus-summary-limit-to-extra}).  If given a prefix, exclude
matching articles.

@item / u
@itemx x
@kindex / u (Summary)
@kindex x (Summary)
@findex gnus-summary-limit-to-unread
Limit the summary buffer to articles not marked as read
(@code{gnus-summary-limit-to-unread}).  If given a prefix, limit the
buffer to articles strictly unread.  This means that ticked and
dormant articles will also be excluded.

@item / m
@kindex / m (Summary)
@findex gnus-summary-limit-to-marks
Ask for a mark and then limit to all articles that have been marked
with that mark (@code{gnus-summary-limit-to-marks}).

@item / t
@kindex / t (Summary)
@findex gnus-summary-limit-to-age
Ask for a number and then limit the summary buffer to articles older than (or equal to) that number of days
(@code{gnus-summary-limit-to-age}).  If given a prefix, limit to
articles younger than that number of days.

@item / n
@kindex / n (Summary)
@findex gnus-summary-limit-to-articles
Limit the summary buffer to the current article
(@code{gnus-summary-limit-to-articles}).  Uses the process/prefix
convention (@pxref{Process/Prefix}).

@item / w
@kindex / w (Summary)
@findex gnus-summary-pop-limit
Pop the previous limit off the stack and restore it
(@code{gnus-summary-pop-limit}).  If given a prefix, pop all limits off
the stack.

@item / .
@kindex / . (Summary)
@findex gnus-summary-limit-to-unseen
Limit the summary buffer to the unseen articles
(@code{gnus-summary-limit-to-unseen}).

@item / v
@kindex / v (Summary)
@findex gnus-summary-limit-to-score
Limit the summary buffer to articles that have a score at or above some
score (@code{gnus-summary-limit-to-score}).

@item / p
@kindex / p (Summary)
@findex gnus-summary-limit-to-display-predicate
Limit the summary buffer to articles that satisfy the @code{display}
group parameter predicate
(@code{gnus-summary-limit-to-display-predicate}).  @xref{Group
Parameters}, for more on this predicate.

@item / E
@itemx M S
@kindex M S (Summary)
@kindex / E (Summary)
@findex gnus-summary-limit-include-expunged
Include all expunged articles in the limit
(@code{gnus-summary-limit-include-expunged}).

@item / D
@kindex / D (Summary)
@findex gnus-summary-limit-include-dormant
Include all dormant articles in the limit
(@code{gnus-summary-limit-include-dormant}).

@item / *
@kindex / * (Summary)
@findex gnus-summary-limit-include-cached
Include all cached articles in the limit
(@code{gnus-summary-limit-include-cached}).

@item / d
@kindex / d (Summary)
@findex gnus-summary-limit-exclude-dormant
Exclude all dormant articles from the limit
(@code{gnus-summary-limit-exclude-dormant}).

@item / M
@kindex / M (Summary)
@findex gnus-summary-limit-exclude-marks
Exclude all marked articles (@code{gnus-summary-limit-exclude-marks}).

@item / T
@kindex / T (Summary)
@findex gnus-summary-limit-include-thread
Include all the articles in the current thread in the limit.

@item / c
@kindex / c (Summary)
@findex gnus-summary-limit-exclude-childless-dormant
Exclude all dormant articles that have no children from the limit@*
(@code{gnus-summary-limit-exclude-childless-dormant}).

@item / C
@kindex / C (Summary)
@findex gnus-summary-limit-mark-excluded-as-read
Mark all excluded unread articles as read
(@code{gnus-summary-limit-mark-excluded-as-read}).  If given a prefix,
also mark excluded ticked and dormant articles as read.

@item / N
@kindex / N (Summary)
@findex gnus-summary-insert-new-articles
Insert all new articles in the summary buffer.  It scans for new emails
if @var{back-end}@code{-get-new-mail} is non-@code{nil}.

@item / o
@kindex / o (Summary)
@findex gnus-summary-insert-old-articles
Insert all old articles in the summary buffer.  If given a numbered
prefix, fetch this number of articles.

@end table


@node Threading
@section Threading
@cindex threading
@cindex article threading

Gnus threads articles by default.  @dfn{To thread} is to put responses
to articles directly after the articles they respond to---in a
hierarchical fashion.

Threading is done by looking at the @code{References} headers of the
articles.  In a perfect world, this would be enough to build pretty
trees, but unfortunately, the @code{References} header is often broken
or simply missing.  Weird news propagation exacerbates the problem,
so one has to employ other heuristics to get pleasing results.  A
plethora of approaches exists, as detailed in horrible detail in
@ref{Customizing Threading}.

First, a quick overview of the concepts:

@table @dfn
@item root
The top-most article in a thread; the first article in the thread.

@item thread
A tree-like article structure.

@item sub-thread
A small(er) section of this tree-like structure.

@item loose threads
Threads often lose their roots due to article expiry, or due to the root
already having been read in a previous session, and not displayed in the
summary buffer.  We then typically have many sub-threads that really
belong to one thread, but are without connecting roots.  These are
called loose threads.

@item thread gathering
An attempt to gather loose threads into bigger threads.

@item sparse threads
A thread where the missing articles have been ``guessed'' at, and are
displayed as empty lines in the summary buffer.

@end table


@menu
* Customizing Threading::       Variables you can change to affect the threading.
* Thread Commands::             Thread based commands in the summary buffer.
@end menu


@node Customizing Threading
@subsection Customizing Threading
@cindex customizing threading

@menu
* Loose Threads::               How Gnus gathers loose threads into bigger threads.
* Filling In Threads::          Making the threads displayed look fuller.
* More Threading::              Even more variables for fiddling with threads.
* Low-Level Threading::         You thought it was over@dots{} but you were wrong!
@end menu


@node Loose Threads
@subsubsection Loose Threads
@cindex <
@cindex >
@cindex loose threads

@table @code
@item gnus-summary-make-false-root
@vindex gnus-summary-make-false-root
If non-@code{nil}, gnus will gather all loose subtrees into one big tree
and create a dummy root at the top.  (Wait a minute.  Root at the top?
Yup.)  Loose subtrees occur when the real root has expired, or you've
read or killed the root in a previous session.

When there is no real root of a thread, gnus will have to fudge
something.  This variable says what fudging method gnus should use.
There are four possible values:

@iftex
@iflatex
\gnusfigure{The Summary Buffer}{390}{
\put(0,0){\epsfig{figure=ps/summary-adopt,width=7.5cm}}
\put(445,0){\makebox(0,0)[br]{\epsfig{figure=ps/summary-empty,width=7.5cm}}}
\put(0,400){\makebox(0,0)[tl]{\epsfig{figure=ps/summary-none,width=7.5cm}}}
\put(445,400){\makebox(0,0)[tr]{\epsfig{figure=ps/summary-dummy,width=7.5cm}}}
}
@end iflatex
@end iftex

@cindex adopting articles

@table @code

@item adopt
Gnus will make the first of the orphaned articles the parent.  This
parent will adopt all the other articles.  The adopted articles will be
marked as such by pointy brackets (@samp{<>}) instead of the standard
square brackets (@samp{[]}).  This is the default method.

@item dummy
@vindex gnus-summary-dummy-line-format
@vindex gnus-summary-make-false-root-always
Gnus will create a dummy summary line that will pretend to be the
parent.  This dummy line does not correspond to any real article, so
selecting it will just select the first real article after the dummy
article.  @code{gnus-summary-dummy-line-format} is used to specify the
format of the dummy roots.  It accepts only one format spec:  @samp{S},
which is the subject of the article.  @xref{Formatting Variables}.
If you want all threads to have a dummy root, even the non-gathered
ones, set @code{gnus-summary-make-false-root-always} to @code{t}.

@item empty
Gnus won't actually make any article the parent, but simply leave the
subject field of all orphans except the first empty.  (Actually, it will
use @code{gnus-summary-same-subject} as the subject (@pxref{Summary
Buffer Format}).)

@item none
Don't make any article parent at all.  Just gather the threads and
display them after one another.

@item nil
Don't gather loose threads.
@end table

@item gnus-summary-gather-subject-limit
@vindex gnus-summary-gather-subject-limit
Loose threads are gathered by comparing subjects of articles.  If this
variable is @code{nil}, gnus requires an exact match between the
subjects of the loose threads before gathering them into one big
super-thread.  This might be too strict a requirement, what with the
presence of stupid newsreaders that chop off long subject lines.  If
you think so, set this variable to, say, 20 to require that only the
first 20 characters of the subjects have to match.  If you set this
variable to a really low number, you'll find that gnus will gather
everything in sight into one thread, which isn't very helpful.

@cindex fuzzy article gathering
If you set this variable to the special value @code{fuzzy}, gnus will
use a fuzzy string comparison algorithm on the subjects (@pxref{Fuzzy
Matching}).

@item gnus-simplify-subject-fuzzy-regexp
@vindex gnus-simplify-subject-fuzzy-regexp
This can either be a regular expression or list of regular expressions
that match strings that will be removed from subjects if fuzzy subject
simplification is used.

@item gnus-simplify-ignored-prefixes
@vindex gnus-simplify-ignored-prefixes
If you set @code{gnus-summary-gather-subject-limit} to something as low
as 10, you might consider setting this variable to something sensible:

@c Written by Michael Ernst <mernst@cs.rice.edu>
@lisp
(setq gnus-simplify-ignored-prefixes
      (concat
       "\\`\\[?\\("
       (mapconcat
        'identity
        '("looking"
          "wanted" "followup" "summary\\( of\\)?"
          "help" "query" "problem" "question"
          "answer" "reference" "announce"
          "How can I" "How to" "Comparison of"
          ;; ...
          )
        "\\|")
       "\\)\\s *\\("
       (mapconcat 'identity
                  '("for" "for reference" "with" "about")
                  "\\|")
       "\\)?\\]?:?[ \t]*"))
@end lisp

All words that match this regexp will be removed before comparing two
subjects.

@item gnus-simplify-subject-functions
@vindex gnus-simplify-subject-functions
If non-@code{nil}, this variable overrides
@code{gnus-summary-gather-subject-limit}.  This variable should be a
list of functions to apply to the @code{Subject} string iteratively to
arrive at the simplified version of the string.

Useful functions to put in this list include:

@table @code
@item gnus-simplify-subject-re
@findex gnus-simplify-subject-re
Strip the leading @samp{Re:}.

@item gnus-simplify-subject-fuzzy
@findex gnus-simplify-subject-fuzzy
Simplify fuzzily.

@item gnus-simplify-whitespace
@findex gnus-simplify-whitespace
Remove excessive whitespace.

@item gnus-simplify-all-whitespace
@findex gnus-simplify-all-whitespace
Remove all whitespace.
@end table

You may also write your own functions, of course.


@item gnus-summary-gather-exclude-subject
@vindex gnus-summary-gather-exclude-subject
Since loose thread gathering is done on subjects only, that might lead
to many false hits, especially with certain common subjects like
@samp{} and @samp{(none)}.  To make the situation slightly better,
you can use the regexp @code{gnus-summary-gather-exclude-subject} to say
what subjects should be excluded from the gathering process.@*
The default is @samp{^ *$\\|^(none)$}.

@item gnus-summary-thread-gathering-function
@vindex gnus-summary-thread-gathering-function
Gnus gathers threads by looking at @code{Subject} headers.  This means
that totally unrelated articles may end up in the same ``thread'', which
is confusing.  An alternate approach is to look at all the
@code{Message-ID}s in all the @code{References} headers to find matches.
This will ensure that no gathered threads ever include unrelated
articles, but it also means that people who have posted with broken
newsreaders won't be gathered properly.  The choice is yours---plague or
cholera:

@table @code
@item gnus-gather-threads-by-subject
@findex gnus-gather-threads-by-subject
This function is the default gathering function and looks at
@code{Subject}s exclusively.

@item gnus-gather-threads-by-references
@findex gnus-gather-threads-by-references
This function looks at @code{References} headers exclusively.
@end table

If you want to test gathering by @code{References}, you could say
something like:

@lisp
(setq gnus-summary-thread-gathering-function
      'gnus-gather-threads-by-references)
@end lisp

@end table


@node Filling In Threads
@subsubsection Filling In Threads

@table @code
@item gnus-fetch-old-headers
@vindex gnus-fetch-old-headers
If non-@code{nil}, gnus will attempt to build old threads by fetching
more old headers---headers to articles marked as read.  If you
would like to display as few summary lines as possible, but still
connect as many loose threads as possible, you should set this variable
to @code{some} or a number.  If you set it to a number, no more than
that number of extra old headers will be fetched.  In either case,
fetching old headers only works if the back end you are using carries
overview files---this would normally be @code{nntp}, @code{nnspool},
@code{nnml}, and @code{nnmaildir}.  Also remember that if the root of
the thread has been expired by the server, there's not much Gnus can do
about that.

This variable can also be set to @code{invisible}.  This won't have any
visible effects, but is useful if you use the @kbd{A T} command a lot
(@pxref{Finding the Parent}).

@item gnus-fetch-old-ephemeral-headers
@vindex gnus-fetch-old-ephemeral-headers
Same as @code{gnus-fetch-old-headers}, but only used for ephemeral
newsgroups.

@item gnus-build-sparse-threads
@vindex gnus-build-sparse-threads
Fetching old headers can be slow.  A low-rent similar effect can be
gotten by setting this variable to @code{some}.  Gnus will then look at
the complete @code{References} headers of all articles and try to string
together articles that belong in the same thread.  This will leave
@dfn{gaps} in the threading display where gnus guesses that an article
is missing from the thread.  (These gaps appear like normal summary
lines.  If you select a gap, gnus will try to fetch the article in
question.)  If this variable is @code{t}, gnus will display all these
``gaps'' without regard for whether they are useful for completing the
thread or not.  Finally, if this variable is @code{more}, gnus won't cut
off sparse leaf nodes that don't lead anywhere.  This variable is
@code{nil} by default.

@item gnus-read-all-available-headers
@vindex gnus-read-all-available-headers
This is a rather obscure variable that few will find useful.  It's
intended for those non-news newsgroups where the back end has to fetch
quite a lot to present the summary buffer, and where it's impossible to
go back to parents of articles.  This is mostly the case in the
web-based groups, like the @code{nnultimate} groups.

If you don't use those, then it's safe to leave this as the default
@code{nil}.  If you want to use this variable, it should be a regexp
that matches the group name, or @code{t} for all groups.

@end table


@node More Threading
@subsubsection More Threading

@table @code
@item gnus-show-threads
@vindex gnus-show-threads
If this variable is @code{nil}, no threading will be done, and all of
the rest of the variables here will have no effect.  Turning threading
off will speed group selection up a bit, but it is sure to make reading
slower and more awkward.

@item gnus-thread-hide-subtree
@vindex gnus-thread-hide-subtree
If non-@code{nil}, all threads will be hidden when the summary buffer is
generated.

This can also be a predicate specifier (@pxref{Predicate Specifiers}).
Available predicates are @code{gnus-article-unread-p} and
@code{gnus-article-unseen-p}.

Here's an example:

@lisp
(setq gnus-thread-hide-subtree
      '(or gnus-article-unread-p
           gnus-article-unseen-p))
@end lisp

(It's a pretty nonsensical example, since all unseen articles are also
unread, but you get my drift.)


@item gnus-thread-expunge-below
@vindex gnus-thread-expunge-below
All threads that have a total score (as defined by
@code{gnus-thread-score-function}) less than this number will be
expunged.  This variable is @code{nil} by default, which means that no
threads are expunged.

@item gnus-thread-hide-killed
@vindex gnus-thread-hide-killed
if you kill a thread and this variable is non-@code{nil}, the subtree
will be hidden.

@item gnus-thread-ignore-subject
@vindex gnus-thread-ignore-subject
Sometimes somebody changes the subject in the middle of a thread.  If
this variable is non-@code{nil}, which is the default, the subject
change is ignored.  If it is @code{nil}, a change in the subject will
result in a new thread.

@item gnus-thread-indent-level
@vindex gnus-thread-indent-level
This is a number that says how much each sub-thread should be indented.
The default is 4.

@item gnus-sort-gathered-threads-function
@vindex gnus-sort-gathered-threads-function
Sometimes, particularly with mailing lists, the order in which mails
arrive locally is not necessarily the same as the order in which they
arrived on the mailing list.  Consequently, when sorting sub-threads
using the default @code{gnus-thread-sort-by-number}, responses can end
up appearing before the article to which they are responding to.
Setting this variable to an alternate value
(e.g. @code{gnus-thread-sort-by-date}), in a group's parameters or in an
appropriate hook (e.g. @code{gnus-summary-generate-hook}) can produce a
more logical sub-thread ordering in such instances.

@end table


@node Low-Level Threading
@subsubsection Low-Level Threading

@table @code

@item gnus-parse-headers-hook
@vindex gnus-parse-headers-hook
Hook run before parsing any headers.  The default value is
@code{(gnus-set-summary-default-charset)}, which sets up local value of
@code{default-mime-charset} in summary buffer based on variable
@code{gnus-newsgroup-default-charset-alist}.

@item gnus-alter-header-function
@vindex gnus-alter-header-function
If non-@code{nil}, this function will be called to allow alteration of
article header structures.  The function is called with one parameter,
the article header vector, which it may alter in any way.  For instance,
if you have a mail-to-news gateway which alters the @code{Message-ID}s
in systematic ways (by adding prefixes and such), you can use this
variable to un-scramble the @code{Message-ID}s so that they are more
meaningful.  Here's one example:

@lisp
(setq gnus-alter-header-function 'my-alter-message-id)

(defun my-alter-message-id (header)
  (let ((id (mail-header-id header)))
    (when (string-match
           "\\(<[^<>@@]*\\)\\.?cygnus\\..*@@\\([^<>@@]*>\\)" id)
      (mail-header-set-id
       (concat (match-string 1 id) "@@" (match-string 2 id))
       header))))
@end lisp

@end table


@node Thread Commands
@subsection Thread Commands
@cindex thread commands

@table @kbd

@item T k
@itemx C-M-k
@kindex T k (Summary)
@kindex C-M-k (Summary)
@findex gnus-summary-kill-thread
Mark all articles in the current (sub-)thread as read
(@code{gnus-summary-kill-thread}).  If the prefix argument is positive,
remove all marks instead.  If the prefix argument is negative, tick
articles instead.

@item T l
@itemx C-M-l
@kindex T l (Summary)
@kindex C-M-l (Summary)
@findex gnus-summary-lower-thread
Lower the score of the current (sub-)thread
(@code{gnus-summary-lower-thread}).

@item T i
@kindex T i (Summary)
@findex gnus-summary-raise-thread
Increase the score of the current (sub-)thread
(@code{gnus-summary-raise-thread}).

@item T #
@kindex T # (Summary)
@findex gnus-uu-mark-thread
Set the process mark on the current (sub-)thread
(@code{gnus-uu-mark-thread}).

@item T M-#
@kindex T M-# (Summary)
@findex gnus-uu-unmark-thread
Remove the process mark from the current (sub-)thread
(@code{gnus-uu-unmark-thread}).

@item T T
@kindex T T (Summary)
@findex gnus-summary-toggle-threads
Toggle threading (@code{gnus-summary-toggle-threads}).

@item T s
@kindex T s (Summary)
@findex gnus-summary-show-thread
Expose the (sub-)thread hidden under the current article, if any@*
(@code{gnus-summary-show-thread}).

@item T h
@kindex T h (Summary)
@findex gnus-summary-hide-thread
Hide the current (sub-)thread (@code{gnus-summary-hide-thread}).

@item T S
@kindex T S (Summary)
@findex gnus-summary-show-all-threads
Expose all hidden threads (@code{gnus-summary-show-all-threads}).

@item T H
@kindex T H (Summary)
@findex gnus-summary-hide-all-threads
Hide all threads (@code{gnus-summary-hide-all-threads}).

@item T t
@kindex T t (Summary)
@findex gnus-summary-rethread-current
Re-thread the current article's thread
(@code{gnus-summary-rethread-current}).  This works even when the
summary buffer is otherwise unthreaded.

@item T ^
@kindex T ^ (Summary)
@findex gnus-summary-reparent-thread
Make the current article the child of the marked (or previous) article
(@code{gnus-summary-reparent-thread}).

@end table

The following commands are thread movement commands.  They all
understand the numeric prefix.

@table @kbd

@item T n
@kindex T n (Summary)
@itemx C-M-f
@kindex C-M-n (Summary)
@itemx M-down
@kindex M-down (Summary)
@findex gnus-summary-next-thread
Go to the next thread (@code{gnus-summary-next-thread}).

@item T p
@kindex T p (Summary)
@itemx C-M-b
@kindex C-M-p (Summary)
@itemx M-up
@kindex M-up (Summary)
@findex gnus-summary-prev-thread
Go to the previous thread (@code{gnus-summary-prev-thread}).

@item T d
@kindex T d (Summary)
@findex gnus-summary-down-thread
Descend the thread (@code{gnus-summary-down-thread}).

@item T u
@kindex T u (Summary)
@findex gnus-summary-up-thread
Ascend the thread (@code{gnus-summary-up-thread}).

@item T o
@kindex T o (Summary)
@findex gnus-summary-top-thread
Go to the top of the thread (@code{gnus-summary-top-thread}).
@end table

@vindex gnus-thread-operation-ignore-subject
If you ignore subject while threading, you'll naturally end up with
threads that have several different subjects in them.  If you then issue
a command like @kbd{T k} (@code{gnus-summary-kill-thread}) you might not
wish to kill the entire thread, but just those parts of the thread that
have the same subject as the current article.  If you like this idea,
you can fiddle with @code{gnus-thread-operation-ignore-subject}.  If it
is non-@code{nil} (which it is by default), subjects will be ignored
when doing thread commands.  If this variable is @code{nil}, articles in
the same thread with different subjects will not be included in the
operation in question.  If this variable is @code{fuzzy}, only articles
that have subjects fuzzily equal will be included (@pxref{Fuzzy
Matching}).


@node Sorting the Summary Buffer
@section Sorting the Summary Buffer

@findex gnus-thread-sort-by-total-score
@findex gnus-thread-sort-by-date
@findex gnus-thread-sort-by-score
@findex gnus-thread-sort-by-subject
@findex gnus-thread-sort-by-author
@findex gnus-thread-sort-by-number
@findex gnus-thread-sort-by-random
@vindex gnus-thread-sort-functions
@findex gnus-thread-sort-by-most-recent-number
@findex gnus-thread-sort-by-most-recent-date
If you are using a threaded summary display, you can sort the threads by
setting @code{gnus-thread-sort-functions}, which can be either a single
function, a list of functions, or a list containing functions and
@code{(not some-function)} elements.

By default, sorting is done on article numbers.  Ready-made sorting
predicate functions include @code{gnus-thread-sort-by-number},
@code{gnus-thread-sort-by-author}, @code{gnus-thread-sort-by-subject},
@code{gnus-thread-sort-by-date}, @code{gnus-thread-sort-by-score},
@code{gnus-thread-sort-by-most-recent-number},
@code{gnus-thread-sort-by-most-recent-date},
@code{gnus-thread-sort-by-random} and
@code{gnus-thread-sort-by-total-score}.

Each function takes two threads and returns non-@code{nil} if the first
thread should be sorted before the other.  Note that sorting really is
normally done by looking only at the roots of each thread.

If you use more than one function, the primary sort key should be the
last function in the list.  You should probably always include
@code{gnus-thread-sort-by-number} in the list of sorting
functions---preferably first.  This will ensure that threads that are
equal with respect to the other sort criteria will be displayed in
ascending article order.

If you would like to sort by reverse score, then by subject, and finally
by number, you could do something like:

@lisp
(setq gnus-thread-sort-functions
      '(gnus-thread-sort-by-number
        gnus-thread-sort-by-subject
        (not gnus-thread-sort-by-total-score)))
@end lisp

The threads that have highest score will be displayed first in the
summary buffer.  When threads have the same score, they will be sorted
alphabetically.  The threads that have the same score and the same
subject will be sorted by number, which is (normally) the sequence in
which the articles arrived.

If you want to sort by score and then reverse arrival order, you could
say something like:

@lisp
(setq gnus-thread-sort-functions
      '((lambda (t1 t2)
          (not (gnus-thread-sort-by-number t1 t2)))
        gnus-thread-sort-by-score))
@end lisp

@vindex gnus-thread-score-function
The function in the @code{gnus-thread-score-function} variable (default
@code{+}) is used for calculating the total score of a thread.  Useful
functions might be @code{max}, @code{min}, or squared means, or whatever
tickles your fancy.

@findex gnus-article-sort-functions
@findex gnus-article-sort-by-date
@findex gnus-article-sort-by-score
@findex gnus-article-sort-by-subject
@findex gnus-article-sort-by-author
@findex gnus-article-sort-by-random
@findex gnus-article-sort-by-number
If you are using an unthreaded display for some strange reason or
other, you have to fiddle with the @code{gnus-article-sort-functions}
variable.  It is very similar to the
@code{gnus-thread-sort-functions}, except that it uses slightly
different functions for article comparison.  Available sorting
predicate functions are @code{gnus-article-sort-by-number},
@code{gnus-article-sort-by-author},
@code{gnus-article-sort-by-subject}, @code{gnus-article-sort-by-date},
@code{gnus-article-sort-by-random}, and
@code{gnus-article-sort-by-score}.

If you want to sort an unthreaded summary display by subject, you could
say something like:

@lisp
(setq gnus-article-sort-functions
      '(gnus-article-sort-by-number
        gnus-article-sort-by-subject))
@end lisp



@node Asynchronous Fetching
@section Asynchronous Article Fetching
@cindex asynchronous article fetching
@cindex article pre-fetch
@cindex pre-fetch

If you read your news from an @acronym{NNTP} server that's far away, the
network latencies may make reading articles a chore.  You have to wait
for a while after pressing @kbd{n} to go to the next article before the
article appears.  Why can't gnus just go ahead and fetch the article
while you are reading the previous one?  Why not, indeed.

First, some caveats.  There are some pitfalls to using asynchronous
article fetching, especially the way gnus does it.

Let's say you are reading article 1, which is short, and article 2 is
quite long, and you are not interested in reading that.  Gnus does not
know this, so it goes ahead and fetches article 2.  You decide to read
article 3, but since gnus is in the process of fetching article 2, the
connection is blocked.

To avoid these situations, gnus will open two (count 'em two)
connections to the server.  Some people may think this isn't a very nice
thing to do, but I don't see any real alternatives.  Setting up that
extra connection takes some time, so gnus startup will be slower.

Gnus will fetch more articles than you will read.  This will mean that
the link between your machine and the @acronym{NNTP} server will become more
loaded than if you didn't use article pre-fetch.  The server itself will
also become more loaded---both with the extra article requests, and the
extra connection.

Ok, so now you know that you shouldn't really use this thing@dots{} unless
you really want to.

@vindex gnus-asynchronous
Here's how:  Set @code{gnus-asynchronous} to @code{t}.  The rest should
happen automatically.

@vindex gnus-use-article-prefetch
You can control how many articles are to be pre-fetched by setting
@code{gnus-use-article-prefetch}.  This is 30 by default, which means
that when you read an article in the group, the back end will pre-fetch
the next 30 articles.  If this variable is @code{t}, the back end will
pre-fetch all the articles it can without bound.  If it is
@code{nil}, no pre-fetching will be done.

@vindex gnus-async-prefetch-article-p
@findex gnus-async-read-p
There are probably some articles that you don't want to pre-fetch---read
articles, for instance.  The @code{gnus-async-prefetch-article-p}
variable controls whether an article is to be pre-fetched.  This
function should return non-@code{nil} when the article in question is
to be pre-fetched.  The default is @code{gnus-async-read-p}, which
returns @code{nil} on read articles.  The function is called with an
article data structure as the only parameter.

If, for instance, you wish to pre-fetch only unread articles shorter
than 100 lines, you could say something like:

@lisp
(defun my-async-short-unread-p (data)
  "Return non-nil for short, unread articles."
  (and (gnus-data-unread-p data)
       (< (mail-header-lines (gnus-data-header data))
          100)))

(setq gnus-async-prefetch-article-p 'my-async-short-unread-p)
@end lisp

These functions will be called many, many times, so they should
preferably be short and sweet to avoid slowing down gnus too much.
It's probably a good idea to byte-compile things like this.

@vindex gnus-prefetched-article-deletion-strategy
Articles have to be removed from the asynch buffer sooner or later.  The
@code{gnus-prefetched-article-deletion-strategy} says when to remove
articles.  This is a list that may contain the following elements:

@table @code
@item read
Remove articles when they are read.

@item exit
Remove articles when exiting the group.
@end table

The default value is @code{(read exit)}.

@c @vindex gnus-use-header-prefetch
@c If @code{gnus-use-header-prefetch} is non-@code{nil}, prefetch articles
@c from the next group.


@node Article Caching
@section Article Caching
@cindex article caching
@cindex caching

If you have an @emph{extremely} slow @acronym{NNTP} connection, you may
consider turning article caching on.  Each article will then be stored
locally under your home directory.  As you may surmise, this could
potentially use @emph{huge} amounts of disk space, as well as eat up all
your inodes so fast it will make your head swim.  In vodka.

Used carefully, though, it could be just an easier way to save articles.

@vindex gnus-use-long-file-name
@vindex gnus-cache-directory
@vindex gnus-use-cache
To turn caching on, set @code{gnus-use-cache} to @code{t}.  By default,
all articles ticked or marked as dormant will then be copied
over to your local cache (@code{gnus-cache-directory}).  Whether this
cache is flat or hierarchical is controlled by the
@code{gnus-use-long-file-name} variable, as usual.

When re-selecting a ticked or dormant article, it will be fetched from the
cache instead of from the server.  As articles in your cache will never
expire, this might serve as a method of saving articles while still
keeping them where they belong.  Just mark all articles you want to save
as dormant, and don't worry.

When an article is marked as read, is it removed from the cache.

@vindex gnus-cache-remove-articles
@vindex gnus-cache-enter-articles
The entering/removal of articles from the cache is controlled by the
@code{gnus-cache-enter-articles} and @code{gnus-cache-remove-articles}
variables.  Both are lists of symbols.  The first is @code{(ticked
dormant)} by default, meaning that ticked and dormant articles will be
put in the cache.  The latter is @code{(read)} by default, meaning that
articles marked as read are removed from the cache.  Possibly
symbols in these two lists are @code{ticked}, @code{dormant},
@code{unread} and @code{read}.

@findex gnus-jog-cache
So where does the massive article-fetching and storing come into the
picture?  The @code{gnus-jog-cache} command will go through all
subscribed newsgroups, request all unread articles, score them, and
store them in the cache.  You should only ever, ever ever ever, use this
command if 1) your connection to the @acronym{NNTP} server is really, really,
really slow and 2) you have a really, really, really huge disk.
Seriously.  One way to cut down on the number of articles downloaded is
to score unwanted articles down and have them marked as read.  They will
not then be downloaded by this command.

@vindex gnus-uncacheable-groups
@vindex gnus-cacheable-groups
It is likely that you do not want caching on all groups.  For instance,
if your @code{nnml} mail is located under your home directory, it makes no
sense to cache it somewhere else under your home directory.  Unless you
feel that it's neat to use twice as much space.

To limit the caching, you could set @code{gnus-cacheable-groups} to a
regexp of groups to cache, @samp{^nntp} for instance, or set the
@code{gnus-uncacheable-groups} regexp to @samp{^nnml}, for instance.
Both variables are @code{nil} by default.  If a group matches both
variables, the group is not cached.

@findex gnus-cache-generate-nov-databases
@findex gnus-cache-generate-active
@vindex gnus-cache-active-file
The cache stores information on what articles it contains in its active
file (@code{gnus-cache-active-file}).  If this file (or any other parts
of the cache) becomes all messed up for some reason or other, gnus
offers two functions that will try to set things right.  @kbd{M-x
gnus-cache-generate-nov-databases} will (re)build all the @acronym{NOV}
files, and @kbd{gnus-cache-generate-active} will (re)generate the active
file.

@findex gnus-cache-move-cache
@code{gnus-cache-move-cache} will move your whole
@code{gnus-cache-directory} to some other location.  You get asked to
where, isn't that cool?

@node Persistent Articles
@section Persistent Articles
@cindex persistent articles

Closely related to article caching, we have @dfn{persistent articles}.
In fact, it's just a different way of looking at caching, and much more
useful in my opinion.

Say you're reading a newsgroup, and you happen on to some valuable gem
that you want to keep and treasure forever.  You'd normally just save it
(using one of the many saving commands) in some file.  The problem with
that is that it's just, well, yucky.  Ideally you'd prefer just having
the article remain in the group where you found it forever; untouched by
the expiry going on at the news server.

This is what a @dfn{persistent article} is---an article that just won't
be deleted.  It's implemented using the normal cache functions, but
you use two explicit commands for managing persistent articles:

@table @kbd

@item *
@kindex * (Summary)
@findex gnus-cache-enter-article
Make the current article persistent (@code{gnus-cache-enter-article}).

@item M-*
@kindex M-* (Summary)
@findex gnus-cache-remove-article
Remove the current article from the persistent articles
(@code{gnus-cache-remove-article}).  This will normally delete the
article.
@end table

Both these commands understand the process/prefix convention.

To avoid having all ticked articles (and stuff) entered into the cache,
you should set @code{gnus-use-cache} to @code{passive} if you're just
interested in persistent articles:

@lisp
(setq gnus-use-cache 'passive)
@end lisp


@node Article Backlog
@section Article Backlog
@cindex backlog
@cindex article backlog

If you have a slow connection, but the idea of using caching seems
unappealing to you (and it is, really), you can help the situation some
by switching on the @dfn{backlog}.  This is where gnus will buffer
already read articles so that it doesn't have to re-fetch articles
you've already read.  This only helps if you are in the habit of
re-selecting articles you've recently read, of course.  If you never do
that, turning the backlog on will slow gnus down a little bit, and
increase memory usage some.

@vindex gnus-keep-backlog
If you set @code{gnus-keep-backlog} to a number @var{n}, gnus will store
at most @var{n} old articles in a buffer for later re-fetching.  If this
variable is non-@code{nil} and is not a number, gnus will store
@emph{all} read articles, which means that your Emacs will grow without
bound before exploding and taking your machine down with you.  I put
that in there just to keep y'all on your toes.

The default value is 20.


@node Saving Articles
@section Saving Articles
@cindex saving articles

Gnus can save articles in a number of ways.  Below is the documentation
for saving articles in a fairly straight-forward fashion (i.e., little
processing of the article is done before it is saved).  For a different
approach (uudecoding, unsharing) you should use @code{gnus-uu}
(@pxref{Decoding Articles}).

For the commands listed here, the target is a file.  If you want to
save to a group, see the @kbd{B c} (@code{gnus-summary-copy-article})
command (@pxref{Mail Group Commands}).

@vindex gnus-save-all-headers
If @code{gnus-save-all-headers} is non-@code{nil}, gnus will not delete
unwanted headers before saving the article.

@vindex gnus-saved-headers
If the preceding variable is @code{nil}, all headers that match the
@code{gnus-saved-headers} regexp will be kept, while the rest will be
deleted before saving.

@table @kbd

@item O o
@itemx o
@kindex O o (Summary)
@kindex o (Summary)
@findex gnus-summary-save-article
@c @icon{gnus-summary-save-article}
Save the current article using the default article saver
(@code{gnus-summary-save-article}).

@item O m
@kindex O m (Summary)
@findex gnus-summary-save-article-mail
Save the current article in mail format
(@code{gnus-summary-save-article-mail}).

@item O r
@kindex O r (Summary)
@findex gnus-summary-save-article-rmail
Save the current article in Rmail format
(@code{gnus-summary-save-article-rmail}).

@item O f
@kindex O f (Summary)
@findex gnus-summary-save-article-file
@c @icon{gnus-summary-save-article-file}
Save the current article in plain file format
(@code{gnus-summary-save-article-file}).

@item O F
@kindex O F (Summary)
@findex gnus-summary-write-article-file
Write the current article in plain file format, overwriting any previous
file contents (@code{gnus-summary-write-article-file}).

@item O b
@kindex O b (Summary)
@findex gnus-summary-save-article-body-file
Save the current article body in plain file format
(@code{gnus-summary-save-article-body-file}).

@item O h
@kindex O h (Summary)
@findex gnus-summary-save-article-folder
Save the current article in mh folder format
(@code{gnus-summary-save-article-folder}).

@item O v
@kindex O v (Summary)
@findex gnus-summary-save-article-vm
Save the current article in a VM folder
(@code{gnus-summary-save-article-vm}).

@item O p
@itemx |
@kindex O p (Summary)
@kindex | (Summary)
@findex gnus-summary-pipe-output
Save the current article in a pipe.  Uhm, like, what I mean is---Pipe
the current article to a process (@code{gnus-summary-pipe-output}).
If given a symbolic prefix (@pxref{Symbolic Prefixes}), include the
complete headers in the piped output.

@item O P
@kindex O P (Summary)
@findex gnus-summary-muttprint
@vindex gnus-summary-muttprint-program
Save the current article into muttprint.  That is, print it using the
external program @uref{http://muttprint.sourceforge.net/,
Muttprint}.  The program name and options to use is controlled by the
variable @code{gnus-summary-muttprint-program}.
(@code{gnus-summary-muttprint}).

@end table

@vindex gnus-prompt-before-saving
All these commands use the process/prefix convention
(@pxref{Process/Prefix}).  If you save bunches of articles using these
functions, you might get tired of being prompted for files to save each
and every article in.  The prompting action is controlled by
the @code{gnus-prompt-before-saving} variable, which is @code{always} by
default, giving you that excessive prompting action you know and
loathe.  If you set this variable to @code{t} instead, you'll be prompted
just once for each series of articles you save.  If you like to really
have Gnus do all your thinking for you, you can even set this variable
to @code{nil}, which means that you will never be prompted for files to
save articles in.  Gnus will simply save all the articles in the default
files.


@vindex gnus-default-article-saver
You can customize the @code{gnus-default-article-saver} variable to make
gnus do what you want it to.  You can use any of the six ready-made
functions below, or you can create your own.

@table @code

@item gnus-summary-save-in-rmail
@findex gnus-summary-save-in-rmail
@vindex gnus-rmail-save-name
@findex gnus-plain-save-name
This is the default format, @dfn{Babyl}.  Uses the function in the
@code{gnus-rmail-save-name} variable to get a file name to save the
article in.  The default is @code{gnus-plain-save-name}.

@item gnus-summary-save-in-mail
@findex gnus-summary-save-in-mail
@vindex gnus-mail-save-name
Save in a Unix mail (mbox) file.  Uses the function in the
@code{gnus-mail-save-name} variable to get a file name to save the
article in.  The default is @code{gnus-plain-save-name}.

@item gnus-summary-save-in-file
@findex gnus-summary-save-in-file
@vindex gnus-file-save-name
@findex gnus-numeric-save-name
Append the article straight to an ordinary file.  Uses the function in
the @code{gnus-file-save-name} variable to get a file name to save the
article in.  The default is @code{gnus-numeric-save-name}.

@item gnus-summary-write-to-file
@findex gnus-summary-write-to-file
Write the article straight to an ordinary file.  The file is
overwritten if it exists.  Uses the function in the
@code{gnus-file-save-name} variable to get a file name to save the
article in.  The default is @code{gnus-numeric-save-name}.

@item gnus-summary-save-body-in-file
@findex gnus-summary-save-body-in-file
Append the article body to an ordinary file.  Uses the function in the
@code{gnus-file-save-name} variable to get a file name to save the
article in.  The default is @code{gnus-numeric-save-name}.

@item gnus-summary-save-in-folder
@findex gnus-summary-save-in-folder
@findex gnus-folder-save-name
@findex gnus-Folder-save-name
@vindex gnus-folder-save-name
@cindex rcvstore
@cindex MH folders
Save the article to an MH folder using @code{rcvstore} from the MH
library.  Uses the function in the @code{gnus-folder-save-name} variable
to get a file name to save the article in.  The default is
@code{gnus-folder-save-name}, but you can also use
@code{gnus-Folder-save-name}, which creates capitalized names.

@item gnus-summary-save-in-vm
@findex gnus-summary-save-in-vm
Save the article in a VM folder.  You have to have the VM mail
reader to use this setting.
@end table

@vindex gnus-article-save-directory
All of these functions, except for the last one, will save the article
in the @code{gnus-article-save-directory}, which is initialized from the
@env{SAVEDIR} environment variable.  This is @file{~/News/} by
default.

As you can see above, the functions use different functions to find a
suitable name of a file to save the article in.  Below is a list of
available functions that generate names:

@table @code

@item gnus-Numeric-save-name
@findex gnus-Numeric-save-name
File names like @file{~/News/Alt.andrea-dworkin/45}.

@item gnus-numeric-save-name
@findex gnus-numeric-save-name
File names like @file{~/News/alt.andrea-dworkin/45}.

@item gnus-Plain-save-name
@findex gnus-Plain-save-name
File names like @file{~/News/Alt.andrea-dworkin}.

@item gnus-plain-save-name
@findex gnus-plain-save-name
File names like @file{~/News/alt.andrea-dworkin}.

@item gnus-sender-save-name
@findex gnus-sender-save-name
File names like @file{~/News/larsi}.
@end table

@vindex gnus-split-methods
You can have gnus suggest where to save articles by plonking a regexp into
the @code{gnus-split-methods} alist.  For instance, if you would like to
save articles related to gnus in the file @file{gnus-stuff}, and articles
related to VM in @file{vm-stuff}, you could set this variable to something
like:

@lisp
(("^Subject:.*gnus\\|^Newsgroups:.*gnus" "gnus-stuff")
 ("^Subject:.*vm\\|^Xref:.*vm" "vm-stuff")
 (my-choosing-function "../other-dir/my-stuff")
 ((equal gnus-newsgroup-name "mail.misc") "mail-stuff"))
@end lisp

We see that this is a list where each element is a list that has two
elements---the @dfn{match} and the @dfn{file}.  The match can either be
a string (in which case it is used as a regexp to match on the article
head); it can be a symbol (which will be called as a function with the
group name as a parameter); or it can be a list (which will be
@code{eval}ed).  If any of these actions have a non-@code{nil} result,
the @dfn{file} will be used as a default prompt.  In addition, the
result of the operation itself will be used if the function or form
called returns a string or a list of strings.

You basically end up with a list of file names that might be used when
saving the current article.  (All ``matches'' will be used.)  You will
then be prompted for what you really want to use as a name, with file
name completion over the results from applying this variable.

This variable is @code{((gnus-article-archive-name))} by default, which
means that gnus will look at the articles it saves for an
@code{Archive-name} line and use that as a suggestion for the file
name.

Here's an example function to clean up file names somewhat.  If you have
lots of mail groups called things like
@samp{nnml:mail.whatever}, you may want to chop off the beginning of
these group names before creating the file name to save to.  The
following will do just that:

@lisp
(defun my-save-name (group)
  (when (string-match "^nnml:mail." group)
    (substring group (match-end 0))))

(setq gnus-split-methods
      '((gnus-article-archive-name)
        (my-save-name)))
@end lisp


@vindex gnus-use-long-file-name
Finally, you have the @code{gnus-use-long-file-name} variable.  If it is
@code{nil}, all the preceding functions will replace all periods
(@samp{.}) in the group names with slashes (@samp{/})---which means that
the functions will generate hierarchies of directories instead of having
all the files in the top level directory
(@file{~/News/alt/andrea-dworkin} instead of
@file{~/News/alt.andrea-dworkin}.)  This variable is @code{t} by default
on most systems.  However, for historical reasons, this is @code{nil} on
Xenix and usg-unix-v machines by default.

This function also affects kill and score file names.  If this variable
is a list, and the list contains the element @code{not-score}, long file
names will not be used for score files, if it contains the element
@code{not-save}, long file names will not be used for saving, and if it
contains the element @code{not-kill}, long file names will not be used
for kill files.

If you'd like to save articles in a hierarchy that looks something like
a spool, you could

@lisp
(setq gnus-use-long-file-name '(not-save)) ; @r{to get a hierarchy}
(setq gnus-default-article-saver
      'gnus-summary-save-in-file)          ; @r{no encoding}
@end lisp

Then just save with @kbd{o}.  You'd then read this hierarchy with
ephemeral @code{nneething} groups---@kbd{G D} in the group buffer, and
the top level directory as the argument (@file{~/News/}).  Then just walk
around to the groups/directories with @code{nneething}.


@node Decoding Articles
@section Decoding Articles
@cindex decoding articles

Sometime users post articles (or series of articles) that have been
encoded in some way or other.  Gnus can decode them for you.

@menu
* Uuencoded Articles::          Uudecode articles.
* Shell Archives::              Unshar articles.
* PostScript Files::            Split PostScript.
* Other Files::                 Plain save and binhex.
* Decoding Variables::          Variables for a happy decoding.
* Viewing Files::               You want to look at the result of the decoding?
@end menu

@cindex series
@cindex article series
All these functions use the process/prefix convention
(@pxref{Process/Prefix}) for finding out what articles to work on, with
the extension that a ``single article'' means ``a single series''.  Gnus
can find out by itself what articles belong to a series, decode all the
articles and unpack/view/save the resulting file(s).

Gnus guesses what articles are in the series according to the following
simplish rule: The subjects must be (nearly) identical, except for the
last two numbers of the line.  (Spaces are largely ignored, however.)

For example: If you choose a subject called @samp{cat.gif (2/3)}, gnus
will find all the articles that match the regexp @samp{^cat.gif
([0-9]+/[0-9]+).*$}.

Subjects that are non-standard, like @samp{cat.gif (2/3) Part 6 of a
series}, will not be properly recognized by any of the automatic viewing
commands, and you have to mark the articles manually with @kbd{#}.


@node Uuencoded Articles
@subsection Uuencoded Articles
@cindex uudecode
@cindex uuencoded articles

@table @kbd

@item X u
@kindex X u (Summary)
@findex gnus-uu-decode-uu
@c @icon{gnus-uu-decode-uu}
Uudecodes the current series (@code{gnus-uu-decode-uu}).

@item X U
@kindex X U (Summary)
@findex gnus-uu-decode-uu-and-save
Uudecodes and saves the current series
(@code{gnus-uu-decode-uu-and-save}).

@item X v u
@kindex X v u (Summary)
@findex gnus-uu-decode-uu-view
Uudecodes and views the current series (@code{gnus-uu-decode-uu-view}).

@item X v U
@kindex X v U (Summary)
@findex gnus-uu-decode-uu-and-save-view
Uudecodes, views and saves the current series
(@code{gnus-uu-decode-uu-and-save-view}).

@end table

Remember that these all react to the presence of articles marked with
the process mark.  If, for instance, you'd like to decode and save an
entire newsgroup, you'd typically do @kbd{M P a}
(@code{gnus-uu-mark-all}) and then @kbd{X U}
(@code{gnus-uu-decode-uu-and-save}).

All this is very much different from how @code{gnus-uu} worked with
@sc{gnus 4.1}, where you had explicit keystrokes for everything under
the sun.  This version of @code{gnus-uu} generally assumes that you mark
articles in some way (@pxref{Setting Process Marks}) and then press
@kbd{X u}.

@vindex gnus-uu-notify-files
Note: When trying to decode articles that have names matching
@code{gnus-uu-notify-files}, which is hard-coded to
@samp{[Cc][Ii][Nn][Dd][Yy][0-9]+.\\(gif\\|jpg\\)}, @code{gnus-uu} will
automatically post an article on @samp{comp.unix.wizards} saying that
you have just viewed the file in question.  This feature can't be turned
off.


@node Shell Archives
@subsection Shell Archives
@cindex unshar
@cindex shell archives
@cindex shared articles

Shell archives (``shar files'') used to be a popular way to distribute
sources, but it isn't used all that much today.  In any case, we have
some commands to deal with these:

@table @kbd

@item X s
@kindex X s (Summary)
@findex gnus-uu-decode-unshar
Unshars the current series (@code{gnus-uu-decode-unshar}).

@item X S
@kindex X S (Summary)
@findex gnus-uu-decode-unshar-and-save
Unshars and saves the current series (@code{gnus-uu-decode-unshar-and-save}).

@item X v s
@kindex X v s (Summary)
@findex gnus-uu-decode-unshar-view
Unshars and views the current series (@code{gnus-uu-decode-unshar-view}).

@item X v S
@kindex X v S (Summary)
@findex gnus-uu-decode-unshar-and-save-view
Unshars, views and saves the current series
(@code{gnus-uu-decode-unshar-and-save-view}).
@end table


@node PostScript Files
@subsection PostScript Files
@cindex PostScript

@table @kbd

@item X p
@kindex X p (Summary)
@findex gnus-uu-decode-postscript
Unpack the current PostScript series (@code{gnus-uu-decode-postscript}).

@item X P
@kindex X P (Summary)
@findex gnus-uu-decode-postscript-and-save
Unpack and save the current PostScript series
(@code{gnus-uu-decode-postscript-and-save}).

@item X v p
@kindex X v p (Summary)
@findex gnus-uu-decode-postscript-view
View the current PostScript series
(@code{gnus-uu-decode-postscript-view}).

@item X v P
@kindex X v P (Summary)
@findex gnus-uu-decode-postscript-and-save-view
View and save the current PostScript series
(@code{gnus-uu-decode-postscript-and-save-view}).
@end table


@node Other Files
@subsection Other Files

@table @kbd
@item X o
@kindex X o (Summary)
@findex gnus-uu-decode-save
Save the current series
(@code{gnus-uu-decode-save}).

@item X b
@kindex X b (Summary)
@findex gnus-uu-decode-binhex
Unbinhex the current series (@code{gnus-uu-decode-binhex}).  This
doesn't really work yet.
@end table


@node Decoding Variables
@subsection Decoding Variables

Adjective, not verb.

@menu
* Rule Variables::              Variables that say how a file is to be viewed.
* Other Decode Variables::      Other decode variables.
* Uuencoding and Posting::      Variables for customizing uuencoding.
@end menu


@node Rule Variables
@subsubsection Rule Variables
@cindex rule variables

Gnus uses @dfn{rule variables} to decide how to view a file.  All these
variables are of the form

@lisp
      (list '(regexp1 command2)
            '(regexp2 command2)
            ...)
@end lisp

@table @code

@item gnus-uu-user-view-rules
@vindex gnus-uu-user-view-rules
@cindex sox
This variable is consulted first when viewing files.  If you wish to use,
for instance, @code{sox} to convert an @file{.au} sound file, you could
say something like:
@lisp
(setq gnus-uu-user-view-rules
      (list '("\\\\.au$" "sox %s -t .aiff > /dev/audio")))
@end lisp

@item gnus-uu-user-view-rules-end
@vindex gnus-uu-user-view-rules-end
This variable is consulted if gnus couldn't make any matches from the
user and default view rules.

@item gnus-uu-user-archive-rules
@vindex gnus-uu-user-archive-rules
This variable can be used to say what commands should be used to unpack
archives.
@end table


@node Other Decode Variables
@subsubsection Other Decode Variables

@table @code
@vindex gnus-uu-grabbed-file-functions

@item gnus-uu-grabbed-file-functions
All functions in this list will be called right after each file has been
successfully decoded---so that you can move or view files right away,
and don't have to wait for all files to be decoded before you can do
anything.  Ready-made functions you can put in this list are:

@table @code

@item gnus-uu-grab-view
@findex gnus-uu-grab-view
View the file.

@item gnus-uu-grab-move
@findex gnus-uu-grab-move
Move the file (if you're using a saving function.)
@end table

@item gnus-uu-be-dangerous
@vindex gnus-uu-be-dangerous
Specifies what to do if unusual situations arise during decoding.  If
@code{nil}, be as conservative as possible.  If @code{t}, ignore things
that didn't work, and overwrite existing files.  Otherwise, ask each
time.

@item gnus-uu-ignore-files-by-name
@vindex gnus-uu-ignore-files-by-name
Files with name matching this regular expression won't be viewed.

@item gnus-uu-ignore-files-by-type
@vindex gnus-uu-ignore-files-by-type
Files with a @acronym{MIME} type matching this variable won't be viewed.
Note that Gnus tries to guess what type the file is based on the name.
@code{gnus-uu} is not a @acronym{MIME} package (yet), so this is slightly
kludgey.

@item gnus-uu-tmp-dir
@vindex gnus-uu-tmp-dir
Where @code{gnus-uu} does its work.

@item gnus-uu-do-not-unpack-archives
@vindex gnus-uu-do-not-unpack-archives
Non-@code{nil} means that @code{gnus-uu} won't peek inside archives
looking for files to display.

@item gnus-uu-view-and-save
@vindex gnus-uu-view-and-save
Non-@code{nil} means that the user will always be asked to save a file
after viewing it.

@item gnus-uu-ignore-default-view-rules
@vindex gnus-uu-ignore-default-view-rules
Non-@code{nil} means that @code{gnus-uu} will ignore the default viewing
rules.

@item gnus-uu-ignore-default-archive-rules
@vindex gnus-uu-ignore-default-archive-rules
Non-@code{nil} means that @code{gnus-uu} will ignore the default archive
unpacking commands.

@item gnus-uu-kill-carriage-return
@vindex gnus-uu-kill-carriage-return
Non-@code{nil} means that @code{gnus-uu} will strip all carriage returns
from articles.

@item gnus-uu-unmark-articles-not-decoded
@vindex gnus-uu-unmark-articles-not-decoded
Non-@code{nil} means that @code{gnus-uu} will mark unsuccessfully
decoded articles as unread.

@item gnus-uu-correct-stripped-uucode
@vindex gnus-uu-correct-stripped-uucode
Non-@code{nil} means that @code{gnus-uu} will @emph{try} to fix
uuencoded files that have had trailing spaces deleted.

@item gnus-uu-pre-uudecode-hook
@vindex gnus-uu-pre-uudecode-hook
Hook run before sending a message to @code{uudecode}.

@item gnus-uu-view-with-metamail
@vindex gnus-uu-view-with-metamail
@cindex metamail
Non-@code{nil} means that @code{gnus-uu} will ignore the viewing
commands defined by the rule variables and just fudge a @acronym{MIME}
content type based on the file name.  The result will be fed to
@code{metamail} for viewing.

@item gnus-uu-save-in-digest
@vindex gnus-uu-save-in-digest
Non-@code{nil} means that @code{gnus-uu}, when asked to save without
decoding, will save in digests.  If this variable is @code{nil},
@code{gnus-uu} will just save everything in a file without any
embellishments.  The digesting almost conforms to RFC 1153---no easy way
to specify any meaningful volume and issue numbers were found, so I
simply dropped them.

@end table


@node Uuencoding and Posting
@subsubsection Uuencoding and Posting

@table @code

@item gnus-uu-post-include-before-composing
@vindex gnus-uu-post-include-before-composing
Non-@code{nil} means that @code{gnus-uu} will ask for a file to encode
before you compose the article.  If this variable is @code{t}, you can
either include an encoded file with @kbd{C-c C-i} or have one included
for you when you post the article.

@item gnus-uu-post-length
@vindex gnus-uu-post-length
Maximum length of an article.  The encoded file will be split into how
many articles it takes to post the entire file.

@item gnus-uu-post-threaded
@vindex gnus-uu-post-threaded
Non-@code{nil} means that @code{gnus-uu} will post the encoded file in a
thread.  This may not be smart, as no other decoder I have seen is able
to follow threads when collecting uuencoded articles.  (Well, I have
seen one package that does that---@code{gnus-uu}, but somehow, I don't
think that counts@dots{}) Default is @code{nil}.

@item gnus-uu-post-separate-description
@vindex gnus-uu-post-separate-description
Non-@code{nil} means that the description will be posted in a separate
article.  The first article will typically be numbered (0/x).  If this
variable is @code{nil}, the description the user enters will be included
at the beginning of the first article, which will be numbered (1/x).
Default is @code{t}.

@end table


@node Viewing Files
@subsection Viewing Files
@cindex viewing files
@cindex pseudo-articles

After decoding, if the file is some sort of archive, gnus will attempt
to unpack the archive and see if any of the files in the archive can be
viewed.  For instance, if you have a gzipped tar file @file{pics.tar.gz}
containing the files @file{pic1.jpg} and @file{pic2.gif}, gnus will
uncompress and de-tar the main file, and then view the two pictures.
This unpacking process is recursive, so if the archive contains archives
of archives, it'll all be unpacked.

Finally, gnus will normally insert a @dfn{pseudo-article} for each
extracted file into the summary buffer.  If you go to these
``articles'', you will be prompted for a command to run (usually Gnus
will make a suggestion), and then the command will be run.

@vindex gnus-view-pseudo-asynchronously
If @code{gnus-view-pseudo-asynchronously} is @code{nil}, Emacs will wait
until the viewing is done before proceeding.

@vindex gnus-view-pseudos
If @code{gnus-view-pseudos} is @code{automatic}, Gnus will not insert
the pseudo-articles into the summary buffer, but view them
immediately.  If this variable is @code{not-confirm}, the user won't even
be asked for a confirmation before viewing is done.

@vindex gnus-view-pseudos-separately
If @code{gnus-view-pseudos-separately} is non-@code{nil}, one
pseudo-article will be created for each file to be viewed.  If
@code{nil}, all files that use the same viewing command will be given as
a list of parameters to that command.

@vindex gnus-insert-pseudo-articles
If @code{gnus-insert-pseudo-articles} is non-@code{nil}, insert
pseudo-articles when decoding.  It is @code{t} by default.

So; there you are, reading your @emph{pseudo-articles} in your
@emph{virtual newsgroup} from the @emph{virtual server}; and you think:
Why isn't anything real anymore? How did we get here?


@node Article Treatment
@section Article Treatment

Reading through this huge manual, you may have quite forgotten that the
object of newsreaders is to actually, like, read what people have
written.  Reading articles.  Unfortunately, people are quite bad at
writing, so there are tons of functions and variables to make reading
these articles easier.

@menu
* Article Highlighting::        You want to make the article look like fruit salad.
* Article Fontisizing::         Making emphasized text look nice.
* Article Hiding::              You also want to make certain info go away.
* Article Washing::             Lots of way-neat functions to make life better.
* Article Header::              Doing various header transformations.
* Article Buttons::             Click on URLs, Message-IDs, addresses and the like.
* Article Button Levels::       Controlling appearance of buttons.
* Article Date::                Grumble, UT!
* Article Display::             Display various stuff---X-Face, Picons, Smileys
* Article Signature::           What is a signature?
* Article Miscellanea::         Various other stuff.
@end menu


@node Article Highlighting
@subsection Article Highlighting
@cindex highlighting

Not only do you want your article buffer to look like fruit salad, but
you want it to look like technicolor fruit salad.

@table @kbd

@item W H a
@kindex W H a (Summary)
@findex gnus-article-highlight
@findex gnus-article-maybe-highlight
Do much highlighting of the current article
(@code{gnus-article-highlight}).  This function highlights header, cited
text, the signature, and adds buttons to the body and the head.

@item W H h
@kindex W H h (Summary)
@findex gnus-article-highlight-headers
@vindex gnus-header-face-alist
Highlight the headers (@code{gnus-article-highlight-headers}).  The
highlighting will be done according to the @code{gnus-header-face-alist}
variable, which is a list where each element has the form
@code{(@var{regexp} @var{name} @var{content})}.
@var{regexp} is a regular expression for matching the
header, @var{name} is the face used for highlighting the header name
(@pxref{Faces and Fonts}) and @var{content} is the face for highlighting
the header value.  The first match made will be used.  Note that
@var{regexp} shouldn't have @samp{^} prepended---Gnus will add one.

@item W H c
@kindex W H c (Summary)
@findex gnus-article-highlight-citation
Highlight cited text (@code{gnus-article-highlight-citation}).

Some variables to customize the citation highlights:

@table @code
@vindex gnus-cite-parse-max-size

@item gnus-cite-parse-max-size
If the article size if bigger than this variable (which is 25000 by
default), no citation highlighting will be performed.

@item gnus-cite-max-prefix
@vindex gnus-cite-max-prefix
Maximum possible length for a citation prefix (default 20).

@item gnus-cite-face-list
@vindex gnus-cite-face-list
List of faces used for highlighting citations (@pxref{Faces and Fonts}).
When there are citations from multiple articles in the same message,
gnus will try to give each citation from each article its own face.
This should make it easier to see who wrote what.

@item gnus-supercite-regexp
@vindex gnus-supercite-regexp
Regexp matching normal Supercite attribution lines.

@item gnus-supercite-secondary-regexp
@vindex gnus-supercite-secondary-regexp
Regexp matching mangled Supercite attribution lines.

@item gnus-cite-minimum-match-count
@vindex gnus-cite-minimum-match-count
Minimum number of identical prefixes we have to see before we believe
that it's a citation.

@item gnus-cite-attribution-prefix
@vindex gnus-cite-attribution-prefix
Regexp matching the beginning of an attribution line.

@item gnus-cite-attribution-suffix
@vindex gnus-cite-attribution-suffix
Regexp matching the end of an attribution line.

@item gnus-cite-attribution-face
@vindex gnus-cite-attribution-face
Face used for attribution lines.  It is merged with the face for the
cited text belonging to the attribution.

@end table


@item W H s
@kindex W H s (Summary)
@vindex gnus-signature-separator
@vindex gnus-signature-face
@findex gnus-article-highlight-signature
Highlight the signature (@code{gnus-article-highlight-signature}).
Everything after @code{gnus-signature-separator} (@pxref{Article
Signature}) in an article will be considered a signature and will be
highlighted with @code{gnus-signature-face}, which is @code{italic} by
default.

@end table

@xref{Customizing Articles}, for how to highlight articles automatically.


@node Article Fontisizing
@subsection Article Fontisizing
@cindex emphasis
@cindex article emphasis

@findex gnus-article-emphasize
@kindex W e (Summary)
People commonly add emphasis to words in news articles by writing things
like @samp{_this_} or @samp{*this*} or @samp{/this/}.  Gnus can make
this look nicer by running the article through the @kbd{W e}
(@code{gnus-article-emphasize}) command.

@vindex gnus-emphasis-alist
How the emphasis is computed is controlled by the
@code{gnus-emphasis-alist} variable.  This is an alist where the first
element is a regular expression to be matched.  The second is a number
that says what regular expression grouping is used to find the entire
emphasized word.  The third is a number that says what regexp grouping
should be displayed and highlighted.  (The text between these two
groupings will be hidden.)  The fourth is the face used for
highlighting.

@lisp
(setq gnus-emphasis-alist
      '(("_\\(\\w+\\)_" 0 1 gnus-emphasis-underline)
        ("\\*\\(\\w+\\)\\*" 0 1 gnus-emphasis-bold)))
@end lisp

@cindex slash
@cindex asterisk
@cindex underline
@cindex /
@cindex *

@vindex gnus-emphasis-underline
@vindex gnus-emphasis-bold
@vindex gnus-emphasis-italic
@vindex gnus-emphasis-underline-bold
@vindex gnus-emphasis-underline-italic
@vindex gnus-emphasis-bold-italic
@vindex gnus-emphasis-underline-bold-italic
By default, there are seven rules, and they use the following faces:
@code{gnus-emphasis-bold}, @code{gnus-emphasis-italic},
@code{gnus-emphasis-underline}, @code{gnus-emphasis-bold-italic},
@code{gnus-emphasis-underline-italic},
@code{gnus-emphasis-underline-bold}, and
@code{gnus-emphasis-underline-bold-italic}.

If you want to change these faces, you can either use @kbd{M-x
customize}, or you can use @code{copy-face}.  For instance, if you want
to make @code{gnus-emphasis-italic} use a red face instead, you could
say something like:

@lisp
(copy-face 'red 'gnus-emphasis-italic)
@end lisp

@vindex gnus-group-highlight-words-alist

If you want to highlight arbitrary words, you can use the
@code{gnus-group-highlight-words-alist} variable, which uses the same
syntax as @code{gnus-emphasis-alist}.  The @code{highlight-words} group
parameter (@pxref{Group Parameters}) can also be used.

@xref{Customizing Articles}, for how to fontize articles automatically.


@node Article Hiding
@subsection Article Hiding
@cindex article hiding

Or rather, hiding certain things in each article.  There usually is much
too much cruft in most articles.

@table @kbd

@item W W a
@kindex W W a (Summary)
@findex gnus-article-hide
Do quite a lot of hiding on the article buffer
(@kbd{gnus-article-hide}).  In particular, this function will hide
headers, @acronym{PGP}, cited text and the signature.

@item W W h
@kindex W W h (Summary)
@findex gnus-article-hide-headers
Hide headers (@code{gnus-article-hide-headers}).  @xref{Hiding
Headers}.

@item W W b
@kindex W W b (Summary)
@findex gnus-article-hide-boring-headers
Hide headers that aren't particularly interesting
(@code{gnus-article-hide-boring-headers}).  @xref{Hiding Headers}.

@item W W s
@kindex W W s (Summary)
@findex gnus-article-hide-signature
Hide signature (@code{gnus-article-hide-signature}).  @xref{Article
Signature}.

@item W W l
@kindex W W l (Summary)
@findex gnus-article-hide-list-identifiers
@vindex gnus-list-identifiers
Strip list identifiers specified in @code{gnus-list-identifiers}.  These
are strings some mailing list servers add to the beginning of all
@code{Subject} headers---for example, @samp{[zebra 4711]}.  Any leading
@samp{Re: } is skipped before stripping.  @code{gnus-list-identifiers}
may not contain @code{\\(..\\)}.

@table @code

@item gnus-list-identifiers
@vindex gnus-list-identifiers
A regular expression that matches list identifiers to be removed from
subject.  This can also be a list of regular expressions.

@end table

@item W W P
@kindex W W P (Summary)
@findex gnus-article-hide-pem
Hide @acronym{PEM} (privacy enhanced messages) cruft
(@code{gnus-article-hide-pem}).

@item W W B
@kindex W W B (Summary)
@findex gnus-article-strip-banner
@vindex gnus-article-banner-alist
@vindex gnus-article-address-banner-alist
@cindex banner
@cindex OneList
@cindex stripping advertisements
@cindex advertisements
Strip the banner specified by the @code{banner} group parameter
(@code{gnus-article-strip-banner}).  This is mainly used to hide those
annoying banners and/or signatures that some mailing lists and moderated
groups adds to all the messages.  The way to use this function is to add
the @code{banner} group parameter (@pxref{Group Parameters}) to the
group you want banners stripped from.  The parameter either be a string,
which will be interpreted as a regular expression matching text to be
removed, or the symbol @code{signature}, meaning that the (last)
signature should be removed, or other symbol, meaning that the
corresponding regular expression in @code{gnus-article-banner-alist} is
used.

Regardless of a group, you can hide things like advertisements only when
the sender of an article has a certain mail address specified in
@code{gnus-article-address-banner-alist}.

@table @code

@item gnus-article-address-banner-alist
@vindex gnus-article-address-banner-alist
Alist of mail addresses and banners.  Each element has the form
@code{(@var{address} . @var{banner})}, where @var{address} is a regexp
matching a mail address in the From header, @var{banner} is one of a
symbol @code{signature}, an item in @code{gnus-article-banner-alist},
a regexp and @code{nil}.  If @var{address} matches author's mail
address, it will remove things like advertisements.  For example, if a
sender has the mail address @samp{hail@@yoo-hoo.co.jp} and there is a
banner something like @samp{Do You Yoo-hoo!?} in all articles he
sends, you can use the following element to remove them:

@lisp
("@@yoo-hoo\\.co\\.jp\\'" .
 "\n_+\nDo You Yoo-hoo!\\?\n.*\n.*\n")
@end lisp

@end table

@item W W c
@kindex W W c (Summary)
@findex gnus-article-hide-citation
Hide citation (@code{gnus-article-hide-citation}).  Some variables for
customizing the hiding:

@table @code

@item gnus-cited-opened-text-button-line-format
@itemx gnus-cited-closed-text-button-line-format
@vindex gnus-cited-closed-text-button-line-format
@vindex gnus-cited-opened-text-button-line-format
Gnus adds buttons to show where the cited text has been hidden, and to
allow toggle hiding the text.  The format of the variable is specified
by these format-like variable (@pxref{Formatting Variables}).  These
specs are valid:

@table @samp
@item b
Starting point of the hidden text.
@item e
Ending point of the hidden text.
@item l
Number of characters in the hidden region.
@item n
Number of lines of hidden text.
@end table

@item gnus-cited-lines-visible
@vindex gnus-cited-lines-visible
The number of lines at the beginning of the cited text to leave
shown.  This can also be a cons cell with the number of lines at the top
and bottom of the text, respectively, to remain visible.

@end table

@item W W C-c
@kindex W W C-c (Summary)
@findex gnus-article-hide-citation-maybe

Hide citation (@code{gnus-article-hide-citation-maybe}) depending on the
following two variables:

@table @code
@item gnus-cite-hide-percentage
@vindex gnus-cite-hide-percentage
If the cited text is of a bigger percentage than this variable (default
50), hide the cited text.

@item gnus-cite-hide-absolute
@vindex gnus-cite-hide-absolute
The cited text must have at least this length (default 10) before it
is hidden.
@end table

@item W W C
@kindex W W C (Summary)
@findex gnus-article-hide-citation-in-followups
Hide cited text in articles that aren't roots
(@code{gnus-article-hide-citation-in-followups}).  This isn't very
useful as an interactive command, but might be a handy function to stick
have happen automatically (@pxref{Customizing Articles}).

@end table

All these ``hiding'' commands are toggles, but if you give a negative
prefix to these commands, they will show what they have previously
hidden.  If you give a positive prefix, they will always hide.

Also @pxref{Article Highlighting} for further variables for
citation customization.

@xref{Customizing Articles}, for how to hide article elements
automatically.


@node Article Washing
@subsection Article Washing
@cindex washing
@cindex article washing

We call this ``article washing'' for a really good reason.  Namely, the
@kbd{A} key was taken, so we had to use the @kbd{W} key instead.

@dfn{Washing} is defined by us as ``changing something from something to
something else'', but normally results in something looking better.
Cleaner, perhaps.

@xref{Customizing Articles}, if you want to change how Gnus displays
articles by default.

@table @kbd

@item C-u g
This is not really washing, it's sort of the opposite of washing.  If
you type this, you see the article exactly as it exists on disk or on
the server.

@item g
Force redisplaying of the current article
(@code{gnus-summary-show-article}).  This is also not really washing.
If you type this, you see the article without any previously applied
interactive Washing functions but with all default treatments
(@pxref{Customizing Articles}).

@item W l
@kindex W l (Summary)
@findex gnus-summary-stop-page-breaking
Remove page breaks from the current article
(@code{gnus-summary-stop-page-breaking}).  @xref{Misc Article}, for page
delimiters.

@item W r
@kindex W r (Summary)
@findex gnus-summary-caesar-message
@c @icon{gnus-summary-caesar-message}
Do a Caesar rotate (rot13) on the article buffer
(@code{gnus-summary-caesar-message}).
Unreadable articles that tell you to read them with Caesar rotate or rot13.
(Typically offensive jokes and such.)

It's commonly called ``rot13'' because each letter is rotated 13
positions in the alphabet, e. g. @samp{B} (letter #2) -> @samp{O} (letter
#15).  It is sometimes referred to as ``Caesar rotate'' because Caesar
is rumored to have employed this form of, uh, somewhat weak encryption.

@item W m
@kindex W m (Summary)
@findex gnus-summary-morse-message
Morse decode the article buffer (@code{gnus-summary-morse-message}).

@item W t
@item t
@kindex W t (Summary)
@kindex t (Summary)
@findex gnus-summary-toggle-header
Toggle whether to display all headers in the article buffer
(@code{gnus-summary-toggle-header}).

@item W v
@kindex W v (Summary)
@findex gnus-summary-verbose-headers
Toggle whether to display all headers in the article buffer permanently
(@code{gnus-summary-verbose-headers}).

@item W m
@kindex W m (Summary)
@findex gnus-summary-toggle-mime
Toggle whether to run the article through @acronym{MIME} before
displaying (@code{gnus-summary-toggle-mime}).

@item W o
@kindex W o (Summary)
@findex gnus-article-treat-overstrike
Treat overstrike (@code{gnus-article-treat-overstrike}).

@item W d
@kindex W d (Summary)
@findex gnus-article-treat-dumbquotes
@vindex gnus-article-dumbquotes-map
@cindex Smartquotes
@cindex M****s*** sm*rtq**t*s
@cindex Latin 1
Treat M****s*** sm*rtq**t*s according to
@code{gnus-article-dumbquotes-map}
(@code{gnus-article-treat-dumbquotes}).  Note that this function guesses
whether a character is a sm*rtq**t* or not, so it should only be used
interactively.

Sm*rtq**t*s are M****s***'s unilateral extension to the character map in
an attempt to provide more quoting characters.  If you see something
like @code{\222} or @code{\264} where you're expecting some kind of
apostrophe or quotation mark, then try this wash.

@item W Y f
@kindex W Y f (Summary)
@findex gnus-article-outlook-deuglify-article
@cindex Outlook Express
Full deuglify of broken Outlook (Express) articles: Treat dumbquotes,
unwrap lines, repair attribution and rearrange citation.
(@code{gnus-article-outlook-deuglify-article}).

@item W Y u
@kindex W Y u (Summary)
@findex gnus-article-outlook-unwrap-lines
@vindex gnus-outlook-deuglify-unwrap-min
@vindex gnus-outlook-deuglify-unwrap-max
Unwrap lines that appear to be wrapped citation lines.  You can control
what lines will be unwrapped by frobbing
@code{gnus-outlook-deuglify-unwrap-min} and
@code{gnus-outlook-deuglify-unwrap-max}, indicating the minimum and
maximum length of an unwrapped citation line.
(@code{gnus-article-outlook-unwrap-lines}).

@item W Y a
@kindex W Y a (Summary)
@findex gnus-article-outlook-repair-attribution
Repair a broken attribution line.@*
(@code{gnus-article-outlook-repair-attribution}).

@item W Y c
@kindex W Y c (Summary)
@findex gnus-article-outlook-rearrange-citation
Repair broken citations by rearranging the text.
(@code{gnus-article-outlook-rearrange-citation}).

@item W w
@kindex W w (Summary)
@findex gnus-article-fill-cited-article
Do word wrap (@code{gnus-article-fill-cited-article}).

You can give the command a numerical prefix to specify the width to use
when filling.

@item W Q
@kindex W Q (Summary)
@findex gnus-article-fill-long-lines
Fill long lines (@code{gnus-article-fill-long-lines}).

@item W C
@kindex W C (Summary)
@findex gnus-article-capitalize-sentences
Capitalize the first word in each sentence
(@code{gnus-article-capitalize-sentences}).

@item W c
@kindex W c (Summary)
@findex gnus-article-remove-cr
Translate CRLF pairs (i. e., @samp{^M}s on the end of the lines) into LF
(this takes care of DOS line endings), and then translate any remaining
CRs into LF (this takes care of Mac line endings)
(@code{gnus-article-remove-cr}).

@kindex W q (Summary)
@findex gnus-article-de-quoted-unreadable
Treat quoted-printable (@code{gnus-article-de-quoted-unreadable}).
Quoted-Printable is one common @acronym{MIME} encoding employed when
sending non-@acronym{ASCII} (i.e., 8-bit) articles.  It typically
makes strings like @samp{déjà vu} look like @samp{d=E9j=E0 vu}, which
doesn't look very readable to me.  Note that this is usually done
automatically by Gnus if the message in question has a
@code{Content-Transfer-Encoding} header that says that this encoding
has been done.  If a prefix is given, a charset will be asked for.

@item W 6
@kindex W 6 (Summary)
@findex gnus-article-de-base64-unreadable
Treat base64 (@code{gnus-article-de-base64-unreadable}).  Base64 is
one common @acronym{MIME} encoding employed when sending
non-@acronym{ASCII} (i.e., 8-bit) articles.  Note that this is
usually done automatically by Gnus if the message in question has a
@code{Content-Transfer-Encoding} header that says that this encoding
has been done.  If a prefix is given, a charset will be asked for.

@item W Z
@kindex W Z (Summary)
@findex gnus-article-decode-HZ
Treat HZ or HZP (@code{gnus-article-decode-HZ}).  HZ (or HZP) is one
common encoding employed when sending Chinese articles.  It typically
makes strings look like @samp{~@{<:Ky2;S@{#,NpJ)l6HK!#~@}}.

@item W u
@kindex W u (Summary)
@findex gnus-article-unsplit-urls
Remove newlines from within URLs.  Some mailers insert newlines into
outgoing email messages to keep lines short.  This reformatting can
split long URLs onto multiple lines.  Repair those URLs by removing
the newlines (@code{gnus-article-unsplit-urls}).

@item W h
@kindex W h (Summary)
@findex gnus-article-wash-html
Treat @acronym{HTML} (@code{gnus-article-wash-html}).  Note that this is
usually done automatically by Gnus if the message in question has a
@code{Content-Type} header that says that the message is @acronym{HTML}.

If a prefix is given, a charset will be asked for.

@vindex gnus-article-wash-function
The default is to use the function specified by
@code{mm-text-html-renderer} (@pxref{Display Customization, ,Display
Customization, emacs-mime, The Emacs MIME Manual}) to convert the
@acronym{HTML}, but this is controlled by the
@code{gnus-article-wash-function} variable.  Pre-defined functions you
can use include:

@table @code
@item w3
Use Emacs/w3.

@item w3m
Use @uref{http://emacs-w3m.namazu.org/, emacs-w3m}.

@item links
Use @uref{http://links.sf.net/, Links}.

@item lynx
Use @uref{http://lynx.isc.org/, Lynx}.

@item html2text
Use html2text---a simple @acronym{HTML} converter included with Gnus.

@end table

@item W b
@kindex W b (Summary)
@findex gnus-article-add-buttons
Add clickable buttons to the article (@code{gnus-article-add-buttons}).
@xref{Article Buttons}.

@item W B
@kindex W B (Summary)
@findex gnus-article-add-buttons-to-head
Add clickable buttons to the article headers
(@code{gnus-article-add-buttons-to-head}).

@item W p
@kindex W p (Summary)
@findex gnus-article-verify-x-pgp-sig
Verify a signed control message
(@code{gnus-article-verify-x-pgp-sig}).  Control messages such as
@code{newgroup} and @code{checkgroups} are usually signed by the
hierarchy maintainer.  You need to add the @acronym{PGP} public key of
the maintainer to your keyring to verify the
message.@footnote{@acronym{PGP} keys for many hierarchies are
available at @uref{ftp://ftp.isc.org/pub/pgpcontrol/README.html}}

@item W s
@kindex W s (Summary)
@findex gnus-summary-force-verify-and-decrypt
Verify a signed (@acronym{PGP}, @acronym{PGP/MIME} or
@acronym{S/MIME}) message
(@code{gnus-summary-force-verify-and-decrypt}). @xref{Security}.

@item W a
@kindex W a (Summary)
@findex gnus-article-strip-headers-in-body
Strip headers like the @code{X-No-Archive} header from the beginning of
article bodies (@code{gnus-article-strip-headers-in-body}).

@item W E l
@kindex W E l (Summary)
@findex gnus-article-strip-leading-blank-lines
Remove all blank lines from the beginning of the article
(@code{gnus-article-strip-leading-blank-lines}).

@item W E m
@kindex W E m (Summary)
@findex gnus-article-strip-multiple-blank-lines
Replace all blank lines with empty lines and then all multiple empty
lines with a single empty line.
(@code{gnus-article-strip-multiple-blank-lines}).

@item W E t
@kindex W E t (Summary)
@findex gnus-article-remove-trailing-blank-lines
Remove all blank lines at the end of the article
(@code{gnus-article-remove-trailing-blank-lines}).

@item W E a
@kindex W E a (Summary)
@findex gnus-article-strip-blank-lines
Do all the three commands above
(@code{gnus-article-strip-blank-lines}).

@item W E A
@kindex W E A (Summary)
@findex gnus-article-strip-all-blank-lines
Remove all blank lines
(@code{gnus-article-strip-all-blank-lines}).

@item W E s
@kindex W E s (Summary)
@findex gnus-article-strip-leading-space
Remove all white space from the beginning of all lines of the article
body (@code{gnus-article-strip-leading-space}).

@item W E e
@kindex W E e (Summary)
@findex gnus-article-strip-trailing-space
Remove all white space from the end of all lines of the article
body (@code{gnus-article-strip-trailing-space}).

@end table

@xref{Customizing Articles}, for how to wash articles automatically.


@node Article Header
@subsection Article Header

These commands perform various transformations of article header.

@table @kbd

@item W G u
@kindex W G u (Summary)
@findex gnus-article-treat-unfold-headers
Unfold folded header lines (@code{gnus-article-treat-unfold-headers}).

@item W G n
@kindex W G n (Summary)
@findex gnus-article-treat-fold-newsgroups
Fold the @code{Newsgroups} and @code{Followup-To} headers
(@code{gnus-article-treat-fold-newsgroups}).

@item W G f
@kindex W G f (Summary)
@findex gnus-article-treat-fold-headers
Fold all the message headers
(@code{gnus-article-treat-fold-headers}).

@item W E w
@kindex W E w
@findex gnus-article-remove-leading-whitespace
Remove excessive whitespace from all headers
(@code{gnus-article-remove-leading-whitespace}).

@end table


@node Article Buttons
@subsection Article Buttons
@cindex buttons

People often include references to other stuff in articles, and it would
be nice if Gnus could just fetch whatever it is that people talk about
with the minimum of fuzz when you hit @kbd{RET} or use the middle mouse
button on these references.

@vindex gnus-button-man-handler
Gnus adds @dfn{buttons} to certain standard references by default:
Well-formed URLs, mail addresses, Message-IDs, Info links, man pages and
Emacs or Gnus related references.  This is controlled by two variables,
one that handles article bodies and one that handles article heads:

@table @code

@item gnus-button-alist
@vindex gnus-button-alist
This is an alist where each entry has this form:

@lisp
(@var{regexp} @var{button-par} @var{use-p} @var{function} @var{data-par})
@end lisp

@table @var

@item regexp
All text that match this regular expression (case insensitive) will be
considered an external reference.  Here's a typical regexp that matches
embedded URLs: @samp{<URL:\\([^\n\r>]*\\)>}.  This can also be a
variable containing a regexp, useful variables to use include
@code{gnus-button-url-regexp} and @code{gnus-button-mid-or-mail-regexp}.

@item button-par
Gnus has to know which parts of the matches is to be highlighted.  This
is a number that says what sub-expression of the regexp is to be
highlighted.  If you want it all highlighted, you use 0 here.

@item use-p
This form will be @code{eval}ed, and if the result is non-@code{nil},
this is considered a match.  This is useful if you want extra sifting to
avoid false matches.  Often variables named
@code{gnus-button-@var{*}-level} are used here, @xref{Article Button
Levels}, but any other form may be used too.

@c @code{use-p} is @code{eval}ed only if @code{regexp} matches.

@item function
This function will be called when you click on this button.

@item data-par
As with @var{button-par}, this is a sub-expression number, but this one
says which part of the match is to be sent as data to @var{function}.

@end table

So the full entry for buttonizing URLs is then

@lisp
("<URL:\\([^\n\r>]*\\)>" 0 t gnus-button-url 1)
@end lisp

@item gnus-header-button-alist
@vindex gnus-header-button-alist
This is just like the other alist, except that it is applied to the
article head only, and that each entry has an additional element that is
used to say what headers to apply the buttonize coding to:

@lisp
(@var{header} @var{regexp} @var{button-par} @var{use-p} @var{function} @var{data-par})
@end lisp

@var{header} is a regular expression.
@end table

@subsubsection Related variables and functions

@table @code
@item gnus-button-@var{*}-level
@xref{Article Button Levels}.

@c Stuff related to gnus-button-browse-level

@item gnus-button-url-regexp
@vindex gnus-button-url-regexp
A regular expression that matches embedded URLs.  It is used in the
default values of the variables above.

@c Stuff related to gnus-button-man-level

@item gnus-button-man-handler
@vindex gnus-button-man-handler
The function to use for displaying man pages.  It must take at least one
argument with a string naming the man page.

@c Stuff related to gnus-button-message-level

@item gnus-button-mid-or-mail-regexp
@vindex gnus-button-mid-or-mail-regexp
Regular expression that matches a message ID or a mail address.

@item gnus-button-prefer-mid-or-mail
@vindex gnus-button-prefer-mid-or-mail
This variable determines what to do when the button on a string as
@samp{foo123@@bar.invalid} is pushed.  Strings like this can be either a
message ID or a mail address.  If it is one of the symbols @code{mid} or
@code{mail}, Gnus will always assume that the string is a message ID or
a mail address, respectively.  If this variable is set to the symbol
@code{ask}, always query the user what do do.  If it is a function, this
function will be called with the string as its only argument.  The
function must return @code{mid}, @code{mail}, @code{invalid} or
@code{ask}.  The default value is the function
@code{gnus-button-mid-or-mail-heuristic}.

@item gnus-button-mid-or-mail-heuristic
@findex gnus-button-mid-or-mail-heuristic
Function that guesses whether its argument is a message ID or a mail
address.  Returns @code{mid} if it's a message IDs, @code{mail} if
it's a mail address, @code{ask} if unsure and @code{invalid} if the
string is invalid.

@item gnus-button-mid-or-mail-heuristic-alist
@vindex gnus-button-mid-or-mail-heuristic-alist
An alist of @code{(RATE . REGEXP)} pairs used by the function
@code{gnus-button-mid-or-mail-heuristic}.

@c Stuff related to gnus-button-tex-level

@item gnus-button-ctan-handler
@findex gnus-button-ctan-handler
The function to use for displaying CTAN links.  It must take one
argument, the string naming the URL.

@item gnus-ctan-url
@vindex gnus-ctan-url
Top directory of a CTAN (Comprehensive TeX Archive Network) archive used
by @code{gnus-button-ctan-handler}.

@c Misc stuff

@item gnus-article-button-face
@vindex gnus-article-button-face
Face used on buttons.

@item gnus-article-mouse-face
@vindex gnus-article-mouse-face
Face used when the mouse cursor is over a button.

@end table

@xref{Customizing Articles}, for how to buttonize articles automatically.


@node Article Button Levels
@subsection Article button levels
@cindex button levels
The higher the value of the variables @code{gnus-button-@var{*}-level},
the more buttons will appear.  If the level is zero, no corresponding
buttons are displayed.  With the default value (which is 5) you should
already see quite a lot of buttons.  With higher levels, you will see
more buttons, but you may also get more false positives.  To avoid them,
you can set the variables @code{gnus-button-@var{*}-level} local to
specific groups (@pxref{Group Parameters}).  Here's an example for the
variable @code{gnus-parameters}:

@lisp
;; @r{increase @code{gnus-button-*-level} in some groups:}
(setq gnus-parameters
      '(("\\<\\(emacs\\|gnus\\)\\>" (gnus-button-emacs-level 10))
        ("\\<unix\\>"               (gnus-button-man-level 10))
        ("\\<tex\\>"                (gnus-button-tex-level 10))))
@end lisp

@table @code

@item gnus-button-browse-level
@vindex gnus-button-browse-level
Controls the display of references to message IDs, mail addresses and
news URLs.  Related variables and functions include
@code{gnus-button-url-regexp}, @code{browse-url}, and
@code{browse-url-browser-function}.

@item gnus-button-emacs-level
@vindex gnus-button-emacs-level
Controls the display of Emacs or Gnus references.  Related functions are
@code{gnus-button-handle-custom},
@code{gnus-button-handle-describe-function},
@code{gnus-button-handle-describe-variable},
@code{gnus-button-handle-symbol},
@code{gnus-button-handle-describe-key},
@code{gnus-button-handle-apropos},
@code{gnus-button-handle-apropos-command},
@code{gnus-button-handle-apropos-variable},
@code{gnus-button-handle-apropos-documentation}, and
@code{gnus-button-handle-library}.

@item gnus-button-man-level
@vindex gnus-button-man-level
Controls the display of references to (Unix) man pages.
See @code{gnus-button-man-handler}.

@item gnus-button-message-level
@vindex gnus-button-message-level
Controls the display of message IDs, mail addresses and news URLs.
Related variables and functions include
@code{gnus-button-mid-or-mail-regexp},
@code{gnus-button-prefer-mid-or-mail},
@code{gnus-button-mid-or-mail-heuristic}, and
@code{gnus-button-mid-or-mail-heuristic-alist}.

@item gnus-button-tex-level
@vindex gnus-button-tex-level
Controls the display of references to @TeX{} or LaTeX stuff, e.g. for CTAN
URLs.  See the variables @code{gnus-ctan-url},
@code{gnus-button-ctan-handler},
@code{gnus-button-ctan-directory-regexp}, and
@code{gnus-button-handle-ctan-bogus-regexp}.

@end table


@node Article Date
@subsection Article Date

The date is most likely generated in some obscure timezone you've never
heard of, so it's quite nice to be able to find out what the time was
when the article was sent.

@table @kbd

@item W T u
@kindex W T u (Summary)
@findex gnus-article-date-ut
Display the date in UT (aka. GMT, aka ZULU)
(@code{gnus-article-date-ut}).

@item W T i
@kindex W T i (Summary)
@findex gnus-article-date-iso8601
@cindex ISO 8601
Display the date in international format, aka. ISO 8601
(@code{gnus-article-date-iso8601}).

@item W T l
@kindex W T l (Summary)
@findex gnus-article-date-local
Display the date in the local timezone (@code{gnus-article-date-local}).

@item W T p
@kindex W T p (Summary)
@findex gnus-article-date-english
Display the date in a format that's easily pronounceable in English
(@code{gnus-article-date-english}).

@item W T s
@kindex W T s (Summary)
@vindex gnus-article-time-format
@findex gnus-article-date-user
@findex format-time-string
Display the date using a user-defined format
(@code{gnus-article-date-user}).  The format is specified by the
@code{gnus-article-time-format} variable, and is a string that's passed
to @code{format-time-string}.  See the documentation of that variable
for a list of possible format specs.

@item W T e
@kindex W T e (Summary)
@findex gnus-article-date-lapsed
@findex gnus-start-date-timer
@findex gnus-stop-date-timer
Say how much time has elapsed between the article was posted and now
(@code{gnus-article-date-lapsed}).  It looks something like:

@example
X-Sent: 6 weeks, 4 days, 1 hour, 3 minutes, 8 seconds ago
@end example

@vindex gnus-article-date-lapsed-new-header
The value of @code{gnus-article-date-lapsed-new-header} determines
whether this header will just be added below the old Date one, or will
replace it.

An advantage of using Gnus to read mail is that it converts simple bugs
into wonderful absurdities.

If you want to have this line updated continually, you can put

@lisp
(gnus-start-date-timer)
@end lisp

in your @file{~/.gnus.el} file, or you can run it off of some hook.  If
you want to stop the timer, you can use the @code{gnus-stop-date-timer}
command.

@item W T o
@kindex W T o (Summary)
@findex gnus-article-date-original
Display the original date (@code{gnus-article-date-original}).  This can
be useful if you normally use some other conversion function and are
worried that it might be doing something totally wrong.  Say, claiming
that the article was posted in 1854.  Although something like that is
@emph{totally} impossible.  Don't you trust me? *titter*

@end table

@xref{Customizing Articles}, for how to display the date in your
preferred format automatically.


@node Article Display
@subsection Article Display
@cindex picons
@cindex x-face
@cindex smileys

These commands add various frivolous display gimmicks to the article
buffer in Emacs versions that support them.

@code{X-Face} headers are small black-and-white images supplied by the
message headers (@pxref{X-Face}).

@code{Face} headers are small colored images supplied by the message
headers (@pxref{Face}).

Smileys are those little @samp{:-)} symbols that people like to litter
their messages with (@pxref{Smileys}).

Picons, on the other hand, reside on your own system, and Gnus will
try to match the headers to what you have (@pxref{Picons}).

All these functions are toggles---if the elements already exist,
they'll be removed.

@table @kbd
@item W D x
@kindex W D x (Summary)
@findex gnus-article-display-x-face
Display an @code{X-Face} in the @code{From} header.
(@code{gnus-article-display-x-face}).

@item W D d
@kindex W D d (Summary)
@findex gnus-article-display-face
Display a @code{Face} in the @code{From} header.
(@code{gnus-article-display-face}).

@item W D s
@kindex W D s (Summary)
@findex gnus-treat-smiley
Display smileys (@code{gnus-treat-smiley}).

@item W D f
@kindex W D f (Summary)
@findex gnus-treat-from-picon
Piconify the @code{From} header (@code{gnus-treat-from-picon}).

@item W D m
@kindex W D m (Summary)
@findex gnus-treat-mail-picon
Piconify all mail headers (i. e., @code{Cc}, @code{To})
(@code{gnus-treat-mail-picon}).

@item W D n
@kindex W D n (Summary)
@findex gnus-treat-newsgroups-picon
Piconify all news headers (i. e., @code{Newsgroups} and
@code{Followup-To}) (@code{gnus-treat-newsgroups-picon}).

@item W D D
@kindex W D D (Summary)
@findex gnus-article-remove-images
Remove all images from the article buffer
(@code{gnus-article-remove-images}).

@end table



@node Article Signature
@subsection Article Signature
@cindex signatures
@cindex article signature

@vindex gnus-signature-separator
Each article is divided into two parts---the head and the body.  The
body can be divided into a signature part and a text part.  The variable
that says what is to be considered a signature is
@code{gnus-signature-separator}.  This is normally the standard
@samp{^-- $} as mandated by son-of-RFC 1036.  However, many people use
non-standard signature separators, so this variable can also be a list
of regular expressions to be tested, one by one.  (Searches are done
from the end of the body towards the beginning.)  One likely value is:

@lisp
(setq gnus-signature-separator
      '("^-- $"         ; @r{The standard}
        "^-- *$"        ; @r{A common mangling}
        "^-------*$"    ; @r{Many people just use a looong}
                        ; @r{line of dashes.  Shame!}
        "^ *--------*$" ; @r{Double-shame!}
        "^________*$"   ; @r{Underscores are also popular}
        "^========*$")) ; @r{Pervert!}
@end lisp

The more permissive you are, the more likely it is that you'll get false
positives.

@vindex gnus-signature-limit
@code{gnus-signature-limit} provides a limit to what is considered a
signature when displaying articles.

@enumerate
@item
If it is an integer, no signature may be longer (in characters) than
that integer.
@item
If it is a floating point number, no signature may be longer (in lines)
than that number.
@item
If it is a function, the function will be called without any parameters,
and if it returns @code{nil}, there is no signature in the buffer.
@item
If it is a string, it will be used as a regexp.  If it matches, the text
in question is not a signature.
@end enumerate

This variable can also be a list where the elements may be of the types
listed above.  Here's an example:

@lisp
(setq gnus-signature-limit
      '(200.0 "^---*Forwarded article"))
@end lisp

This means that if there are more than 200 lines after the signature
separator, or the text after the signature separator is matched by
the regular expression @samp{^---*Forwarded article}, then it isn't a
signature after all.


@node Article Miscellanea
@subsection Article Miscellanea

@table @kbd
@item A t
@kindex A t (Summary)
@findex gnus-article-babel
Translate the article from one language to another
(@code{gnus-article-babel}).

@end table


@node MIME Commands
@section MIME Commands
@cindex MIME decoding
@cindex attachments
@cindex viewing attachments

The following commands all understand the numerical prefix.  For
instance, @kbd{3 b} means ``view the third @acronym{MIME} part''.

@table @kbd
@item b
@itemx K v
@kindex b (Summary)
@kindex K v (Summary)
View the @acronym{MIME} part.

@item K o
@kindex K o (Summary)
Save the @acronym{MIME} part.

@item K c
@kindex K c (Summary)
Copy the @acronym{MIME} part.

@item K e
@kindex K e (Summary)
View the @acronym{MIME} part externally.

@item K i
@kindex K i (Summary)
View the @acronym{MIME} part internally.

@item K |
@kindex K | (Summary)
Pipe the @acronym{MIME} part to an external command.
@end table

The rest of these @acronym{MIME} commands do not use the numerical prefix in
the same manner:

@table @kbd
@item K b
@kindex K b (Summary)
Make all the @acronym{MIME} parts have buttons in front of them.  This is
mostly useful if you wish to save (or perform other actions) on inlined
parts.

@item K m
@kindex K m (Summary)
@findex gnus-summary-repair-multipart
Some multipart messages are transmitted with missing or faulty headers.
This command will attempt to ``repair'' these messages so that they can
be viewed in a more pleasant manner
(@code{gnus-summary-repair-multipart}).

@item X m
@kindex X m (Summary)
@findex gnus-summary-save-parts
Save all parts matching a @acronym{MIME} type to a directory
(@code{gnus-summary-save-parts}).  Understands the process/prefix
convention (@pxref{Process/Prefix}).

@item M-t
@kindex M-t (Summary)
@findex gnus-summary-toggle-display-buttonized
Toggle the buttonized display of the article buffer
(@code{gnus-summary-toggle-display-buttonized}).

@item W M w
@kindex W M w (Summary)
@findex gnus-article-decode-mime-words
Decode RFC 2047-encoded words in the article headers
(@code{gnus-article-decode-mime-words}).

@item W M c
@kindex W M c (Summary)
@findex gnus-article-decode-charset
Decode encoded article bodies as well as charsets
(@code{gnus-article-decode-charset}).

This command looks in the @code{Content-Type} header to determine the
charset.  If there is no such header in the article, you can give it a
prefix, which will prompt for the charset to decode as.  In regional
groups where people post using some common encoding (but do not
include @acronym{MIME} headers), you can set the @code{charset} group/topic
parameter to the required charset (@pxref{Group Parameters}).

@item W M v
@kindex W M v (Summary)
@findex gnus-mime-view-all-parts
View all the @acronym{MIME} parts in the current article
(@code{gnus-mime-view-all-parts}).

@end table

Relevant variables:

@table @code
@item gnus-ignored-mime-types
@vindex gnus-ignored-mime-types
This is a list of regexps.  @acronym{MIME} types that match a regexp from
this list will be completely ignored by Gnus.  The default value is
@code{nil}.

To have all Vcards be ignored, you'd say something like this:

@lisp
(setq gnus-ignored-mime-types
      '("text/x-vcard"))
@end lisp

@item gnus-article-loose-mime
@vindex gnus-article-loose-mime
If non-@code{nil}, Gnus won't require the @samp{MIME-Version} header
before interpreting the message as a @acronym{MIME} message.  This helps
when reading messages from certain broken mail user agents.  The
default is @code{nil}.

@item gnus-article-emulate-mime
@vindex gnus-article-emulate-mime
There are other, non-@acronym{MIME} encoding methods used.  The most common
is @samp{uuencode}, but yEncode is also getting to be popular.  If
this variable is non-@code{nil}, Gnus will look in message bodies to
see if it finds these encodings, and if so, it'll run them through the
Gnus @acronym{MIME} machinery.  The default is @code{t}.

@item gnus-unbuttonized-mime-types
@vindex gnus-unbuttonized-mime-types
This is a list of regexps.  @acronym{MIME} types that match a regexp from
this list won't have @acronym{MIME} buttons inserted unless they aren't
displayed or this variable is overridden by
@code{gnus-buttonized-mime-types}.  The default value is
@code{(".*/.*")}.  This variable is only used when
@code{gnus-inhibit-mime-unbuttonizing} is @code{nil}.

@item gnus-buttonized-mime-types
@vindex gnus-buttonized-mime-types
This is a list of regexps.  @acronym{MIME} types that match a regexp from
this list will have @acronym{MIME} buttons inserted unless they aren't
displayed.  This variable overrides
@code{gnus-unbuttonized-mime-types}.  The default value is @code{nil}.
This variable is only used when @code{gnus-inhibit-mime-unbuttonizing}
is @code{nil}.

To see e.g. security buttons but no other buttons, you could set this
variable to @code{("multipart/signed")} and leave
@code{gnus-unbuttonized-mime-types} at the default value.

@item gnus-inhibit-mime-unbuttonizing
@vindex gnus-inhibit-mime-unbuttonizing
If this is non-@code{nil}, then all @acronym{MIME} parts get buttons.  The
default value is @code{nil}.

@item gnus-article-mime-part-function
@vindex gnus-article-mime-part-function
For each @acronym{MIME} part, this function will be called with the @acronym{MIME}
handle as the parameter.  The function is meant to be used to allow
users to gather information from the article (e. g., add Vcard info to
the bbdb database) or to do actions based on parts (e. g., automatically
save all jpegs into some directory).

Here's an example function the does the latter:

@lisp
(defun my-save-all-jpeg-parts (handle)
  (when (equal (car (mm-handle-type handle)) "image/jpeg")
    (with-temp-buffer
      (insert (mm-get-part handle))
      (write-region (point-min) (point-max)
                    (read-file-name "Save jpeg to: ")))))
(setq gnus-article-mime-part-function
      'my-save-all-jpeg-parts)
@end lisp

@vindex gnus-mime-multipart-functions
@item gnus-mime-multipart-functions
Alist of @acronym{MIME} multipart types and functions to handle them.

@vindex mm-file-name-rewrite-functions
@item mm-file-name-rewrite-functions
List of functions used for rewriting file names of @acronym{MIME} parts.
Each function takes a file name as input and returns a file name.

Ready-made functions include@*
@code{mm-file-name-delete-whitespace},
@code{mm-file-name-trim-whitespace},
@code{mm-file-name-collapse-whitespace}, and
@code{mm-file-name-replace-whitespace}.  The later uses the value of
the variable @code{mm-file-name-replace-whitespace} to replace each
whitespace character in a file name with that string; default value
is @code{"_"} (a single underscore).
@findex mm-file-name-delete-whitespace
@findex mm-file-name-trim-whitespace
@findex mm-file-name-collapse-whitespace
@findex mm-file-name-replace-whitespace
@vindex mm-file-name-replace-whitespace

The standard functions @code{capitalize}, @code{downcase},
@code{upcase}, and @code{upcase-initials} may be useful, too.

Everybody knows that whitespace characters in file names are evil,
except those who don't know.  If you receive lots of attachments from
such unenlightened users, you can make live easier by adding

@lisp
(setq mm-file-name-rewrite-functions
      '(mm-file-name-trim-whitespace
        mm-file-name-collapse-whitespace
        mm-file-name-replace-whitespace))
@end lisp

@noindent
to your @file{~/.gnus.el} file.

@end table


@node Charsets
@section Charsets
@cindex charsets

People use different charsets, and we have @acronym{MIME} to let us know what
charsets they use.  Or rather, we wish we had.  Many people use
newsreaders and mailers that do not understand or use @acronym{MIME}, and
just send out messages without saying what character sets they use.  To
help a bit with this, some local news hierarchies have policies that say
what character set is the default.  For instance, the @samp{fj}
hierarchy uses @code{iso-2022-jp-2}.

@vindex gnus-group-charset-alist
This knowledge is encoded in the @code{gnus-group-charset-alist}
variable, which is an alist of regexps (use the first item to match full
group names) and default charsets to be used when reading these groups.

@vindex gnus-newsgroup-ignored-charsets
In addition, some people do use soi-disant @acronym{MIME}-aware agents that
aren't.  These blithely mark messages as being in @code{iso-8859-1}
even if they really are in @code{koi-8}.  To help here, the
@code{gnus-newsgroup-ignored-charsets} variable can be used.  The
charsets that are listed here will be ignored.  The variable can be
set on a group-by-group basis using the group parameters (@pxref{Group
Parameters}).  The default value is @code{(unknown-8bit x-unknown)},
which includes values some agents insist on having in there.

@vindex gnus-group-posting-charset-alist
When posting, @code{gnus-group-posting-charset-alist} is used to
determine which charsets should not be encoded using the @acronym{MIME}
encodings.  For instance, some hierarchies discourage using
quoted-printable header encoding.

This variable is an alist of regexps and permitted unencoded charsets
for posting.  Each element of the alist has the form @code{(}@var{test
header body-list}@code{)}, where:

@table @var
@item test
is either a regular expression matching the newsgroup header or a
variable to query,
@item header
is the charset which may be left unencoded in the header (@code{nil}
means encode all charsets),
@item body-list
is a list of charsets which may be encoded using 8bit content-transfer
encoding in the body, or one of the special values @code{nil} (always
encode using quoted-printable) or @code{t} (always use 8bit).
@end table

@cindex Russian
@cindex koi8-r
@cindex koi8-u
@cindex iso-8859-5
@cindex coding system aliases
@cindex preferred charset

Other charset tricks that may be useful, although not Gnus-specific:

If there are several @acronym{MIME} charsets that encode the same Emacs
charset, you can choose what charset to use by saying the following:

@lisp
(put-charset-property 'cyrillic-iso8859-5
                      'preferred-coding-system 'koi8-r)
@end lisp

This means that Russian will be encoded using @code{koi8-r} instead of
the default @code{iso-8859-5} @acronym{MIME} charset.

If you want to read messages in @code{koi8-u}, you can cheat and say

@lisp
(define-coding-system-alias 'koi8-u 'koi8-r)
@end lisp

This will almost do the right thing.

And finally, to read charsets like @code{windows-1251}, you can say
something like

@lisp
(codepage-setup 1251)
(define-coding-system-alias 'windows-1251 'cp1251)
@end lisp


@node Article Commands
@section Article Commands

@table @kbd

@item A P
@cindex PostScript
@cindex printing
@kindex A P (Summary)
@vindex gnus-ps-print-hook
@findex gnus-summary-print-article
Generate and print a PostScript image of the article buffer
(@code{gnus-summary-print-article}).  @code{gnus-ps-print-hook} will
be run just before printing the buffer.  An alternative way to print
article is to use Muttprint (@pxref{Saving Articles}).

@end table


@node Summary Sorting
@section Summary Sorting
@cindex summary sorting

You can have the summary buffer sorted in various ways, even though I
can't really see why you'd want that.

@table @kbd

@item C-c C-s C-n
@kindex C-c C-s C-n (Summary)
@findex gnus-summary-sort-by-number
Sort by article number (@code{gnus-summary-sort-by-number}).

@item C-c C-s C-a
@kindex C-c C-s C-a (Summary)
@findex gnus-summary-sort-by-author
Sort by author (@code{gnus-summary-sort-by-author}).

@item C-c C-s C-s
@kindex C-c C-s C-s (Summary)
@findex gnus-summary-sort-by-subject
Sort by subject (@code{gnus-summary-sort-by-subject}).

@item C-c C-s C-d
@kindex C-c C-s C-d (Summary)
@findex gnus-summary-sort-by-date
Sort by date (@code{gnus-summary-sort-by-date}).

@item C-c C-s C-l
@kindex C-c C-s C-l (Summary)
@findex gnus-summary-sort-by-lines
Sort by lines (@code{gnus-summary-sort-by-lines}).

@item C-c C-s C-c
@kindex C-c C-s C-c (Summary)
@findex gnus-summary-sort-by-chars
Sort by article length (@code{gnus-summary-sort-by-chars}).

@item C-c C-s C-i
@kindex C-c C-s C-i (Summary)
@findex gnus-summary-sort-by-score
Sort by score (@code{gnus-summary-sort-by-score}).

@item C-c C-s C-r
@kindex C-c C-s C-r (Summary)
@findex gnus-summary-sort-by-random
Randomize (@code{gnus-summary-sort-by-random}).

@item C-c C-s C-o
@kindex C-c C-s C-o (Summary)
@findex gnus-summary-sort-by-original
Sort using the default sorting method
(@code{gnus-summary-sort-by-original}).
@end table

These functions will work both when you use threading and when you don't
use threading.  In the latter case, all summary lines will be sorted,
line by line.  In the former case, sorting will be done on a
root-by-root basis, which might not be what you were looking for.  To
toggle whether to use threading, type @kbd{T T} (@pxref{Thread
Commands}).


@node Finding the Parent
@section Finding the Parent
@cindex parent articles
@cindex referring articles

@table @kbd
@item ^
@kindex ^ (Summary)
@findex gnus-summary-refer-parent-article
If you'd like to read the parent of the current article, and it is not
displayed in the summary buffer, you might still be able to.  That is,
if the current group is fetched by @acronym{NNTP}, the parent hasn't expired
and the @code{References} in the current article are not mangled, you
can just press @kbd{^} or @kbd{A r}
(@code{gnus-summary-refer-parent-article}).  If everything goes well,
you'll get the parent.  If the parent is already displayed in the
summary buffer, point will just move to this article.

If given a positive numerical prefix, fetch that many articles back into
the ancestry.  If given a negative numerical prefix, fetch just that
ancestor.  So if you say @kbd{3 ^}, gnus will fetch the parent, the
grandparent and the grandgrandparent of the current article.  If you say
@kbd{-3 ^}, gnus will only fetch the grandgrandparent of the current
article.

@item A R (Summary)
@findex gnus-summary-refer-references
@kindex A R (Summary)
Fetch all articles mentioned in the @code{References} header of the
article (@code{gnus-summary-refer-references}).

@item A T (Summary)
@findex gnus-summary-refer-thread
@kindex A T (Summary)
Display the full thread where the current article appears
(@code{gnus-summary-refer-thread}).  This command has to fetch all the
headers in the current group to work, so it usually takes a while.  If
you do it often, you may consider setting @code{gnus-fetch-old-headers}
to @code{invisible} (@pxref{Filling In Threads}).  This won't have any
visible effects normally, but it'll make this command work a whole lot
faster.  Of course, it'll make group entry somewhat slow.

@vindex gnus-refer-thread-limit
The @code{gnus-refer-thread-limit} variable says how many old (i. e.,
articles before the first displayed in the current group) headers to
fetch when doing this command.  The default is 200.  If @code{t}, all
the available headers will be fetched.  This variable can be overridden
by giving the @kbd{A T} command a numerical prefix.

@item M-^ (Summary)
@findex gnus-summary-refer-article
@kindex M-^ (Summary)
@cindex Message-ID
@cindex fetching by Message-ID
You can also ask the @acronym{NNTP} server for an arbitrary article, no
matter what group it belongs to.  @kbd{M-^}
(@code{gnus-summary-refer-article}) will ask you for a
@code{Message-ID}, which is one of those long, hard-to-read thingies
that look something like @samp{<38o6up$6f2@@hymir.ifi.uio.no>}.  You
have to get it all exactly right.  No fuzzy searches, I'm afraid.
@end table

The current select method will be used when fetching by
@code{Message-ID} from non-news select method, but you can override this
by giving this command a prefix.

@vindex gnus-refer-article-method
If the group you are reading is located on a back end that does not
support fetching by @code{Message-ID} very well (like @code{nnspool}),
you can set @code{gnus-refer-article-method} to an @acronym{NNTP} method.  It
would, perhaps, be best if the @acronym{NNTP} server you consult is the one
updating the spool you are reading from, but that's not really
necessary.

It can also be a list of select methods, as well as the special symbol
@code{current}, which means to use the current select method.  If it
is a list, Gnus will try all the methods in the list until it finds a
match.

Here's an example setting that will first try the current method, and
then ask Google if that fails:

@lisp
(setq gnus-refer-article-method
      '(current
        (nnweb "google" (nnweb-type google))))
@end lisp

Most of the mail back ends support fetching by @code{Message-ID}, but
do not do a particularly excellent job at it.  That is, @code{nnmbox},
@code{nnbabyl}, and @code{nnmaildir} are able to locate articles from
any groups, while @code{nnml}, @code{nnfolder}, and @code{nnimap} are
only able to locate articles that have been posted to the current group.
(Anything else would be too time consuming.)  @code{nnmh} does not
support this at all.


@node Alternative Approaches
@section Alternative Approaches

Different people like to read news using different methods.  This being
gnus, we offer a small selection of minor modes for the summary buffers.

@menu
* Pick and Read::               First mark articles and then read them.
* Binary Groups::               Auto-decode all articles.
@end menu


@node Pick and Read
@subsection Pick and Read
@cindex pick and read

Some newsreaders (like @code{nn} and, uhm, @code{Netnews} on VM/CMS) use
a two-phased reading interface.  The user first marks in a summary
buffer the articles she wants to read.  Then she starts reading the
articles with just an article buffer displayed.

@findex gnus-pick-mode
@kindex M-x gnus-pick-mode
Gnus provides a summary buffer minor mode that allows
this---@code{gnus-pick-mode}.  This basically means that a few process
mark commands become one-keystroke commands to allow easy marking, and
it provides one additional command for switching to the summary buffer.

Here are the available keystrokes when using pick mode:

@table @kbd
@item .
@kindex . (Pick)
@findex gnus-pick-article-or-thread
Pick the article or thread on the current line
(@code{gnus-pick-article-or-thread}).  If the variable
@code{gnus-thread-hide-subtree} is true, then this key selects the
entire thread when used at the first article of the thread.  Otherwise,
it selects just the article.  If given a numerical prefix, go to that
thread or article and pick it.  (The line number is normally displayed
at the beginning of the summary pick lines.)

@item SPACE
@kindex SPACE (Pick)
@findex gnus-pick-next-page
Scroll the summary buffer up one page (@code{gnus-pick-next-page}).  If
at the end of the buffer, start reading the picked articles.

@item u
@kindex u (Pick)
@findex gnus-pick-unmark-article-or-thread.
Unpick the thread or article
(@code{gnus-pick-unmark-article-or-thread}).  If the variable
@code{gnus-thread-hide-subtree} is true, then this key unpicks the
thread if used at the first article of the thread.  Otherwise it unpicks
just the article.  You can give this key a numerical prefix to unpick
the thread or article at that line.

@item RET
@kindex RET (Pick)
@findex gnus-pick-start-reading
@vindex gnus-pick-display-summary
Start reading the picked articles (@code{gnus-pick-start-reading}).  If
given a prefix, mark all unpicked articles as read first.  If
@code{gnus-pick-display-summary} is non-@code{nil}, the summary buffer
will still be visible when you are reading.

@end table

All the normal summary mode commands are still available in the
pick-mode, with the exception of @kbd{u}.  However @kbd{!} is available
which is mapped to the same function
@code{gnus-summary-tick-article-forward}.

If this sounds like a good idea to you, you could say:

@lisp
(add-hook 'gnus-summary-mode-hook 'gnus-pick-mode)
@end lisp

@vindex gnus-pick-mode-hook
@code{gnus-pick-mode-hook} is run in pick minor mode buffers.

@vindex gnus-mark-unpicked-articles-as-read
If @code{gnus-mark-unpicked-articles-as-read} is non-@code{nil}, mark
all unpicked articles as read.  The default is @code{nil}.

@vindex gnus-summary-pick-line-format
The summary line format in pick mode is slightly different from the
standard format.  At the beginning of each line the line number is
displayed.  The pick mode line format is controlled by the
@code{gnus-summary-pick-line-format} variable (@pxref{Formatting
Variables}).  It accepts the same format specs that
@code{gnus-summary-line-format} does (@pxref{Summary Buffer Lines}).


@node Binary Groups
@subsection Binary Groups
@cindex binary groups

@findex gnus-binary-mode
@kindex M-x gnus-binary-mode
If you spend much time in binary groups, you may grow tired of hitting
@kbd{X u}, @kbd{n}, @kbd{RET} all the time.  @kbd{M-x gnus-binary-mode}
is a minor mode for summary buffers that makes all ordinary Gnus article
selection functions uudecode series of articles and display the result
instead of just displaying the articles the normal way.

@kindex g (Binary)
@findex gnus-binary-show-article
The only way, in fact, to see the actual articles is the @kbd{g}
command, when you have turned on this mode
(@code{gnus-binary-show-article}).

@vindex gnus-binary-mode-hook
@code{gnus-binary-mode-hook} is called in binary minor mode buffers.


@node Tree Display
@section Tree Display
@cindex trees

@vindex gnus-use-trees
If you don't like the normal gnus summary display, you might try setting
@code{gnus-use-trees} to @code{t}.  This will create (by default) an
additional @dfn{tree buffer}.  You can execute all summary mode commands
in the tree buffer.

There are a few variables to customize the tree display, of course:

@table @code
@item gnus-tree-mode-hook
@vindex gnus-tree-mode-hook
A hook called in all tree mode buffers.

@item gnus-tree-mode-line-format
@vindex gnus-tree-mode-line-format
A format string for the mode bar in the tree mode buffers (@pxref{Mode
Line Formatting}).  The default is @samp{Gnus: %%b %S %Z}.  For a list
of valid specs, @pxref{Summary Buffer Mode Line}.

@item gnus-selected-tree-face
@vindex gnus-selected-tree-face
Face used for highlighting the selected article in the tree buffer.  The
default is @code{modeline}.

@item gnus-tree-line-format
@vindex gnus-tree-line-format
A format string for the tree nodes.  The name is a bit of a misnomer,
though---it doesn't define a line, but just the node.  The default value
is @samp{%(%[%3,3n%]%)}, which displays the first three characters of
the name of the poster.  It is vital that all nodes are of the same
length, so you @emph{must} use @samp{%4,4n}-like specifiers.

Valid specs are:

@table @samp
@item n
The name of the poster.
@item f
The @code{From} header.
@item N
The number of the article.
@item [
The opening bracket.
@item ]
The closing bracket.
@item s
The subject.
@end table

@xref{Formatting Variables}.

Variables related to the display are:

@table @code
@item gnus-tree-brackets
@vindex gnus-tree-brackets
This is used for differentiating between ``real'' articles and
``sparse'' articles.  The format is
@example
((@var{real-open} . @var{real-close})
 (@var{sparse-open} . @var{sparse-close})
 (@var{dummy-open} . @var{dummy-close}))
@end example
and the default is @code{((?[ . ?]) (?( . ?)) (?@{ . ?@}) (?< . ?>))}.

@item gnus-tree-parent-child-edges
@vindex gnus-tree-parent-child-edges
This is a list that contains the characters used for connecting parent
nodes to their children.  The default is @code{(?- ?\\ ?|)}.

@end table

@item gnus-tree-minimize-window
@vindex gnus-tree-minimize-window
If this variable is non-@code{nil}, gnus will try to keep the tree
buffer as small as possible to allow more room for the other gnus
windows.  If this variable is a number, the tree buffer will never be
higher than that number.  The default is @code{t}.  Note that if you
have several windows displayed side-by-side in a frame and the tree
buffer is one of these, minimizing the tree window will also resize all
other windows displayed next to it.

You may also wish to add the following hook to keep the window minimized
at all times:

@lisp
(add-hook 'gnus-configure-windows-hook
          'gnus-tree-perhaps-minimize)
@end lisp

@item gnus-generate-tree-function
@vindex gnus-generate-tree-function
@findex gnus-generate-horizontal-tree
@findex gnus-generate-vertical-tree
The function that actually generates the thread tree.  Two predefined
functions are available: @code{gnus-generate-horizontal-tree} and
@code{gnus-generate-vertical-tree} (which is the default).

@end table

Here's an example from a horizontal tree buffer:

@example
@{***@}-(***)-[odd]-[Gun]
     |      \[Jan]
     |      \[odd]-[Eri]
     |      \(***)-[Eri]
     |            \[odd]-[Paa]
     \[Bjo]
     \[Gun]
     \[Gun]-[Jor]
@end example

Here's the same thread displayed in a vertical tree buffer:

@example
@group
@{***@}
  |--------------------------\-----\-----\
(***)                         [Bjo] [Gun] [Gun]
  |--\-----\-----\                          |
[odd] [Jan] [odd] (***)                   [Jor]
  |           |     |--\
[Gun]       [Eri] [Eri] [odd]
                          |
                        [Paa]
@end group
@end example

If you're using horizontal trees, it might be nice to display the trees
side-by-side with the summary buffer.  You could add something like the
following to your @file{~/.gnus.el} file:

@lisp
(setq gnus-use-trees t
      gnus-generate-tree-function 'gnus-generate-horizontal-tree
      gnus-tree-minimize-window nil)
(gnus-add-configuration
 '(article
   (vertical 1.0
             (horizontal 0.25
                         (summary 0.75 point)
                         (tree 1.0))
             (article 1.0))))
@end lisp

@xref{Window Layout}.


@node Mail Group Commands
@section Mail Group Commands
@cindex mail group commands

Some commands only make sense in mail groups.  If these commands are
invalid in the current group, they will raise a hell and let you know.

All these commands (except the expiry and edit commands) use the
process/prefix convention (@pxref{Process/Prefix}).

@table @kbd

@item B e
@kindex B e (Summary)
@findex gnus-summary-expire-articles
Run all expirable articles in the current group through the expiry
process (@code{gnus-summary-expire-articles}).  That is, delete all
expirable articles in the group that have been around for a while.
(@pxref{Expiring Mail}).

@item B C-M-e
@kindex B C-M-e (Summary)
@findex gnus-summary-expire-articles-now
Delete all the expirable articles in the group
(@code{gnus-summary-expire-articles-now}).  This means that @strong{all}
articles eligible for expiry in the current group will
disappear forever into that big @file{/dev/null} in the sky.

@item B DEL
@kindex B DEL (Summary)
@findex gnus-summary-delete-article
@c @icon{gnus-summary-mail-delete}
Delete the mail article.  This is ``delete'' as in ``delete it from your
disk forever and ever, never to return again.'' Use with caution.
(@code{gnus-summary-delete-article}).

@item B m
@kindex B m (Summary)
@cindex move mail
@findex gnus-summary-move-article
@vindex gnus-preserve-marks
Move the article from one mail group to another
(@code{gnus-summary-move-article}).  Marks will be preserved if
@code{gnus-preserve-marks} is non-@code{nil} (which is the default).

@item B c
@kindex B c (Summary)
@cindex copy mail
@findex gnus-summary-copy-article
@c @icon{gnus-summary-mail-copy}
Copy the article from one group (mail group or not) to a mail group
(@code{gnus-summary-copy-article}).  Marks will be preserved if
@code{gnus-preserve-marks} is non-@code{nil} (which is the default).

@item B B
@kindex B B (Summary)
@cindex crosspost mail
@findex gnus-summary-crosspost-article
Crosspost the current article to some other group
(@code{gnus-summary-crosspost-article}).  This will create a new copy of
the article in the other group, and the Xref headers of the article will
be properly updated.

@item B i
@kindex B i (Summary)
@findex gnus-summary-import-article
Import an arbitrary file into the current mail newsgroup
(@code{gnus-summary-import-article}).  You will be prompted for a file
name, a @code{From} header and a @code{Subject} header.

@item B I
@kindex B I (Summary)
@findex gnus-summary-create-article
Create an empty article in the current mail newsgroups
(@code{gnus-summary-create-article}).  You will be prompted for a
@code{From} header and a @code{Subject} header.

@item B r
@kindex B r (Summary)
@findex gnus-summary-respool-article
@vindex gnus-summary-respool-default-method
Respool the mail article (@code{gnus-summary-respool-article}).
@code{gnus-summary-respool-default-method} will be used as the default
select method when respooling.  This variable is @code{nil} by default,
which means that the current group select method will be used instead.
Marks will be preserved if @code{gnus-preserve-marks} is non-@code{nil}
(which is the default).

@item B w
@itemx e
@kindex B w (Summary)
@kindex e (Summary)
@findex gnus-summary-edit-article
@kindex C-c C-c (Article)
@findex gnus-summary-edit-article-done
Edit the current article (@code{gnus-summary-edit-article}).  To finish
editing and make the changes permanent, type @kbd{C-c C-c}
(@code{gnus-summary-edit-article-done}).  If you give a prefix to the
@kbd{C-c C-c} command, gnus won't re-highlight the article.

@item B q
@kindex B q (Summary)
@findex gnus-summary-respool-query
If you want to re-spool an article, you might be curious as to what group
the article will end up in before you do the re-spooling.  This command
will tell you (@code{gnus-summary-respool-query}).

@item B t
@kindex B t (Summary)
@findex gnus-summary-respool-trace
Similarly, this command will display all fancy splitting patterns used
when respooling, if any (@code{gnus-summary-respool-trace}).

@item B p
@kindex B p (Summary)
@findex gnus-summary-article-posted-p
Some people have a tendency to send you ``courtesy'' copies when they
follow up to articles you have posted.  These usually have a
@code{Newsgroups} header in them, but not always.  This command
(@code{gnus-summary-article-posted-p}) will try to fetch the current
article from your news server (or rather, from
@code{gnus-refer-article-method} or @code{gnus-select-method}) and will
report back whether it found the article or not.  Even if it says that
it didn't find the article, it may have been posted anyway---mail
propagation is much faster than news propagation, and the news copy may
just not have arrived yet.

@item K E
@kindex K E (Summary)
@findex gnus-article-encrypt-body
@vindex gnus-article-encrypt-protocol
Encrypt the body of an article (@code{gnus-article-encrypt-body}).
The body is encrypted with the encryption protocol specified by the
variable @code{gnus-article-encrypt-protocol}.

@end table

@vindex gnus-move-split-methods
@cindex moving articles
If you move (or copy) articles regularly, you might wish to have gnus
suggest where to put the articles.  @code{gnus-move-split-methods} is a
variable that uses the same syntax as @code{gnus-split-methods}
(@pxref{Saving Articles}).  You may customize that variable to create
suggestions you find reasonable.  (Note that
@code{gnus-move-split-methods} uses group names where
@code{gnus-split-methods} uses file names.)

@lisp
(setq gnus-move-split-methods
      '(("^From:.*Lars Magne" "nnml:junk")
        ("^Subject:.*gnus" "nnfolder:important")
        (".*" "nnml:misc")))
@end lisp


@node Various Summary Stuff
@section Various Summary Stuff

@menu
* Summary Group Information::   Information oriented commands.
* Searching for Articles::      Multiple article commands.
* Summary Generation Commands::
* Really Various Summary Commands::  Those pesky non-conformant commands.
@end menu

@table @code
@vindex gnus-summary-display-while-building
@item gnus-summary-display-while-building
If non-@code{nil}, show and update the summary buffer as it's being
built.  If @code{t}, update the buffer after every line is inserted.
If the value is an integer, @var{n}, update the display every @var{n}
lines.  The default is @code{nil}.

@vindex gnus-summary-display-arrow
@item gnus-summary-display-arrow
If non-@code{nil}, display an arrow in the fringe to indicate the
current article.

@vindex gnus-summary-mode-hook
@item gnus-summary-mode-hook
This hook is called when creating a summary mode buffer.

@vindex gnus-summary-generate-hook
@item gnus-summary-generate-hook
This is called as the last thing before doing the threading and the
generation of the summary buffer.  It's quite convenient for customizing
the threading variables based on what data the newsgroup has.  This hook
is called from the summary buffer after most summary buffer variables
have been set.

@vindex gnus-summary-prepare-hook
@item gnus-summary-prepare-hook
It is called after the summary buffer has been generated.  You might use
it to, for instance, highlight lines or modify the look of the buffer in
some other ungodly manner.  I don't care.

@vindex gnus-summary-prepared-hook
@item gnus-summary-prepared-hook
A hook called as the very last thing after the summary buffer has been
generated.

@vindex gnus-summary-ignore-duplicates
@item gnus-summary-ignore-duplicates
When gnus discovers two articles that have the same @code{Message-ID},
it has to do something drastic.  No articles are allowed to have the
same @code{Message-ID}, but this may happen when reading mail from some
sources.  Gnus allows you to customize what happens with this variable.
If it is @code{nil} (which is the default), gnus will rename the
@code{Message-ID} (for display purposes only) and display the article as
any other article.  If this variable is @code{t}, it won't display the
article---it'll be as if it never existed.

@vindex gnus-alter-articles-to-read-function
@item gnus-alter-articles-to-read-function
This function, which takes two parameters (the group name and the list
of articles to be selected), is called to allow the user to alter the
list of articles to be selected.

For instance, the following function adds the list of cached articles to
the list in one particular group:

@lisp
(defun my-add-cached-articles (group articles)
  (if (string= group "some.group")
      (append gnus-newsgroup-cached articles)
    articles))
@end lisp

@vindex gnus-newsgroup-variables
@item gnus-newsgroup-variables
A list of newsgroup (summary buffer) local variables, or cons of
variables and their default values (when the default values are not
@code{nil}), that should be made global while the summary buffer is
active.  These variables can be used to set variables in the group
parameters while still allowing them to affect operations done in
other buffers.  For example:

@lisp
(setq gnus-newsgroup-variables
      '(message-use-followup-to
        (gnus-visible-headers .
 "^From:\\|^Newsgroups:\\|^Subject:\\|^Date:\\|^To:")))
@end lisp

@end table


@node Summary Group Information
@subsection Summary Group Information

@table @kbd

@item H f
@kindex H f (Summary)
@findex gnus-summary-fetch-faq
@vindex gnus-group-faq-directory
Try to fetch the @acronym{FAQ} (list of frequently asked questions)
for the current group (@code{gnus-summary-fetch-faq}).  Gnus will try
to get the @acronym{FAQ} from @code{gnus-group-faq-directory}, which
is usually a directory on a remote machine.  This variable can also be
a list of directories.  In that case, giving a prefix to this command
will allow you to choose between the various sites.  @code{ange-ftp}
or @code{efs} will probably be used for fetching the file.

@item H d
@kindex H d (Summary)
@findex gnus-summary-describe-group
Give a brief description of the current group
(@code{gnus-summary-describe-group}).  If given a prefix, force
rereading the description from the server.

@item H h
@kindex H h (Summary)
@findex gnus-summary-describe-briefly
Give an extremely brief description of the most important summary
keystrokes (@code{gnus-summary-describe-briefly}).

@item H i
@kindex H i (Summary)
@findex gnus-info-find-node
Go to the gnus info node (@code{gnus-info-find-node}).
@end table


@node Searching for Articles
@subsection Searching for Articles

@table @kbd

@item M-s
@kindex M-s (Summary)
@findex gnus-summary-search-article-forward
Search through all subsequent (raw) articles for a regexp
(@code{gnus-summary-search-article-forward}).

@item M-r
@kindex M-r (Summary)
@findex gnus-summary-search-article-backward
Search through all previous (raw) articles for a regexp
(@code{gnus-summary-search-article-backward}).

@item &
@kindex & (Summary)
@findex gnus-summary-execute-command
This command will prompt you for a header, a regular expression to match
on this field, and a command to be executed if the match is made
(@code{gnus-summary-execute-command}).  If the header is an empty
string, the match is done on the entire article.  If given a prefix,
search backward instead.

For instance, @kbd{& RET some.*string RET #} will put the process mark on
all articles that have heads or bodies that match @samp{some.*string}.

@item M-&
@kindex M-& (Summary)
@findex gnus-summary-universal-argument
Perform any operation on all articles that have been marked with
the process mark (@code{gnus-summary-universal-argument}).
@end table

@node Summary Generation Commands
@subsection Summary Generation Commands

@table @kbd

@item Y g
@kindex Y g (Summary)
@findex gnus-summary-prepare
Regenerate the current summary buffer (@code{gnus-summary-prepare}).

@item Y c
@kindex Y c (Summary)
@findex gnus-summary-insert-cached-articles
Pull all cached articles (for the current group) into the summary buffer
(@code{gnus-summary-insert-cached-articles}).

@item Y d
@kindex Y d (Summary)
@findex gnus-summary-insert-dormant-articles
Pull all dormant articles (for the current group) into the summary buffer
(@code{gnus-summary-insert-dormant-articles}).

@end table


@node Really Various Summary Commands
@subsection Really Various Summary Commands

@table @kbd

@item A D
@itemx C-d
@kindex C-d (Summary)
@kindex A D (Summary)
@findex gnus-summary-enter-digest-group
If the current article is a collection of other articles (for instance,
a digest), you might use this command to enter a group based on the that
article (@code{gnus-summary-enter-digest-group}).  Gnus will try to
guess what article type is currently displayed unless you give a prefix
to this command, which forces a ``digest'' interpretation.  Basically,
whenever you see a message that is a collection of other messages of
some format, you @kbd{C-d} and read these messages in a more convenient
fashion.

@item C-M-d
@kindex C-M-d (Summary)
@findex gnus-summary-read-document
This command is very similar to the one above, but lets you gather
several documents into one biiig group
(@code{gnus-summary-read-document}).  It does this by opening several
@code{nndoc} groups for each document, and then opening an
@code{nnvirtual} group on top of these @code{nndoc} groups.  This
command understands the process/prefix convention
(@pxref{Process/Prefix}).

@item C-t
@kindex C-t (Summary)
@findex gnus-summary-toggle-truncation
Toggle truncation of summary lines
(@code{gnus-summary-toggle-truncation}).  This will probably confuse the
line centering function in the summary buffer, so it's not a good idea
to have truncation switched off while reading articles.

@item =
@kindex = (Summary)
@findex gnus-summary-expand-window
Expand the summary buffer window (@code{gnus-summary-expand-window}).
If given a prefix, force an @code{article} window configuration.

@item C-M-e
@kindex C-M-e (Summary)
@findex gnus-summary-edit-parameters
Edit the group parameters (@pxref{Group Parameters}) of the current
group (@code{gnus-summary-edit-parameters}).

@item C-M-a
@kindex C-M-a (Summary)
@findex gnus-summary-customize-parameters
Customize the group parameters (@pxref{Group Parameters}) of the current
group (@code{gnus-summary-customize-parameters}).

@end table


@node Exiting the Summary Buffer
@section Exiting the Summary Buffer
@cindex summary exit
@cindex exiting groups

Exiting from the summary buffer will normally update all info on the
group and return you to the group buffer.

@table @kbd

@item Z Z
@itemx Z Q
@itemx q
@kindex Z Z (Summary)
@kindex Z Q (Summary)
@kindex q (Summary)
@findex gnus-summary-exit
@vindex gnus-summary-exit-hook
@vindex gnus-summary-prepare-exit-hook
@vindex gnus-group-no-more-groups-hook
@c @icon{gnus-summary-exit}
Exit the current group and update all information on the group
(@code{gnus-summary-exit}).  @code{gnus-summary-prepare-exit-hook} is
called before doing much of the exiting, which calls
@code{gnus-summary-expire-articles} by default.
@code{gnus-summary-exit-hook} is called after finishing the exit
process.  @code{gnus-group-no-more-groups-hook} is run when returning to
group mode having no more (unread) groups.

@item Z E
@itemx Q
@kindex Z E (Summary)
@kindex Q (Summary)
@findex gnus-summary-exit-no-update
Exit the current group without updating any information on the group
(@code{gnus-summary-exit-no-update}).

@item Z c
@itemx c
@kindex Z c (Summary)
@kindex c (Summary)
@findex gnus-summary-catchup-and-exit
@c @icon{gnus-summary-catchup-and-exit}
Mark all unticked articles in the group as read and then exit
(@code{gnus-summary-catchup-and-exit}).

@item Z C
@kindex Z C (Summary)
@findex gnus-summary-catchup-all-and-exit
Mark all articles, even the ticked ones, as read and then exit
(@code{gnus-summary-catchup-all-and-exit}).

@item Z n
@kindex Z n (Summary)
@findex gnus-summary-catchup-and-goto-next-group
Mark all articles as read and go to the next group
(@code{gnus-summary-catchup-and-goto-next-group}).

@item Z R
@itemx C-x C-s
@kindex Z R (Summary)
@kindex C-x C-s (Summary)
@findex gnus-summary-reselect-current-group
Exit this group, and then enter it again
(@code{gnus-summary-reselect-current-group}).  If given a prefix, select
all articles, both read and unread.

@item Z G
@itemx M-g
@kindex Z G (Summary)
@kindex M-g (Summary)
@findex gnus-summary-rescan-group
@c @icon{gnus-summary-mail-get}
Exit the group, check for new articles in the group, and select the
group (@code{gnus-summary-rescan-group}).  If given a prefix, select all
articles, both read and unread.

@item Z N
@kindex Z N (Summary)
@findex gnus-summary-next-group
Exit the group and go to the next group
(@code{gnus-summary-next-group}).

@item Z P
@kindex Z P (Summary)
@findex gnus-summary-prev-group
Exit the group and go to the previous group
(@code{gnus-summary-prev-group}).

@item Z s
@kindex Z s (Summary)
@findex gnus-summary-save-newsrc
Save the current number of read/marked articles in the dribble buffer
and then save the dribble buffer (@code{gnus-summary-save-newsrc}).  If
given a prefix, also save the @file{.newsrc} file(s).  Using this
command will make exit without updating (the @kbd{Q} command) worthless.
@end table

@vindex gnus-exit-group-hook
@code{gnus-exit-group-hook} is called when you exit the current group
with an ``updating'' exit.  For instance @kbd{Q}
(@code{gnus-summary-exit-no-update}) does not call this hook.

@findex gnus-summary-wake-up-the-dead
@findex gnus-dead-summary-mode
@vindex gnus-kill-summary-on-exit
If you're in the habit of exiting groups, and then changing your mind
about it, you might set @code{gnus-kill-summary-on-exit} to @code{nil}.
If you do that, gnus won't kill the summary buffer when you exit it.
(Quelle surprise!)  Instead it will change the name of the buffer to
something like @samp{*Dead Summary ... *} and install a minor mode
called @code{gnus-dead-summary-mode}.  Now, if you switch back to this
buffer, you'll find that all keys are mapped to a function called
@code{gnus-summary-wake-up-the-dead}.  So tapping any keys in a dead
summary buffer will result in a live, normal summary buffer.

There will never be more than one dead summary buffer at any one time.

@vindex gnus-use-cross-reference
The data on the current group will be updated (which articles you have
read, which articles you have replied to, etc.) when you exit the
summary buffer.  If the @code{gnus-use-cross-reference} variable is
@code{t} (which is the default), articles that are cross-referenced to
this group and are marked as read, will also be marked as read in the
other subscribed groups they were cross-posted to.  If this variable is
neither @code{nil} nor @code{t}, the article will be marked as read in
both subscribed and unsubscribed groups (@pxref{Crosspost Handling}).


@node Crosspost Handling
@section Crosspost Handling

@cindex velveeta
@cindex spamming
Marking cross-posted articles as read ensures that you'll never have to
read the same article more than once.  Unless, of course, somebody has
posted it to several groups separately.  Posting the same article to
several groups (not cross-posting) is called @dfn{spamming}, and you are
by law required to send nasty-grams to anyone who perpetrates such a
heinous crime.  You may want to try NoCeM handling to filter out spam
(@pxref{NoCeM}).

Remember: Cross-posting is kinda ok, but posting the same article
separately to several groups is not.  Massive cross-posting (aka.
@dfn{velveeta}) is to be avoided at all costs, and you can even use the
@code{gnus-summary-mail-crosspost-complaint} command to complain about
excessive crossposting (@pxref{Summary Mail Commands}).

@cindex cross-posting
@cindex Xref
@cindex @acronym{NOV}
One thing that may cause Gnus to not do the cross-posting thing
correctly is if you use an @acronym{NNTP} server that supports @sc{xover}
(which is very nice, because it speeds things up considerably) which
does not include the @code{Xref} header in its @acronym{NOV} lines.  This is
Evil, but all too common, alas, alack.  Gnus tries to Do The Right Thing
even with @sc{xover} by registering the @code{Xref} lines of all
articles you actually read, but if you kill the articles, or just mark
them as read without reading them, Gnus will not get a chance to snoop
the @code{Xref} lines out of these articles, and will be unable to use
the cross reference mechanism.

@cindex LIST overview.fmt
@cindex overview.fmt
To check whether your @acronym{NNTP} server includes the @code{Xref} header
in its overview files, try @samp{telnet your.nntp.server nntp},
@samp{MODE READER} on @code{inn} servers, and then say @samp{LIST
overview.fmt}.  This may not work, but if it does, and the last line you
get does not read @samp{Xref:full}, then you should shout and whine at
your news admin until she includes the @code{Xref} header in the
overview files.

@vindex gnus-nov-is-evil
If you want Gnus to get the @code{Xref}s right all the time, you have to
set @code{gnus-nov-is-evil} to @code{t}, which slows things down
considerably.

C'est la vie.

For an alternative approach, @pxref{Duplicate Suppression}.


@node Duplicate Suppression
@section Duplicate Suppression

By default, gnus tries to make sure that you don't have to read the same
article more than once by utilizing the crossposting mechanism
(@pxref{Crosspost Handling}).  However, that simple and efficient
approach may not work satisfactory for some users for various
reasons.

@enumerate
@item
The @acronym{NNTP} server may fail to generate the @code{Xref} header.  This
is evil and not very common.

@item
The @acronym{NNTP} server may fail to include the @code{Xref} header in the
@file{.overview} data bases.  This is evil and all too common, alas.

@item
You may be reading the same group (or several related groups) from
different @acronym{NNTP} servers.

@item
You may be getting mail that duplicates articles posted to groups.
@end enumerate

I'm sure there are other situations where @code{Xref} handling fails as
well, but these four are the most common situations.

If, and only if, @code{Xref} handling fails for you, then you may
consider switching on @dfn{duplicate suppression}.  If you do so, Gnus
will remember the @code{Message-ID}s of all articles you have read or
otherwise marked as read, and then, as if by magic, mark them as read
all subsequent times you see them---in @emph{all} groups.  Using this
mechanism is quite likely to be somewhat inefficient, but not overly
so.  It's certainly preferable to reading the same articles more than
once.

Duplicate suppression is not a very subtle instrument.  It's more like a
sledge hammer than anything else.  It works in a very simple
fashion---if you have marked an article as read, it adds this Message-ID
to a cache.  The next time it sees this Message-ID, it will mark the
article as read with the @samp{M} mark.  It doesn't care what group it
saw the article in.

@table @code
@item gnus-suppress-duplicates
@vindex gnus-suppress-duplicates
If non-@code{nil}, suppress duplicates.

@item gnus-save-duplicate-list
@vindex gnus-save-duplicate-list
If non-@code{nil}, save the list of duplicates to a file.  This will
make startup and shutdown take longer, so the default is @code{nil}.
However, this means that only duplicate articles read in a single gnus
session are suppressed.

@item gnus-duplicate-list-length
@vindex gnus-duplicate-list-length
This variable says how many @code{Message-ID}s to keep in the duplicate
suppression list.  The default is 10000.

@item gnus-duplicate-file
@vindex gnus-duplicate-file
The name of the file to store the duplicate suppression list in.  The
default is @file{~/News/suppression}.
@end table

If you have a tendency to stop and start gnus often, setting
@code{gnus-save-duplicate-list} to @code{t} is probably a good idea.  If
you leave gnus running for weeks on end, you may have it @code{nil}.  On
the other hand, saving the list makes startup and shutdown much slower,
so that means that if you stop and start gnus often, you should set
@code{gnus-save-duplicate-list} to @code{nil}.  Uhm.  I'll leave this up
to you to figure out, I think.

@node Security
@section Security

Gnus is able to verify signed messages or decrypt encrypted messages.
The formats that are supported are @acronym{PGP}, @acronym{PGP/MIME}
and @acronym{S/MIME}, however you need some external programs to get
things to work:

@enumerate
@item
To handle @acronym{PGP} and @acronym{PGP/MIME} messages, you have to
install an OpenPGP implementation such as GnuPG.  The Lisp interface
to GnuPG included with Gnus is called PGG (@pxref{Top, ,PGG, pgg, PGG
Manual}), but Mailcrypt and gpg.el are also supported.

@item
To handle @acronym{S/MIME} message, you need to install OpenSSL.  OpenSSL 0.9.6
or newer is recommended.

@end enumerate

More information on how to set things up can be found in the message
manual (@pxref{Security, ,Security, message, Message Manual}).

@table @code
@item mm-verify-option
@vindex mm-verify-option
Option of verifying signed parts.  @code{never}, not verify;
@code{always}, always verify; @code{known}, only verify known
protocols.  Otherwise, ask user.

@item mm-decrypt-option
@vindex mm-decrypt-option
Option of decrypting encrypted parts.  @code{never}, no decryption;
@code{always}, always decrypt; @code{known}, only decrypt known
protocols.  Otherwise, ask user.

@item mml1991-use
@vindex mml1991-use
Symbol indicating elisp interface to OpenPGP implementation for
@acronym{PGP} messages.  The default is @code{pgg}, but
@code{mailcrypt} and @code{gpg} are also supported although
deprecated.

@item mml2015-use
@vindex mml2015-use
Symbol indicating elisp interface to OpenPGP implementation for
@acronym{PGP/MIME} messages.  The default is @code{pgg}, but
@code{mailcrypt} and @code{gpg} are also supported although
deprecated.

@end table

@cindex snarfing keys
@cindex importing PGP keys
@cindex PGP key ring import
Snarfing OpenPGP keys (i.e., importing keys from articles into your
key ring) is not supported explicitly through a menu item or command,
rather Gnus do detect and label keys as @samp{application/pgp-keys},
allowing you to specify whatever action you think is appropriate
through the usual @acronym{MIME} infrastructure.  You can use a
@file{~/.mailcap} entry (@pxref{mailcap, , mailcap, emacs-mime, The
Emacs MIME Manual}) such as the following to import keys using GNU
Privacy Guard when you click on the @acronym{MIME} button
(@pxref{Using MIME}).

@example
application/pgp-keys; gpg --import --interactive --verbose; needsterminal
@end example
@noindent
This happens to also be the default action defined in
@code{mailcap-mime-data}.

@node Mailing List
@section Mailing List
@cindex mailing list
@cindex RFC 2396

@kindex A M (summary)
@findex gnus-mailing-list-insinuate
Gnus understands some mailing list fields of RFC 2369.  To enable it,
add a @code{to-list} group parameter (@pxref{Group Parameters}),
possibly using @kbd{A M} (@code{gnus-mailing-list-insinuate}) in the
summary buffer.

That enables the following commands to the summary buffer:

@table @kbd

@item C-c C-n h
@kindex C-c C-n h (Summary)
@findex gnus-mailing-list-help
Send a message to fetch mailing list help, if List-Help field exists.

@item C-c C-n s
@kindex C-c C-n s (Summary)
@findex gnus-mailing-list-subscribe
Send a message to subscribe the mailing list, if List-Subscribe field exists.

@item C-c C-n u
@kindex C-c C-n u (Summary)
@findex gnus-mailing-list-unsubscribe
Send a message to unsubscribe the mailing list, if List-Unsubscribe
field exists.

@item C-c C-n p
@kindex C-c C-n p (Summary)
@findex gnus-mailing-list-post
Post to the mailing list, if List-Post field exists.

@item C-c C-n o
@kindex C-c C-n o (Summary)
@findex gnus-mailing-list-owner
Send a message to the mailing list owner, if List-Owner field exists.

@item C-c C-n a
@kindex C-c C-n a (Summary)
@findex gnus-mailing-list-owner
Browse the mailing list archive, if List-Archive field exists.

@end table


@node Article Buffer
@chapter Article Buffer
@cindex article buffer

The articles are displayed in the article buffer, of which there is only
one.  All the summary buffers share the same article buffer unless you
tell gnus otherwise.

@menu
* Hiding Headers::              Deciding what headers should be displayed.
* Using MIME::                  Pushing articles through @acronym{MIME} before reading them.
* Customizing Articles::        Tailoring the look of the articles.
* Article Keymap::              Keystrokes available in the article buffer.
* Misc Article::                Other stuff.
@end menu


@node Hiding Headers
@section Hiding Headers
@cindex hiding headers
@cindex deleting headers

The top section of each article is the @dfn{head}.  (The rest is the
@dfn{body}, but you may have guessed that already.)

@vindex gnus-show-all-headers
There is a lot of useful information in the head: the name of the person
who wrote the article, the date it was written and the subject of the
article.  That's well and nice, but there's also lots of information
most people do not want to see---what systems the article has passed
through before reaching you, the @code{Message-ID}, the
@code{References}, etc. ad nauseam---and you'll probably want to get rid
of some of those lines.  If you want to keep all those lines in the
article buffer, you can set @code{gnus-show-all-headers} to @code{t}.

Gnus provides you with two variables for sifting headers:

@table @code

@item gnus-visible-headers
@vindex gnus-visible-headers
If this variable is non-@code{nil}, it should be a regular expression
that says what headers you wish to keep in the article buffer.  All
headers that do not match this variable will be hidden.

For instance, if you only want to see the name of the person who wrote
the article and the subject, you'd say:

@lisp
(setq gnus-visible-headers "^From:\\|^Subject:")
@end lisp

This variable can also be a list of regexps to match headers to
remain visible.

@item gnus-ignored-headers
@vindex gnus-ignored-headers
This variable is the reverse of @code{gnus-visible-headers}.  If this
variable is set (and @code{gnus-visible-headers} is @code{nil}), it
should be a regular expression that matches all lines that you want to
hide.  All lines that do not match this variable will remain visible.

For instance, if you just want to get rid of the @code{References} field
and the @code{Xref} field, you might say:

@lisp
(setq gnus-ignored-headers "^References:\\|^Xref:")
@end lisp

This variable can also be a list of regexps to match headers to
be removed.

Note that if @code{gnus-visible-headers} is non-@code{nil}, this
variable will have no effect.

@end table

@vindex gnus-sorted-header-list
Gnus can also sort the headers for you.  (It does this by default.)  You
can control the sorting by setting the @code{gnus-sorted-header-list}
variable.  It is a list of regular expressions that says in what order
the headers are to be displayed.

For instance, if you want the name of the author of the article first,
and then the subject, you might say something like:

@lisp
(setq gnus-sorted-header-list '("^From:" "^Subject:"))
@end lisp

Any headers that are to remain visible, but are not listed in this
variable, will be displayed in random order after all the headers listed in this variable.

@findex gnus-article-hide-boring-headers
@vindex gnus-boring-article-headers
You can hide further boring headers by setting
@code{gnus-treat-hide-boring-headers} to @code{head}.  What this function
does depends on the @code{gnus-boring-article-headers} variable.  It's a
list, but this list doesn't actually contain header names.  Instead is
lists various @dfn{boring conditions} that Gnus can check and remove
from sight.

These conditions are:
@table @code
@item empty
Remove all empty headers.
@item followup-to
Remove the @code{Followup-To} header if it is identical to the
@code{Newsgroups} header.
@item reply-to
Remove the @code{Reply-To} header if it lists the same address as the
@code{From} header, or if the @code{broken-reply-to} group parameter is
set.
@item newsgroups
Remove the @code{Newsgroups} header if it only contains the current group
name.
@item to-address
Remove the @code{To} header if it only contains the address identical to
the current group's @code{to-address} parameter.
@item to-list
Remove the @code{To} header if it only contains the address identical to
the current group's @code{to-list} parameter.
@item cc-list
Remove the @code{CC} header if it only contains the address identical to
the current group's @code{to-list} parameter.
@item date
Remove the @code{Date} header if the article is less than three days
old.
@item long-to
Remove the @code{To} header if it is very long.
@item many-to
Remove all @code{To} headers if there are more than one.
@end table

To include these three elements, you could say something like:

@lisp
(setq gnus-boring-article-headers
      '(empty followup-to reply-to))
@end lisp

This is also the default value for this variable.


@node Using MIME
@section Using MIME
@cindex @acronym{MIME}

Mime is a standard for waving your hands through the air, aimlessly,
while people stand around yawning.

@acronym{MIME}, however, is a standard for encoding your articles, aimlessly,
while all newsreaders die of fear.

@acronym{MIME} may specify what character set the article uses, the encoding
of the characters, and it also makes it possible to embed pictures and
other naughty stuff in innocent-looking articles.

@vindex gnus-show-mime
@vindex gnus-article-display-method-for-mime
@findex gnus-article-display-mime-message
gnus handles @acronym{MIME} by pushing the articles through
@code{gnus-article-display-method-for-mime}, which is
@code{gnus-article-display-mime-message} by default.  This function
calls the @acronym{SEMI} MIME-View program to actually do the work.  For
more information on @acronym{SEMI} MIME-View, see its manual page
(however it is not existed yet, sorry).

Set @code{gnus-show-mime} to @code{t} if you want to use
@acronym{MIME} all the time.  If you have @code{gnus-show-mime} set,
then you'll see some unfortunate display glitches in the article buffer.
These can't be avoided.

In GNUS or Gnus, it might be best to just use the toggling functions
from the summary buffer to avoid getting nasty surprises. (For instance,
you enter the group @samp{alt.sing-a-long} and, before you know it,
@acronym{MIME} has decoded the sound file in the article and some
horrible sing-a-long song comes screaming out your speakers, and you
can't find the volume button, because there isn't one, and people are
starting to look at you, and you try to stop the program, but you can't,
and you can't find the program to control the volume, and everybody else
in the room suddenly decides to look at you disdainfully, and you'll
feel rather stupid.)

Any similarity to real events and people is purely coincidental.  Ahem.

To avoid such kind of situation, gnus stops to use
@code{metamail-buffer}.  So now, you can set @code{gnus-show-mime} to
non-@code{nil} every-time, then you can push button in the article
buffer when there are nobody else.

Also @pxref{MIME Commands}.


@node Customizing Articles
@section Customizing Articles
@cindex article customization

A slew of functions for customizing how the articles are to look like
exist.  You can call these functions interactively
(@pxref{Article Washing}), or you can have them
called automatically when you select the articles.

To have them called automatically, you should set the corresponding
``treatment'' variable.  For instance, to have headers hidden, you'd set
@code{gnus-treat-hide-headers}.  Below is a list of variables that can
be set, but first we discuss the values these variables can have.

Note: Some values, while valid, make little sense.  Check the list below
for sensible values.

@enumerate
@item
@code{nil}: Don't do this treatment.

@item
@code{t}: Do this treatment on all body parts.

@item
@code{head}: Do the treatment on the headers.

@item
@code{last}: Do this treatment on the last part.

@item
An integer: Do this treatment on all body parts that have a length less
than this number.

@item
A list of strings: Do this treatment on all body parts that are in
articles that are read in groups that have names that match one of the
regexps in the list.

@item
A list where the first element is not a string:

The list is evaluated recursively.  The first element of the list is a
predicate.  The following predicates are recognized: @code{or},
@code{and}, @code{not} and @code{typep}.  Here's an example:

@lisp
(or last
    (typep "text/x-vcard"))
@end lisp

@item
@code{mime}: Do this treatment if the value of @code{gnus-show-mime}' is
non-nil.

@end enumerate

You may have noticed that the word @dfn{part} is used here.  This refers
to the fact that some messages are @acronym{MIME} multipart articles that may
be divided into several parts.  Articles that are not multiparts are
considered to contain just a single part.

@vindex gnus-article-treat-types
Are the treatments applied to all sorts of multipart parts?  Yes, if you
want to, but by default, only @samp{text/plain} parts are given the
treatment.  This is controlled by the @code{gnus-article-treat-types}
variable, which is a list of regular expressions that are matched to the
type of the part.  This variable is ignored if the value of the
controlling variable is a predicate list, as described above.

The following treatment options are available.  The easiest way to
customize this is to examine the @code{gnus-article-treat} customization
group.  Values in parenthesis are suggested sensible values.  Others are
possible but those listed are probably sufficient for most people.

@table @code
@item gnus-treat-buttonize (t, integer)
@item gnus-treat-buttonize-head (head)

@xref{Article Buttons}.

@item gnus-treat-capitalize-sentences (t, integer)
@item gnus-treat-overstrike (t, integer)
@item gnus-treat-strip-cr (t, integer)
@item gnus-treat-strip-headers-in-body (t, integer)
@item gnus-treat-strip-leading-blank-lines (t, integer)
@item gnus-treat-strip-multiple-blank-lines (t, integer)
@item gnus-treat-strip-pem (t, last, integer)
@item gnus-treat-strip-trailing-blank-lines (t, last, integer)
@item gnus-treat-unsplit-urls (t, integer)
@item gnus-treat-wash-html (t, integer)
@item gnus-treat-decode-article-as-default-mime-charset (t, integer)

@xref{Article Washing}.

@item gnus-treat-date-english (head)
@item gnus-treat-date-iso8601 (head)
@item gnus-treat-date-lapsed (head)
@item gnus-treat-date-local (head)
@item gnus-treat-date-original (head)
@item gnus-treat-date-user-defined (head)
@item gnus-treat-date-ut (head)

@xref{Article Date}.

@item gnus-treat-from-picon (head)
@item gnus-treat-mail-picon (head)
@item gnus-treat-newsgroups-picon (head)

@xref{Picons}.

@item gnus-treat-display-smileys (t, integer)

@item gnus-treat-body-boundary (head)

@vindex gnus-body-boundary-delimiter
Adds a delimiter between header and body, the string used as delimiter
is controlled by @code{gnus-body-boundary-delimiter}.

@xref{Smileys}.

@item gnus-treat-display-x-face (head)

@xref{X-Face}.

@item gnus-treat-display-face (head)

@xref{Face}.

@item gnus-treat-emphasize (t, head, integer)
@item gnus-treat-fill-article (t, integer)
@item gnus-treat-fill-long-lines (t, integer)
@item gnus-treat-hide-boring-headers (head)
@item gnus-treat-hide-citation (t, integer)
@item gnus-treat-hide-citation-maybe (t, integer)
@item gnus-treat-hide-headers (head)
@item gnus-treat-hide-signature (t, last)
@item gnus-treat-strip-banner (t, last)
@item gnus-treat-strip-list-identifiers (head)

@xref{Article Hiding}.

@item gnus-treat-highlight-citation (t, integer)
@item gnus-treat-highlight-headers (head)
@item gnus-treat-highlight-signature (t, last, integer)

@xref{Article Highlighting}.

@item gnus-treat-play-sounds
@item gnus-treat-translate
@item gnus-treat-x-pgp-sig (head)

@item gnus-treat-unfold-headers (head)
@item gnus-treat-fold-headers (head)
@item gnus-treat-fold-newsgroups (head)
@item gnus-treat-leading-whitespace (head)

@xref{Article Header}.


@end table

@vindex gnus-part-display-hook
You can, of course, write your own functions to be called from
@code{gnus-part-display-hook}.  The functions are called narrowed to the
part, and you can do anything you like, pretty much.  There is no
information that you have to keep in the buffer---you can change
everything.


@node Article Keymap
@section Article Keymap

Most of the keystrokes in the summary buffer can also be used in the
article buffer.  They should behave as if you typed them in the summary
buffer, which means that you don't actually have to have a summary
buffer displayed while reading.  You can do it all from the article
buffer.

A few additional keystrokes are available:

@table @kbd

@item SPACE
@kindex SPACE (Article)
@findex gnus-article-next-page
Scroll forwards one page (@code{gnus-article-next-page}).
This is exactly the same as @kbd{h SPACE h}.

@item DEL
@kindex DEL (Article)
@findex gnus-article-prev-page
Scroll backwards one page (@code{gnus-article-prev-page}).
This is exactly the same as @kbd{h DEL h}.

@item C-c ^
@kindex C-c ^ (Article)
@findex gnus-article-refer-article
If point is in the neighborhood of a @code{Message-ID} and you press
@kbd{C-c ^}, Gnus will try to get that article from the server
(@code{gnus-article-refer-article}).

@item C-c C-m
@kindex C-c C-m (Article)
@findex gnus-article-mail
Send a reply to the address near point (@code{gnus-article-mail}).  If
given a prefix, include the mail.

@item s
@kindex s (Article)
@findex gnus-article-show-summary
Reconfigure the buffers so that the summary buffer becomes visible
(@code{gnus-article-show-summary}).

@item ?
@kindex ? (Article)
@findex gnus-article-describe-briefly
Give a very brief description of the available keystrokes
(@code{gnus-article-describe-briefly}).

@item TAB
@kindex TAB (Article)
@findex gnus-article-next-button
Go to the next button, if any (@code{gnus-article-next-button}).  This
only makes sense if you have buttonizing turned on.

@item M-TAB
@kindex M-TAB (Article)
@findex gnus-article-prev-button
Go to the previous button, if any (@code{gnus-article-prev-button}).

@item R
@kindex R (Article)
@findex gnus-article-reply-with-original
Send a reply to the current article and yank the current article
(@code{gnus-article-reply-with-original}).  If given a prefix, make a
wide reply.  If the region is active, only yank the text in the
region.

@item F
@kindex F (Article)
@findex gnus-article-followup-with-original
Send a followup to the current article and yank the current article
(@code{gnus-article-followup-with-original}).  If given a prefix, make
a wide reply.  If the region is active, only yank the text in the
region.


@end table


@node Misc Article
@section Misc Article

@table @code

@item gnus-single-article-buffer
@vindex gnus-single-article-buffer
If non-@code{nil}, use the same article buffer for all the groups.
(This is the default.)  If @code{nil}, each group will have its own
article buffer.

@vindex gnus-article-decode-hook
@item gnus-article-decode-hook
@cindex @acronym{MIME}
Hook used to decode @acronym{MIME} articles.  The default value is
@code{(article-decode-charset article-decode-encoded-words)}

@vindex gnus-article-prepare-hook
@item gnus-article-prepare-hook
This hook is called right after the article has been inserted into the
article buffer.  It is mainly intended for functions that do something
depending on the contents; it should probably not be used for changing
the contents of the article buffer.

@item gnus-article-mode-hook
@vindex gnus-article-mode-hook
Hook called in article mode buffers.

@item gnus-article-mode-syntax-table
@vindex gnus-article-mode-syntax-table
Syntax table used in article buffers.  It is initialized from
@code{text-mode-syntax-table}.

@vindex gnus-article-over-scroll
@item gnus-article-over-scroll
If non-@code{nil}, allow scrolling the article buffer even when there
no more new text to scroll in.  The default is @code{nil}.

@vindex gnus-article-mode-line-format
@item gnus-article-mode-line-format
This variable is a format string along the same lines as
@code{gnus-summary-mode-line-format} (@pxref{Mode Line Formatting}).  It
accepts the same format specifications as that variable, with two
extensions:

@table @samp

@item w
The @dfn{wash status} of the article.  This is a short string with one
character for each possible article wash operation that may have been
performed.  The characters and their meaning:

@table @samp

@item c
Displayed when cited text may be hidden in the article buffer.

@item h
Displayed when headers are hidden in the article buffer.

@item p
Displayed when article is digitally signed or encrypted, and Gnus has
hidden the security headers.  (N.B. does not tell anything about
security status, i.e. good or bad signature.)

@item s
Displayed when the signature has been hidden in the Article buffer.

@item o
Displayed when Gnus has treated overstrike characters in the article buffer.

@item e
Displayed when Gnus has treated emphasised strings in the article buffer.

@end table

@item m
The number of @acronym{MIME} parts in the article.

@end table

@vindex gnus-break-pages

@item gnus-break-pages
Controls whether @dfn{page breaking} is to take place.  If this variable
is non-@code{nil}, the articles will be divided into pages whenever a
page delimiter appears in the article.  If this variable is @code{nil},
paging will not be done.

@item gnus-page-delimiter
@vindex gnus-page-delimiter
This is the delimiter mentioned above.  By default, it is @samp{^L}
(formfeed).

@cindex IDNA
@cindex internationalized domain names
@vindex gnus-use-idna
@item gnus-use-idna
This variable controls whether Gnus performs IDNA decoding of
internationalized domain names inside @samp{From}, @samp{To} and
@samp{Cc} headers.  This requires
@uref{http://www.gnu.org/software/libidn/, GNU Libidn}, and this
variable is only enabled if you have installed it.

@end table


@node Composing Messages
@chapter Composing Messages
@cindex composing messages
@cindex messages
@cindex mail
@cindex sending mail
@cindex reply
@cindex followup
@cindex post
@cindex using gpg
@cindex using s/mime
@cindex using smime

@kindex C-c C-c (Post)
All commands for posting and mailing will put you in a message buffer
where you can edit the article all you like, before you send the
article by pressing @kbd{C-c C-c}.  @xref{Top, , Overview, message,
Message Manual}.  Where the message will be posted/mailed to depends
on your setup (@pxref{Posting Server}).

@menu
* Mail::                        Mailing and replying.
* Posting Server::              What server should you post and mail via?
* Mail and Post::               Mailing and posting at the same time.
* Archived Messages::           Where Gnus stores the messages you've sent.
* Posting Styles::              An easier way to specify who you are.
* Drafts::                      Postponing messages and rejected messages.
* Rejected Articles::           What happens if the server doesn't like your article?
* Signing and encrypting::      How to compose secure messages.
@end menu

Also @pxref{Canceling and Superseding} for information on how to
remove articles you shouldn't have posted.


@node Mail
@section Mail

Variables for customizing outgoing mail:

@table @code
@item gnus-uu-digest-headers
@vindex gnus-uu-digest-headers
List of regexps to match headers included in digested messages.  The
headers will be included in the sequence they are matched.  If
@code{nil} include all headers.

@item gnus-add-to-list
@vindex gnus-add-to-list
If non-@code{nil}, add a @code{to-list} group parameter to mail groups
that have none when you do a @kbd{a}.

@item gnus-confirm-mail-reply-to-news
@vindex gnus-confirm-mail-reply-to-news
This can also be a function receiving the group name as the only
parameter which should return non-@code{nil} if a confirmation is
needed, or a regular expression matching group names, where
confirmation is should be asked for.

If you find yourself never wanting to reply to mail, but occasionally
press R anyway, this variable might be for you.

@item gnus-confirm-treat-mail-like-news
@vindex gnus-confirm-treat-mail-like-news
If non-@code{nil}, Gnus also requests confirmation according to
@code{gnus-confirm-mail-reply-to-news} when replying to mail.  This is
useful for treating mailing lists like newsgroups.

@end table


@node Posting Server
@section Posting Server

When you press those magical @kbd{C-c C-c} keys to ship off your latest
(extremely intelligent, of course) article, where does it go?

Thank you for asking.  I hate you.

It can be quite complicated.

@vindex gnus-post-method
When posting news, Message usually invokes @code{message-send-news}
(@pxref{News Variables, , News Variables, message, Message Manual}).
Normally, Gnus will post using the same select method as you're
reading from (which might be convenient if you're reading lots of
groups from different private servers).  However.  If the server
you're reading from doesn't allow posting, just reading, you probably
want to use some other server to post your (extremely intelligent and
fabulously interesting) articles.  You can then set the
@code{gnus-post-method} to some other method:

@lisp
(setq gnus-post-method '(nnspool ""))
@end lisp

Now, if you've done this, and then this server rejects your article, or
this server is down, what do you do then?  To override this variable you
can use a non-zero prefix to the @kbd{C-c C-c} command to force using
the ``current'' server, to get back the default behavior, for posting.

If you give a zero prefix (i.e., @kbd{C-u 0 C-c C-c}) to that command,
gnus will prompt you for what method to use for posting.

You can also set @code{gnus-post-method} to a list of select methods.
If that's the case, gnus will always prompt you for what method to use
for posting.

Finally, if you want to always post using the native select method,
you can set this variable to @code{native}.

When sending mail, Message invokes @code{message-send-mail-function}.
The default function, @code{message-send-mail-with-sendmail}, pipes
your article to the @code{sendmail} binary for further queuing and
sending.  When your local system is not configured for sending mail
using @code{sendmail}, and you have access to a remote @acronym{SMTP}
server, you can set @code{message-send-mail-function} to
@code{smtpmail-send-it} and make sure to setup the @code{smtpmail}
package correctly.  An example:

@lisp
(setq message-send-mail-function 'smtpmail-send-it
      smtpmail-default-smtp-server "YOUR SMTP HOST")
;; The following variable needs to be set because of the FLIM version of
;; smtpmail.el.  Which smtpmail.el is used depends on the `load-path'.
(setq smtp-default-smtp-server "YOUR SMTP HOST")
@end lisp

To the thing similar to this, there is
@code{message-smtpmail-send-it}.  It is useful if your ISP requires
the @acronym{POP}-before-@acronym{SMTP} authentication.  See the
documentation for the function @code{mail-source-touch-pop}.

Other possible choices for @code{message-send-mail-function} includes
@code{message-send-mail-with-mh}, @code{message-send-mail-with-qmail},
and @code{feedmail-send-it}.

@node Mail and Post
@section Mail and Post

Here's a list of variables relevant to both mailing and
posting:

@table @code
@item gnus-mailing-list-groups
@findex gnus-mailing-list-groups
@cindex mailing lists

If your news server offers groups that are really mailing lists
gatewayed to the @acronym{NNTP} server, you can read those groups without
problems, but you can't post/followup to them without some difficulty.
One solution is to add a @code{to-address} to the group parameters
(@pxref{Group Parameters}).  An easier thing to do is set the
@code{gnus-mailing-list-groups} to a regexp that matches the groups that
really are mailing lists.  Then, at least, followups to the mailing
lists will work most of the time.  Posting to these groups (@kbd{a}) is
still a pain, though.

@item gnus-user-agent
@vindex gnus-user-agent
@cindex User-Agent

This variable controls which information should be exposed in the
User-Agent header.  It can be one of the symbols @code{gnus} (show only
Gnus version), @code{emacs-gnus} (show only Emacs and Gnus versions),
@code{emacs-gnus-config} (same as @code{emacs-gnus} plus system
configuration), @code{emacs-gnus-type} (same as @code{emacs-gnus} plus
system type) or a custom string.  If you set it to a string, be sure to
use a valid format, see RFC 2616.

@end table

You may want to do spell-checking on messages that you send out.  Or, if
you don't want to spell-check by hand, you could add automatic
spell-checking via the @code{ispell} package:

@cindex ispell
@findex ispell-message
@lisp
(add-hook 'message-send-hook 'ispell-message)
@end lisp

If you want to change the @code{ispell} dictionary based on what group
you're in, you could say something like the following:

@lisp
(add-hook 'gnus-select-group-hook
          (lambda ()
            (cond
             ((string-match
               "^de\\." (gnus-group-real-name gnus-newsgroup-name))
              (ispell-change-dictionary "deutsch"))
             (t
              (ispell-change-dictionary "english")))))
@end lisp

Modify to suit your needs.


@node Archived Messages
@section Archived Messages
@cindex archived messages
@cindex sent messages

Gnus provides a few different methods for storing the mail and news you
send.  The default method is to use the @dfn{archive virtual server} to
store the messages.  If you want to disable this completely, the
@code{gnus-message-archive-group} variable should be @code{nil}, which
is the default.

For archiving interesting messages in a group you read, see the
@kbd{B c} (@code{gnus-summary-copy-article}) command (@pxref{Mail
Group Commands}).

@vindex gnus-message-archive-method
@code{gnus-message-archive-method} says what virtual server gnus is to
use to store sent messages.  The default is:

@lisp
(nnfolder "archive"
          (nnfolder-directory   "~/Mail/archive")
          (nnfolder-active-file "~/Mail/archive/active")
          (nnfolder-get-new-mail nil)
          (nnfolder-inhibit-expiry t))
@end lisp

You can, however, use any mail select method (@code{nnml},
@code{nnmbox}, etc.).  @code{nnfolder} is a quite likable select method
for doing this sort of thing, though.  If you don't like the default
directory chosen, you could say something like:

@lisp
(setq gnus-message-archive-method
      '(nnfolder "archive"
                 (nnfolder-inhibit-expiry t)
                 (nnfolder-active-file "~/News/sent-mail/active")
                 (nnfolder-directory "~/News/sent-mail/")))
@end lisp

@vindex gnus-message-archive-group
@cindex Gcc
Gnus will insert @code{Gcc} headers in all outgoing messages that point
to one or more group(s) on that server.  Which group to use is
determined by the @code{gnus-message-archive-group} variable.

This variable can be used to do the following:

@table @asis
@item a string
Messages will be saved in that group.

Note that you can include a select method in the group name, then the
message will not be stored in the select method given by
@code{gnus-message-archive-method}, but in the select method specified
by the group name, instead.  Suppose @code{gnus-message-archive-method}
has the default value shown above.  Then setting
@code{gnus-message-archive-group} to @code{"foo"} means that outgoing
messages are stored in @samp{nnfolder+archive:foo}, but if you use the
value @code{"nnml:foo"}, then outgoing messages will be stored in
@samp{nnml:foo}.

@item a list of strings
Messages will be saved in all those groups.

@item an alist of regexps, functions and forms
When a key ``matches'', the result is used.

@item @code{nil}
No message archiving will take place.  This is the default.
@end table

Let's illustrate:

Just saving to a single group called @samp{MisK}:
@lisp
(setq gnus-message-archive-group "MisK")
@end lisp

Saving to two groups, @samp{MisK} and @samp{safe}:
@lisp
(setq gnus-message-archive-group '("MisK" "safe"))
@end lisp

Save to different groups based on what group you are in:
@lisp
(setq gnus-message-archive-group
      '(("^alt" "sent-to-alt")
        ("mail" "sent-to-mail")
        (".*" "sent-to-misc")))
@end lisp

More complex stuff:
@lisp
(setq gnus-message-archive-group
      '((if (message-news-p)
            "misc-news"
          "misc-mail")))
@end lisp

How about storing all news messages in one file, but storing all mail
messages in one file per month:

@lisp
(setq gnus-message-archive-group
      '((if (message-news-p)
            "misc-news"
          (concat "mail." (format-time-string "%Y-%m")))))
@end lisp

@c (XEmacs 19.13 doesn't have @code{format-time-string}, so you'll have to
@c use a different value for @code{gnus-message-archive-group} there.)

Now, when you send a message off, it will be stored in the appropriate
group.  (If you want to disable storing for just one particular message,
you can just remove the @code{Gcc} header that has been inserted.)  The
archive group will appear in the group buffer the next time you start
gnus, or the next time you press @kbd{F} in the group buffer.  You can
enter it and read the articles in it just like you'd read any other
group.  If the group gets really big and annoying, you can simply rename
if (using @kbd{G r} in the group buffer) to something
nice---@samp{misc-mail-september-1995}, or whatever.  New messages will
continue to be stored in the old (now empty) group.

That's the default method of archiving sent messages.  Gnus offers a
different way for the people who don't like the default method.  In that
case you should set @code{gnus-message-archive-group} to @code{nil};
this will disable archiving.

@table @code
@item gnus-outgoing-message-group
@vindex gnus-outgoing-message-group
All outgoing messages will be put in this group.  If you want to store
all your outgoing mail and articles in the group @samp{nnml:archive},
you set this variable to that value.  This variable can also be a list of
group names.

If you want to have greater control over what group to put each
message in, you can set this variable to a function that checks the
current newsgroup name and then returns a suitable group name (or list
of names).

This variable can be used instead of @code{gnus-message-archive-group},
but the latter is the preferred method.

@item gnus-gcc-mark-as-read
@vindex gnus-gcc-mark-as-read
If non-@code{nil}, automatically mark @code{Gcc} articles as read.

@item gnus-gcc-externalize-attachments
@vindex gnus-gcc-externalize-attachments
If @code{nil}, attach files as normal parts in Gcc copies; if a regexp
and matches the Gcc group name, attach files as external parts; if it is
@code{all}, attach local files as external parts; if it is other
non-@code{nil}, the behavior is the same as @code{all}, but it may be
changed in the future.

@end table


@node Posting Styles
@section Posting Styles
@cindex posting styles
@cindex styles

All them variables, they make my head swim.

So what if you want a different @code{Organization} and signature based
on what groups you post to?  And you post both from your home machine
and your work machine, and you want different @code{From} lines, and so
on?

@vindex gnus-posting-styles
One way to do stuff like that is to write clever hooks that change the
variables you need to have changed.  That's a bit boring, so somebody
came up with the bright idea of letting the user specify these things in
a handy alist.  Here's an example of a @code{gnus-posting-styles}
variable:

@lisp
((".*"
  (signature "Peace and happiness")
  (organization "What me?"))
 ("^comp"
  (signature "Death to everybody"))
 ("comp.emacs.i-love-it"
  (organization "Emacs is it")))
@end lisp

As you might surmise from this example, this alist consists of several
@dfn{styles}.  Each style will be applicable if the first element
``matches'', in some form or other.  The entire alist will be iterated
over, from the beginning towards the end, and each match will be
applied, which means that attributes in later styles that match override
the same attributes in earlier matching styles.  So
@samp{comp.programming.literate} will have the @samp{Death to everybody}
signature and the @samp{What me?} @code{Organization} header.

The first element in each style is called the @code{match}.  If it's a
string, then Gnus will try to regexp match it against the group name.
If it is the form @code{(header @var{match} @var{regexp})}, then Gnus
will look in the original article for a header whose name is
@var{match} and compare that @var{regexp}.  @var{match} and
@var{regexp} are strings.  (The original article is the one you are
replying or following up to.  If you are not composing a reply or a
followup, then there is nothing to match against.)  If the
@code{match} is a function symbol, that function will be called with
no arguments.  If it's a variable symbol, then the variable will be
referenced.  If it's a list, then that list will be @code{eval}ed.  In
any case, if this returns a non-@code{nil} value, then the style is
said to @dfn{match}.

Each style may contain an arbitrary amount of @dfn{attributes}.  Each
attribute consists of a @code{(@var{name} @var{value})} pair.  The
attribute name can be one of:

@itemize @bullet
@item @code{signature}
@item @code{signature-file}
@item @code{x-face-file}
@item @code{address}, overriding @code{user-mail-address}
@item @code{name}, overriding @code{(user-full-name)}
@item @code{body}
@end itemize

The attribute name can also be a string or a symbol.  In that case,
this will be used as a header name, and the value will be inserted in
the headers of the article; if the value is @code{nil}, the header
name will be removed.  If the attribute name is @code{eval}, the form
is evaluated, and the result is thrown away.

The attribute value can be a string (used verbatim), a function with
zero arguments (the return value will be used), a variable (its value
will be used) or a list (it will be @code{eval}ed and the return value
will be used).  The functions and sexps are called/@code{eval}ed in the
message buffer that is being set up.  The headers of the current article
are available through the @code{message-reply-headers} variable, which
is a vector of the following headers: number subject from date id
references chars lines xref extra.

@vindex message-reply-headers

If you wish to check whether the message you are about to compose is
meant to be a news article or a mail message, you can check the values
of the @code{message-news-p} and @code{message-mail-p} functions.

@findex message-mail-p
@findex message-news-p

So here's a new example:

@lisp
(setq gnus-posting-styles
      '((".*"
         (signature-file "~/.signature")
         (name "User Name")
         ("X-Home-Page" (getenv "WWW_HOME"))
         (organization "People's Front Against MWM"))
        ("^rec.humor"
         (signature my-funny-signature-randomizer))
        ((equal (system-name) "gnarly")  ;; @r{A form}
         (signature my-quote-randomizer))
        (message-news-p        ;; @r{A function symbol}
         (signature my-news-signature))
        (window-system         ;; @r{A value symbol}
         ("X-Window-System" (format "%s" window-system)))
        ;; @r{If I'm replying to Larsi, set the Organization header.}
        ((header "from" "larsi.*org")
         (Organization "Somewhere, Inc."))
        ((posting-from-work-p) ;; @r{A user defined function}
         (signature-file "~/.work-signature")
         (address "user@@bar.foo")
         (body "You are fired.\n\nSincerely, your boss.")
         (organization "Important Work, Inc"))
        ("nnml:.*"
         (From (save-excursion
                 (set-buffer gnus-article-buffer)
                 (message-fetch-field "to"))))
        ("^nn.+:"
         (signature-file "~/.mail-signature"))))
@end lisp

The @samp{nnml:.*} rule means that you use the @code{To} address as the
@code{From} address in all your outgoing replies, which might be handy
if you fill many roles.

Setting the @code{gnus-named-posting-styles} variable will make
posting-styles allow to have distinctive names.  You can specify an
arbitrary posting-style when article posting with @kbd{S P} in the
summary buffer.  @code{gnus-named-posting-styles} is an alist which maps
the names to styles.  Once a posting-style is added to the alist, we can
import it from @code{gnus-posting-styles}.  If an attribute whose name
is @code{import} is found, Gnus will look for the attribute value in
@code{gnus-named-posting-styles} and expand it in place.

Here's an example:

@lisp
(setq gnus-named-posting-styles
      '(("Default"
         (signature-file "~/.signature")
         (name "User Name")
         ("X-Home-Page" (getenv "WWW_HOME"))
         (organization "People's Front Against MWM"))
        ("Emacs"
         (import "Default")
         (organization "The Church of Emacs"))))
@end lisp

The posting-style named "Emacs" will inherit all the attributes from
"Default" except @code{organization}.


@node Drafts
@section Drafts
@cindex drafts

If you are writing a message (mail or news) and suddenly remember that
you have a steak in the oven (or some pesto in the food processor, you
craaazy vegetarians), you'll probably wish there was a method to save
the message you are writing so that you can continue editing it some
other day, and send it when you feel its finished.

Well, don't worry about it.  Whenever you start composing a message of
some sort using the gnus mail and post commands, the buffer you get will
automatically associate to an article in a special @dfn{draft} group.
If you save the buffer the normal way (@kbd{C-x C-s}, for instance), the
article will be saved there.  (Auto-save files also go to the draft
group.)

@cindex nndraft
@vindex nndraft-directory
The draft group is a special group (which is implemented as an
@code{nndraft} group, if you absolutely have to know) called
@samp{nndraft:drafts}.  The variable @code{nndraft-directory} says where
@code{nndraft} is to store its files.  What makes this group special is
that you can't tick any articles in it or mark any articles as
read---all articles in the group are permanently unread.

If the group doesn't exist, it will be created and you'll be subscribed
to it.  The only way to make it disappear from the Group buffer is to
unsubscribe it.  The special properties of the draft group comes from
a group property (@pxref{Group Parameters}), and if lost the group
behaves like any other group.  This means the commands below will not
be available.  To restore the special properties of the group, the
simplest way is to kill the group, using @kbd{C-k}, and restart
Gnus.  The group is automatically created again with the
correct parameters.  The content of the group is not lost.

@c @findex gnus-dissociate-buffer-from-draft
@c @kindex C-c M-d (Mail)
@c @kindex C-c M-d (Post)
@c @findex gnus-associate-buffer-with-draft
@c @kindex C-c C-d (Mail)
@c @kindex C-c C-d (Post)
@c If you're writing some super-secret message that you later want to
@c encode with PGP before sending, you may wish to turn the auto-saving
@c (and association with the draft group) off.  You never know who might be
@c interested in reading all your extremely valuable and terribly horrible
@c and interesting secrets.  The @kbd{C-c M-d}
@c (@code{gnus-dissociate-buffer-from-draft}) command does that for you.
@c If you change your mind and want to turn the auto-saving back on again,
@c @kbd{C-c C-d} (@code{gnus-associate-buffer-with-draft} does that.
@c
@c @vindex gnus-use-draft
@c To leave association with the draft group off by default, set
@c @code{gnus-use-draft} to @code{nil}.  It is @code{t} by default.

@findex gnus-draft-edit-message
@kindex D e (Draft)
When you want to continue editing the article, you simply enter the
draft group and push @kbd{D e} (@code{gnus-draft-edit-message}) to do
that.  You will be placed in a buffer where you left off.

Rejected articles will also be put in this draft group (@pxref{Rejected
Articles}).

@findex gnus-draft-send-all-messages
@kindex D s (Draft)
@findex gnus-draft-send-message
@kindex D S (Draft)
If you have lots of rejected messages you want to post (or mail) without
doing further editing, you can use the @kbd{D s} command
(@code{gnus-draft-send-message}).  This command understands the
process/prefix convention (@pxref{Process/Prefix}).  The @kbd{D S}
command (@code{gnus-draft-send-all-messages}) will ship off all messages
in the buffer.

@findex gnus-draft-toggle-sending
@kindex D t (Draft)
If you have some messages that you wish not to send, you can use the
@kbd{D t} (@code{gnus-draft-toggle-sending}) command to mark the message
as unsendable.  This is a toggling command.


@node Rejected Articles
@section Rejected Articles
@cindex rejected articles

Sometimes a news server will reject an article.  Perhaps the server
doesn't like your face.  Perhaps it just feels miserable.  Perhaps
@emph{there be demons}.  Perhaps you have included too much cited text.
Perhaps the disk is full.  Perhaps the server is down.

These situations are, of course, totally beyond the control of gnus.
(Gnus, of course, loves the way you look, always feels great, has angels
fluttering around inside of it, doesn't care about how much cited text
you include, never runs full and never goes down.)  So gnus saves these
articles until some later time when the server feels better.

The rejected articles will automatically be put in a special draft group
(@pxref{Drafts}).  When the server comes back up again, you'd then
typically enter that group and send all the articles off.

@node Signing and encrypting
@section Signing and encrypting
@cindex using gpg
@cindex using s/mime
@cindex using smime

Gnus can digitally sign and encrypt your messages, using vanilla
@acronym{PGP} format or @acronym{PGP/MIME} or @acronym{S/MIME}.  For
decoding such messages, see the @code{mm-verify-option} and
@code{mm-decrypt-option} options (@pxref{Security}).

@vindex gnus-message-replysign
@vindex gnus-message-replyencrypt
@vindex gnus-message-replysignencrypted
Often, you would like to sign replies to people who send you signed
messages.  Even more often, you might want to encrypt messages which
are in reply to encrypted messages.  Gnus offers
@code{gnus-message-replysign} to enable the former, and
@code{gnus-message-replyencrypt} for the latter.  In addition, setting
@code{gnus-message-replysignencrypted} (on by default) will sign
automatically encrypted messages.

Instructing @acronym{MML} to perform security operations on a
@acronym{MIME} part is done using the @kbd{C-c C-m s} key map for
signing and the @kbd{C-c C-m c} key map for encryption, as follows.

@table @kbd

@item C-c C-m s s
@kindex C-c C-m s s
@findex mml-secure-message-sign-smime

Digitally sign current message using @acronym{S/MIME}.

@item C-c C-m s o
@kindex C-c C-m s o
@findex mml-secure-message-sign-pgp

Digitally sign current message using @acronym{PGP}.

@item C-c C-m s p
@kindex C-c C-m s p
@findex mml-secure-message-sign-pgp

Digitally sign current message using @acronym{PGP/MIME}.

@item C-c C-m c s
@kindex C-c C-m c s
@findex mml-secure-message-encrypt-smime

Digitally encrypt current message using @acronym{S/MIME}.

@item C-c C-m c o
@kindex C-c C-m c o
@findex mml-secure-message-encrypt-pgp

Digitally encrypt current message using @acronym{PGP}.

@item C-c C-m c p
@kindex C-c C-m c p
@findex mml-secure-message-encrypt-pgpmime

Digitally encrypt current message using @acronym{PGP/MIME}.

@item C-c C-m C-n
@kindex C-c C-m C-n
@findex mml-unsecure-message
Remove security related @acronym{MML} tags from message.

@end table

@xref{Security, ,Security, message, Message Manual}, for more information.

@node Select Methods
@chapter Select Methods
@cindex foreign groups
@cindex select methods

A @dfn{foreign group} is a group not read by the usual (or
default) means.  It could be, for instance, a group from a different
@acronym{NNTP} server, it could be a virtual group, or it could be your own
personal mail group.

A foreign group (or any group, really) is specified by a @dfn{name} and
a @dfn{select method}.  To take the latter first, a select method is a
list where the first element says what back end to use (e.g. @code{nntp},
@code{nnspool}, @code{nnml}) and the second element is the @dfn{server
name}.  There may be additional elements in the select method, where the
value may have special meaning for the back end in question.

One could say that a select method defines a @dfn{virtual server}---so
we do just that (@pxref{Server Buffer}).

The @dfn{name} of the group is the name the back end will recognize the
group as.

For instance, the group @samp{soc.motss} on the @acronym{NNTP} server
@samp{some.where.edu} will have the name @samp{soc.motss} and select
method @code{(nntp "some.where.edu")}.  Gnus will call this group
@samp{nntp+some.where.edu:soc.motss}, even though the @code{nntp}
back end just knows this group as @samp{soc.motss}.

The different methods all have their peculiarities, of course.

@menu
* Server Buffer::               Making and editing virtual servers.
* Getting News::                Reading USENET news with Gnus.
* Getting Mail::                Reading your personal mail with Gnus.
* Browsing the Web::            Getting messages from a plethora of Web sources.
* IMAP::                        Using Gnus as a @acronym{IMAP} client.
* Other Sources::               Reading directories, files, SOUP packets.
* Combined Groups::             Combining groups into one group.
* Gnus Unplugged::              Reading news and mail offline.
@end menu


@node Server Buffer
@section Server Buffer

Traditionally, a @dfn{server} is a machine or a piece of software that
one connects to, and then requests information from.  Gnus does not
connect directly to any real servers, but does all transactions through
one back end or other.  But that's just putting one layer more between
the actual media and Gnus, so we might just as well say that each
back end represents a virtual server.

For instance, the @code{nntp} back end may be used to connect to several
different actual @acronym{NNTP} servers, or, perhaps, to many different ports
on the same actual @acronym{NNTP} server.  You tell Gnus which back end to
use, and what parameters to set by specifying a @dfn{select method}.

These select method specifications can sometimes become quite
complicated---say, for instance, that you want to read from the
@acronym{NNTP} server @samp{news.funet.fi} on port number 13, which
hangs if queried for @acronym{NOV} headers and has a buggy select.  Ahem.
Anyway, if you had to specify that for each group that used this
server, that would be too much work, so Gnus offers a way of naming
select methods, which is what you do in the server buffer.

To enter the server buffer, use the @kbd{^}
(@code{gnus-group-enter-server-mode}) command in the group buffer.

@menu
* Server Buffer Format::        You can customize the look of this buffer.
* Server Commands::             Commands to manipulate servers.
* Example Methods::             Examples server specifications.
* Creating a Virtual Server::   An example session.
* Server Variables::            Which variables to set.
* Servers and Methods::         You can use server names as select methods.
* Unavailable Servers::         Some servers you try to contact may be down.
@end menu

@vindex gnus-server-mode-hook
@code{gnus-server-mode-hook} is run when creating the server buffer.


@node Server Buffer Format
@subsection Server Buffer Format
@cindex server buffer format

@vindex gnus-server-line-format
You can change the look of the server buffer lines by changing the
@code{gnus-server-line-format} variable.  This is a @code{format}-like
variable, with some simple extensions:

@table @samp

@item h
How the news is fetched---the back end name.

@item n
The name of this server.

@item w
Where the news is to be fetched from---the address.

@item s
The opened/closed/denied status of the server.
@end table

@vindex gnus-server-mode-line-format
The mode line can also be customized by using the
@code{gnus-server-mode-line-format} variable (@pxref{Mode Line
Formatting}).  The following specs are understood:

@table @samp
@item S
Server name.

@item M
Server method.
@end table

Also @pxref{Formatting Variables}.


@node Server Commands
@subsection Server Commands
@cindex server commands

@table @kbd

@item a
@kindex a (Server)
@findex gnus-server-add-server
Add a new server (@code{gnus-server-add-server}).

@item e
@kindex e (Server)
@findex gnus-server-edit-server
Edit a server (@code{gnus-server-edit-server}).

@item SPACE
@kindex SPACE (Server)
@findex gnus-server-read-server
Browse the current server (@code{gnus-server-read-server}).

@item q
@kindex q (Server)
@findex gnus-server-exit
Return to the group buffer (@code{gnus-server-exit}).

@item k
@kindex k (Server)
@findex gnus-server-kill-server
Kill the current server (@code{gnus-server-kill-server}).

@item y
@kindex y (Server)
@findex gnus-server-yank-server
Yank the previously killed server (@code{gnus-server-yank-server}).

@item c
@kindex c (Server)
@findex gnus-server-copy-server
Copy the current server (@code{gnus-server-copy-server}).

@item l
@kindex l (Server)
@findex gnus-server-list-servers
List all servers (@code{gnus-server-list-servers}).

@item s
@kindex s (Server)
@findex gnus-server-scan-server
Request that the server scan its sources for new articles
(@code{gnus-server-scan-server}).  This is mainly sensible with mail
servers.

@item g
@kindex g (Server)
@findex gnus-server-regenerate-server
Request that the server regenerate all its data structures
(@code{gnus-server-regenerate-server}).  This can be useful if you have
a mail back end that has gotten out of sync.

@end table


@node Example Methods
@subsection Example Methods

Most select methods are pretty simple and self-explanatory:

@lisp
(nntp "news.funet.fi")
@end lisp

Reading directly from the spool is even simpler:

@lisp
(nnspool "")
@end lisp

As you can see, the first element in a select method is the name of the
back end, and the second is the @dfn{address}, or @dfn{name}, if you
will.

After these two elements, there may be an arbitrary number of
@code{(@var{variable} @var{form})} pairs.

To go back to the first example---imagine that you want to read from
port 15 on that machine.  This is what the select method should
look like then:

@lisp
(nntp "news.funet.fi" (nntp-port-number 15))
@end lisp

You should read the documentation to each back end to find out what
variables are relevant, but here's an @code{nnmh} example:

@code{nnmh} is a mail back end that reads a spool-like structure.  Say
you have two structures that you wish to access: One is your private
mail spool, and the other is a public one.  Here's the possible spec for
your private mail:

@lisp
(nnmh "private" (nnmh-directory "~/private/mail/"))
@end lisp

(This server is then called @samp{private}, but you may have guessed
that.)

Here's the method for a public spool:

@lisp
(nnmh "public"
      (nnmh-directory "/usr/information/spool/")
      (nnmh-get-new-mail nil))
@end lisp

@cindex proxy
@cindex firewall

If you are behind a firewall and only have access to the @acronym{NNTP}
server from the firewall machine, you can instruct Gnus to @code{rlogin}
on the firewall machine and telnet from there to the @acronym{NNTP} server.
Doing this can be rather fiddly, but your virtual server definition
should probably look something like this:

@lisp
(nntp "firewall"
      (nntp-open-connection-function nntp-open-via-rlogin-and-telnet)
      (nntp-via-address "the.firewall.machine")
      (nntp-address "the.real.nntp.host")
      (nntp-end-of-line "\n"))
@end lisp

If you want to use the wonderful @code{ssh} program to provide a
compressed connection over the modem line, you could add the following
configuration to the example above:

@lisp
      (nntp-via-rlogin-command "ssh")
@end lisp

See also @code{nntp-via-rlogin-command-switches}.

If you're behind a firewall, but have direct access to the outside world
through a wrapper command like "runsocks", you could open a socksified
telnet connection to the news server as follows:

@lisp
(nntp "outside"
      (nntp-pre-command "runsocks")
      (nntp-open-connection-function nntp-open-via-telnet)
      (nntp-address "the.news.server")
      (nntp-end-of-line "\n"))
@end lisp

This means that you have to have set up @code{ssh-agent} correctly to
provide automatic authorization, of course.  And to get a compressed
connection, you have to have the @samp{Compression} option in the
@code{ssh} @file{config} file.


@node Creating a Virtual Server
@subsection Creating a Virtual Server

If you're saving lots of articles in the cache by using persistent
articles, you may want to create a virtual server to read the cache.

First you need to add a new server.  The @kbd{a} command does that.  It
would probably be best to use @code{nnml} to read the cache.  You
could also use @code{nnspool} or @code{nnmh}, though.

Type @kbd{a nnml RET cache RET}.

You should now have a brand new @code{nnml} virtual server called
@samp{cache}.  You now need to edit it to have the right definitions.
Type @kbd{e} to edit the server.  You'll be entered into a buffer that
will contain the following:

@lisp
(nnml "cache")
@end lisp

Change that to:

@lisp
(nnml "cache"
         (nnml-directory "~/News/cache/")
         (nnml-active-file "~/News/cache/active"))
@end lisp

Type @kbd{C-c C-c} to return to the server buffer.  If you now press
@kbd{RET} over this virtual server, you should be entered into a browse
buffer, and you should be able to enter any of the groups displayed.


@node Server Variables
@subsection Server Variables
@cindex server variables
@cindex server parameters

One sticky point when defining variables (both on back ends and in Emacs
in general) is that some variables are typically initialized from other
variables when the definition of the variables is being loaded.  If you
change the ``base'' variable after the variables have been loaded, you
won't change the ``derived'' variables.

This typically affects directory and file variables.  For instance,
@code{nnml-directory} is @file{~/Mail/} by default, and all @code{nnml}
directory variables are initialized from that variable, so
@code{nnml-active-file} will be @file{~/Mail/active}.  If you define a
new virtual @code{nnml} server, it will @emph{not} suffice to set just
@code{nnml-directory}---you have to explicitly set all the file
variables to be what you want them to be.  For a complete list of
variables for each back end, see each back end's section later in this
manual, but here's an example @code{nnml} definition:

@lisp
(nnml "public"
      (nnml-directory "~/my-mail/")
      (nnml-active-file "~/my-mail/active")
      (nnml-newsgroups-file "~/my-mail/newsgroups"))
@end lisp

Server variables are often called @dfn{server parameters}.

@node Servers and Methods
@subsection Servers and Methods

Wherever you would normally use a select method
(e.g. @code{gnus-secondary-select-method}, in the group select method,
when browsing a foreign server) you can use a virtual server name
instead.  This could potentially save lots of typing.  And it's nice all
over.


@node Unavailable Servers
@subsection Unavailable Servers

If a server seems to be unreachable, Gnus will mark that server as
@code{denied}.  That means that any subsequent attempt to make contact
with that server will just be ignored.  ``It can't be opened,'' Gnus
will tell you, without making the least effort to see whether that is
actually the case or not.

That might seem quite naughty, but it does make sense most of the time.
Let's say you have 10 groups subscribed to on server
@samp{nephelococcygia.com}.  This server is located somewhere quite far
away from you and the machine is quite slow, so it takes 1 minute just
to find out that it refuses connection to you today.  If Gnus were to
attempt to do that 10 times, you'd be quite annoyed, so Gnus won't
attempt to do that.  Once it has gotten a single ``connection refused'',
it will regard that server as ``down''.

So, what happens if the machine was only feeling unwell temporarily?
How do you test to see whether the machine has come up again?

You jump to the server buffer (@pxref{Server Buffer}) and poke it
with the following commands:

@table @kbd

@item O
@kindex O (Server)
@findex gnus-server-open-server
Try to establish connection to the server on the current line
(@code{gnus-server-open-server}).

@item C
@kindex C (Server)
@findex gnus-server-close-server
Close the connection (if any) to the server
(@code{gnus-server-close-server}).

@item D
@kindex D (Server)
@findex gnus-server-deny-server
Mark the current server as unreachable
(@code{gnus-server-deny-server}).

@item M-o
@kindex M-o (Server)
@findex gnus-server-open-all-servers
Open the connections to all servers in the buffer
(@code{gnus-server-open-all-servers}).

@item M-c
@kindex M-c (Server)
@findex gnus-server-close-all-servers
Close the connections to all servers in the buffer
(@code{gnus-server-close-all-servers}).

@item R
@kindex R (Server)
@findex gnus-server-remove-denials
Remove all marks to whether Gnus was denied connection from any servers
(@code{gnus-server-remove-denials}).

@item L
@kindex L (Server)
@findex gnus-server-offline-server
Set server status to offline (@code{gnus-server-offline-server}).

@end table


@node Getting News
@section Getting News
@cindex reading news
@cindex news back ends

A newsreader is normally used for reading news.  Gnus currently provides
only two methods of getting news---it can read from an @acronym{NNTP} server,
or it can read from a local spool.

@menu
* NNTP::                        Reading news from an @acronym{NNTP} server.
* News Spool::                  Reading news from the local spool.
@end menu


@node NNTP
@subsection NNTP
@cindex nntp

Subscribing to a foreign group from an @acronym{NNTP} server is rather easy.
You just specify @code{nntp} as method and the address of the @acronym{NNTP}
server as the, uhm, address.

If the @acronym{NNTP} server is located at a non-standard port, setting the
third element of the select method to this port number should allow you
to connect to the right port.  You'll have to edit the group info for
that (@pxref{Foreign Groups}).

The name of the foreign group can be the same as a native group.  In
fact, you can subscribe to the same group from as many different servers
you feel like.  There will be no name collisions.

The following variables can be used to create a virtual @code{nntp}
server:

@table @code

@item nntp-server-opened-hook
@vindex nntp-server-opened-hook
@cindex @sc{mode reader}
@cindex authinfo
@cindex authentification
@cindex nntp authentification
@findex nntp-send-authinfo
@findex nntp-send-mode-reader
is run after a connection has been made.  It can be used to send
commands to the @acronym{NNTP} server after it has been contacted.  By
default it sends the command @code{MODE READER} to the server with the
@code{nntp-send-mode-reader} function.  This function should always be
present in this hook.

@item nntp-authinfo-function
@vindex nntp-authinfo-function
@findex nntp-send-authinfo
@vindex nntp-authinfo-file
This function will be used to send @samp{AUTHINFO} to the @acronym{NNTP}
server.  The default function is @code{nntp-send-authinfo}, which looks
through your @file{~/.authinfo} (or whatever you've set the
@code{nntp-authinfo-file} variable to) for applicable entries.  If none
are found, it will prompt you for a login name and a password.  The
format of the @file{~/.authinfo} file is (almost) the same as the
@code{ftp} @file{~/.netrc} file, which is defined in the @code{ftp}
manual page, but here are the salient facts:

@enumerate
@item
The file contains one or more line, each of which define one server.

@item
Each line may contain an arbitrary number of token/value pairs.

The valid tokens include @samp{machine}, @samp{login}, @samp{password},
@samp{default}.  In addition Gnus introduces two new tokens, not present
in the original @file{.netrc}/@code{ftp} syntax, namely @samp{port} and
@samp{force}.  (This is the only way the @file{.authinfo} file format
deviates from the @file{.netrc} file format.)  @samp{port} is used to
indicate what port on the server the credentials apply to and
@samp{force} is explained below.

@end enumerate

Here's an example file:

@example
machine news.uio.no login larsi password geheimnis
machine nntp.ifi.uio.no login larsi force yes
@end example

The token/value pairs may appear in any order; @samp{machine} doesn't
have to be first, for instance.

In this example, both login name and password have been supplied for the
former server, while the latter has only the login name listed, and the
user will be prompted for the password.  The latter also has the
@samp{force} tag, which means that the authinfo will be sent to the
@var{nntp} server upon connection; the default (i.e., when there is not
@samp{force} tag) is to not send authinfo to the @var{nntp} server
until the @var{nntp} server asks for it.

You can also add @samp{default} lines that will apply to all servers
that don't have matching @samp{machine} lines.

@example
default force yes
@end example

This will force sending @samp{AUTHINFO} commands to all servers not
previously mentioned.

Remember to not leave the @file{~/.authinfo} file world-readable.

@item nntp-server-action-alist
@vindex nntp-server-action-alist
This is a list of regexps to match on server types and actions to be
taken when matches are made.  For instance, if you want Gnus to beep
every time you connect to innd, you could say something like:

@lisp
(setq nntp-server-action-alist
      '(("innd" (ding))))
@end lisp

You probably don't want to do that, though.

The default value is

@lisp
'(("nntpd 1\\.5\\.11t"
   (remove-hook 'nntp-server-opened-hook
                'nntp-send-mode-reader)))
@end lisp

This ensures that Gnus doesn't send the @code{MODE READER} command to
nntpd 1.5.11t, since that command chokes that server, I've been told.

@item nntp-maximum-request
@vindex nntp-maximum-request
If the @acronym{NNTP} server doesn't support @acronym{NOV} headers, this back end
will collect headers by sending a series of @code{head} commands.  To
speed things up, the back end sends lots of these commands without
waiting for reply, and then reads all the replies.  This is controlled
by the @code{nntp-maximum-request} variable, and is 400 by default.  If
your network is buggy, you should set this to 1.

@item nntp-connection-timeout
@vindex nntp-connection-timeout
If you have lots of foreign @code{nntp} groups that you connect to
regularly, you're sure to have problems with @acronym{NNTP} servers not
responding properly, or being too loaded to reply within reasonable
time.  This is can lead to awkward problems, which can be helped
somewhat by setting @code{nntp-connection-timeout}.  This is an integer
that says how many seconds the @code{nntp} back end should wait for a
connection before giving up.  If it is @code{nil}, which is the default,
no timeouts are done.

@c @item nntp-command-timeout
@c @vindex nntp-command-timeout
@c @cindex PPP connections
@c @cindex dynamic IP addresses
@c If you're running Gnus on a machine that has a dynamically assigned
@c address, Gnus may become confused.  If the address of your machine
@c changes after connecting to the @acronym{NNTP} server, Gnus will simply sit
@c waiting forever for replies from the server.  To help with this
@c unfortunate problem, you can set this command to a number.  Gnus will
@c then, if it sits waiting for a reply from the server longer than that
@c number of seconds, shut down the connection, start a new one, and resend
@c the command.  This should hopefully be transparent to the user.  A
@c likely number is 30 seconds.
@c
@c @item nntp-retry-on-break
@c @vindex nntp-retry-on-break
@c If this variable is non-@code{nil}, you can also @kbd{C-g} if Gnus
@c hangs.  This will have much the same effect as the command timeout
@c described above.

@item nntp-server-hook
@vindex nntp-server-hook
This hook is run as the last step when connecting to an @acronym{NNTP}
server.

@item nntp-buggy-select
@vindex nntp-buggy-select
Set this to non-@code{nil} if your select routine is buggy.

@item nntp-nov-is-evil
@vindex nntp-nov-is-evil
If the @acronym{NNTP} server does not support @acronym{NOV}, you could set this
variable to @code{t}, but @code{nntp} usually checks automatically whether @acronym{NOV}
can be used.

@item nntp-xover-commands
@vindex nntp-xover-commands
@cindex @acronym{NOV}
@cindex XOVER
List of strings used as commands to fetch @acronym{NOV} lines from a
server.  The default value of this variable is @code{("XOVER"
"XOVERVIEW")}.

@item nntp-nov-gap
@vindex nntp-nov-gap
@code{nntp} normally sends just one big request for @acronym{NOV} lines to
the server.  The server responds with one huge list of lines.  However,
if you have read articles 2-5000 in the group, and only want to read
article 1 and 5001, that means that @code{nntp} will fetch 4999 @acronym{NOV}
lines that you will not need.  This variable says how
big a gap between two consecutive articles is allowed to be before the
@code{XOVER} request is split into several request.  Note that if your
network is fast, setting this variable to a really small number means
that fetching will probably be slower.  If this variable is @code{nil},
@code{nntp} will never split requests.  The default is 5.

@item nntp-prepare-server-hook
@vindex nntp-prepare-server-hook
A hook run before attempting to connect to an @acronym{NNTP} server.

@item nntp-warn-about-losing-connection
@vindex nntp-warn-about-losing-connection
If this variable is non-@code{nil}, some noise will be made when a
server closes connection.

@item nntp-record-commands
@vindex nntp-record-commands
If non-@code{nil}, @code{nntp} will log all commands it sends to the
@acronym{NNTP} server (along with a timestamp) in the @samp{*nntp-log*}
buffer.  This is useful if you are debugging a Gnus/@acronym{NNTP} connection
that doesn't seem to work.

@item nntp-open-connection-function
@vindex nntp-open-connection-function
It is possible to customize how the connection to the nntp server will
be opened.  If you specify an @code{nntp-open-connection-function}
parameter, Gnus will use that function to establish the connection.
Five pre-made functions are supplied.  These functions can be grouped in
two categories: direct connection functions (three pre-made), and
indirect ones (two pre-made).

@item nntp-prepare-post-hook
@vindex nntp-prepare-post-hook
A hook run just before posting an article.  If there is no
@code{Message-ID} header in the article and the news server provides the
recommended ID, it will be added to the article before running this
hook.  It is useful to make @code{Cancel-Lock} headers even if you
inhibit Gnus to add a @code{Message-ID} header, you could say:

@lisp
(add-hook 'nntp-prepare-post-hook 'canlock-insert-header)
@end lisp

Note that not all servers support the recommended ID.  This works for
INN versions 2.3.0 and later, for instance.

@item nntp-read-timeout
@vindex nntp-read-timeout
How long nntp should wait between checking for the end of output.
Shorter values mean quicker response, but is more CPU intensive.  The
default is 0.1 seconds.  If you have a slow line to the server (and
don't like to see Emacs eat your available CPU power), you might set
this to, say, 1.

@item nntp-list-options
@vindex nntp-list-options
List of newsgroup name used for a option of the LIST command to restrict
the listing output to only the specified newsgroups.  Each newsgroup name
can be a shell-style wildcard, for instance, @dfn{fj.*}, @dfn{japan.*},
etc.  Fortunately, if the server can accept such a option, it will
probably make gnus run faster.  You may use it as a server variable as
follows:

@lisp
(setq gnus-select-method
      '(nntp "news.somewhere.edu"
             (nntp-list-options ("fj.*" "japan.*"))))
@end lisp

@item nntp-options-subscribe
@vindex nntp-options-subscribe
Regexp matching the newsgroup names which will be subscribed
unconditionally.  Use @dfn{ } instead of @dfn{$} for a regexp string.
It may be effective as well as @code{nntp-list-options} even though the
server could not accept a shell-style wildcard as a option of the LIST
command.  You may use it as a server variable as follows:

@lisp
(setq gnus-select-method
      '(nntp "news.somewhere.edu"
             (nntp-options-subscribe "^fj\\.\\|^japan\\.")))
@end lisp

@item nntp-options-not-subscribe
@vindex nntp-options-not-subscribe
Regexp matching the newsgroup names which will not be subscribed
unconditionally.  Use @dfn{ } instead of @dfn{$} for a regexp string.
It may be effective as well as @code{nntp-list-options} even though the
server could not accept a shell-style wildcard as a option of the LIST
command.  You may use it as a server variable as follows:

@lisp
(setq gnus-select-method
      '(nntp "news.somewhere.edu"
             (nntp-options-not-subscribe "\\.binaries\\.")))
@end lisp
@end table

@menu
* Direct Functions::            Connecting directly to the server.
* Indirect Functions::          Connecting indirectly to the server.
* Common Variables::            Understood by several connection functions.
@end menu


@node Direct Functions
@subsubsection Direct Functions
@cindex direct connection functions

These functions are called direct because they open a direct connection
between your machine and the @acronym{NNTP} server.  The behavior of these
functions is also affected by commonly understood variables
(@pxref{Common Variables}).

@table @code
@findex nntp-open-network-stream
@item nntp-open-network-stream
This is the default, and simply connects to some port or other on the
remote system.

@findex nntp-open-tls-stream
@item nntp-open-tls-stream
Opens a connection to a server over a @dfn{secure} channel.  To use
this you must have @uref{http://www.gnu.org/software/gnutls/, GNUTLS}
installed.  You then define a server as follows:

@lisp
;; @r{"nntps" is port 563 and is predefined in our @file{/etc/services}}
;; @r{however, @samp{gnutls-cli -p} doesn't like named ports.}
;;
(nntp "snews.bar.com"
      (nntp-open-connection-function nntp-open-tls-stream)
      (nntp-port-number )
      (nntp-address "snews.bar.com"))
@end lisp

@findex nntp-open-ssl-stream
@item nntp-open-ssl-stream
Opens a connection to a server over a @dfn{secure} channel.  To use
this you must have @uref{http://www.openssl.org, OpenSSL} or
@uref{ftp://ftp.psy.uq.oz.au/pub/Crypto/SSL, SSLeay} installed.  You
then define a server as follows:

@lisp
;; @r{"snews" is port 563 and is predefined in our @file{/etc/services}}
;; @r{however, @samp{openssl s_client -port} doesn't like named ports.}
;;
(nntp "snews.bar.com"
      (nntp-open-connection-function nntp-open-ssl-stream)
      (nntp-port-number 563)
      (nntp-address "snews.bar.com"))
@end lisp

@findex nntp-open-telnet-stream
@item nntp-open-telnet-stream
Opens a connection to an @acronym{NNTP} server by simply @samp{telnet}'ing
it.  You might wonder why this function exists, since we have the
default @code{nntp-open-network-stream} which would do the job.  (One
of) the reason(s) is that if you are behind a firewall but have direct
connections to the outside world thanks to a command wrapper like
@code{runsocks}, you can use it like this:

@lisp
(nntp "socksified"
      (nntp-pre-command "runsocks")
      (nntp-open-connection-function nntp-open-telnet-stream)
      (nntp-address "the.news.server"))
@end lisp

With the default method, you would need to wrap your whole Emacs
session, which is not a good idea.
@end table


@node Indirect Functions
@subsubsection Indirect Functions
@cindex indirect connection functions

These functions are called indirect because they connect to an
intermediate host before actually connecting to the @acronym{NNTP} server.
All of these functions and related variables are also said to belong to
the ``via'' family of connection: they're all prefixed with ``via'' to make
things cleaner.  The behavior of these functions is also affected by
commonly understood variables (@pxref{Common Variables}).

@table @code
@item nntp-open-via-rlogin-and-telnet
@findex nntp-open-via-rlogin-and-telnet
Does an @samp{rlogin} on a remote system, and then does a @samp{telnet}
to the real @acronym{NNTP} server from there.  This is useful for instance if
you need to connect to a firewall machine first.

@code{nntp-open-via-rlogin-and-telnet}-specific variables:

@table @code
@item nntp-via-rlogin-command
@vindex nntp-via-rlogin-command
Command used to log in on the intermediate host.  The default is
@samp{rsh}, but @samp{ssh} is a popular alternative.

@item nntp-via-rlogin-command-switches
@vindex nntp-via-rlogin-command-switches
List of strings to be used as the switches to
@code{nntp-via-rlogin-command}.  The default is @code{nil}.  If you use
@samp{ssh} for @code{nntp-via-rlogin-command}, you may set this to
@samp{("-C")} in order to compress all data connections, otherwise set
this to @samp{("-t" "-e" "none")} or @samp{("-C" "-t" "-e" "none")} if
the telnet command requires a pseudo-tty allocation on an intermediate
host.
@end table

@item nntp-open-via-telnet-and-telnet
@findex nntp-open-via-telnet-and-telnet
Does essentially the same, but uses @samp{telnet} instead of
@samp{rlogin} to connect to the intermediate host.

@code{nntp-open-via-telnet-and-telnet}-specific variables:

@table @code
@item nntp-via-telnet-command
@vindex nntp-via-telnet-command
Command used to @code{telnet} the intermediate host.  The default is
@samp{telnet}.

@item nntp-via-telnet-switches
@vindex nntp-via-telnet-switches
List of strings to be used as the switches to the
@code{nntp-via-telnet-command} command.  The default is @samp{("-8")}.

@item nntp-via-user-password
@vindex nntp-via-user-password
Password to use when logging in on the intermediate host.

@item nntp-via-envuser
@vindex nntp-via-envuser
If non-@code{nil}, the intermediate @code{telnet} session (client and
server both) will support the @code{ENVIRON} option and not prompt for
login name.  This works for Solaris @code{telnet}, for instance.

@item nntp-via-shell-prompt
@vindex nntp-via-shell-prompt
Regexp matching the shell prompt on the intermediate host.  The default
is @samp{bash\\|\$ *\r?$\\|> *\r?}.

@end table

@end table


Here are some additional variables that are understood by all the above
functions:

@table @code

@item nntp-via-user-name
@vindex nntp-via-user-name
User name to use when connecting to the intermediate host.

@item nntp-via-address
@vindex nntp-via-address
Address of the intermediate host to connect to.

@end table


@node Common Variables
@subsubsection Common Variables

The following variables affect the behavior of all, or several of the
pre-made connection functions.  When not specified, all functions are
affected.

@table @code

@item nntp-pre-command
@vindex nntp-pre-command
A command wrapper to use when connecting through a non native
connection function (all except @code{nntp-open-network-stream},
@code{nntp-open-tls-stream}, and @code{nntp-open-ssl-stream}.  This is
where you would put a @samp{SOCKS} wrapper for instance.

@item nntp-address
@vindex nntp-address
The address of the @acronym{NNTP} server.

@item nntp-port-number
@vindex nntp-port-number
Port number to connect to the @acronym{NNTP} server.  The default is
@samp{nntp}.  If you use @acronym{NNTP} over
@acronym{TLS}/@acronym{SSL}, you may want to use integer ports rather
than named ports (i.e, use @samp{563} instead of @samp{snews} or
@samp{nntps}), because external @acronym{TLS}/@acronym{SSL} tools may
not work with named ports.

@item nntp-end-of-line
@vindex nntp-end-of-line
String to use as end-of-line marker when talking to the @acronym{NNTP}
server.  This is @samp{\r\n} by default, but should be @samp{\n} when
using a non native connection function.

@item nntp-telnet-command
@vindex nntp-telnet-command
Command to use when connecting to the @acronym{NNTP} server through
@samp{telnet}.  This is @emph{not} for an intermediate host.  This is
just for the real @acronym{NNTP} server.  The default is
@samp{telnet}.

@item nntp-telnet-switches
@vindex nntp-telnet-switches
A list of switches to pass to @code{nntp-telnet-command}.  The default
is @samp{("-8")}.

@end table


@node News Spool
@subsection News Spool
@cindex nnspool
@cindex news spool

Subscribing to a foreign group from the local spool is extremely easy,
and might be useful, for instance, to speed up reading groups that
contain very big articles---@samp{alt.binaries.pictures.furniture}, for
instance.

Anyway, you just specify @code{nnspool} as the method and @code{""} (or
anything else) as the address.

If you have access to a local spool, you should probably use that as the
native select method (@pxref{Finding the News}).  It is normally faster
than using an @code{nntp} select method, but might not be.  It depends.
You just have to try to find out what's best at your site.

@table @code

@item nnspool-inews-program
@vindex nnspool-inews-program
Program used to post an article.

@item nnspool-inews-switches
@vindex nnspool-inews-switches
Parameters given to the inews program when posting an article.

@item nnspool-spool-directory
@vindex nnspool-spool-directory
Where @code{nnspool} looks for the articles.  This is normally
@file{/usr/spool/news/}.

@item nnspool-nov-directory
@vindex nnspool-nov-directory
Where @code{nnspool} will look for @acronym{NOV} files.  This is normally@*
@file{/usr/spool/news/over.view/}.

@item nnspool-lib-dir
@vindex nnspool-lib-dir
Where the news lib dir is (@file{/usr/lib/news/} by default).

@item nnspool-active-file
@vindex nnspool-active-file
The name of the active file.

@item nnspool-newsgroups-file
@vindex nnspool-newsgroups-file
The name of the group descriptions file.

@item nnspool-history-file
@vindex nnspool-history-file
The name of the news history file.

@item nnspool-active-times-file
@vindex nnspool-active-times-file
The name of the active date file.

@item nnspool-nov-is-evil
@vindex nnspool-nov-is-evil
If non-@code{nil}, @code{nnspool} won't try to use any @acronym{NOV} files
that it finds.

@item nnspool-sift-nov-with-sed
@vindex nnspool-sift-nov-with-sed
@cindex sed
If non-@code{nil}, which is the default, use @code{sed} to get the
relevant portion from the overview file.  If @code{nil},
@code{nnspool} will load the entire file into a buffer and process it
there.

@end table


@node Getting Mail
@section Getting Mail
@cindex reading mail
@cindex mail

Reading mail with a newsreader---isn't that just plain WeIrD? But of
course.

@menu
* Mail in a Newsreader::        Important introductory notes.
* Getting Started Reading Mail::  A simple cookbook example.
* Splitting Mail::              How to create mail groups.
* Mail Sources::                How to tell Gnus where to get mail from.
* Mail Back End Variables::     Variables for customizing mail handling.
* Fancy Mail Splitting::        Gnus can do hairy splitting of incoming mail.
* Group Mail Splitting::        Use group customize to drive mail splitting.
* Incorporating Old Mail::      What about the old mail you have?
* Expiring Mail::               Getting rid of unwanted mail.
* Washing Mail::                Removing cruft from the mail you get.
* Duplicates::                  Dealing with duplicated mail.
* Not Reading Mail::            Using mail back ends for reading other files.
* Choosing a Mail Back End::    Gnus can read a variety of mail formats.
@end menu


@node Mail in a Newsreader
@subsection Mail in a Newsreader

If you are used to traditional mail readers, but have decided to switch
to reading mail with Gnus, you may find yourself experiencing something
of a culture shock.

Gnus does not behave like traditional mail readers.  If you want to make
it behave that way, you can, but it's an uphill battle.

Gnus, by default, handles all its groups using the same approach.  This
approach is very newsreaderly---you enter a group, see the new/unread
messages, and when you read the messages, they get marked as read, and
you don't see them any more.  (Unless you explicitly ask for them.)

In particular, you do not do anything explicitly to delete messages.

Does this mean that all the messages that have been marked as read are
deleted?  How awful!

But, no, it means that old messages are @dfn{expired} according to some
scheme or other.  For news messages, the expire process is controlled by
the news administrator; for mail, the expire process is controlled by
you.  The expire process for mail is covered in depth in @ref{Expiring
Mail}.

What many Gnus users find, after using it a while for both news and
mail, is that the transport mechanism has very little to do with how
they want to treat a message.

Many people subscribe to several mailing lists.  These are transported
via @acronym{SMTP}, and are therefore mail.  But we might go for weeks without
answering, or even reading these messages very carefully.  We may not
need to save them because if we should need to read one again, they are
archived somewhere else.

Some people have local news groups which have only a handful of readers.
These are transported via @acronym{NNTP}, and are therefore news.  But we may need
to read and answer a large fraction of the messages very carefully in
order to do our work.  And there may not be an archive, so we may need
to save the interesting messages the same way we would personal mail.

The important distinction turns out to be not the transport mechanism,
but other factors such as how interested we are in the subject matter,
or how easy it is to retrieve the message if we need to read it again.

Gnus provides many options for sorting mail into ``groups'' which behave
like newsgroups, and for treating each group (whether mail or news)
differently.

Some users never get comfortable using the Gnus (ahem) paradigm and wish
that Gnus should grow up and be a male, er, mail reader.  It is possible
to whip Gnus into a more mailreaderly being, but, as said before, it's
not easy.  People who prefer proper mail readers should try @sc{vm}
instead, which is an excellent, and proper, mail reader.

I don't mean to scare anybody off, but I want to make it clear that you
may be required to learn a new way of thinking about messages.  After
you've been subjected to The Gnus Way, you will come to love it.  I can
guarantee it.  (At least the guy who sold me the Emacs Subliminal
Brain-Washing Functions that I've put into Gnus did guarantee it.  You
Will Be Assimilated.  You Love Gnus.  You Love The Gnus Mail Way.
You Do.)


@node Getting Started Reading Mail
@subsection Getting Started Reading Mail

It's quite easy to use Gnus to read your new mail.  You just plonk the
mail back end of your choice into @code{gnus-secondary-select-methods},
and things will happen automatically.

For instance, if you want to use @code{nnml} (which is a ``one file per
mail'' back end), you could put the following in your @file{~/.gnus.el} file:

@lisp
(setq gnus-secondary-select-methods '((nnml "")))
@end lisp

Now, the next time you start Gnus, this back end will be queried for new
articles, and it will move all the messages in your spool file to its
directory, which is @file{~/Mail/} by default.  The new group that will
be created (@samp{mail.misc}) will be subscribed, and you can read it
like any other group.

You will probably want to split the mail into several groups, though:

@lisp
(setq nnmail-split-methods
      '(("junk" "^From:.*Lars Ingebrigtsen")
        ("crazy" "^Subject:.*die\\|^Organization:.*flabby")
        ("other" "")))
@end lisp

This will result in three new @code{nnml} mail groups being created:
@samp{nnml:junk}, @samp{nnml:crazy}, and @samp{nnml:other}.  All the
mail that doesn't fit into the first two groups will be placed in the
last group.

This should be sufficient for reading mail with Gnus.  You might want to
give the other sections in this part of the manual a perusal, though.
Especially @pxref{Choosing a Mail Back End} and @pxref{Expiring Mail}.


@node Splitting Mail
@subsection Splitting Mail
@cindex splitting mail
@cindex mail splitting
@cindex mail filtering (splitting)

@vindex nnmail-split-methods
The @code{nnmail-split-methods} variable says how the incoming mail is
to be split into groups.

@lisp
(setq nnmail-split-methods
  '(("mail.junk" "^From:.*Lars Ingebrigtsen")
    ("mail.crazy" "^Subject:.*die\\|^Organization:.*flabby")
    ("mail.other" "")))
@end lisp

This variable is a list of lists, where the first element of each of
these lists is the name of the mail group (they do not have to be called
something beginning with @samp{mail}, by the way), and the second
element is a regular expression used on the header of each mail to
determine if it belongs in this mail group.  The first string may
contain @samp{\\1} forms, like the ones used by @code{replace-match} to
insert sub-expressions from the matched text.  For instance:

@lisp
("list.\\1" "From:.* \\(.*\\)-list@@majordomo.com")
@end lisp

The second element can also be a function.  In that case, it will be
called narrowed to the headers with the first element of the rule as the
argument.  It should return a non-@code{nil} value if it thinks that the
mail belongs in that group.

The last of these groups should always be a general one, and the regular
expression should @emph{always} be @samp{*} so that it matches any mails
that haven't been matched by any of the other regexps.  (These rules are
processed from the beginning of the alist toward the end.  The first
rule to make a match will ``win'', unless you have crossposting enabled.
In that case, all matching rules will ``win''.)

If you like to tinker with this yourself, you can set this variable to a
function of your choice.  This function will be called without any
arguments in a buffer narrowed to the headers of an incoming mail
message.  The function should return a list of group names that it
thinks should carry this mail message.

Note that the mail back ends are free to maul the poor, innocent,
incoming headers all they want to.  They all add @code{Lines} headers;
some add @code{X-Gnus-Group} headers; most rename the Unix mbox
@code{From<SPACE>} line to something else.

@vindex nnmail-crosspost
The mail back ends all support cross-posting.  If several regexps match,
the mail will be ``cross-posted'' to all those groups.
@code{nnmail-crosspost} says whether to use this mechanism or not.  Note
that no articles are crossposted to the general (@samp{*}) group.

@vindex nnmail-crosspost-link-function
@cindex crosspost
@cindex links
@code{nnmh} and @code{nnml} makes crossposts by creating hard links to
the crossposted articles.  However, not all file systems support hard
links.  If that's the case for you, set
@code{nnmail-crosspost-link-function} to @code{copy-file}.  (This
variable is @code{add-name-to-file} by default.)

@kindex M-x nnmail-split-history
@findex nnmail-split-history
If you wish to see where the previous mail split put the messages, you
can use the @kbd{M-x nnmail-split-history} command.  If you wish to see
where re-spooling messages would put the messages, you can use
@code{gnus-summary-respool-trace} and related commands (@pxref{Mail
Group Commands}).

@vindex nnmail-split-header-length-limit
Header lines longer than the value of
@code{nnmail-split-header-length-limit} are excluded from the split
function.

@vindex nnmail-mail-splitting-charset
@vindex nnmail-mail-splitting-decodes
By default the splitting codes @acronym{MIME} decodes headers so you
can match on non-@acronym{ASCII} strings.  The
@code{nnmail-mail-splitting-charset} variable specifies the default
charset for decoding.  The behaviour can be turned off completely by
binding @code{nnmail-mail-splitting-decodes} to @code{nil}, which is
useful if you want to match articles based on the raw header data.

@vindex nnmail-resplit-incoming
By default, splitting is performed on all incoming messages.  If you
specify a @code{directory} entry for the variable @code{mail-sources}
(@pxref{Mail Source Specifiers}), however, then splitting does
@emph{not} happen by default.  You can set the variable
@code{nnmail-resplit-incoming} to a non-@code{nil} value to make
splitting happen even in this case.  (This variable has no effect on
other kinds of entries.)

Gnus gives you all the opportunity you could possibly want for shooting
yourself in the foot.  Let's say you create a group that will contain
all the mail you get from your boss.  And then you accidentally
unsubscribe from the group.  Gnus will still put all the mail from your
boss in the unsubscribed group, and so, when your boss mails you ``Have
that report ready by Monday or you're fired!'', you'll never see it and,
come Tuesday, you'll still believe that you're gainfully employed while
you really should be out collecting empty bottles to save up for next
month's rent money.


@node Mail Sources
@subsection Mail Sources

Mail can be gotten from many different sources---the mail spool, from
a @acronym{POP} mail server, from a procmail directory, or from a
maildir, for instance.

@menu
* Mail Source Specifiers::      How to specify what a mail source is.
* Mail Source Customization::   Some variables that influence things.
* Fetching Mail::               Using the mail source specifiers.
@end menu


@node Mail Source Specifiers
@subsubsection Mail Source Specifiers
@cindex POP
@cindex mail server
@cindex procmail
@cindex mail spool
@cindex mail source

You tell Gnus how to fetch mail by setting @code{mail-sources}
(@pxref{Fetching Mail}) to a @dfn{mail source specifier}.

Here's an example:

@lisp
(pop :server "pop3.mailserver.com" :user "myname")
@end lisp

As can be observed, a mail source specifier is a list where the first
element is a @dfn{mail source type}, followed by an arbitrary number of
@dfn{keywords}.  Keywords that are not explicitly specified are given
default values.

The following mail source types are available:

@table @code
@item file
Get mail from a single file; typically from the mail spool.

Keywords:

@table @code
@item :path
The file name.  Defaults to the value of the @env{MAIL}
environment variable or the value of @code{rmail-spool-directory}
(usually something like @file{/usr/mail/spool/user-name}).

@item :prescript
@itemx :postscript
Script run before/after fetching mail.
@end table

An example file mail source:

@lisp
(file :path "/usr/spool/mail/user-name")
@end lisp

Or using the default file name:

@lisp
(file)
@end lisp

If the mail spool file is not located on the local machine, it's best
to use @acronym{POP} or @acronym{IMAP} or the like to fetch the mail.
You can not use ange-ftp file names here---it has no way to lock the
mail spool while moving the mail.

If it's impossible to set up a proper server, you can use ssh instead.

@lisp
(setq mail-sources
      '((file :prescript "ssh host bin/getmail >%t")))
@end lisp

The @samp{getmail} script would look something like the following:

@example
#!/bin/sh
#  getmail - move mail from spool to stdout
#  flu@@iki.fi

MOVEMAIL=/usr/lib/emacs/20.3/i386-redhat-linux/movemail
TMP=$HOME/Mail/tmp
rm -f $TMP; $MOVEMAIL $MAIL $TMP >/dev/null && cat $TMP
@end example

Alter this script to fit find the @samp{movemail} you want to use.


@item directory
@vindex nnmail-scan-directory-mail-source-once
Get mail from several files in a directory.  This is typically used
when you have procmail split the incoming mail into several files.
That is, there is a one-to-one correspondence between files in that
directory and groups, so that mail from the file @file{foo.bar.spool}
will be put in the group @code{foo.bar}.  (You can change the suffix
to be used instead of @code{.spool}.)  Setting
@code{nnmail-scan-directory-mail-source-once} to non-@code{nil} forces
Gnus to scan the mail source only once.  This is particularly useful
if you want to scan mail groups at a specified level.

@vindex nnmail-resplit-incoming
There is also the variable @code{nnmail-resplit-incoming}, if you set
that to a non-@code{nil} value, then the normal splitting process is
applied to all the files from the directory, @ref{Splitting Mail}.

Keywords:

@table @code
@item :path
The name of the directory where the files are.  There is no default
value.

@item :suffix
Only files ending with this suffix are used.  The default is
@samp{.spool}.

@item :predicate
Only files that have this predicate return non-@code{nil} are returned.
The default is @code{identity}.  This is used as an additional
filter---only files that have the right suffix @emph{and} satisfy this
predicate are considered.

@item :prescript
@itemx :postscript
Script run before/after fetching mail.

@end table

An example directory mail source:

@lisp
(directory :path "/home/user-name/procmail-dir/"
           :suffix ".prcml")
@end lisp

@item pop
Get mail from a @acronym{POP} server.

Keywords:

@table @code
@item :server
The name of the @acronym{POP} server.  The default is taken from the
@env{MAILHOST} environment variable.

@item :port
The port number of the @acronym{POP} server.  This can be a number (eg,
@samp{:port 1234}) or a string (eg, @samp{:port "pop3"}).  If it is a
string, it should be a service name as listed in @file{/etc/services} on
Unix systems.  The default is @samp{"pop3"}.  On some systems you might
need to specify it as @samp{"pop-3"} instead.

@item :user
The user name to give to the @acronym{POP} server.  The default is the login
name.

@item :password
The password to give to the @acronym{POP} server.  If not specified,
the user is prompted.

@item :program
The program to use to fetch mail from the @acronym{POP} server.  This
should be a @code{format}-like string.  Here's an example:

@example
fetchmail %u@@%s -P %p %t
@end example

The valid format specifier characters are:

@table @samp
@item t
The name of the file the mail is to be moved to.  This must always be
included in this string.

@item s
The name of the server.

@item P
The port number of the server.

@item u
The user name to use.

@item p
The password to use.
@end table

The values used for these specs are taken from the values you give the
corresponding keywords.

@item :prescript
A script to be run before fetching the mail.  The syntax is the same as
the @code{:program} keyword.  This can also be a function to be run.

@item :postscript
A script to be run after fetching the mail.  The syntax is the same as
the @code{:program} keyword.  This can also be a function to be run.

@item :function
The function to use to fetch mail from the @acronym{POP} server.  The
function is called with one parameter---the name of the file where the
mail should be moved to.

@item :authentication
This can be either the symbol @code{password} or the symbol @code{apop}
and says what authentication scheme to use.  The default is
@code{password}.

@item :connection
What stream to use for connecting to the server, this can be the symbol
@code{ssl}, the symbol @code{tls} or others.  The default is @code{nil}
and use insecure connections.  Note that for SSL/TLS, you need external
programs and libraries:

@itemize @bullet
@item
@dfn{ssl:} Connect through SSL@. Requires OpenSSL (the program
@samp{openssl}) or SSLeay (@samp{s_client}) as well as the external
library @samp{ssl.el}.
@item
@dfn{starttls:} Connect via the STARTTLS extension (similar to SSL)@.
Requires the external library @samp{starttls.el} and program
@samp{starttls}.
@end itemize

@item :leave
Non-@code{nil} if mail is to be left on the server and UIDL used for
message retrieval.  The default is @code{nil}.

@end table

If the @code{:program} and @code{:function} keywords aren't specified,
@code{pop3-movemail} will be used.

Here are some examples.  Fetch from the default @acronym{POP} server,
using the default user name, and default fetcher:

@lisp
(pop)
@end lisp

Fetch from a named server with a named user and password:

@lisp
(pop :server "my.pop.server"
     :user "user-name" :password "secret")
@end lisp

Use @samp{movemail} to move the mail:

@lisp
(pop :program "movemail po:%u %t %p")
@end lisp

@item maildir
Get mail from a maildir.  This is a type of mailbox that is supported by
at least qmail and postfix, where each file in a special directory
contains exactly one mail.

Keywords:

@table @code
@item :path
The name of the directory where the mails are stored.  The default is
taken from the @env{MAILDIR} environment variable or
@file{~/Maildir/}.
@item :subdirs
The subdirectories of the Maildir.  The default is
@samp{("new" "cur")}.

@c If you sometimes look at your mail through a pop3 daemon before fetching
@c them with Gnus, you may also have to fetch your mails from the
@c @code{cur} directory inside the maildir, like in the first example
@c below.

You can also get mails from remote hosts (because maildirs don't suffer
from locking problems).

@end table

Two example maildir mail sources:

@lisp
(maildir :path "/home/user-name/Maildir/"
         :subdirs ("cur" "new"))
@end lisp

@lisp
(maildir :path "/user@@remotehost.org:~/Maildir/"
         :subdirs ("new"))
@end lisp

@item imap
Get mail from a @acronym{IMAP} server.  If you don't want to use
@acronym{IMAP} as intended, as a network mail reading protocol (ie
with nnimap), for some reason or other, Gnus let you treat it similar
to a @acronym{POP} server and fetches articles from a given
@acronym{IMAP} mailbox.  @xref{IMAP}, for more information.

Note that for the Kerberos, GSSAPI, @acronym{TLS}/@acronym{SSL} and STARTTLS support you
may need external programs and libraries, @xref{IMAP}.

Keywords:

@table @code
@item :server
The name of the @acronym{IMAP} server.  The default is taken from the
@env{MAILHOST} environment variable.

@item :port
The port number of the @acronym{IMAP} server.  The default is @samp{143}, or
@samp{993} for @acronym{TLS}/@acronym{SSL} connections.

@item :user
The user name to give to the @acronym{IMAP} server.  The default is the login
name.

@item :password
The password to give to the @acronym{IMAP} server.  If not specified, the user is
prompted.

@item :stream
What stream to use for connecting to the server, this is one of the
symbols in @code{imap-stream-alist}.  Right now, this means
@samp{gssapi}, @samp{kerberos4}, @samp{starttls}, @samp{tls},
@samp{ssl}, @samp{shell} or the default @samp{network}.

@item :authentication
Which authenticator to use for authenticating to the server, this is
one of the symbols in @code{imap-authenticator-alist}.  Right now,
this means @samp{gssapi}, @samp{kerberos4}, @samp{digest-md5},
@samp{cram-md5}, @samp{anonymous} or the default @samp{login}.

@item :program
When using the `shell' :stream, the contents of this variable is
mapped into the @code{imap-shell-program} variable.  This should be a
@code{format}-like string (or list of strings).  Here's an example:

@example
ssh %s imapd
@end example

The valid format specifier characters are:

@table @samp
@item s
The name of the server.

@item l
User name from @code{imap-default-user}.

@item p
The port number of the server.
@end table

The values used for these specs are taken from the values you give the
corresponding keywords.

@item :mailbox
The name of the mailbox to get mail from.  The default is @samp{INBOX}
which normally is the mailbox which receive incoming mail.

@item :predicate
The predicate used to find articles to fetch.  The default, @samp{UNSEEN
UNDELETED}, is probably the best choice for most people, but if you
sometimes peek in your mailbox with a @acronym{IMAP} client and mark some
articles as read (or; SEEN) you might want to set this to @samp{1:*}.
Then all articles in the mailbox is fetched, no matter what.  For a
complete list of predicates, see RFC 2060 section 6.4.4.

@item :fetchflag
How to flag fetched articles on the server, the default @samp{\Deleted}
will mark them as deleted, an alternative would be @samp{\Seen} which
would simply mark them as read.  These are the two most likely choices,
but more flags are defined in RFC 2060 section 2.3.2.

@item :dontexpunge
If non-@code{nil}, don't remove all articles marked as deleted in the
mailbox after finishing the fetch.

@end table

An example @acronym{IMAP} mail source:

@lisp
(imap :server "mail.mycorp.com"
      :stream kerberos4
      :fetchflag "\\Seen")
@end lisp

@item webmail
Get mail from a webmail server, such as @uref{http://www.hotmail.com/},
@uref{http://webmail.netscape.com/}, @uref{http://www.netaddress.com/},
@uref{http://mail.yahoo.com/}.

NOTE: Webmail largely depends on cookies.  A "one-line-cookie" patch is
required for url "4.0pre.46".

WARNING: Mails may be lost.  NO WARRANTY.

Keywords:

@table @code
@item :subtype
The type of the webmail server.  The default is @code{hotmail}.  The
alternatives are @code{netscape}, @code{netaddress}, @code{my-deja}.

@item :user
The user name to give to the webmail server.  The default is the login
name.

@item :password
The password to give to the webmail server.  If not specified, the user is
prompted.

@item :dontexpunge
If non-@code{nil}, only fetch unread articles and don't move them to
trash folder after finishing the fetch.

@end table

An example webmail source:

@lisp
(webmail :subtype 'hotmail
         :user "user-name"
         :password "secret")
@end lisp
@end table

@table @dfn
@item Common Keywords
Common keywords can be used in any type of mail source.

Keywords:

@table @code
@item :plugged
If non-@code{nil}, fetch the mail even when Gnus is unplugged.  If you
use directory source to get mail, you can specify it as in this
example:

@lisp
(setq mail-sources
      '((directory :path "/home/pavel/.Spool/"
                   :suffix ""
                   :plugged t)))
@end lisp

Gnus will then fetch your mail even when you are unplugged.  This is
useful when you use local mail and news.

@end table
@end table

@subsubsection Function Interface

Some of the above keywords specify a Lisp function to be executed.
For each keyword @code{:foo}, the Lisp variable @code{foo} is bound to
the value of the keyword while the function is executing.  For example,
consider the following mail-source setting:

@lisp
(setq mail-sources '((pop :user "jrl"
                          :server "pophost" :function fetchfunc)))
@end lisp

While the function @code{fetchfunc} is executing, the symbol @code{user}
is bound to @code{"jrl"}, and the symbol @code{server} is bound to
@code{"pophost"}.  The symbols @code{port}, @code{password},
@code{program}, @code{prescript}, @code{postscript}, @code{function},
and @code{authentication} are also bound (to their default values).

See above for a list of keywords for each type of mail source.


@node Mail Source Customization
@subsubsection Mail Source Customization

The following is a list of variables that influence how the mail is
fetched.  You would normally not need to set or change any of these
variables.

@table @code
@item mail-source-crash-box
@vindex mail-source-crash-box
File where mail will be stored while processing it.  The default is@*
@file{~/.emacs-mail-crash-box}.

@item mail-source-delete-incoming
@vindex mail-source-delete-incoming
If non-@code{nil}, delete incoming files after handling them.  If
@code{t}, delete the files immediately, if @code{nil}, never delete any
files.  If a positive number, delete files older than number of days
(This will only happen, when receiving new mail).  You may also set
@code{mail-source-delete-incoming} to @code{nil} and call
@code{mail-source-delete-old-incoming} from a hook or interactively.

@item mail-source-delete-old-incoming-confirm
@vindex mail-source-delete-old-incoming-confirm
If non-@code{nil}, ask for for confirmation before deleting old incoming
files.  This variable only applies when
@code{mail-source-delete-incoming} is a positive number.

@item mail-source-ignore-errors
@vindex mail-source-ignore-errors
If non-@code{nil}, ignore errors when reading mail from a mail source.

@item mail-source-directory
@vindex mail-source-directory
Directory where files (if any) will be stored.  The default is
@file{~/Mail/}.  At present, the only thing this is used for is to say
where the incoming files will be stored if the previous variable is
@code{nil}.

@item mail-source-incoming-file-prefix
@vindex mail-source-incoming-file-prefix
Prefix for file name for storing incoming mail.  The default is
@file{Incoming}, in which case files will end up with names like
@file{Incoming30630D_} or @file{Incoming298602ZD}.  This is really only
relevant if @code{mail-source-delete-incoming} is @code{nil}.

@item mail-source-default-file-modes
@vindex mail-source-default-file-modes
All new mail files will get this file mode.  The default is 384.

@item mail-source-movemail-program
@vindex mail-source-movemail-program
If non-@code{nil}, name of program for fetching new mail.  If
@code{nil}, @code{movemail} in @var{exec-directory}.

@end table


@node Fetching Mail
@subsubsection Fetching Mail

@vindex mail-sources
@vindex nnmail-spool-file
The way to actually tell Gnus where to get new mail from is to set
@code{mail-sources} to a list of mail source specifiers
(@pxref{Mail Source Specifiers}).

If this variable (and the obsolescent @code{nnmail-spool-file}) is
@code{nil}, the mail back ends will never attempt to fetch mail by
themselves.

If you want to fetch mail both from your local spool as well as a
@acronym{POP} mail server, you'd say something like:

@lisp
(setq mail-sources
      '((file)
        (pop :server "pop3.mail.server"
             :password "secret")))
@end lisp

Or, if you don't want to use any of the keyword defaults:

@lisp
(setq mail-sources
      '((file :path "/var/spool/mail/user-name")
        (pop :server "pop3.mail.server"
             :user "user-name"
             :port "pop3"
             :password "secret")))
@end lisp


When you use a mail back end, Gnus will slurp all your mail from your
inbox and plonk it down in your home directory.  Gnus doesn't move any
mail if you're not using a mail back end---you have to do a lot of magic
invocations first.  At the time when you have finished drawing the
pentagram, lightened the candles, and sacrificed the goat, you really
shouldn't be too surprised when Gnus moves your mail.



@node Mail Back End Variables
@subsection Mail Back End Variables

These variables are (for the most part) pertinent to all the various
mail back ends.

@table @code
@vindex nnmail-read-incoming-hook
@item nnmail-read-incoming-hook
The mail back ends all call this hook after reading new mail.  You can
use this hook to notify any mail watch programs, if you want to.

@vindex nnmail-split-hook
@item nnmail-split-hook
@findex gnus-article-decode-encoded-words
@cindex RFC 1522 decoding
@cindex RFC 2047 decoding
Hook run in the buffer where the mail headers of each message is kept
just before the splitting based on these headers is done.  The hook is
free to modify the buffer contents in any way it sees fit---the buffer
is discarded after the splitting has been done, and no changes performed
in the buffer will show up in any files.
@code{gnus-article-decode-encoded-words} is one likely function to add
to this hook.

@vindex nnmail-pre-get-new-mail-hook
@vindex nnmail-post-get-new-mail-hook
@item nnmail-pre-get-new-mail-hook
@itemx nnmail-post-get-new-mail-hook
These are two useful hooks executed when treating new incoming
mail---@code{nnmail-pre-get-new-mail-hook} (is called just before
starting to handle the new mail) and
@code{nnmail-post-get-new-mail-hook} (is called when the mail handling
is done).  Here's and example of using these two hooks to change the
default file modes the new mail files get:

@lisp
(add-hook 'nnmail-pre-get-new-mail-hook
          (lambda () (set-default-file-modes 511)))

(add-hook 'nnmail-post-get-new-mail-hook
          (lambda () (set-default-file-modes 551)))
@end lisp

@item nnmail-use-long-file-names
@vindex nnmail-use-long-file-names
If non-@code{nil}, the mail back ends will use long file and directory
names.  Groups like @samp{mail.misc} will end up in directories
(assuming use of @code{nnml} back end) or files (assuming use of
@code{nnfolder} back end) like @file{mail.misc}.  If it is @code{nil},
the same group will end up in @file{mail/misc}.

@item nnmail-delete-file-function
@vindex nnmail-delete-file-function
@findex delete-file
Function called to delete files.  It is @code{delete-file} by default.

@item nnmail-cache-accepted-message-ids
@vindex nnmail-cache-accepted-message-ids
If non-@code{nil}, put the @code{Message-ID}s of articles imported into
the back end (via @code{Gcc}, for instance) into the mail duplication
discovery cache.  The default is @code{nil}.

@item nnmail-cache-ignore-groups
@vindex nnmail-cache-ignore-groups
This can be a regular expression or a list of regular expressions.
Group names that match any of the regular expressions will never be
recorded in the @code{Message-ID} cache.

This can be useful, for example, when using Fancy Splitting
(@pxref{Fancy Mail Splitting}) together with the function
@code{nnmail-split-fancy-with-parent}.

@end table


@node Fancy Mail Splitting
@subsection Fancy Mail Splitting
@cindex mail splitting
@cindex fancy mail splitting

@vindex nnmail-split-fancy
@findex nnmail-split-fancy
If the rather simple, standard method for specifying how to split mail
doesn't allow you to do what you want, you can set
@code{nnmail-split-methods} to @code{nnmail-split-fancy}.  Then you can
play with the @code{nnmail-split-fancy} variable.

Let's look at an example value of this variable first:

@lisp
;; @r{Messages from the mailer daemon are not crossposted to any of}
;; @r{the ordinary groups.  Warnings are put in a separate group}
;; @r{from real errors.}
(| ("from" mail (| ("subject" "warn.*" "mail.warning")
                   "mail.misc"))
   ;; @r{Non-error messages are crossposted to all relevant}
   ;; @r{groups, but we don't crosspost between the group for the}
   ;; @r{(ding) list and the group for other (ding) related mail.}
   (& (| (any "ding@@ifi\\.uio\\.no" "ding.list")
         ("subject" "ding" "ding.misc"))
      ;; @r{Other mailing lists@dots{}}
      (any "procmail@@informatik\\.rwth-aachen\\.de" "procmail.list")
      (any "SmartList@@informatik\\.rwth-aachen\\.de" "SmartList.list")
      ;; @r{Both lists below have the same suffix, so prevent}
      ;; @r{cross-posting to mkpkg.list of messages posted only to}
      ;; @r{the bugs- list, but allow cross-posting when the}
      ;; @r{message was really cross-posted.}
      (any "bugs-mypackage@@somewhere" "mypkg.bugs")
      (any "mypackage@@somewhere\" - "bugs-mypackage" "mypkg.list")
      ;; @r{People@dots{}}
      (any "larsi@@ifi\\.uio\\.no" "people.Lars_Magne_Ingebrigtsen"))
   ;; @r{Unmatched mail goes to the catch all group.}
   "misc.misc")
@end lisp

This variable has the format of a @dfn{split}.  A split is a
(possibly) recursive structure where each split may contain other
splits.  Here are the possible split syntaxes:

@table @code

@item group 
If the split is a string, that will be taken as a group name.  Normal
regexp match expansion will be done.  See below for examples.

@item (@var{field} @var{value} [- @var{restrict} [@dots{}] ] @var{split})
If the split is a list, the first element of which is a string, then
store the message as specified by @var{split}, if header @var{field}
(a regexp) contains @var{value} (also a regexp).  If @var{restrict}
(yet another regexp) matches some string after @var{field} and before
the end of the matched @var{value}, the @var{split} is ignored.  If
none of the @var{restrict} clauses match, @var{split} is processed.

@item (| @var{split} @dots{})
If the split is a list, and the first element is @code{|} (vertical
bar), then process each @var{split} until one of them matches.  A
@var{split} is said to match if it will cause the mail message to be
stored in one or more groups.

@item (& @var{split} @dots{})
If the split is a list, and the first element is @code{&}, then
process all @var{split}s in the list.

@item junk
If the split is the symbol @code{junk}, then don't save (i.e., delete)
this message.  Use with extreme caution.

@item (: @var{function} @var{arg1} @var{arg2} @dots{})
If the split is a list, and the first element is @samp{:}, then the
second element will be called as a function with @var{args} given as
arguments.  The function should return a @var{split}.

@cindex body split
For instance, the following function could be used to split based on the
body of the messages:

@lisp
(defun split-on-body ()
  (save-excursion
    (widen)
    (goto-char (point-min))
    (when (re-search-forward "Some.*string" nil t)
      "string.group")))
@end lisp

The buffer is narrowed to the message in question when @var{function}
is run.  That's why @code{(widen)} needs to be called after
@code{save-excursion} in the example above.  Also note that with the
nnimap backend, message bodies will not be downloaded by default.  You
need to set @code{nnimap-split-download-body} to t to do that
(@pxref{Splitting in IMAP}).

@item (! @var{func} @var{split})
If the split is a list, and the first element is @code{!}, then
@var{split} will be processed, and @var{func} will be called as a
function with the result of @var{split} as argument.  @var{func}
should return a split.

@item nil
If the split is @code{nil}, it is ignored.

@end table

In these splits, @var{field} must match a complete field name.
@var{value} must match a complete word according to the fundamental mode
syntax table.  You can use @code{.*} in the regexps to match partial
field names or words.  In other words, all @var{value}'s are wrapped in
@samp{\<} and @samp{\>} pairs.

@vindex nnmail-split-abbrev-alist
@var{field} and @var{value} can also be Lisp symbols, in that case
they are expanded as specified by the variable
@code{nnmail-split-abbrev-alist}.  This is an alist of cons cells,
where the @sc{car} of a cell contains the key, and the @sc{cdr}
contains the associated value.  Predefined entries in
@code{nnmail-split-abbrev-alist} include:

@table @code
@item from
Matches the @samp{From}, @samp{Sender} and @samp{Resent-From} fields.
@item to
Matches the @samp{To}, @samp{Cc}, @samp{Apparently-To},
@samp{Resent-To} and @samp{Resent-Cc} fields.
@item any
Is the union of the @code{from} and @code{to} entries.
@end table

@vindex nnmail-split-fancy-syntax-table
@code{nnmail-split-fancy-syntax-table} is the syntax table in effect
when all this splitting is performed.

If you want to have Gnus create groups dynamically based on some
information in the headers (i.e., do @code{replace-match}-like
substitutions in the group names), you can say things like:

@example
(any "debian-\\b\\(\\w+\\)@@lists.debian.org" "mail.debian.\\1")
@end example

In this example, messages sent to @samp{debian-foo@@lists.debian.org}
will be filed in @samp{mail.debian.foo}.

If the string contains the element @samp{\&}, then the previously
matched string will be substituted.  Similarly, the elements @samp{\\1}
up to @samp{\\9} will be substituted with the text matched by the
groupings 1 through 9.

@findex nnmail-split-fancy-with-parent
@code{nnmail-split-fancy-with-parent} is a function which allows you to
split followups into the same groups their parents are in.  Sometimes
you can't make splitting rules for all your mail.  For example, your
boss might send you personal mail regarding different projects you are
working on, and as you can't tell your boss to put a distinguishing
string into the subject line, you have to resort to manually moving the
messages into the right group.  With this function, you only have to do
it once per thread.

To use this feature, you have to set @code{nnmail-treat-duplicates}
and @code{nnmail-cache-accepted-message-ids} to a non-@code{nil}
value.  And then you can include @code{nnmail-split-fancy-with-parent}
using the colon feature, like so:
@lisp
(setq nnmail-treat-duplicates 'warn     ; @r{or @code{delete}}
      nnmail-cache-accepted-message-ids t
      nnmail-split-fancy
      '(| (: nnmail-split-fancy-with-parent)
          ;; @r{other splits go here}
        ))
@end lisp

This feature works as follows: when @code{nnmail-treat-duplicates} is
non-@code{nil}, Gnus records the message id of every message it sees
in the file specified by the variable
@code{nnmail-message-id-cache-file}, together with the group it is in
(the group is omitted for non-mail messages).  When mail splitting is
invoked, the function @code{nnmail-split-fancy-with-parent} then looks
at the References (and In-Reply-To) header of each message to split
and searches the file specified by @code{nnmail-message-id-cache-file}
for the message ids.  When it has found a parent, it returns the
corresponding group name unless the group name matches the regexp
@code{nnmail-split-fancy-with-parent-ignore-groups}.  It is
recommended that you set @code{nnmail-message-id-cache-length} to a
somewhat higher number than the default so that the message ids are
still in the cache.  (A value of 5000 appears to create a file some
300 kBytes in size.)
@vindex nnmail-cache-accepted-message-ids
When @code{nnmail-cache-accepted-message-ids} is non-@code{nil}, Gnus
also records the message ids of moved articles, so that the followup
messages goes into the new group.

Also see the variable @code{nnmail-cache-ignore-groups} if you don't
want certain groups to be recorded in the cache.  For example, if all
outgoing messages are written to an ``outgoing'' group, you could set
@code{nnmail-cache-ignore-groups} to match that group name.
Otherwise, answers to all your messages would end up in the
``outgoing'' group.


@node Group Mail Splitting
@subsection Group Mail Splitting
@cindex mail splitting
@cindex group mail splitting

@findex gnus-group-split
If you subscribe to dozens of mailing lists but you don't want to
maintain mail splitting rules manually, group mail splitting is for you.
You just have to set @code{to-list} and/or @code{to-address} in group
parameters or group customization and set @code{nnmail-split-methods} to
@code{gnus-group-split}.  This splitting function will scan all groups
for those parameters and split mail accordingly, i.e., messages posted
from or to the addresses specified in the parameters @code{to-list} or
@code{to-address} of a mail group will be stored in that group.

Sometimes, mailing lists have multiple addresses, and you may want mail
splitting to recognize them all: just set the @code{extra-aliases} group
parameter to the list of additional addresses and it's done.  If you'd
rather use a regular expression, set @code{split-regexp}.

All these parameters in a group will be used to create an
@code{nnmail-split-fancy} split, in which the @var{field} is @samp{any},
the @var{value} is a single regular expression that matches
@code{to-list}, @code{to-address}, all of @code{extra-aliases} and all
matches of @code{split-regexp}, and the @var{split} is the name of the
group.  @var{restrict}s are also supported: just set the
@code{split-exclude} parameter to a list of regular expressions.

If you can't get the right split to be generated using all these
parameters, or you just need something fancier, you can set the
parameter @code{split-spec} to an @code{nnmail-split-fancy} split.  In
this case, all other aforementioned parameters will be ignored by
@code{gnus-group-split}.  In particular, @code{split-spec} may be set to
@code{nil}, in which case the group will be ignored by
@code{gnus-group-split}.

@vindex gnus-group-split-default-catch-all-group
@code{gnus-group-split} will do cross-posting on all groups that match,
by defining a single @code{&} fancy split containing one split for each
group.  If a message doesn't match any split, it will be stored in the
group named in @code{gnus-group-split-default-catch-all-group}, unless
some group has @code{split-spec} set to @code{catch-all}, in which case
that group is used as the catch-all group.  Even though this variable is
often used just to name a group, it may also be set to an arbitrarily
complex fancy split (after all, a group name is a fancy split), and this
may be useful to split mail that doesn't go to any mailing list to
personal mail folders.  Note that this fancy split is added as the last
element of a @code{|} split list that also contains a @code{&} split
with the rules extracted from group parameters.

It's time for an example.  Assume the following group parameters have
been defined:

@example
nnml:mail.bar:
((to-address . "bar@@femail.com")
 (split-regexp . ".*@@femail\\.com"))
nnml:mail.foo:
((to-list . "foo@@nowhere.gov")
 (extra-aliases "foo@@localhost" "foo-redist@@home")
 (split-exclude "bugs-foo" "rambling-foo")
 (admin-address . "foo-request@@nowhere.gov"))
nnml:mail.others:
((split-spec . catch-all))
@end example

Setting @code{nnmail-split-methods} to @code{gnus-group-split} will
behave as if @code{nnmail-split-fancy} had been selected and variable
@code{nnmail-split-fancy} had been set as follows:

@lisp
(| (& (any "\\(bar@@femail\\.com\\|.*@@femail\\.com\\)" "mail.bar")
      (any "\\(foo@@nowhere\\.gov\\|foo@@localhost\\|foo-redist@@home\\)"
           - "bugs-foo" - "rambling-foo" "mail.foo"))
   "mail.others")
@end lisp

@findex gnus-group-split-fancy
If you'd rather not use group splitting for all your mail groups, you
may use it for only some of them, by using @code{nnmail-split-fancy}
splits like this:

@lisp
(: gnus-group-split-fancy @var{groups} @var{no-crosspost} @var{catch-all})
@end lisp

@var{groups} may be a regular expression or a list of group names whose
parameters will be scanned to generate the output split.
@var{no-crosspost} can be used to disable cross-posting; in this case, a
single @code{|} split will be output.  @var{catch-all} is the fall back
fancy split, used like @code{gnus-group-split-default-catch-all-group}.
If @var{catch-all} is @code{nil}, or if @code{split-regexp} matches the
empty string in any selected group, no catch-all split will be issued.
Otherwise, if some group has @code{split-spec} set to @code{catch-all},
this group will override the value of the @var{catch-all} argument.

@findex gnus-group-split-setup
Unfortunately, scanning all groups and their parameters can be quite
slow, especially considering that it has to be done for every message.
But don't despair!  The function @code{gnus-group-split-setup} can be
used to enable @code{gnus-group-split} in a much more efficient way.  It
sets @code{nnmail-split-methods} to @code{nnmail-split-fancy} and sets
@code{nnmail-split-fancy} to the split produced by
@code{gnus-group-split-fancy}.  Thus, the group parameters are only
scanned once, no matter how many messages are split.

@findex gnus-group-split-update
However, if you change group parameters, you'd have to update
@code{nnmail-split-fancy} manually.  You can do it by running
@code{gnus-group-split-update}.  If you'd rather have it updated
automatically, just tell @code{gnus-group-split-setup} to do it for
you.  For example, add to your @file{~/.gnus.el}:

@lisp
(gnus-group-split-setup @var{auto-update} @var{catch-all})
@end lisp

If @var{auto-update} is non-@code{nil}, @code{gnus-group-split-update}
will be added to @code{nnmail-pre-get-new-mail-hook}, so you won't ever
have to worry about updating @code{nnmail-split-fancy} again.  If you
don't omit @var{catch-all} (it's optional, equivalent to @code{nil}),
@code{gnus-group-split-default-catch-all-group} will be set to its
value.

@vindex gnus-group-split-updated-hook
Because you may want to change @code{nnmail-split-fancy} after it is set
by @code{gnus-group-split-update}, this function will run
@code{gnus-group-split-updated-hook} just before finishing.

@node Incorporating Old Mail
@subsection Incorporating Old Mail
@cindex incorporating old mail
@cindex import old mail

Most people have lots of old mail stored in various file formats.  If
you have set up Gnus to read mail using one of the spiffy Gnus mail
back ends, you'll probably wish to have that old mail incorporated into
your mail groups.

Doing so can be quite easy.

To take an example: You're reading mail using @code{nnml}
(@pxref{Mail Spool}), and have set @code{nnmail-split-methods} to a
satisfactory value (@pxref{Splitting Mail}).  You have an old Unix mbox
file filled with important, but old, mail.  You want to move it into
your @code{nnml} groups.

Here's how:

@enumerate
@item
Go to the group buffer.

@item
Type @kbd{G f} and give the file name to the mbox file when prompted to create an
@code{nndoc} group from the mbox file (@pxref{Foreign Groups}).

@item
Type @kbd{SPACE} to enter the newly created group.

@item
Type @kbd{M P b} to process-mark all articles in this group's buffer
(@pxref{Setting Process Marks}).

@item
Type @kbd{B r} to respool all the process-marked articles, and answer
@samp{nnml} when prompted (@pxref{Mail Group Commands}).
@end enumerate

All the mail messages in the mbox file will now also be spread out over
all your @code{nnml} groups.  Try entering them and check whether things
have gone without a glitch.  If things look ok, you may consider
deleting the mbox file, but I wouldn't do that unless I was absolutely
sure that all the mail has ended up where it should be.

Respooling is also a handy thing to do if you're switching from one mail
back end to another.  Just respool all the mail in the old mail groups
using the new mail back end.


@node Expiring Mail
@subsection Expiring Mail
@cindex article expiry

Traditional mail readers have a tendency to remove mail articles when
you mark them as read, in some way.  Gnus takes a fundamentally
different approach to mail reading.

Gnus basically considers mail just to be news that has been received in
a rather peculiar manner.  It does not think that it has the power to
actually change the mail, or delete any mail messages.  If you enter a
mail group, and mark articles as ``read'', or kill them in some other
fashion, the mail articles will still exist on the system.  I repeat:
Gnus will not delete your old, read mail.  Unless you ask it to, of
course.

To make Gnus get rid of your unwanted mail, you have to mark the
articles as @dfn{expirable}.  (With the default key bindings, this means
that you have to type @kbd{E}.)  This does not mean that the articles
will disappear right away, however.  In general, a mail article will be
deleted from your system if, 1) it is marked as expirable, AND 2) it is
more than one week old.  If you do not mark an article as expirable, it
will remain on your system until hell freezes over.  This bears
repeating one more time, with some spurious capitalizations: IF you do
NOT mark articles as EXPIRABLE, Gnus will NEVER delete those ARTICLES.

You do not have to mark articles as expirable by hand.  Gnus provides
two features, called ``auto-expire'' and ``total-expire'', that can help you
with this.  In a nutshell, ``auto-expire'' means that Gnus hits @kbd{E}
for you when you select an article.  And ``total-expire'' means that Gnus
considers all articles as expirable that are read.  So, in addition to
the articles marked @samp{E}, also the articles marked @samp{r},
@samp{R}, @samp{O}, @samp{K}, @samp{Y} and so on are considered
expirable.

When should either auto-expire or total-expire be used?  Most people
who are subscribed to mailing lists split each list into its own group
and then turn on auto-expire or total-expire for those groups.
(@xref{Splitting Mail}, for more information on splitting each list
into its own group.)

Which one is better, auto-expire or total-expire?  It's not easy to
answer.  Generally speaking, auto-expire is probably faster.  Another
advantage of auto-expire is that you get more marks to work with: for
the articles that are supposed to stick around, you can still choose
between tick and dormant and read marks.  But with total-expire, you
only have dormant and ticked to choose from.  The advantage of
total-expire is that it works well with adaptive scoring (@pxref{Adaptive
Scoring}).  Auto-expire works with normal scoring but not with adaptive
scoring.

@vindex gnus-auto-expirable-newsgroups
Groups that match the regular expression
@code{gnus-auto-expirable-newsgroups} will have all articles that you
read marked as expirable automatically.  All articles marked as
expirable have an @samp{E} in the first column in the summary buffer.

By default, if you have auto expiry switched on, Gnus will mark all the
articles you read as expirable, no matter if they were read or unread
before.  To avoid having articles marked as read marked as expirable
automatically, you can put something like the following in your
@file{~/.gnus.el} file:

@vindex gnus-mark-article-hook
@lisp
(remove-hook 'gnus-mark-article-hook
             'gnus-summary-mark-read-and-unread-as-read)
(add-hook 'gnus-mark-article-hook 'gnus-summary-mark-unread-as-read)
@end lisp

Note that making a group auto-expirable doesn't mean that all read
articles are expired---only the articles marked as expirable
will be expired.  Also note that using the @kbd{d} command won't make
articles expirable---only semi-automatic marking of articles as read will
mark the articles as expirable in auto-expirable groups.

Let's say you subscribe to a couple of mailing lists, and you want the
articles you have read to disappear after a while:

@lisp
(setq gnus-auto-expirable-newsgroups
      "mail.nonsense-list\\|mail.nice-list")
@end lisp

Another way to have auto-expiry happen is to have the element
@code{auto-expire} in the group parameters of the group.

If you use adaptive scoring (@pxref{Adaptive Scoring}) and
auto-expiring, you'll have problems.  Auto-expiring and adaptive scoring
don't really mix very well.

@vindex nnmail-expiry-wait
The @code{nnmail-expiry-wait} variable supplies the default time an
expirable article has to live.  Gnus starts counting days from when the
message @emph{arrived}, not from when it was sent.  The default is seven
days.

Gnus also supplies a function that lets you fine-tune how long articles
are to live, based on what group they are in.  Let's say you want to
have one month expiry period in the @samp{mail.private} group, a one day
expiry period in the @samp{mail.junk} group, and a six day expiry period
everywhere else:

@vindex nnmail-expiry-wait-function
@lisp
(setq nnmail-expiry-wait-function
      (lambda (group)
       (cond ((string= group "mail.private")
               31)
             ((string= group "mail.junk")
               1)
             ((string= group "important")
               'never)
             (t
               6))))
@end lisp

The group names this function is fed are ``unadorned'' group
names---no @samp{nnml:} prefixes and the like.

The @code{nnmail-expiry-wait} variable and
@code{nnmail-expiry-wait-function} function can either be a number (not
necessarily an integer) or one of the symbols @code{immediate} or
@code{never}.

You can also use the @code{expiry-wait} group parameter to selectively
change the expiry period (@pxref{Group Parameters}).

@vindex nnmail-expiry-target
The normal action taken when expiring articles is to delete them.
However, in some circumstances it might make more sense to move them
to other groups instead of deleting them.  The variable
@code{nnmail-expiry-target} (and the @code{expiry-target} group
parameter) controls this.  The variable supplies a default value for
all groups, which can be overridden for specific groups by the group
parameter.  default value is @code{delete}, but this can also be a
string (which should be the name of the group the message should be
moved to), or a function (which will be called in a buffer narrowed to
the message in question, and with the name of the group being moved
from as its parameter) which should return a target---either a group
name or @code{delete}.

Here's an example for specifying a group name:
@lisp
(setq nnmail-expiry-target "nnml:expired")
@end lisp

@findex nnmail-fancy-expiry-target
@vindex nnmail-fancy-expiry-targets
Gnus provides a function @code{nnmail-fancy-expiry-target} which will
expire mail to groups according to the variable
@code{nnmail-fancy-expiry-targets}.  Here's an example:

@lisp
 (setq nnmail-expiry-target 'nnmail-fancy-expiry-target
       nnmail-fancy-expiry-targets
       '((to-from "boss" "nnfolder:Work")
         ("subject" "IMPORTANT" "nnfolder:IMPORTANT.%Y.%b")
         ("from" ".*" "nnfolder:Archive-%Y")))
@end lisp

With this setup, any mail that has @code{IMPORTANT} in its Subject
header and was sent in the year @code{YYYY} and month @code{MMM}, will
get expired to the group @code{nnfolder:IMPORTANT.YYYY.MMM}.  If its
From or To header contains the string @code{boss}, it will get expired
to @code{nnfolder:Work}.  All other mail will get expired to
@code{nnfolder:Archive-YYYY}.

@vindex nnmail-keep-last-article
If @code{nnmail-keep-last-article} is non-@code{nil}, Gnus will never
expire the final article in a mail newsgroup.  This is to make life
easier for procmail users.

@vindex gnus-total-expirable-newsgroups
By the way: That line up there, about Gnus never expiring non-expirable
articles, is a lie.  If you put @code{total-expire} in the group
parameters, articles will not be marked as expirable, but all read
articles will be put through the expiry process.  Use with extreme
caution.  Even more dangerous is the
@code{gnus-total-expirable-newsgroups} variable.  All groups that match
this regexp will have all read articles put through the expiry process,
which means that @emph{all} old mail articles in the groups in question
will be deleted after a while.  Use with extreme caution, and don't come
crying to me when you discover that the regexp you used matched the
wrong group and all your important mail has disappeared.  Be a
@emph{man}!  Or a @emph{woman}!  Whatever you feel more comfortable
with!  So there!

Most people make most of their mail groups total-expirable, though.

@vindex gnus-inhibit-user-auto-expire
If @code{gnus-inhibit-user-auto-expire} is non-@code{nil}, user marking
commands will not mark an article as expirable, even if the group has
auto-expire turned on.


@node Washing Mail
@subsection Washing Mail
@cindex mail washing
@cindex list server brain damage
@cindex incoming mail treatment

Mailers and list servers are notorious for doing all sorts of really,
really stupid things with mail.  ``Hey, RFC 822 doesn't explicitly
prohibit us from adding the string @code{wE aRe ElItE!!!!!1!!} to the
end of all lines passing through our server, so let's do that!!!!1!''
Yes, but RFC 822 wasn't designed to be read by morons.  Things that were
considered to be self-evident were not discussed.  So.  Here we are.

Case in point:  The German version of Microsoft Exchange adds @samp{AW:
} to the subjects of replies instead of @samp{Re: }.  I could pretend to
be shocked and dismayed by this, but I haven't got the energy.  It is to
laugh.

Gnus provides a plethora of functions for washing articles while
displaying them, but it might be nicer to do the filtering before
storing the mail to disk.  For that purpose, we have three hooks and
various functions that can be put in these hooks.

@table @code
@item nnmail-prepare-incoming-hook
@vindex nnmail-prepare-incoming-hook
This hook is called before doing anything with the mail and is meant for
grand, sweeping gestures.  It is called in a buffer that contains all
the new, incoming mail.  Functions to be used include:

@table @code
@item nnheader-ms-strip-cr
@findex nnheader-ms-strip-cr
Remove trailing carriage returns from each line.  This is default on
Emacs running on MS machines.

@end table

@item nnmail-prepare-incoming-header-hook
@vindex nnmail-prepare-incoming-header-hook
This hook is called narrowed to each header.  It can be used when
cleaning up the headers.  Functions that can be used include:

@table @code
@item nnmail-remove-leading-whitespace
@findex nnmail-remove-leading-whitespace
Clear leading white space that ``helpful'' listservs have added to the
headers to make them look nice.  Aaah.

(Note that this function works on both the header on the body of all
messages, so it is a potentially dangerous function to use (if a body
of a message contains something that looks like a header line).  So
rather than fix the bug, it is of course the right solution to make it
into a feature by documenting it.)

@item nnmail-remove-list-identifiers
@findex nnmail-remove-list-identifiers
Some list servers add an identifier---for example, @samp{(idm)}---to the
beginning of all @code{Subject} headers.  I'm sure that's nice for
people who use stone age mail readers.  This function will remove
strings that match the @code{nnmail-list-identifiers} regexp, which can
also be a list of regexp.  @code{nnmail-list-identifiers} may not contain
@code{\\(..\\)}.

For instance, if you want to remove the @samp{(idm)} and the
@samp{nagnagnag} identifiers:

@lisp
(setq nnmail-list-identifiers
      '("(idm)" "nagnagnag"))
@end lisp

This can also be done non-destructively with
@code{gnus-list-identifiers}, @xref{Article Hiding}.

@item nnmail-remove-tabs
@findex nnmail-remove-tabs
Translate all @samp{TAB} characters into @samp{SPACE} characters.

@item nnmail-fix-eudora-headers
@findex nnmail-fix-eudora-headers
@cindex Eudora
Eudora produces broken @code{References} headers, but OK
@code{In-Reply-To} headers.  This function will get rid of the
@code{References} headers.

@end table

@item nnmail-prepare-incoming-message-hook
@vindex nnmail-prepare-incoming-message-hook
This hook is called narrowed to each message.  Functions to be used
include:

@table @code
@item article-de-quoted-unreadable
@findex article-de-quoted-unreadable
Decode Quoted Readable encoding.

@end table
@end table


@node Duplicates
@subsection Duplicates

@vindex nnmail-treat-duplicates
@vindex nnmail-message-id-cache-length
@vindex nnmail-message-id-cache-file
@cindex duplicate mails
If you are a member of a couple of mailing lists, you will sometimes
receive two copies of the same mail.  This can be quite annoying, so
@code{nnmail} checks for and treats any duplicates it might find.  To do
this, it keeps a cache of old @code{Message-ID}s---
@code{nnmail-message-id-cache-file}, which is @file{~/.nnmail-cache} by
default.  The approximate maximum number of @code{Message-ID}s stored
there is controlled by the @code{nnmail-message-id-cache-length}
variable, which is 1000 by default.  (So 1000 @code{Message-ID}s will be
stored.) If all this sounds scary to you, you can set
@code{nnmail-treat-duplicates} to @code{warn} (which is what it is by
default), and @code{nnmail} won't delete duplicate mails.  Instead it
will insert a warning into the head of the mail saying that it thinks
that this is a duplicate of a different message.

This variable can also be a function.  If that's the case, the function
will be called from a buffer narrowed to the message in question with
the @code{Message-ID} as a parameter.  The function must return either
@code{nil}, @code{warn}, or @code{delete}.

You can turn this feature off completely by setting the variable to
@code{nil}.

If you want all the duplicate mails to be put into a special
@dfn{duplicates} group, you could do that using the normal mail split
methods:

@lisp
(setq nnmail-split-fancy
      '(| ;; @r{Messages duplicates go to a separate group.}
        ("gnus-warning" "duplicat\\(e\\|ion\\) of message" "duplicate")
        ;; @r{Message from daemons, postmaster, and the like to another.}
        (any mail "mail.misc")
        ;; @r{Other rules.}
        [...] ))
@end lisp
@noindent
Or something like:
@lisp
(setq nnmail-split-methods
      '(("duplicates" "^Gnus-Warning:.*duplicate")
        ;; @r{Other rules.}
        [...]))
@end lisp

Here's a neat feature: If you know that the recipient reads her mail
with Gnus, and that she has @code{nnmail-treat-duplicates} set to
@code{delete}, you can send her as many insults as you like, just by
using a @code{Message-ID} of a mail that you know that she's already
received.  Think of all the fun!  She'll never see any of it!  Whee!


@node Not Reading Mail
@subsection Not Reading Mail

If you start using any of the mail back ends, they have the annoying
habit of assuming that you want to read mail with them.  This might not
be unreasonable, but it might not be what you want.

If you set @code{mail-sources} and @code{nnmail-spool-file} to
@code{nil}, none of the back ends will ever attempt to read incoming
mail, which should help.

@vindex nnbabyl-get-new-mail
@vindex nnmbox-get-new-mail
@vindex nnml-get-new-mail
@vindex nnmh-get-new-mail
@vindex nnfolder-get-new-mail
This might be too much, if, for instance, you are reading mail quite
happily with @code{nnml} and just want to peek at some old Rmail
file you have stashed away with @code{nnbabyl}.  All back ends have
variables called back-end-@code{get-new-mail}.  If you want to disable
the @code{nnbabyl} mail reading, you edit the virtual server for the
group to have a setting where @code{nnbabyl-get-new-mail} to @code{nil}.

All the mail back ends will call @code{nn}*@code{-prepare-save-mail-hook}
narrowed to the article to be saved before saving it when reading
incoming mail.


@node Choosing a Mail Back End
@subsection Choosing a Mail Back End

Gnus will read the mail spool when you activate a mail group.  The mail
file is first copied to your home directory.  What happens after that
depends on what format you want to store your mail in.

There are six different mail back ends in the standard Gnus, and more
back ends are available separately.  The mail back end most people use
(because it is possibly the fastest) is @code{nnml} (@pxref{Mail
Spool}).

@menu
* Unix Mail Box::               Using the (quite) standard Un*x mbox.
* Rmail Babyl::                 Emacs programs use the Rmail Babyl format.
* Mail Spool::                  Store your mail in a private spool?
* MH Spool::                    An mhspool-like back end.
* Maildir::                     Another one-file-per-message format.
* Mail Folders::                Having one file for each group.
* Comparing Mail Back Ends::    An in-depth looks at pros and cons.
@end menu


@node Unix Mail Box
@subsubsection Unix Mail Box
@cindex nnmbox
@cindex unix mail box

@vindex nnmbox-active-file
@vindex nnmbox-mbox-file
The @dfn{nnmbox} back end will use the standard Un*x mbox file to store
mail.  @code{nnmbox} will add extra headers to each mail article to say
which group it belongs in.

Virtual server settings:

@table @code
@item nnmbox-mbox-file
@vindex nnmbox-mbox-file
The name of the mail box in the user's home directory.  Default is
@file{~/mbox}.

@item nnmbox-active-file
@vindex nnmbox-active-file
The name of the active file for the mail box.  Default is
@file{~/.mbox-active}.

@item nnmbox-get-new-mail
@vindex nnmbox-get-new-mail
If non-@code{nil}, @code{nnmbox} will read incoming mail and split it
into groups.  Default is @code{t}.
@end table


@node Rmail Babyl
@subsubsection Rmail Babyl
@cindex nnbabyl
@cindex Rmail mbox

@vindex nnbabyl-active-file
@vindex nnbabyl-mbox-file
The @dfn{nnbabyl} back end will use a Babyl mail box (aka. @dfn{Rmail
mbox}) to store mail.  @code{nnbabyl} will add extra headers to each
mail article to say which group it belongs in.

Virtual server settings:

@table @code
@item nnbabyl-mbox-file
@vindex nnbabyl-mbox-file
The name of the Rmail mbox file.  The default is @file{~/RMAIL}

@item nnbabyl-active-file
@vindex nnbabyl-active-file
The name of the active file for the rmail box.  The default is
@file{~/.rmail-active}

@item nnbabyl-get-new-mail
@vindex nnbabyl-get-new-mail
If non-@code{nil}, @code{nnbabyl} will read incoming mail.  Default is
@code{t}
@end table


@node Mail Spool
@subsubsection Mail Spool
@cindex nnml
@cindex mail @acronym{NOV} spool

The @dfn{nnml} spool mail format isn't compatible with any other known
format.  It should be used with some caution.

@vindex nnml-directory
If you use this back end, Gnus will split all incoming mail into files,
one file for each mail, and put the articles into the corresponding
directories under the directory specified by the @code{nnml-directory}
variable.  The default value is @file{~/Mail/}.

You do not have to create any directories beforehand; Gnus will take
care of all that.

If you have a strict limit as to how many files you are allowed to store
in your account, you should not use this back end.  As each mail gets its
own file, you might very well occupy thousands of inodes within a few
weeks.  If this is no problem for you, and it isn't a problem for you
having your friendly systems administrator walking around, madly,
shouting ``Who is eating all my inodes?! Who? Who!?!'', then you should
know that this is probably the fastest format to use.  You do not have
to trudge through a big mbox file just to read your new mail.

@code{nnml} is probably the slowest back end when it comes to article
splitting.  It has to create lots of files, and it also generates
@acronym{NOV} databases for the incoming mails.  This makes it possibly the
fastest back end when it comes to reading mail.

@cindex self contained nnml servers
@cindex marks
When the marks file is used (which it is by default), @code{nnml}
servers have the property that you may backup them using @code{tar} or
similar, and later be able to restore them into Gnus (by adding the
proper @code{nnml} server) and have all your marks be preserved.  Marks
for a group is usually stored in the @code{.marks} file (but see
@code{nnml-marks-file-name}) within each @code{nnml} group's directory.
Individual @code{nnml} groups are also possible to backup, use @kbd{G m}
to restore the group (after restoring the backup into the nnml
directory).

If for some reason you believe your @file{.marks} files are screwed
up, you can just delete them all.  Gnus will then correctly regenerate
them next time it starts.

Virtual server settings:

@table @code
@item nnml-directory
@vindex nnml-directory
All @code{nnml} directories will be placed under this directory.  The
default is the value of @code{message-directory} (whose default value
is @file{~/Mail}).

@item nnml-active-file
@vindex nnml-active-file
The active file for the @code{nnml} server.  The default is
@file{~/Mail/active}.

@item nnml-newsgroups-file
@vindex nnml-newsgroups-file
The @code{nnml} group descriptions file.  @xref{Newsgroups File
Format}.  The default is @file{~/Mail/newsgroups}.

@item nnml-get-new-mail
@vindex nnml-get-new-mail
If non-@code{nil}, @code{nnml} will read incoming mail.  The default is
@code{t}.

@item nnml-nov-is-evil
@vindex nnml-nov-is-evil
If non-@code{nil}, this back end will ignore any @acronym{NOV} files.  The
default is @code{nil}.

@item nnml-nov-file-name
@vindex nnml-nov-file-name
The name of the @acronym{NOV} files.  The default is @file{.overview}.

@item nnml-prepare-save-mail-hook
@vindex nnml-prepare-save-mail-hook
Hook run narrowed to an article before saving.

@item nnml-marks-is-evil
@vindex nnml-marks-is-evil
If non-@code{nil}, this back end will ignore any @sc{marks} files.  The
default is @code{nil}.

@item nnml-marks-file-name
@vindex nnml-marks-file-name
The name of the @dfn{marks} files.  The default is @file{.marks}.

@item nnml-use-compressed-files
@vindex nnml-use-compressed-files
If non-@code{nil}, @code{nnml} will allow using compressed message
files.

@end table

@findex nnml-generate-nov-databases
If your @code{nnml} groups and @acronym{NOV} files get totally out of whack,
you can do a complete update by typing @kbd{M-x
nnml-generate-nov-databases}.  This command will trawl through the
entire @code{nnml} hierarchy, looking at each and every article, so it
might take a while to complete.  A better interface to this
functionality can be found in the server buffer (@pxref{Server
Commands}).


@node MH Spool
@subsubsection MH Spool
@cindex nnmh
@cindex mh-e mail spool

@code{nnmh} is just like @code{nnml}, except that is doesn't generate
@acronym{NOV} databases and it doesn't keep an active file or marks file.
This makes @code{nnmh} a @emph{much} slower back end than @code{nnml},
but it also makes it easier to write procmail scripts for.

Virtual server settings:

@table @code
@item nnmh-directory
@vindex nnmh-directory
All @code{nnmh} directories will be located under this directory.  The
default is the value of @code{message-directory} (whose default is
@file{~/Mail})

@item nnmh-get-new-mail
@vindex nnmh-get-new-mail
If non-@code{nil}, @code{nnmh} will read incoming mail.  The default is
@code{t}.

@item nnmh-be-safe
@vindex nnmh-be-safe
If non-@code{nil}, @code{nnmh} will go to ridiculous lengths to make
sure that the articles in the folder are actually what Gnus thinks they
are.  It will check date stamps and stat everything in sight, so
setting this to @code{t} will mean a serious slow-down.  If you never
use anything but Gnus to read the @code{nnmh} articles, you do not have
to set this variable to @code{t}.  The default is @code{nil}.
@end table


@node Maildir
@subsubsection Maildir
@cindex nnmaildir
@cindex maildir

@code{nnmaildir} stores mail in the maildir format, with each maildir
corresponding to a group in Gnus.  This format is documented here:
@uref{http://cr.yp.to/proto/maildir.html} and here:
@uref{http://www.qmail.org/man/man5/maildir.html}.  nnmaildir also
stores extra information in the @file{.nnmaildir/} directory within a
maildir.

Maildir format was designed to allow concurrent deliveries and
reading, without needing locks.  With other back ends, you would have
your mail delivered to a spool of some kind, and then you would
configure Gnus to split mail from that spool into your groups.  You
can still do that with nnmaildir, but the more common configuration is
to have your mail delivered directly to the maildirs that appear as
group in Gnus.

nnmaildir is designed to be perfectly reliable: @kbd{C-g} will never
corrupt its data in memory, and @code{SIGKILL} will never corrupt its
data in the filesystem.

nnmaildir stores article marks and @acronym{NOV} data in each maildir.  So you
can copy a whole maildir from one Gnus setup to another, and you will
keep your marks.

Virtual server settings:

@table @code
@item directory
For each of your nnmaildir servers (it's very unlikely that you'd need
more than one), you need to create a directory and populate it with
maildirs or symlinks to maildirs (and nothing else; do not choose a
directory already used for other purposes).  Each maildir will be
represented in Gnus as a newsgroup on that server; the filename of the
symlink will be the name of the group.  Any filenames in the directory
starting with @samp{.} are ignored.  The directory is scanned when you
first start Gnus, and each time you type @kbd{g} in the group buffer;
if any maildirs have been removed or added, nnmaildir notices at these
times.

The value of the @code{directory} parameter should be a Lisp form
which is processed by @code{eval} and @code{expand-file-name} to get
the path of the directory for this server.  The form is @code{eval}ed
only when the server is opened; the resulting string is used until the
server is closed.  (If you don't know about forms and @code{eval},
don't worry---a simple string will work.)  This parameter is not
optional; you must specify it.  I don't recommend using
@code{"~/Mail"} or a subdirectory of it; several other parts of Gnus
use that directory by default for various things, and may get confused
if nnmaildir uses it too.  @code{"~/.nnmaildir"} is a typical value.

@item target-prefix
This should be a Lisp form which is processed by @code{eval} and
@code{expand-file-name}.  The form is @code{eval}ed only when the
server is opened; the resulting string is used until the server is
closed.

When you create a group on an nnmaildir server, the maildir is created
with @code{target-prefix} prepended to its name, and a symlink
pointing to that maildir is created, named with the plain group name.
So if @code{directory} is @code{"~/.nnmaildir"} and
@code{target-prefix} is @code{"../maildirs/"}, then when you create
the group @code{foo}, nnmaildir will create
@file{~/.nnmaildir/../maildirs/foo} as a maildir, and will create
@file{~/.nnmaildir/foo} as a symlink pointing to
@file{../maildirs/foo}.

You can set @code{target-prefix} to a string without any slashes to
create both maildirs and symlinks in the same @code{directory}; in
this case, any maildirs found in @code{directory} whose names start
with @code{target-prefix} will not be listed as groups (but the
symlinks pointing to them will be).

As a special case, if @code{target-prefix} is @code{""} (the default),
then when you create a group, the maildir will be created in
@code{directory} without a corresponding symlink.  Beware that you
cannot use @code{gnus-group-delete-group} on such groups without the
@code{force} argument.

@item directory-files
This should be a function with the same interface as
@code{directory-files} (such as @code{directory-files} itself).  It is
used to scan the server's @code{directory} for maildirs.  This
parameter is optional; the default is
@code{nnheader-directory-files-safe} if
@code{nnheader-directory-files-is-safe} is @code{nil}, and
@code{directory-files} otherwise.
(@code{nnheader-directory-files-is-safe} is checked only once when the
server is opened; if you want to check it each time the directory is
scanned, you'll have to provide your own function that does that.)

@item get-new-mail
If non-@code{nil}, then after scanning for new mail in the group
maildirs themselves as usual, this server will also incorporate mail
the conventional Gnus way, from @code{mail-sources} according to
@code{nnmail-split-methods} or @code{nnmail-split-fancy}.  The default
value is @code{nil}.

Do @emph{not} use the same maildir both in @code{mail-sources} and as
an nnmaildir group.  The results might happen to be useful, but that
would be by chance, not by design, and the results might be different
in the future.  If your split rules create new groups, remember to
supply a @code{create-directory} server parameter.
@end table

@subsubsection Group parameters

nnmaildir uses several group parameters.  It's safe to ignore all
this; the default behavior for nnmaildir is the same as the default
behavior for other mail back ends: articles are deleted after one week,
etc.  Except for the expiry parameters, all this functionality is
unique to nnmaildir, so you can ignore it if you're just trying to
duplicate the behavior you already have with another back end.

If the value of any of these parameters is a vector, the first element
is evaluated as a Lisp form and the result is used, rather than the
original value.  If the value is not a vector, the value itself is
evaluated as a Lisp form.  (This is why these parameters use names
different from those of other, similar parameters supported by other
back ends: they have different, though similar, meanings.)  (For
numbers, strings, @code{nil}, and @code{t}, you can ignore the
@code{eval} business again; for other values, remember to use an extra
quote and wrap the value in a vector when appropriate.)

@table @code
@item expire-age
An integer specifying the minimum age, in seconds, of an article before
it will be expired, or the symbol @code{never} to specify that
articles should never be expired.  If this parameter is not set,
nnmaildir falls back to the usual
@code{nnmail-expiry-wait}(@code{-function}) variables (overrideable by
the @code{expiry-wait}(@code{-function}) group parameters.  If you
wanted a value of 3 days, you could use something like @code{[(* 3 24
60 60)]}; nnmaildir will evaluate the form and use the result.  An
article's age is measured starting from the article file's
modification time.  Normally, this is the same as the article's
delivery time, but editing an article makes it younger.  Moving an
article (other than via expiry) may also make an article younger.

@item expire-group
If this is set to a string such as a full Gnus group name, like
@example
"backend+server.address.string:group.name"
@end example
and if it is not the name of the same group that the parameter belongs
to, then articles will be moved to the specified group during expiry
before being deleted.  @emph{If this is set to an nnmaildir group, the
article will be just as old in the destination group as it was in the
source group.}  So be careful with @code{expire-age} in the
destination group.  If this is set to the name of the same group that
the parameter belongs to, then the article is not expired at all.  If
you use the vector form, the first element is evaluated once for each
article.  So that form can refer to
@code{nnmaildir-article-file-name}, etc., to decide where to put the
article.  @emph{If this parameter is not set, nnmaildir does not fall
back to the @code{expiry-target} group parameter or the
@code{nnmail-expiry-target} variable.}

@item read-only
If this is set to @code{t}, nnmaildir will treat the articles in this
maildir as read-only.  This means: articles are not renamed from
@file{new/} into @file{cur/}; articles are only found in @file{new/},
not @file{cur/}; articles are never deleted; articles cannot be
edited.  @file{new/} is expected to be a symlink to the @file{new/}
directory of another maildir---e.g., a system-wide mailbox containing
a mailing list of common interest.  Everything in the maildir outside
@file{new/} is @emph{not} treated as read-only, so for a shared
mailbox, you do still need to set up your own maildir (or have write
permission to the shared mailbox); your maildir just won't contain
extra copies of the articles.

@item directory-files
A function with the same interface as @code{directory-files}.  It is
used to scan the directories in the maildir corresponding to this
group to find articles.  The default is the function specified by the
server's @code{directory-files} parameter.

@item distrust-Lines:
If non-@code{nil}, nnmaildir will always count the lines of an
article, rather than use the @code{Lines:} header field.  If
@code{nil}, the header field will be used if present.

@item always-marks
A list of mark symbols, such as
@code{['(read expire)]}.  Whenever Gnus asks nnmaildir for
article marks, nnmaildir will say that all articles have these
marks, regardless of whether the marks stored in the filesystem
say so.  This is a proof-of-concept feature that will probably be
removed eventually; it ought to be done in Gnus proper, or
abandoned if it's not worthwhile.

@item never-marks
A list of mark symbols, such as @code{['(tick expire)]}.  Whenever
Gnus asks nnmaildir for article marks, nnmaildir will say that no
articles have these marks, regardless of whether the marks stored in
the filesystem say so.  @code{never-marks} overrides
@code{always-marks}.  This is a proof-of-concept feature that will
probably be removed eventually; it ought to be done in Gnus proper, or
abandoned if it's not worthwhile.

@item nov-cache-size
An integer specifying the size of the @acronym{NOV} memory cache.  To speed
things up, nnmaildir keeps @acronym{NOV} data in memory for a limited number of
articles in each group.  (This is probably not worthwhile, and will
probably be removed in the future.)  This parameter's value is noticed
only the first time a group is seen after the server is opened---i.e.,
when you first start Gnus, typically.  The @acronym{NOV} cache is never resized
until the server is closed and reopened.  The default is an estimate
of the number of articles that would be displayed in the summary
buffer: a count of articles that are either marked with @code{tick} or
not marked with @code{read}, plus a little extra.
@end table

@subsubsection Article identification
Articles are stored in the @file{cur/} subdirectory of each maildir.
Each article file is named like @code{uniq:info}, where @code{uniq}
contains no colons.  nnmaildir ignores, but preserves, the
@code{:info} part.  (Other maildir readers typically use this part of
the filename to store marks.)  The @code{uniq} part uniquely
identifies the article, and is used in various places in the
@file{.nnmaildir/} subdirectory of the maildir to store information
about the corresponding article.  The full pathname of an article is
available in the variable @code{nnmaildir-article-file-name} after you
request the article in the summary buffer.

@subsubsection NOV data
An article identified by @code{uniq} has its @acronym{NOV} data (used to
generate lines in the summary buffer) stored in
@code{.nnmaildir/nov/uniq}.  There is no
@code{nnmaildir-generate-nov-databases} function.  (There isn't much
need for it---an article's @acronym{NOV} data is updated automatically when the
article or @code{nnmail-extra-headers} has changed.)  You can force
nnmaildir to regenerate the @acronym{NOV} data for a single article simply by
deleting the corresponding @acronym{NOV} file, but @emph{beware}: this will also
cause nnmaildir to assign a new article number for this article, which
may cause trouble with @code{seen} marks, the Agent, and the cache.

@subsubsection Article marks
An article identified by @code{uniq} is considered to have the mark
@code{flag} when the file @file{.nnmaildir/marks/flag/uniq} exists.
When Gnus asks nnmaildir for a group's marks, nnmaildir looks for such
files and reports the set of marks it finds.  When Gnus asks nnmaildir
to store a new set of marks, nnmaildir creates and deletes the
corresponding files as needed.  (Actually, rather than create a new
file for each mark, it just creates hard links to
@file{.nnmaildir/markfile}, to save inodes.)

You can invent new marks by creating a new directory in
@file{.nnmaildir/marks/}.  You can tar up a maildir and remove it from
your server, untar it later, and keep your marks.  You can add and
remove marks yourself by creating and deleting mark files.  If you do
this while Gnus is running and your nnmaildir server is open, it's
best to exit all summary buffers for nnmaildir groups and type @kbd{s}
in the group buffer first, and to type @kbd{g} or @kbd{M-g} in the
group buffer afterwards.  Otherwise, Gnus might not pick up the
changes, and might undo them.


@node Mail Folders
@subsubsection Mail Folders
@cindex nnfolder
@cindex mbox folders
@cindex mail folders

@code{nnfolder} is a back end for storing each mail group in a separate
file.  Each file is in the standard Un*x mbox format.  @code{nnfolder}
will add extra headers to keep track of article numbers and arrival
dates.

@cindex self contained nnfolder servers
@cindex marks
When the marks file is used (which it is by default), @code{nnfolder}
servers have the property that you may backup them using @code{tar} or
similar, and later be able to restore them into Gnus (by adding the
proper @code{nnfolder} server) and have all your marks be preserved.
Marks for a group is usually stored in a file named as the mbox file
with @code{.mrk} concatenated to it (but see
@code{nnfolder-marks-file-suffix}) within the @code{nnfolder} directory.
Individual @code{nnfolder} groups are also possible to backup, use
@kbd{G m} to restore the group (after restoring the backup into the
@code{nnfolder} directory).

Virtual server settings:

@table @code
@item nnfolder-directory
@vindex nnfolder-directory
All the @code{nnfolder} mail boxes will be stored under this directory.
The default is the value of @code{message-directory} (whose default is
@file{~/Mail})

@item nnfolder-active-file
@vindex nnfolder-active-file
The name of the active file.  The default is @file{~/Mail/active}.

@item nnfolder-newsgroups-file
@vindex nnfolder-newsgroups-file
The name of the group descriptions file.  @xref{Newsgroups File
Format}.  The default is @file{~/Mail/newsgroups}

@item nnfolder-get-new-mail
@vindex nnfolder-get-new-mail
If non-@code{nil}, @code{nnfolder} will read incoming mail.  The default
is @code{t}

@item nnfolder-save-buffer-hook
@vindex nnfolder-save-buffer-hook
@cindex backup files
Hook run before saving the folders.  Note that Emacs does the normal
backup renaming of files even with the @code{nnfolder} buffers.  If you
wish to switch this off, you could say something like the following in
your @file{.emacs} file:

@lisp
(defun turn-off-backup ()
  (set (make-local-variable 'backup-inhibited) t))

(add-hook 'nnfolder-save-buffer-hook 'turn-off-backup)
@end lisp

@item nnfolder-delete-mail-hook
@vindex nnfolder-delete-mail-hook
Hook run in a buffer narrowed to the message that is to be deleted.
This function can be used to copy the message to somewhere else, or to
extract some information from it before removing it.

@item nnfolder-nov-is-evil
@vindex nnfolder-nov-is-evil
If non-@code{nil}, this back end will ignore any @acronym{NOV} files.  The
default is @code{nil}.

@item nnfolder-nov-file-suffix
@vindex nnfolder-nov-file-suffix
The extension for @acronym{NOV} files.  The default is @file{.nov}.

@item nnfolder-nov-directory
@vindex nnfolder-nov-directory
The directory where the @acronym{NOV} files should be stored.  If
@code{nil}, @code{nnfolder-directory} is used.

@item nnfolder-marks-is-evil
@vindex nnfolder-marks-is-evil
If non-@code{nil}, this back end will ignore any @sc{marks} files.  The
default is @code{nil}.

@item nnfolder-marks-file-suffix
@vindex nnfolder-marks-file-suffix
The extension for @sc{marks} files.  The default is @file{.mrk}.

@item nnfolder-marks-directory
@vindex nnfolder-marks-directory
The directory where the @sc{marks} files should be stored.  If
@code{nil}, @code{nnfolder-directory} is used.

@end table


@findex nnfolder-generate-active-file
@kindex M-x nnfolder-generate-active-file
If you have lots of @code{nnfolder}-like files you'd like to read with
@code{nnfolder}, you can use the @kbd{M-x nnfolder-generate-active-file}
command to make @code{nnfolder} aware of all likely files in
@code{nnfolder-directory}.  This only works if you use long file names,
though.

@node Comparing Mail Back Ends
@subsubsection Comparing Mail Back Ends

First, just for terminology, the @dfn{back end} is the common word for a
low-level access method---a transport, if you will, by which something
is acquired.  The sense is that one's mail has to come from somewhere,
and so selection of a suitable back end is required in order to get that
mail within spitting distance of Gnus.

The same concept exists for Usenet itself: Though access to articles is
typically done by @acronym{NNTP} these days, once upon a midnight dreary, everyone
in the world got at Usenet by running a reader on the machine where the
articles lay (the machine which today we call an @acronym{NNTP} server), and
access was by the reader stepping into the articles' directory spool
area directly.  One can still select between either the @code{nntp} or
@code{nnspool} back ends, to select between these methods, if one happens
actually to live on the server (or can see its spool directly, anyway,
via NFS).

The goal in selecting a mail back end is to pick one which
simultaneously represents a suitable way of dealing with the original
format plus leaving mail in a form that is convenient to use in the
future.  Here are some high and low points on each:

@table @code
@item nnmbox

UNIX systems have historically had a single, very common, and well-
defined format.  All messages arrive in a single @dfn{spool file}, and
they are delineated by a line whose regular expression matches
@samp{^From_}.  (My notational use of @samp{_} is to indicate a space,
to make it clear in this instance that this is not the RFC-specified
@samp{From:} header.)  Because Emacs and therefore Gnus emanate
historically from the Unix environment, it is simplest if one does not
mess a great deal with the original mailbox format, so if one chooses
this back end, Gnus' primary activity in getting mail from the real spool
area to Gnus' preferred directory is simply to copy it, with no
(appreciable) format change in the process.  It is the ``dumbest'' way
to move mail into availability in the Gnus environment.  This makes it
fast to move into place, but slow to parse, when Gnus has to look at
what's where.

@item nnbabyl

Once upon a time, there was the DEC-10 and DEC-20, running operating
systems called TOPS and related things, and the usual (only?) mail
reading environment was a thing called Babyl.  I don't know what format
was used for mail landing on the system, but Babyl had its own internal
format to which mail was converted, primarily involving creating a
spool-file-like entity with a scheme for inserting Babyl-specific
headers and status bits above the top of each message in the file.
Rmail was Emacs' first mail reader, it was written by Richard Stallman,
and Stallman came out of that TOPS/Babyl environment, so he wrote Rmail
to understand the mail files folks already had in existence.  Gnus (and
VM, for that matter) continue to support this format because it's
perceived as having some good qualities in those mailer-specific
headers/status bits stuff.  Rmail itself still exists as well, of
course, and is still maintained by Stallman.

Both of the above forms leave your mail in a single file on your
file system, and they must parse that entire file each time you take a
look at your mail.

@item nnml

@code{nnml} is the back end which smells the most as though you were
actually operating with an @code{nnspool}-accessed Usenet system.  (In
fact, I believe @code{nnml} actually derived from @code{nnspool} code,
lo these years ago.)  One's mail is taken from the original spool file,
and is then cut up into individual message files, 1:1.  It maintains a
Usenet-style active file (analogous to what one finds in an INN- or
CNews-based news system in (for instance) @file{/var/lib/news/active},
or what is returned via the @samp{NNTP LIST} verb) and also creates
@dfn{overview} files for efficient group entry, as has been defined for
@acronym{NNTP} servers for some years now.  It is slower in mail-splitting,
due to the creation of lots of files, updates to the @code{nnml} active
file, and additions to overview files on a per-message basis, but it is
extremely fast on access because of what amounts to the indexing support
provided by the active file and overviews.

@code{nnml} costs @dfn{inodes} in a big way; that is, it soaks up the
resource which defines available places in the file system to put new
files.  Sysadmins take a dim view of heavy inode occupation within
tight, shared file systems.  But if you live on a personal machine where
the file system is your own and space is not at a premium, @code{nnml}
wins big.

It is also problematic using this back end if you are living in a
FAT16-based Windows world, since much space will be wasted on all these
tiny files.

@item nnmh

The Rand MH mail-reading system has been around UNIX systems for a very
long time; it operates by splitting one's spool file of messages into
individual files, but with little or no indexing support---@code{nnmh}
is considered to be semantically equivalent to ``@code{nnml} without
active file or overviews''.  This is arguably the worst choice, because
one gets the slowness of individual file creation married to the
slowness of access parsing when learning what's new in one's groups.

@item nnfolder

Basically the effect of @code{nnfolder} is @code{nnmbox} (the first
method described above) on a per-group basis.  That is, @code{nnmbox}
itself puts @emph{all} one's mail in one file; @code{nnfolder} provides a
little bit of optimization to this so that each of one's mail groups has
a Unix mail box file.  It's faster than @code{nnmbox} because each group
can be parsed separately, and still provides the simple Unix mail box
format requiring minimal effort in moving the mail around.  In addition,
it maintains an ``active'' file making it much faster for Gnus to figure
out how many messages there are in each separate group.

If you have groups that are expected to have a massive amount of
messages, @code{nnfolder} is not the best choice, but if you receive
only a moderate amount of mail, @code{nnfolder} is probably the most
friendly mail back end all over.

@item nnmaildir

For configuring expiry and other things, @code{nnmaildir} uses
incompatible group parameters, slightly different from those of other
mail back ends.

@code{nnmaildir} is largely similar to @code{nnml}, with some notable
differences.  Each message is stored in a separate file, but the
filename is unrelated to the article number in Gnus.  @code{nnmaildir}
also stores the equivalent of @code{nnml}'s overview files in one file
per article, so it uses about twice as many inodes as @code{nnml}.  (Use
@code{df -i} to see how plentiful your inode supply is.)  If this slows
you down or takes up very much space, consider switching to
@uref{http://www.namesys.com/, ReiserFS} or another non-block-structured
file system.

Since maildirs don't require locking for delivery, the maildirs you use
as groups can also be the maildirs your mail is directly delivered to.
This means you can skip Gnus' mail splitting if your mail is already
organized into different mailboxes during delivery.  A @code{directory}
entry in @code{mail-sources} would have a similar effect, but would
require one set of mailboxes for spooling deliveries (in mbox format,
thus damaging message bodies), and another set to be used as groups (in
whatever format you like).  A maildir has a built-in spool, in the
@code{new/} subdirectory.  Beware that currently, mail moved from
@code{new/} to @code{cur/} instead of via mail splitting will not
undergo treatment such as duplicate checking.

@code{nnmaildir} stores article marks for a given group in the
corresponding maildir, in a way designed so that it's easy to manipulate
them from outside Gnus.  You can tar up a maildir, unpack it somewhere
else, and still have your marks.  @code{nnml} also stores marks, but
it's not as easy to work with them from outside Gnus as with
@code{nnmaildir}.

@code{nnmaildir} uses a significant amount of memory to speed things up.
(It keeps in memory some of the things that @code{nnml} stores in files
and that @code{nnmh} repeatedly parses out of message files.)  If this
is a problem for you, you can set the @code{nov-cache-size} group
parameter to something small (0 would probably not work, but 1 probably
would) to make it use less memory.  This caching will probably be
removed in the future.

Startup is likely to be slower with @code{nnmaildir} than with other
back ends.  Everything else is likely to be faster, depending in part
on your file system.

@code{nnmaildir} does not use @code{nnoo}, so you cannot use @code{nnoo}
to write an @code{nnmaildir}-derived back end.

@end table


@node Browsing the Web
@section Browsing the Web
@cindex web
@cindex browsing the web
@cindex www
@cindex http

Web-based discussion forums are getting more and more popular.  On many
subjects, the web-based forums have become the most important forums,
eclipsing the importance of mailing lists and news groups.  The reason
is easy to understand---they are friendly to new users; you just point
and click, and there's the discussion.  With mailing lists, you have to
go through a cumbersome subscription procedure, and most people don't
even know what a news group is.

The problem with this scenario is that web browsers are not very good at
being newsreaders.  They do not keep track of what articles you've read;
they do not allow you to score on subjects you're interested in; they do
not allow off-line browsing; they require you to click around and drive
you mad in the end.

So---if web browsers suck at reading discussion forums, why not use Gnus
to do it instead?

Gnus has been getting a bit of a collection of back ends for providing
interfaces to these sources.

@menu
* Archiving Mail::
* Web Searches::                Creating groups from articles that match a string.
* Slashdot::                    Reading the Slashdot comments.
* Ultimate::                    The Ultimate Bulletin Board systems.
* Web Archive::                 Reading mailing list archived on web.
* RSS::                         Reading RDF site summary.
* Customizing w3::              Doing stuff to Emacs/w3 from Gnus.
@end menu

All the web sources require Emacs/w3 and the url library to work.

The main caveat with all these web sources is that they probably won't
work for a very long time.  Gleaning information from the @acronym{HTML} data
is guesswork at best, and when the layout is altered, the Gnus back end
will fail.  If you have reasonably new versions of these back ends,
though, you should be ok.

One thing all these Web methods have in common is that the Web sources
are often down, unavailable or just plain too slow to be fun.  In those
cases, it makes a lot of sense to let the Gnus Agent (@pxref{Gnus
Unplugged}) handle downloading articles, and then you can read them at
leisure from your local disk.  No more World Wide Wait for you.

@node Archiving Mail
@subsection Archiving Mail
@cindex archiving mail
@cindex backup of mail

Some of the back ends, notably @code{nnml}, @code{nnfolder}, and
@code{nnmaildir}, now actually store the article marks with each group.
For these servers, archiving and restoring a group while preserving
marks is fairly simple.

(Preserving the group level and group parameters as well still
requires ritual dancing and sacrifices to the @file{.newsrc.eld} deity
though.)

To archive an entire @code{nnml}, @code{nnfolder}, or @code{nnmaildir}
server, take a recursive copy of the server directory.  There is no need
to shut down Gnus, so archiving may be invoked by @code{cron} or
similar.  You restore the data by restoring the directory tree, and
adding a server definition pointing to that directory in Gnus.  The
@ref{Article Backlog}, @ref{Asynchronous Fetching} and other things
might interfere with overwriting data, so you may want to shut down Gnus
before you restore the data.

It is also possible to archive individual @code{nnml},
@code{nnfolder}, or @code{nnmaildir} groups, while preserving marks.
For @code{nnml} or @code{nnmaildir}, you copy all files in the group's
directory.  For @code{nnfolder} you need to copy both the base folder
file itself (@file{FOO}, say), and the marks file (@file{FOO.mrk} in
this example).  Restoring the group is done with @kbd{G m} from the Group
buffer.  The last step makes Gnus notice the new directory.
@code{nnmaildir} notices the new directory automatically, so @kbd{G m}
is unnecessary in that case.

@node Web Searches
@subsection Web Searches
@cindex nnweb
@cindex Google
@cindex dejanews
@cindex gmane
@cindex Usenet searches
@cindex searching the Usenet

It's, like, too neat to search the Usenet for articles that match a
string, but it, like, totally @emph{sucks}, like, totally, to use one of
those, like, Web browsers, and you, like, have to, rilly, like, look at
the commercials, so, like, with Gnus you can do @emph{rad}, rilly,
searches without having to use a browser.

The @code{nnweb} back end allows an easy interface to the mighty search
engine.  You create an @code{nnweb} group, enter a search pattern, and
then enter the group and read the articles like you would any normal
group.  The @kbd{G w} command in the group buffer (@pxref{Foreign
Groups}) will do this in an easy-to-use fashion.

@code{nnweb} groups don't really lend themselves to being solid
groups---they have a very fleeting idea of article numbers.  In fact,
each time you enter an @code{nnweb} group (not even changing the search
pattern), you are likely to get the articles ordered in a different
manner.  Not even using duplicate suppression (@pxref{Duplicate
Suppression}) will help, since @code{nnweb} doesn't even know the
@code{Message-ID} of the articles before reading them using some search
engines (Google, for instance).  The only possible way to keep track
of which articles you've read is by scoring on the @code{Date}
header---mark all articles posted before the last date you read the
group as read.

If the search engine changes its output substantially, @code{nnweb}
won't be able to parse it and will fail.  One could hardly fault the Web
providers if they were to do this---their @emph{raison d'être} is to
make money off of advertisements, not to provide services to the
community.  Since @code{nnweb} washes the ads off all the articles, one
might think that the providers might be somewhat miffed.  We'll see.

You must have the @code{url} and @code{w3} package installed to be able
to use @code{nnweb}.

Virtual server variables:

@table @code
@item nnweb-type
@vindex nnweb-type
What search engine type is being used.  The currently supported types
are @code{google}, @code{dejanews}, and @code{gmane}.  Note that
@code{dejanews} is an alias to @code{google}.

@item nnweb-search
@vindex nnweb-search
The search string to feed to the search engine.

@item nnweb-max-hits
@vindex nnweb-max-hits
Advisory maximum number of hits per search to display.  The default is
999.

@item nnweb-type-definition
@vindex nnweb-type-definition
Type-to-definition alist.  This alist says what @code{nnweb} should do
with the various search engine types.  The following elements must be
present:

@table @code
@item article
Function to decode the article and provide something that Gnus
understands.

@item map
Function to create an article number to message header and URL alist.

@item search
Function to send the search string to the search engine.

@item address
The address the aforementioned function should send the search string
to.

@item id
Format string URL to fetch an article by @code{Message-ID}.
@end table

@end table


@node Slashdot
@subsection Slashdot
@cindex Slashdot
@cindex nnslashdot

@uref{http://slashdot.org/, Slashdot} is a popular news site, with
lively discussion following the news articles.  @code{nnslashdot} will
let you read this forum in a convenient manner.

The easiest way to read this source is to put something like the
following in your @file{~/.gnus.el} file:

@lisp
(setq gnus-secondary-select-methods
      '((nnslashdot "")))
@end lisp

This will make Gnus query the @code{nnslashdot} back end for new comments
and groups.  The @kbd{F} command will subscribe each new news article as
a new Gnus group, and you can read the comments by entering these
groups.  (Note that the default subscription method is to subscribe new
groups as zombies.  Other methods are available (@pxref{Subscription
Methods}).

If you want to remove an old @code{nnslashdot} group, the @kbd{G DEL}
command is the most handy tool (@pxref{Foreign Groups}).

When following up to @code{nnslashdot} comments (or posting new
comments), some light @acronym{HTML}izations will be performed.  In
particular, text quoted with @samp{> } will be quoted with
@code{blockquote} instead, and signatures will have @code{br} added to
the end of each line.  Other than that, you can just write @acronym{HTML}
directly into the message buffer.  Note that Slashdot filters out some
@acronym{HTML} forms.

The following variables can be altered to change its behavior:

@table @code
@item nnslashdot-threaded
Whether @code{nnslashdot} should display threaded groups or not.  The
default is @code{t}.  To be able to display threads, @code{nnslashdot}
has to retrieve absolutely all comments in a group upon entry.  If a
threaded display is not required, @code{nnslashdot} will only retrieve
the comments that are actually wanted by the user.  Threading is nicer,
but much, much slower than unthreaded.

@item nnslashdot-login-name
@vindex nnslashdot-login-name
The login name to use when posting.

@item nnslashdot-password
@vindex nnslashdot-password
The password to use when posting.

@item nnslashdot-directory
@vindex nnslashdot-directory
Where @code{nnslashdot} will store its files.  The default is
@file{~/News/slashdot/}.

@item nnslashdot-active-url
@vindex nnslashdot-active-url
The @sc{url} format string that will be used to fetch the information on
news articles and comments.  The default is@*
@samp{http://slashdot.org/search.pl?section=&min=%d}.

@item nnslashdot-comments-url
@vindex nnslashdot-comments-url
The @sc{url} format string that will be used to fetch comments.  The
default is
@samp{http://slashdot.org/comments.pl?sid=%s&threshold=%d&commentsort=%d&mode=flat&startat=%d}.

@item nnslashdot-article-url
@vindex nnslashdot-article-url
The @sc{url} format string that will be used to fetch the news article.  The
default is
@samp{http://slashdot.org/article.pl?sid=%s&mode=nocomment}.

@item nnslashdot-threshold
@vindex nnslashdot-threshold
The score threshold.  The default is -1.

@item nnslashdot-group-number
@vindex nnslashdot-group-number
The number of old groups, in addition to the ten latest, to keep
updated.  The default is 0.

@end table



@node Ultimate
@subsection Ultimate
@cindex nnultimate
@cindex Ultimate Bulletin Board

@uref{http://www.ultimatebb.com/, The Ultimate Bulletin Board} is
probably the most popular Web bulletin board system used.  It has a
quite regular and nice interface, and it's possible to get the
information Gnus needs to keep groups updated.

The easiest way to get started with @code{nnultimate} is to say
something like the following in the group buffer:  @kbd{B nnultimate RET
http://www.tcj.com/messboard/ubbcgi/ RET}.  (Substitute the @sc{url}
(not including @samp{Ultimate.cgi} or the like at the end) for a forum
you're interested in; there's quite a list of them on the Ultimate web
site.)  Then subscribe to the groups you're interested in from the
server buffer, and read them from the group buffer.

The following @code{nnultimate} variables can be altered:

@table @code
@item nnultimate-directory
@vindex nnultimate-directory
The directory where @code{nnultimate} stores its files.  The default is@*
@file{~/News/ultimate/}.
@end table


@node Web Archive
@subsection Web Archive
@cindex nnwarchive
@cindex Web Archive

Some mailing lists only have archives on Web servers, such as
@uref{http://www.egroups.com/} and
@uref{http://www.mail-archive.com/}.  It has a quite regular and nice
interface, and it's possible to get the information Gnus needs to keep
groups updated.

@findex gnus-group-make-warchive-group
The easiest way to get started with @code{nnwarchive} is to say
something like the following in the group buffer: @kbd{M-x
gnus-group-make-warchive-group RET @var{an_egroup} RET egroups RET
www.egroups.com RET @var{your@@email.address} RET}.  (Substitute the
@var{an_egroup} with the mailing list you subscribed, the
@var{your@@email.address} with your email address.), or to browse the
back end by @kbd{B nnwarchive RET mail-archive RET}.

The following @code{nnwarchive} variables can be altered:

@table @code
@item nnwarchive-directory
@vindex nnwarchive-directory
The directory where @code{nnwarchive} stores its files.  The default is@*
@file{~/News/warchive/}.

@item nnwarchive-login
@vindex nnwarchive-login
The account name on the web server.

@item nnwarchive-passwd
@vindex nnwarchive-passwd
The password for your account on the web server.
@end table

@node RSS
@subsection RSS
@cindex nnrss
@cindex RSS

Some sites have RDF site summary (RSS)
@uref{http://purl.org/rss/1.0/spec}.  It has a quite regular and nice
interface, and it's possible to get the information Gnus needs to keep
groups updated.

The easiest way to get started with @code{nnrss} is to say something
like the following in the group buffer: @kbd{B nnrss RET RET}, then
subscribe groups.

The following @code{nnrss} variables can be altered:

@table @code
@item nnrss-directory
@vindex nnrss-directory
The directory where @code{nnrss} stores its files.  The default is
@file{~/News/rss/}.

@end table

The following code may be helpful, if you want to show the description in
the summary buffer.

@lisp
(add-to-list 'nnmail-extra-headers nnrss-description-field)
(setq gnus-summary-line-format "%U%R%z%I%(%[%4L: %-15,15f%]%) %s%uX\n")

(defun gnus-user-format-function-X (header)
  (let ((descr
         (assq nnrss-description-field (mail-header-extra header))))
    (if descr (concat "\n\t" (cdr descr)) "")))
@end lisp

The following code may be useful to open an nnrss url directly from the
summary buffer.
@lisp
(require 'browse-url)

(defun browse-nnrss-url( arg )
  (interactive "p")
  (let ((url (assq nnrss-url-field
                   (mail-header-extra
                    (gnus-data-header
                     (assq (gnus-summary-article-number)
                           gnus-newsgroup-data))))))
    (if url
        (progn
          (browse-url (cdr url))
          (gnus-summary-mark-as-read-forward 1))
      (gnus-summary-scroll-up arg))))

(eval-after-load "gnus"
  #'(define-key gnus-summary-mode-map
      (kbd "<RET>") 'browse-nnrss-url))
(add-to-list 'nnmail-extra-headers nnrss-url-field)
@end lisp

@node Customizing w3
@subsection Customizing w3
@cindex w3
@cindex html
@cindex url
@cindex Netscape

Gnus uses the url library to fetch web pages and Emacs/w3 to display web
pages.  Emacs/w3 is documented in its own manual, but there are some
things that may be more relevant for Gnus users.

For instance, a common question is how to make Emacs/w3 follow links
using the @code{browse-url} functions (which will call some external web
browser like Netscape).  Here's one way:

@lisp
(eval-after-load "w3"
  '(progn
    (fset 'w3-fetch-orig (symbol-function 'w3-fetch))
    (defun w3-fetch (&optional url target)
      (interactive (list (w3-read-url-with-default)))
      (if (eq major-mode 'gnus-article-mode)
          (browse-url url)
        (w3-fetch-orig url target)))))
@end lisp

Put that in your @file{.emacs} file, and hitting links in w3-rendered
@acronym{HTML} in the Gnus article buffers will use @code{browse-url} to
follow the link.


@node IMAP
@section IMAP
@cindex nnimap
@cindex @acronym{IMAP}

@acronym{IMAP} is a network protocol for reading mail (or news, or @dots{}),
think of it as a modernized @acronym{NNTP}.  Connecting to a @acronym{IMAP}
server is much similar to connecting to a news server, you just
specify the network address of the server.

@acronym{IMAP} has two properties.  First, @acronym{IMAP} can do
everything that @acronym{POP} can, it can hence be viewed as a
@acronym{POP++}.  Secondly, @acronym{IMAP} is a mail storage protocol,
similar to @acronym{NNTP} being a news storage protocol---however,
@acronym{IMAP} offers more features than @acronym{NNTP} because news
is more or less read-only whereas mail is read-write.

If you want to use @acronym{IMAP} as a @acronym{POP++}, use an imap
entry in @code{mail-sources}.  With this, Gnus will fetch mails from
the @acronym{IMAP} server and store them on the local disk.  This is
not the usage described in this section---@xref{Mail Sources}.

If you want to use @acronym{IMAP} as a mail storage protocol, use an nnimap
entry in @code{gnus-secondary-select-methods}.  With this, Gnus will
manipulate mails stored on the @acronym{IMAP} server.  This is the kind of
usage explained in this section.

A server configuration in @file{~/.gnus.el} with a few @acronym{IMAP}
servers might look something like the following.  (Note that for
@acronym{TLS}/@acronym{SSL}, you need external programs and libraries,
see below.)

@lisp
(setq gnus-secondary-select-methods
      '((nnimap "simpleserver") ; @r{no special configuration}
        ; @r{perhaps a ssh port forwarded server:}
        (nnimap "dolk"
                (nnimap-address "localhost")
                (nnimap-server-port 1430))
        ; @r{a UW server running on localhost}
        (nnimap "barbar"
                (nnimap-server-port 143)
                (nnimap-address "localhost")
                (nnimap-list-pattern ("INBOX" "mail/*")))
        ; @r{anonymous public cyrus server:}
        (nnimap "cyrus.andrew.cmu.edu"
                (nnimap-authenticator anonymous)
                (nnimap-list-pattern "archive.*")
                (nnimap-stream network))
        ; @r{a ssl server on a non-standard port:}
        (nnimap "vic20"
                (nnimap-address "vic20.somewhere.com")
                (nnimap-server-port 9930)
                (nnimap-stream ssl))))
@end lisp

After defining the new server, you can subscribe to groups on the
server using normal Gnus commands such as @kbd{U} in the Group Buffer
(@pxref{Subscription Commands}) or via the Server Buffer
(@pxref{Server Buffer}).

The following variables can be used to create a virtual @code{nnimap}
server:

@table @code

@item nnimap-address
@vindex nnimap-address

The address of the remote @acronym{IMAP} server.  Defaults to the virtual
server name if not specified.

@item nnimap-server-port
@vindex nnimap-server-port
Port on server to contact.  Defaults to port 143, or 993 for @acronym{TLS}/@acronym{SSL}.

Note that this should be an integer, example server specification:

@lisp
(nnimap "mail.server.com"
        (nnimap-server-port 4711))
@end lisp

@item nnimap-list-pattern
@vindex nnimap-list-pattern
String or list of strings of mailboxes to limit available groups to.
This is used when the server has very many mailboxes and you're only
interested in a few---some servers export your home directory via
@acronym{IMAP}, you'll probably want to limit the mailboxes to those in
@file{~/Mail/*} then.

The string can also be a cons of REFERENCE and the string as above, what
REFERENCE is used for is server specific, but on the University of
Washington server it's a directory that will be concatenated with the
mailbox.

Example server specification:

@lisp
(nnimap "mail.server.com"
        (nnimap-list-pattern ("INBOX" "Mail/*" "alt.sex.*"
                               ("~friend/Mail/" . "list/*"))))
@end lisp

@item nnimap-stream
@vindex nnimap-stream
The type of stream used to connect to your server.  By default, nnimap
will detect and automatically use all of the below, with the exception
of @acronym{TLS}/@acronym{SSL}.  (@acronym{IMAP} over
@acronym{TLS}/@acronym{SSL} is being replaced by STARTTLS, which can
be automatically detected, but it's not widely deployed yet.)

Example server specification:

@lisp
(nnimap "mail.server.com"
        (nnimap-stream ssl))
@end lisp

Please note that the value of @code{nnimap-stream} is a symbol!

@itemize @bullet
@item
@dfn{gssapi:} Connect with GSSAPI (usually Kerberos 5).  Requires the
@samp{gsasl} or @samp{imtest} program.
@item
@dfn{kerberos4:} Connect with Kerberos 4.  Requires the @samp{imtest} program.
@item
@dfn{starttls:} Connect via the STARTTLS extension (similar to
@acronym{TLS}/@acronym{SSL}).  Requires the external library @samp{starttls.el} and program
@samp{starttls}.
@item
@dfn{tls:} Connect through @acronym{TLS}.  Requires GNUTLS (the program
@samp{gnutls-cli}).
@item
@dfn{ssl:} Connect through @acronym{SSL}.  Requires OpenSSL (the program
@samp{openssl}) or SSLeay (@samp{s_client}).
@item
@dfn{shell:} Use a shell command to start @acronym{IMAP} connection.
@item
@dfn{network:} Plain, TCP/IP network connection.
@end itemize

@vindex imap-kerberos4-program
The @samp{imtest} program is shipped with Cyrus IMAPD.  If you're
using @samp{imtest} from Cyrus IMAPD < 2.0.14 (which includes version
1.5.x and 1.6.x) you need to frob @code{imap-process-connection-type}
to make @code{imap.el} use a pty instead of a pipe when communicating
with @samp{imtest}.  You will then suffer from a line length
restrictions on @acronym{IMAP} commands, which might make Gnus seem to hang
indefinitely if you have many articles in a mailbox.  The variable
@code{imap-kerberos4-program} contain parameters to pass to the imtest
program.

For @acronym{TLS} connection, the @code{gnutls-cli} program from GNUTLS is
needed.  It is available from
@uref{http://www.gnu.org/software/gnutls/}.

@vindex imap-gssapi-program
This parameter specifies a list of command lines that invoke a GSSAPI
authenticated @acronym{IMAP} stream in a subshell.  They are tried
sequentially until a connection is made, or the list has been
exhausted.  By default, @samp{gsasl} from GNU SASL, available from
@uref{http://www.gnu.org/software/gsasl/}, and the @samp{imtest}
program from Cyrus IMAPD (see @code{imap-kerberos4-program}), are
tried.

@vindex imap-ssl-program
For @acronym{SSL} connections, the OpenSSL program is available from
@uref{http://www.openssl.org/}.  OpenSSL was formerly known as SSLeay,
and nnimap support it too---although the most recent versions of
SSLeay, 0.9.x, are known to have serious bugs making it
useless.  Earlier versions, especially 0.8.x, of SSLeay are known to
work.  The variable @code{imap-ssl-program} contain parameters to pass
to OpenSSL/SSLeay.

@vindex imap-shell-program
@vindex imap-shell-host
For @acronym{IMAP} connections using the @code{shell} stream, the variable
@code{imap-shell-program} specify what program to call.

@item nnimap-authenticator
@vindex nnimap-authenticator

The authenticator used to connect to the server.  By default, nnimap
will use the most secure authenticator your server is capable of.

Example server specification:

@lisp
(nnimap "mail.server.com"
        (nnimap-authenticator anonymous))
@end lisp

Please note that the value of @code{nnimap-authenticator} is a symbol!

@itemize @bullet
@item
@dfn{gssapi:} GSSAPI (usually kerberos 5) authentication.  Requires
external program @code{gsasl} or @code{imtest}.
@item
@dfn{kerberos4:} Kerberos 4 authentication.  Requires external program
@code{imtest}.
@item
@dfn{digest-md5:} Encrypted username/password via DIGEST-MD5.  Requires
external library @code{digest-md5.el}.
@item
@dfn{cram-md5:} Encrypted username/password via CRAM-MD5.
@item
@dfn{login:} Plain-text username/password via LOGIN.
@item
@dfn{anonymous:} Login as ``anonymous'', supplying your email address as password.
@end itemize

@item nnimap-expunge-on-close
@cindex expunging
@vindex nnimap-expunge-on-close
Unlike Parmenides the @acronym{IMAP} designers have decided things that
don't exist actually do exist.  More specifically, @acronym{IMAP} has
this concept of marking articles @code{Deleted} which doesn't actually
delete them, and this (marking them @code{Deleted}, that is) is what
nnimap does when you delete an article in Gnus (with @kbd{B DEL} or
similar).

Since the articles aren't really removed when we mark them with the
@code{Deleted} flag we'll need a way to actually delete them.  Feel like
running in circles yet?

Traditionally, nnimap has removed all articles marked as @code{Deleted}
when closing a mailbox but this is now configurable by this server
variable.

The possible options are:

@table @code

@item always
The default behavior, delete all articles marked as ``Deleted'' when
closing a mailbox.
@item never
Never actually delete articles.  Currently there is no way of showing
the articles marked for deletion in nnimap, but other @acronym{IMAP} clients
may allow you to do this.  If you ever want to run the EXPUNGE command
manually, @xref{Expunging mailboxes}.
@item ask
When closing mailboxes, nnimap will ask if you wish to expunge deleted
articles or not.

@end table

@item nnimap-importantize-dormant
@vindex nnimap-importantize-dormant

If non-@code{nil} (the default), marks dormant articles as ticked (as
well), for other @acronym{IMAP} clients.  Within Gnus, dormant articles will
naturally still (only) be marked as dormant.  This is to make dormant
articles stand out, just like ticked articles, in other @acronym{IMAP}
clients.  (In other words, Gnus has two ``Tick'' marks and @acronym{IMAP}
has only one.)

Probably the only reason for frobing this would be if you're trying
enable per-user persistent dormant flags, using something like:

@lisp
(setcdr (assq 'dormant nnimap-mark-to-flag-alist)
        (format "gnus-dormant-%s" (user-login-name)))
(setcdr (assq 'dormant nnimap-mark-to-predicate-alist)
        (format "KEYWORD gnus-dormant-%s" (user-login-name)))
@end lisp

In this case, you would not want the per-user dormant flag showing up
as ticked for other users.

@item nnimap-expunge-search-string
@cindex expunging
@vindex nnimap-expunge-search-string

This variable contain the @acronym{IMAP} search command sent to server when
searching for articles eligible for expiring.  The default is
@code{"UID %s NOT SINCE %s"}, where the first @code{%s} is replaced by
UID set and the second @code{%s} is replaced by a date.

Probably the only useful value to change this to is
@code{"UID %s NOT SENTSINCE %s"}, which makes nnimap use the Date: in
messages instead of the internal article date.  See section 6.4.4 of
RFC 2060 for more information on valid strings.

@item nnimap-authinfo-file
@vindex nnimap-authinfo-file

A file containing credentials used to log in on servers.  The format is
(almost) the same as the @code{ftp} @file{~/.netrc} file.  See the
variable @code{nntp-authinfo-file} for exact syntax; also see
@ref{NNTP}.

@item nnimap-need-unselect-to-notice-new-mail
@vindex nnimap-need-unselect-to-notice-new-mail

Unselect mailboxes before looking for new mail in them.  Some servers
seem to need this under some circumstances; it was reported that
Courier 1.7.1 did.

@end table

@menu
* Splitting in IMAP::           Splitting mail with nnimap.
* Expiring in IMAP::            Expiring mail with nnimap.
* Editing IMAP ACLs::           Limiting/enabling other users access to a mailbox.
* Expunging mailboxes::         Equivalent of a ``compress mailbox'' button.
* A note on namespaces::        How to (not) use @acronym{IMAP} namespace in Gnus.
@end menu



@node Splitting in IMAP
@subsection Splitting in IMAP
@cindex splitting imap mail

Splitting is something Gnus users have loved and used for years, and now
the rest of the world is catching up.  Yeah, dream on, not many
@acronym{IMAP} servers have server side splitting and those that have
splitting seem to use some non-standard protocol.  This means that
@acronym{IMAP} support for Gnus has to do its own splitting.

And it does.

(Incidentally, people seem to have been dreaming on, and Sieve has
gaining a market share and is supported by several IMAP servers.
Fortunately, Gnus support it too, @xref{Sieve Commands}.)

Here are the variables of interest:

@table @code

@item nnimap-split-crosspost
@cindex splitting, crosspost
@cindex crosspost
@vindex nnimap-split-crosspost

If non-@code{nil}, do crossposting if several split methods match the
mail.  If @code{nil}, the first match in @code{nnimap-split-rule}
found will be used.

Nnmail equivalent: @code{nnmail-crosspost}.

@item nnimap-split-inbox
@cindex splitting, inbox
@cindex inbox
@vindex nnimap-split-inbox

A string or a list of strings that gives the name(s) of @acronym{IMAP}
mailboxes to split from.  Defaults to @code{nil}, which means that
splitting is disabled!

@lisp
(setq nnimap-split-inbox
      '("INBOX" ("~/friend/Mail" . "lists/*") "lists.imap"))
@end lisp

No nnmail equivalent.

@item nnimap-split-rule
@cindex splitting, rules
@vindex nnimap-split-rule

New mail found in @code{nnimap-split-inbox} will be split according to
this variable.

This variable contains a list of lists, where the first element in the
sublist gives the name of the @acronym{IMAP} mailbox to move articles
matching the regexp in the second element in the sublist.  Got that?
Neither did I, we need examples.

@lisp
(setq nnimap-split-rule
      '(("INBOX.nnimap"
         "^Sender: owner-nnimap@@vic20.globalcom.se")
        ("INBOX.junk"    "^Subject:.*MAKE MONEY")
        ("INBOX.private" "")))
@end lisp

This will put all articles from the nnimap mailing list into mailbox
INBOX.nnimap, all articles containing MAKE MONEY in the Subject: line
into INBOX.junk and everything else in INBOX.private.

The first string may contain @samp{\\1} forms, like the ones used by
replace-match to insert sub-expressions from the matched text.  For
instance:

@lisp
("INBOX.lists.\\1"     "^Sender: owner-\\([a-z-]+\\)@@")
@end lisp

The first element can also be the symbol @code{junk} to indicate that
matching messages should simply be deleted.  Use with care.

The second element can also be a function.  In that case, it will be
called with the first element of the rule as the argument, in a buffer
containing the headers of the article.  It should return a
non-@code{nil} value if it thinks that the mail belongs in that group.

Nnmail users might recollect that the last regexp had to be empty to
match all articles (like in the example above).  This is not required in
nnimap.  Articles not matching any of the regexps will not be moved out
of your inbox.  (This might affect performance if you keep lots of
unread articles in your inbox, since the splitting code would go over
them every time you fetch new mail.)

These rules are processed from the beginning of the alist toward the
end.  The first rule to make a match will ``win'', unless you have
crossposting enabled.  In that case, all matching rules will ``win''.

This variable can also have a function as its value, the function will
be called with the headers narrowed and should return a group where it
thinks the article should be split to.  See @code{nnimap-split-fancy}.

The splitting code tries to create mailboxes if it needs to.

To allow for different split rules on different virtual servers, and
even different split rules in different inboxes on the same server,
the syntax of this variable have been extended along the lines of:

@lisp
(setq nnimap-split-rule
      '(("my1server"    (".*" (("ding"    "ding@@gnus.org")
                               ("junk"    "From:.*Simon"))))
        ("my2server"    ("INBOX" nnimap-split-fancy))
        ("my[34]server" (".*" (("private" "To:.*Simon")
                               ("junk"    my-junk-func))))))
@end lisp

The virtual server name is in fact a regexp, so that the same rules
may apply to several servers.  In the example, the servers
@code{my3server} and @code{my4server} both use the same rules.
Similarly, the inbox string is also a regexp.  The actual splitting
rules are as before, either a function, or a list with group/regexp or
group/function elements.

Nnmail equivalent: @code{nnmail-split-methods}.

@item nnimap-split-predicate
@cindex splitting
@vindex nnimap-split-predicate

Mail matching this predicate in @code{nnimap-split-inbox} will be
split, it is a string and the default is @samp{UNSEEN UNDELETED}.

This might be useful if you use another @acronym{IMAP} client to read mail in
your inbox but would like Gnus to split all articles in the inbox
regardless of readedness.  Then you might change this to
@samp{UNDELETED}.

@item nnimap-split-fancy
@cindex splitting, fancy
@findex nnimap-split-fancy
@vindex nnimap-split-fancy

It's possible to set @code{nnimap-split-rule} to
@code{nnmail-split-fancy} if you want to use fancy
splitting.  @xref{Fancy Mail Splitting}.

However, to be able to have different fancy split rules for nnmail and
nnimap back ends you can set @code{nnimap-split-rule} to
@code{nnimap-split-fancy} and define the nnimap specific fancy split
rule in @code{nnimap-split-fancy}.

Example:

@lisp
(setq nnimap-split-rule 'nnimap-split-fancy
      nnimap-split-fancy ...)
@end lisp

Nnmail equivalent: @code{nnmail-split-fancy}.

@item nnimap-split-download-body
@findex nnimap-split-download-body
@vindex nnimap-split-download-body

Set to non-@code{nil} to download entire articles during splitting.
This is generally not required, and will slow things down
considerably.  You may need it if you want to use an advanced
splitting function that analyses the body to split the article.

@end table

@node Expiring in IMAP
@subsection Expiring in IMAP
@cindex expiring imap mail

Even though @code{nnimap} is not a proper @code{nnmail} derived back
end, it supports most features in regular expiring (@pxref{Expiring
Mail}).  Unlike splitting in @acronym{IMAP} (@pxref{Splitting in
IMAP}) it does not clone the @code{nnmail} variables (i.e., creating
@var{nnimap-expiry-wait}) but reuse the @code{nnmail} variables.  What
follows below are the variables used by the @code{nnimap} expiry
process.

A note on how the expire mark is stored on the @acronym{IMAP} server is
appropriate here as well.  The expire mark is translated into a
@code{imap} client specific mark, @code{gnus-expire}, and stored on the
message.  This means that likely only Gnus will understand and treat
the @code{gnus-expire} mark properly, although other clients may allow
you to view client specific flags on the message.  It also means that
your server must support permanent storage of client specific flags on
messages.  Most do, fortunately.

@table @code

@item nnmail-expiry-wait
@item nnmail-expiry-wait-function

These variables are fully supported.  The expire value can be a
number, the symbol @code{immediate} or @code{never}.

@item nnmail-expiry-target

This variable is supported, and internally implemented by calling the
@code{nnmail} functions that handle this.  It contains an optimization
that if the destination is a @acronym{IMAP} group on the same server, the
article is copied instead of appended (that is, uploaded again).

@end table

@node Editing IMAP ACLs
@subsection Editing IMAP ACLs
@cindex editing imap acls
@cindex Access Control Lists
@cindex Editing @acronym{IMAP} ACLs
@kindex G l
@findex gnus-group-nnimap-edit-acl

ACL stands for Access Control List.  ACLs are used in @acronym{IMAP} for
limiting (or enabling) other users access to your mail boxes.  Not all
@acronym{IMAP} servers support this, this function will give an error if it
doesn't.

To edit an ACL for a mailbox, type @kbd{G l}
(@code{gnus-group-edit-nnimap-acl}) and you'll be presented with an ACL
editing window with detailed instructions.

Some possible uses:

@itemize @bullet
@item
Giving ``anyone'' the ``lrs'' rights (lookup, read, keep seen/unseen flags)
on your mailing list mailboxes enables other users on the same server to
follow the list without subscribing to it.
@item
At least with the Cyrus server, you are required to give the user
``anyone'' posting ("p") capabilities to have ``plussing'' work (that is,
mail sent to user+mailbox@@domain ending up in the @acronym{IMAP} mailbox
INBOX.mailbox).
@end itemize

@node Expunging mailboxes
@subsection Expunging mailboxes
@cindex expunging

@cindex expunge
@cindex manual expunging
@kindex G x
@findex gnus-group-nnimap-expunge

If you're using the @code{never} setting of @code{nnimap-expunge-on-close},
you may want the option of expunging all deleted articles in a mailbox
manually.  This is exactly what @kbd{G x} does.

Currently there is no way of showing deleted articles, you can just
delete them.

@node A note on namespaces
@subsection A note on namespaces
@cindex IMAP namespace
@cindex namespaces

The @acronym{IMAP} protocol has a concept called namespaces, described
by the following text in the RFC:

@display
5.1.2.  Mailbox Namespace Naming Convention

   By convention, the first hierarchical element of any mailbox name
   which begins with "#" identifies the "namespace" of the remainder of
   the name.  This makes it possible to disambiguate between different
   types of mailbox stores, each of which have their own namespaces.

      For example, implementations which offer access to USENET
      newsgroups MAY use the "#news" namespace to partition the USENET
      newsgroup namespace from that of other mailboxes.  Thus, the
      comp.mail.misc newsgroup would have an mailbox name of
      "#news.comp.mail.misc", and the name "comp.mail.misc" could refer
      to a different object (e.g. a user's private mailbox).
@end display

While there is nothing in this text that warrants concern for the
@acronym{IMAP} implementation in Gnus, some servers use namespace
prefixes in a way that does not work with how Gnus uses mailbox names.

Specifically, University of Washington's @acronym{IMAP} server uses
mailbox names like @code{#driver.mbx/read-mail} which are valid only
in the @sc{create} and @sc{append} commands.  After the mailbox is
created (or a messages is appended to a mailbox), it must be accessed
without the namespace prefix, i.e. @code{read-mail}.  Since Gnus do
not make it possible for the user to guarantee that user entered
mailbox names will only be used with the CREATE and APPEND commands,
you should simply not use the namespace prefixed mailbox names in
Gnus.

See the UoW IMAPD documentation for the @code{#driver.*/} prefix
for more information on how to use the prefixes.  They are a power
tool and should be used only if you are sure what the effects are.

@node Other Sources
@section Other Sources

Gnus can do more than just read news or mail.  The methods described
below allow Gnus to view directories and files as if they were
newsgroups.

@menu
* Directory Groups::            You can read a directory as if it was a newsgroup.
* Anything Groups::             Dired?  Who needs dired?
* Document Groups::             Single files can be the basis of a group.
* SOUP::                        Reading @sc{soup} packets ``offline''.
* Mail-To-News Gateways::       Posting articles via mail-to-news gateways.
@end menu


@node Directory Groups
@subsection Directory Groups
@cindex nndir
@cindex directory groups

If you have a directory that has lots of articles in separate files in
it, you might treat it as a newsgroup.  The files have to have numerical
names, of course.

This might be an opportune moment to mention @code{ange-ftp} (and its
successor @code{efs}), that most wonderful of all wonderful Emacs
packages.  When I wrote @code{nndir}, I didn't think much about it---a
back end to read directories.  Big deal.

@code{ange-ftp} changes that picture dramatically.  For instance, if you
enter the @code{ange-ftp} file name
@file{/ftp.hpc.uh.edu:/pub/emacs/ding-list/} as the directory name,
@code{ange-ftp} or @code{efs} will actually allow you to read this
directory over at @samp{sina} as a newsgroup.  Distributed news ahoy!

@code{nndir} will use @acronym{NOV} files if they are present.

@code{nndir} is a ``read-only'' back end---you can't delete or expire
articles with this method.  You can use @code{nnmh} or @code{nnml} for
whatever you use @code{nndir} for, so you could switch to any of those
methods if you feel the need to have a non-read-only @code{nndir}.


@node Anything Groups
@subsection Anything Groups
@cindex nneething

From the @code{nndir} back end (which reads a single spool-like
directory), it's just a hop and a skip to @code{nneething}, which
pretends that any arbitrary directory is a newsgroup.  Strange, but
true.

When @code{nneething} is presented with a directory, it will scan this
directory and assign article numbers to each file.  When you enter such
a group, @code{nneething} must create ``headers'' that Gnus can use.
After all, Gnus is a newsreader, in case you're forgetting.
@code{nneething} does this in a two-step process.  First, it snoops each
file in question.  If the file looks like an article (i.e., the first
few lines look like headers), it will use this as the head.  If this is
just some arbitrary file without a head (e.g. a C source file),
@code{nneething} will cobble up a header out of thin air.  It will use
file ownership, name and date and do whatever it can with these
elements.

All this should happen automatically for you, and you will be presented
with something that looks very much like a newsgroup.  Totally like a
newsgroup, to be precise.  If you select an article, it will be displayed
in the article buffer, just as usual.

If you select a line that represents a directory, Gnus will pop you into
a new summary buffer for this @code{nneething} group.  And so on.  You can
traverse the entire disk this way, if you feel like, but remember that
Gnus is not dired, really, and does not intend to be, either.

There are two overall modes to this action---ephemeral or solid.  When
doing the ephemeral thing (i.e., @kbd{G D} from the group buffer), Gnus
will not store information on what files you have read, and what files
are new, and so on.  If you create a solid @code{nneething} group the
normal way with @kbd{G m}, Gnus will store a mapping table between
article numbers and file names, and you can treat this group like any
other groups.  When you activate a solid @code{nneething} group, you will
be told how many unread articles it contains, etc., etc.

Some variables:

@table @code
@item nneething-map-file-directory
@vindex nneething-map-file-directory
All the mapping files for solid @code{nneething} groups will be stored
in this directory, which defaults to @file{~/.nneething/}.

@item nneething-exclude-files
@vindex nneething-exclude-files
All files that match this regexp will be ignored.  Nice to use to exclude
auto-save files and the like, which is what it does by default.

@item nneething-include-files
@vindex nneething-include-files
Regexp saying what files to include in the group.  If this variable is
non-@code{nil}, only files matching this regexp will be included.

@item nneething-map-file
@vindex nneething-map-file
Name of the map files.
@end table


@node Document Groups
@subsection Document Groups
@cindex nndoc
@cindex documentation group
@cindex help group

@code{nndoc} is a cute little thing that will let you read a single file
as a newsgroup.  Several files types are supported:

@table @code
@cindex Babyl
@cindex Rmail mbox

@item babyl
The Babyl (Rmail) mail box.
@cindex mbox
@cindex Unix mbox

@item mbox
The standard Unix mbox file.

@cindex MMDF mail box
@item mmdf
The MMDF mail box format.

@item news
Several news articles appended into a file.

@item rnews
@cindex rnews batch files
The rnews batch transport format.
@cindex forwarded messages

@item forward
Forwarded articles.

@item nsmail
Netscape mail boxes.

@item mime-parts
@acronym{MIME} multipart messages.

@item standard-digest
The standard (RFC 1153) digest format.

@item mime-digest
A @acronym{MIME} digest of messages.

@item lanl-gov-announce
Announcement messages from LANL Gov Announce.

@item rfc822-forward
A message forwarded according to RFC822.

@item outlook
The Outlook mail box.

@item oe-dbx
The Outlook Express dbx mail box.

@item exim-bounce
A bounce message from the Exim MTA.

@item forward
A message forwarded according to informal rules.

@item rfc934
An RFC934-forwarded message.

@item mailman
A mailman digest.

@item clari-briefs
A digest of Clarinet brief news items.

@item slack-digest
Non-standard digest format---matches most things, but does it badly.

@item mail-in-mail
The last resort.
@end table

You can also use the special ``file type'' @code{guess}, which means
that @code{nndoc} will try to guess what file type it is looking at.
@code{digest} means that @code{nndoc} should guess what digest type the
file is.

@code{nndoc} will not try to change the file or insert any extra headers into
it---it will simply, like, let you use the file as the basis for a
group.  And that's it.

If you have some old archived articles that you want to insert into your
new & spiffy Gnus mail back end, @code{nndoc} can probably help you with
that.  Say you have an old @file{RMAIL} file with mail that you now want
to split into your new @code{nnml} groups.  You look at that file using
@code{nndoc} (using the @kbd{G f} command in the group buffer
(@pxref{Foreign Groups})), set the process mark on all the articles in
the buffer (@kbd{M P b}, for instance), and then re-spool (@kbd{B r})
using @code{nnml}.  If all goes well, all the mail in the @file{RMAIL}
file is now also stored in lots of @code{nnml} directories, and you can
delete that pesky @file{RMAIL} file.  If you have the guts!

Virtual server variables:

@table @code
@item nndoc-article-type
@vindex nndoc-article-type
This should be one of @code{mbox}, @code{babyl}, @code{digest},
@code{news}, @code{rnews}, @code{mmdf}, @code{forward}, @code{rfc934},
@code{rfc822-forward}, @code{mime-parts}, @code{standard-digest},
@code{slack-digest}, @code{clari-briefs}, @code{nsmail}, @code{outlook},
@code{oe-dbx}, @code{mailman}, and @code{mail-in-mail} or @code{guess}.

@item nndoc-post-type
@vindex nndoc-post-type
This variable says whether Gnus is to consider the group a news group or
a mail group.  There are two valid values:  @code{mail} (the default)
and @code{news}.
@end table

@menu
* Document Server Internals::   How to add your own document types.
@end menu


@node Document Server Internals
@subsubsection Document Server Internals

Adding new document types to be recognized by @code{nndoc} isn't
difficult.  You just have to whip up a definition of what the document
looks like, write a predicate function to recognize that document type,
and then hook into @code{nndoc}.

First, here's an example document type definition:

@example
(mmdf
 (article-begin .  "^\^A\^A\^A\^A\n")
 (body-end .  "^\^A\^A\^A\^A\n"))
@end example

The definition is simply a unique @dfn{name} followed by a series of
regexp pseudo-variable settings.  Below are the possible
variables---don't be daunted by the number of variables; most document
types can be defined with very few settings:

@table @code
@item first-article
If present, @code{nndoc} will skip past all text until it finds
something that match this regexp.  All text before this will be
totally ignored.

@item article-begin
This setting has to be present in all document type definitions.  It
says what the beginning of each article looks like.

@item head-begin-function
If present, this should be a function that moves point to the head of
the article.

@item nndoc-head-begin
If present, this should be a regexp that matches the head of the
article.

@item nndoc-head-end
This should match the end of the head of the article.  It defaults to
@samp{^$}---the empty line.

@item body-begin-function
If present, this function should move point to the beginning of the body
of the article.

@item body-begin
This should match the beginning of the body of the article.  It defaults
to @samp{^\n}.

@item body-end-function
If present, this function should move point to the end of the body of
the article.

@item body-end
If present, this should match the end of the body of the article.

@item file-end
If present, this should match the end of the file.  All text after this
regexp will be totally ignored.

@end table

So, using these variables @code{nndoc} is able to dissect a document
file into a series of articles, each with a head and a body.  However, a
few more variables are needed since not all document types are all that
news-like---variables needed to transform the head or the body into
something that's palatable for Gnus:

@table @code
@item prepare-body-function
If present, this function will be called when requesting an article.  It
will be called with point at the start of the body, and is useful if the
document has encoded some parts of its contents.

@item article-transform-function
If present, this function is called when requesting an article.  It's
meant to be used for more wide-ranging transformation of both head and
body of the article.

@item generate-head-function
If present, this function is called to generate a head that Gnus can
understand.  It is called with the article number as a parameter, and is
expected to generate a nice head for the article in question.  It is
called when requesting the headers of all articles.

@end table

Let's look at the most complicated example I can come up with---standard
digests:

@example
(standard-digest
 (first-article . ,(concat "^" (make-string 70 ?-) "\n\n+"))
 (article-begin . ,(concat "\n\n" (make-string 30 ?-) "\n\n+"))
 (prepare-body-function . nndoc-unquote-dashes)
 (body-end-function . nndoc-digest-body-end)
 (head-end . "^ ?$")
 (body-begin . "^ ?\n")
 (file-end . "^End of .*digest.*[0-9].*\n\\*\\*\\|^End of.*Digest *$")
 (subtype digest guess))
@end example

We see that all text before a 70-width line of dashes is ignored; all
text after a line that starts with that @samp{^End of} is also ignored;
each article begins with a 30-width line of dashes; the line separating
the head from the body may contain a single space; and that the body is
run through @code{nndoc-unquote-dashes} before being delivered.

To hook your own document definition into @code{nndoc}, use the
@code{nndoc-add-type} function.  It takes two parameters---the first
is the definition itself and the second (optional) parameter says
where in the document type definition alist to put this definition.
The alist is traversed sequentially, and
@code{nndoc-@var{type}-type-p} is called for a given type @var{type}.
So @code{nndoc-mmdf-type-p} is called to see whether a document is of
@code{mmdf} type, and so on.  These type predicates should return
@code{nil} if the document is not of the correct type; @code{t} if it
is of the correct type; and a number if the document might be of the
correct type.  A high number means high probability; a low number
means low probability with @samp{0} being the lowest valid number.


@node SOUP
@subsection SOUP
@cindex SOUP
@cindex offline

In the PC world people often talk about ``offline'' newsreaders.  These
are thingies that are combined reader/news transport monstrosities.
With built-in modem programs.  Yecchh!

Of course, us Unix Weenie types of human beans use things like
@code{uucp} and, like, @code{nntpd} and set up proper news and mail
transport things like Ghod intended.  And then we just use normal
newsreaders.

However, it can sometimes be convenient to do something that's a bit
easier on the brain if you have a very slow modem, and you're not really
that interested in doing things properly.

A file format called @sc{soup} has been developed for transporting news
and mail from servers to home machines and back again.  It can be a bit
fiddly.

First some terminology:

@table @dfn

@item server
This is the machine that is connected to the outside world and where you
get news and/or mail from.

@item home machine
This is the machine that you want to do the actual reading and responding
on.  It is typically not connected to the rest of the world in any way.

@item packet
Something that contains messages and/or commands.  There are two kinds
of packets:

@table @dfn
@item message packets
These are packets made at the server, and typically contain lots of
messages for you to read.  These are called @file{SoupoutX.tgz} by
default, where @var{x} is a number.

@item response packets
These are packets made at the home machine, and typically contains
replies that you've written.  These are called @file{SoupinX.tgz} by
default, where @var{x} is a number.

@end table

@end table


@enumerate

@item
You log in on the server and create a @sc{soup} packet.  You can either
use a dedicated @sc{soup} thingie (like the @code{awk} program), or you
can use Gnus to create the packet with its @sc{soup} commands (@kbd{O
s} and/or @kbd{G s b}; and then @kbd{G s p}) (@pxref{SOUP Commands}).

@item
You transfer the packet home.  Rail, boat, car or modem will do fine.

@item
You put the packet in your home directory.

@item
You fire up Gnus on your home machine using the @code{nnsoup} back end as
the native or secondary server.

@item
You read articles and mail and answer and followup to the things you
want (@pxref{SOUP Replies}).

@item
You do the @kbd{G s r} command to pack these replies into a @sc{soup}
packet.

@item
You transfer this packet to the server.

@item
You use Gnus to mail this packet out with the @kbd{G s s} command.

@item
You then repeat until you die.

@end enumerate

So you basically have a bipartite system---you use @code{nnsoup} for
reading and Gnus for packing/sending these @sc{soup} packets.

@menu
* SOUP Commands::               Commands for creating and sending @sc{soup} packets
* SOUP Groups::                 A back end for reading @sc{soup} packets.
* SOUP Replies::                How to enable @code{nnsoup} to take over mail and news.
@end menu


@node SOUP Commands
@subsubsection SOUP Commands

These are commands for creating and manipulating @sc{soup} packets.

@table @kbd
@item G s b
@kindex G s b (Group)
@findex gnus-group-brew-soup
Pack all unread articles in the current group
(@code{gnus-group-brew-soup}).  This command understands the
process/prefix convention.

@item G s w
@kindex G s w (Group)
@findex gnus-soup-save-areas
Save all @sc{soup} data files (@code{gnus-soup-save-areas}).

@item G s s
@kindex G s s (Group)
@findex gnus-soup-send-replies
Send all replies from the replies packet
(@code{gnus-soup-send-replies}).

@item G s p
@kindex G s p (Group)
@findex gnus-soup-pack-packet
Pack all files into a @sc{soup} packet (@code{gnus-soup-pack-packet}).

@item G s r
@kindex G s r (Group)
@findex nnsoup-pack-replies
Pack all replies into a replies packet (@code{nnsoup-pack-replies}).

@item O s
@kindex O s (Summary)
@findex gnus-soup-add-article
This summary-mode command adds the current article to a @sc{soup} packet
(@code{gnus-soup-add-article}).  It understands the process/prefix
convention (@pxref{Process/Prefix}).

@end table


There are a few variables to customize where Gnus will put all these
thingies:

@table @code

@item gnus-soup-directory
@vindex gnus-soup-directory
Directory where Gnus will save intermediate files while composing
@sc{soup} packets.  The default is @file{~/SoupBrew/}.

@item gnus-soup-replies-directory
@vindex gnus-soup-replies-directory
This is what Gnus will use as a temporary directory while sending our
reply packets.  @file{~/SoupBrew/SoupReplies/} is the default.

@item gnus-soup-prefix-file
@vindex gnus-soup-prefix-file
Name of the file where Gnus stores the last used prefix.  The default is
@samp{gnus-prefix}.

@item gnus-soup-packer
@vindex gnus-soup-packer
A format string command for packing a @sc{soup} packet.  The default is
@samp{tar cf - %s | gzip > $HOME/Soupout%d.tgz}.

@item gnus-soup-unpacker
@vindex gnus-soup-unpacker
Format string command for unpacking a @sc{soup} packet.  The default is
@samp{gunzip -c %s | tar xvf -}.

@item gnus-soup-packet-directory
@vindex gnus-soup-packet-directory
Where Gnus will look for reply packets.  The default is @file{~/}.

@item gnus-soup-packet-regexp
@vindex gnus-soup-packet-regexp
Regular expression matching @sc{soup} reply packets in
@code{gnus-soup-packet-directory}.

@end table


@node SOUP Groups
@subsubsection SOUP Groups
@cindex nnsoup

@code{nnsoup} is the back end for reading @sc{soup} packets.  It will
read incoming packets, unpack them, and put them in a directory where
you can read them at leisure.

These are the variables you can use to customize its behavior:

@table @code

@item nnsoup-tmp-directory
@vindex nnsoup-tmp-directory
When @code{nnsoup} unpacks a @sc{soup} packet, it does it in this
directory.  (@file{/tmp/} by default.)

@item nnsoup-directory
@vindex nnsoup-directory
@code{nnsoup} then moves each message and index file to this directory.
The default is @file{~/SOUP/}.

@item nnsoup-replies-directory
@vindex nnsoup-replies-directory
All replies will be stored in this directory before being packed into a
reply packet.  The default is @file{~/SOUP/replies/}.

@item nnsoup-replies-format-type
@vindex nnsoup-replies-format-type
The @sc{soup} format of the replies packets.  The default is @samp{?n}
(rnews), and I don't think you should touch that variable.  I probably
shouldn't even have documented it.  Drats!  Too late!

@item nnsoup-replies-index-type
@vindex nnsoup-replies-index-type
The index type of the replies packet.  The default is @samp{?n}, which
means ``none''.  Don't fiddle with this one either!

@item nnsoup-active-file
@vindex nnsoup-active-file
Where @code{nnsoup} stores lots of information.  This is not an ``active
file'' in the @code{nntp} sense; it's an Emacs Lisp file.  If you lose
this file or mess it up in any way, you're dead.  The default is
@file{~/SOUP/active}.

@item nnsoup-packer
@vindex nnsoup-packer
Format string command for packing a reply @sc{soup} packet.  The default
is @samp{tar cf - %s | gzip > $HOME/Soupin%d.tgz}.

@item nnsoup-unpacker
@vindex nnsoup-unpacker
Format string command for unpacking incoming @sc{soup} packets.  The
default is @samp{gunzip -c %s | tar xvf -}.

@item nnsoup-packet-directory
@vindex nnsoup-packet-directory
Where @code{nnsoup} will look for incoming packets.  The default is
@file{~/}.

@item nnsoup-packet-regexp
@vindex nnsoup-packet-regexp
Regular expression matching incoming @sc{soup} packets.  The default is
@samp{Soupout}.

@item nnsoup-always-save
@vindex nnsoup-always-save
If non-@code{nil}, save the replies buffer after each posted message.

@end table


@node SOUP Replies
@subsubsection SOUP Replies

Just using @code{nnsoup} won't mean that your postings and mailings end
up in @sc{soup} reply packets automagically.  You have to work a bit
more for that to happen.

@findex nnsoup-set-variables
The @code{nnsoup-set-variables} command will set the appropriate
variables to ensure that all your followups and replies end up in the
@sc{soup} system.

In specific, this is what it does:

@lisp
(setq message-send-news-function 'nnsoup-request-post)
(setq message-send-mail-function 'nnsoup-request-mail)
@end lisp

And that's it, really.  If you only want news to go into the @sc{soup}
system you just use the first line.  If you only want mail to be
@sc{soup}ed you use the second.


@node Mail-To-News Gateways
@subsection Mail-To-News Gateways
@cindex mail-to-news gateways
@cindex gateways

If your local @code{nntp} server doesn't allow posting, for some reason
or other, you can post using one of the numerous mail-to-news gateways.
The @code{nngateway} back end provides the interface.

Note that you can't read anything from this back end---it can only be
used to post with.

Server variables:

@table @code
@item nngateway-address
@vindex nngateway-address
This is the address of the mail-to-news gateway.

@item nngateway-header-transformation
@vindex nngateway-header-transformation
News headers often have to be transformed in some odd way or other
for the mail-to-news gateway to accept it.  This variable says what
transformation should be called, and defaults to
@code{nngateway-simple-header-transformation}.  The function is called
narrowed to the headers to be transformed and with one parameter---the
gateway address.

This default function just inserts a new @code{To} header based on the
@code{Newsgroups} header and the gateway address.
For instance, an article with this @code{Newsgroups} header:

@example
Newsgroups: alt.religion.emacs
@end example

will get this @code{To} header inserted:

@example
To: alt-religion-emacs@@GATEWAY
@end example

The following pre-defined functions exist:

@findex nngateway-simple-header-transformation
@table @code

@item nngateway-simple-header-transformation
Creates a @code{To} header that looks like
@var{newsgroup}@@@code{nngateway-address}.

@findex nngateway-mail2news-header-transformation

@item nngateway-mail2news-header-transformation
Creates a @code{To} header that looks like
@code{nngateway-address}.
@end table

@end table

Here's an example:

@lisp
(setq gnus-post-method
      '(nngateway
        "mail2news@@replay.com"
        (nngateway-header-transformation
         nngateway-mail2news-header-transformation)))
@end lisp

So, to use this, simply say something like:

@lisp
(setq gnus-post-method '(nngateway "GATEWAY.ADDRESS"))
@end lisp



@node Combined Groups
@section Combined Groups

Gnus allows combining a mixture of all the other group types into bigger
groups.

@menu
* Virtual Groups::              Combining articles from many groups.
* Kibozed Groups::              Looking through parts of the newsfeed for articles.
@end menu


@node Virtual Groups
@subsection Virtual Groups
@cindex nnvirtual
@cindex virtual groups
@cindex merging groups

An @dfn{nnvirtual group} is really nothing more than a collection of
other groups.

For instance, if you are tired of reading many small groups, you can
put them all in one big group, and then grow tired of reading one
big, unwieldy group.  The joys of computing!

You specify @code{nnvirtual} as the method.  The address should be a
regexp to match component groups.

All marks in the virtual group will stick to the articles in the
component groups.  So if you tick an article in a virtual group, the
article will also be ticked in the component group from whence it
came.  (And vice versa---marks from the component groups will also be
shown in the virtual group.).  To create an empty virtual group, run
@kbd{G V} (@code{gnus-group-make-empty-virtual}) in the group buffer
and edit the method regexp with @kbd{M-e}
(@code{gnus-group-edit-group-method})

Here's an example @code{nnvirtual} method that collects all Andrea Dworkin
newsgroups into one, big, happy newsgroup:

@lisp
(nnvirtual "^alt\\.fan\\.andrea-dworkin$\\|^rec\\.dworkin.*")
@end lisp

The component groups can be native or foreign; everything should work
smoothly, but if your computer explodes, it was probably my fault.

Collecting the same group from several servers might actually be a good
idea if users have set the Distribution header to limit distribution.
If you would like to read @samp{soc.motss} both from a server in Japan
and a server in Norway, you could use the following as the group regexp:

@example
"^nntp\\+server\\.jp:soc\\.motss$\\|^nntp\\+server\\.no:soc\\.motss$"
@end example

(Remember, though, that if you're creating the group with @kbd{G m}, you
shouldn't double the backslashes, and you should leave off the quote
characters at the beginning and the end of the string.)

This should work kinda smoothly---all articles from both groups should
end up in this one, and there should be no duplicates.  Threading (and
the rest) will still work as usual, but there might be problems with the
sequence of articles.  Sorting on date might be an option here
(@pxref{Selecting a Group}).

One limitation, however---all groups included in a virtual
group have to be alive (i.e., subscribed or unsubscribed).  Killed or
zombie groups can't be component groups for @code{nnvirtual} groups.

@vindex nnvirtual-always-rescan
If the @code{nnvirtual-always-rescan} is non-@code{nil},
@code{nnvirtual} will always scan groups for unread articles when
entering a virtual group.  If this variable is @code{nil} (which is the
default) and you read articles in a component group after the virtual
group has been activated, the read articles from the component group
will show up when you enter the virtual group.  You'll also see this
effect if you have two virtual groups that have a component group in
common.  If that's the case, you should set this variable to @code{t}.
Or you can just tap @code{M-g} on the virtual group every time before
you enter it---it'll have much the same effect.

@code{nnvirtual} can have both mail and news groups as component groups.
When responding to articles in @code{nnvirtual} groups, @code{nnvirtual}
has to ask the back end of the component group the article comes from
whether it is a news or mail back end.  However, when you do a @kbd{^},
there is typically no sure way for the component back end to know this,
and in that case @code{nnvirtual} tells Gnus that the article came from a
not-news back end.  (Just to be on the safe side.)

@kbd{C-c C-n} in the message buffer will insert the @code{Newsgroups}
line from the article you respond to in these cases.

@code{nnvirtual} groups do not inherit anything but articles and marks
from component groups---group parameters, for instance, are not
inherited.


@node Kibozed Groups
@subsection Kibozed Groups
@cindex nnkiboze
@cindex kibozing

@dfn{Kibozing} is defined by the @acronym{OED} as ``grepping through
(parts of) the news feed''.  @code{nnkiboze} is a back end that will
do this for you.  Oh joy!  Now you can grind any @acronym{NNTP} server
down to a halt with useless requests!  Oh happiness!

@kindex G k (Group)
To create a kibozed group, use the @kbd{G k} command in the group
buffer.

The address field of the @code{nnkiboze} method is, as with
@code{nnvirtual}, a regexp to match groups to be ``included'' in the
@code{nnkiboze} group.  That's where most similarities between
@code{nnkiboze} and @code{nnvirtual} end.

In addition to this regexp detailing component groups, an
@code{nnkiboze} group must have a score file to say what articles are
to be included in the group (@pxref{Scoring}).

@kindex M-x nnkiboze-generate-groups
@findex nnkiboze-generate-groups
You must run @kbd{M-x nnkiboze-generate-groups} after creating the
@code{nnkiboze} groups you want to have.  This command will take time.
Lots of time.  Oodles and oodles of time.  Gnus has to fetch the
headers from all the articles in all the component groups and run them
through the scoring process to determine if there are any articles in
the groups that are to be part of the @code{nnkiboze} groups.

Please limit the number of component groups by using restrictive
regexps.  Otherwise your sysadmin may become annoyed with you, and the
@acronym{NNTP} site may throw you off and never let you back in again.
Stranger things have happened.

@code{nnkiboze} component groups do not have to be alive---they can be dead,
and they can be foreign.  No restrictions.

@vindex nnkiboze-directory
The generation of an @code{nnkiboze} group means writing two files in
@code{nnkiboze-directory}, which is @file{~/News/kiboze/} by default.
One contains the @acronym{NOV} header lines for all the articles in
the group, and the other is an additional @file{.newsrc} file to store
information on what groups have been searched through to find
component articles.

Articles marked as read in the @code{nnkiboze} group will have
their @acronym{NOV} lines removed from the @acronym{NOV} file.


@node Gnus Unplugged
@section Gnus Unplugged
@cindex offline
@cindex unplugged
@cindex agent
@cindex Gnus agent
@cindex Gnus unplugged

In olden times (ca. February '88), people used to run their newsreaders
on big machines with permanent connections to the net.  News transport
was dealt with by news servers, and all the newsreaders had to do was to
read news.  Believe it or not.

Nowadays most people read news and mail at home, and use some sort of
modem to connect to the net.  To avoid running up huge phone bills, it
would be nice to have a way to slurp down all the news and mail, hang up
the phone, read for several hours, and then upload any responses you
have to make.  And then you repeat the procedure.

Of course, you can use news servers for doing this as well.  I've used
@code{inn} together with @code{slurp}, @code{pop} and @code{sendmail}
for some years, but doing that's a bore.  Moving the news server
functionality up to the newsreader makes sense if you're the only person
reading news on a machine.

Setting up Gnus as an ``offline'' newsreader is quite simple.  In
fact, you don't even have to configure anything.

Of course, to use it as such, you have to learn a few new commands.

@menu
* Agent Basics::                How it all is supposed to work.
* Agent Categories::            How to tell the Gnus Agent what to download.
* Agent Commands::              New commands for all the buffers.
* Agent Visuals::               Ways that the agent may effect your summary buffer.
* Agent as Cache::              The Agent is a big cache too.
* Agent Expiry::                How to make old articles go away.
* Agent Regeneration::          How to recover from lost connections and other accidents.
* Agent and IMAP::              How to use the Agent with @acronym{IMAP}.
* Outgoing Messages::           What happens when you post/mail something?
* Agent Variables::             Customizing is fun.
* Example Setup::               An example @file{~/.gnus.el} file for offline people.
* Batching Agents::             How to fetch news from a @code{cron} job.
* Agent Caveats::               What you think it'll do and what it does.
@end menu


@node Agent Basics
@subsection Agent Basics

First, let's get some terminology out of the way.

The Gnus Agent is said to be @dfn{unplugged} when you have severed the
connection to the net (and notified the Agent that this is the case).
When the connection to the net is up again (and Gnus knows this), the
Agent is @dfn{plugged}.

The @dfn{local} machine is the one you're running on, and which isn't
connected to the net continuously.

@dfn{Downloading} means fetching things from the net to your local
machine.  @dfn{Uploading} is doing the opposite.

You know that Gnus gives you all the opportunity you'd ever want for
shooting yourself in the foot.  Some people call it flexibility.  Gnus
is also customizable to a great extent, which means that the user has a
say on how Gnus behaves.  Other newsreaders might unconditionally shoot
you in your foot, but with Gnus, you have a choice!

Gnus is never really in plugged or unplugged state.  Rather, it applies
that state to each server individually.  This means that some servers
can be plugged while others can be unplugged.  Additionally, some
servers can be ignored by the Agent altogether (which means that
they're kinda like plugged always).

So when you unplug the Agent and then wonder why is Gnus opening a
connection to the Net, the next step to do is to look whether all
servers are agentized.  If there is an unagentized server, you found
the culprit.

Another thing is the @dfn{offline} state.  Sometimes, servers aren't
reachable.  When Gnus notices this, it asks you whether you want the
server to be switched to offline state.  If you say yes, then the
server will behave somewhat as if it was unplugged, except that Gnus
will ask you whether you want to switch it back online again.

Let's take a typical Gnus session using the Agent.

@itemize @bullet

@item
@findex gnus-unplugged
You start Gnus with @code{gnus-unplugged}.  This brings up the Gnus
Agent in a disconnected state.  You can read all the news that you have
already fetched while in this mode.

@item
You then decide to see whether any new news has arrived.  You connect
your machine to the net (using PPP or whatever), and then hit @kbd{J j}
to make Gnus become @dfn{plugged} and use @kbd{g} to check for new mail
as usual.  To check for new mail in unplugged mode (@pxref{Mail
Source Specifiers}).

@item
You can then read the new news immediately, or you can download the
news onto your local machine.  If you want to do the latter, you press
@kbd{g} to check if there are any new news and then @kbd{J s} to fetch
all the eligible articles in all the groups.  (To let Gnus know which
articles you want to download, @pxref{Agent Categories}).

@item
After fetching the articles, you press @kbd{J j} to make Gnus become
unplugged again, and you shut down the PPP thing (or whatever).  And
then you read the news offline.

@item
And then you go to step 2.
@end itemize

Here are some things you should do the first time (or so) that you use
the Agent.

@itemize @bullet

@item
Decide which servers should be covered by the Agent.  If you have a mail
back end, it would probably be nonsensical to have it covered by the
Agent.  Go to the server buffer (@kbd{^} in the group buffer) and press
@kbd{J a} on the server (or servers) that you wish to have covered by the
Agent (@pxref{Server Agent Commands}), or @kbd{J r} on automatically
added servers you do not wish to have covered by the Agent.  By default,
all @code{nntp} and @code{nnimap} servers in @code{gnus-select-method} and
@code{gnus-secondary-select-methods} are agentized.

@item
Decide on download policy.  It's fairly simple once you decide whether
you are going to use agent categories, topic parameters, and/or group
parameters to implement your policy.  If you're new to gnus, it
is probably best to start with a category, @xref{Agent Categories}.

Both topic parameters (@pxref{Topic Parameters}) and agent categories
(@pxref{Agent Categories}) provide for setting a policy that applies
to multiple groups.  Which you use is entirely up to you.  Topic
parameters do override categories so, if you mix the two, you'll have
to take that into account.  If you have a few groups that deviate from
your policy, you can use group parameters (@pxref{Group Parameters}) to
configure them.

@item
Uhm@dots{} that's it.
@end itemize


@node Agent Categories
@subsection Agent Categories

One of the main reasons to integrate the news transport layer into the
newsreader is to allow greater control over what articles to download.
There's not much point in downloading huge amounts of articles, just to
find out that you're not interested in reading any of them.  It's better
to be somewhat more conservative in choosing what to download, and then
mark the articles for downloading manually if it should turn out that
you're interested in the articles anyway.

One of the more effective methods for controlling what is to be
downloaded is to create a @dfn{category} and then assign some (or all)
groups to this category.  Groups that do not belong in any other
category belong to the @code{default} category.  Gnus has its own
buffer for creating and managing categories.

If you prefer, you can also use group parameters (@pxref{Group
Parameters}) and topic parameters (@pxref{Topic Parameters}) for an
alternative approach to controlling the agent.  The only real
difference is that categories are specific to the agent (so there is
less to learn) while group and topic parameters include the kitchen
sink.

Since you can set agent parameters in several different places we have
a rule to decide which source to believe.  This rule specifies that
the parameter sources are checked in the following order: group
parameters, topic parameters, agent category, and finally customizable
variables.  So you can mix all of these sources to produce a wide range
of behavior, just don't blame me if you don't remember where you put
your settings.

@menu
* Category Syntax::             What a category looks like.
* Category Buffer::             A buffer for maintaining categories.
* Category Variables::          Customize'r'Us.
@end menu


@node Category Syntax
@subsubsection Category Syntax

A category consists of a name, the list of groups belonging to the
category, and a number of optional parameters that override the
customizable variables.  The complete list of agent parameters are
listed below.

@table @code
@item gnus-agent-cat-name
The name of the category.

@item gnus-agent-cat-groups
The list of groups that are in this category.

@item gnus-agent-cat-predicate
A predicate which (generally) gives a rough outline of which articles
are eligible for downloading; and

@item gnus-agent-cat-score-file
a score rule which (generally) gives you a finer granularity when
deciding what articles to download.  (Note that this @dfn{download
score} is not necessarily related to normal scores.)

@item gnus-agent-cat-enable-expiration
a boolean indicating whether the agent should expire old articles in
this group.  Most groups should be expired to conserve disk space.  In
fact, its probably safe to say that the gnus.* hierarchy contains the
only groups that should not be expired.

@item gnus-agent-cat-days-until-old
an integer indicating the number of days that the agent should wait
before deciding that a read article is safe to expire.

@item gnus-agent-cat-low-score
an integer that overrides the value of @code{gnus-agent-low-score}.

@item gnus-agent-cat-high-score
an integer that overrides the value of @code{gnus-agent-high-score}.

@item gnus-agent-cat-length-when-short
an integer that overrides the value of
@code{gnus-agent-short-article}.

@item gnus-agent-cat-length-when-long
an integer that overrides the value of @code{gnus-agent-long-article}.
@end table

The name of a category can not be changed once the category has been
created.

Each category maintains a list of groups that are exclusive members of
that category.  The exclusivity rule is automatically enforced, add a
group to a new category and it is automatically removed from its old
category.

A predicate in its simplest form can be a single predicate such as
@code{true} or @code{false}.  These two will download every available
article or nothing respectively.  In the case of these two special
predicates an additional score rule is superfluous.

Predicates of @code{high} or @code{low} download articles in respect of
their scores in relationship to @code{gnus-agent-high-score} and
@code{gnus-agent-low-score} as described below.

To gain even finer control of what is to be regarded eligible for
download a predicate can consist of a number of predicates with logical
operators sprinkled in between.

Perhaps some examples are in order.

Here's a simple predicate.  (It's the default predicate, in fact, used
for all groups that don't belong to any other category.)

@lisp
short
@end lisp

Quite simple, eh?  This predicate is true if and only if the article is
short (for some value of ``short'').

Here's a more complex predicate:

@lisp
(or high
    (and
     (not low)
     (not long)))
@end lisp

This means that an article should be downloaded if it has a high score,
or if the score is not low and the article is not long.  You get the
drift.

The available logical operators are @code{or}, @code{and} and
@code{not}.  (If you prefer, you can use the more ``C''-ish operators
@samp{|}, @code{&} and @code{!} instead.)

The following predicates are pre-defined, but if none of these fit what
you want to do, you can write your own.

When evaluating each of these predicates, the named constant will be
bound to the value determined by calling
@code{gnus-agent-find-parameter} on the appropriate parameter.  For
example, gnus-agent-short-article will be bound to
@code{(gnus-agent-find-parameter group 'agent-short-article)}.  This
means that you can specify a predicate in your category then tune that
predicate to individual groups.

@table @code
@item short
True iff the article is shorter than @code{gnus-agent-short-article}
lines; default 100.

@item long
True iff the article is longer than @code{gnus-agent-long-article}
lines; default 200.

@item low
True iff the article has a download score less than
@code{gnus-agent-low-score}; default 0.

@item high
True iff the article has a download score greater than
@code{gnus-agent-high-score}; default 0.

@item spam
True iff the Gnus Agent guesses that the article is spam.  The
heuristics may change over time, but at present it just computes a
checksum and sees whether articles match.

@item true
Always true.

@item false
Always false.
@end table

If you want to create your own predicate function, here's what you have
to know:  The functions are called with no parameters, but the
@code{gnus-headers} and @code{gnus-score} dynamic variables are bound to
useful values.

For example, you could decide that you don't want to download articles
that were posted more than a certain number of days ago (e.g. posted
more than @code{gnus-agent-expire-days} ago) you might write a function
something along the lines of the following:

@lisp
(defun my-article-old-p ()
  "Say whether an article is old."
  (< (time-to-days (date-to-time (mail-header-date gnus-headers)))
     (- (time-to-days (current-time)) gnus-agent-expire-days)))
@end lisp

with the predicate then defined as:

@lisp
(not my-article-old-p)
@end lisp

or you could append your predicate to the predefined
@code{gnus-category-predicate-alist} in your @file{~/.gnus.el} or
wherever.

@lisp
(require 'gnus-agent)
(setq  gnus-category-predicate-alist
  (append gnus-category-predicate-alist
         '((old . my-article-old-p))))
@end lisp

and simply specify your predicate as:

@lisp
(not old)
@end lisp

If/when using something like the above, be aware that there are many
misconfigured systems/mailers out there and so an article's date is not
always a reliable indication of when it was posted.  Hell, some people
just don't give a damn.

The above predicates apply to @emph{all} the groups which belong to the
category.  However, if you wish to have a specific predicate for an
individual group within a category, or you're just too lazy to set up a
new category, you can enter a group's individual predicate in its group
parameters like so:

@lisp
(agent-predicate . short)
@end lisp

This is the group/topic parameter equivalent of the agent category default.
Note that when specifying a single word predicate like this, the
@code{agent-predicate} specification must be in dotted pair notation.

The equivalent of the longer example from above would be:

@lisp
(agent-predicate or high (and (not low) (not long)))
@end lisp

The outer parenthesis required in the category specification are not
entered here as, not being in dotted pair notation, the value of the
predicate is assumed to be a list.


Now, the syntax of the download score is the same as the syntax of
normal score files, except that all elements that require actually
seeing the article itself are verboten.  This means that only the
following headers can be scored on: @code{Subject}, @code{From},
@code{Date}, @code{Message-ID}, @code{References}, @code{Chars},
@code{Lines}, and @code{Xref}.

As with predicates, the specification of the @code{download score rule}
to use in respect of a group can be in either the category definition if
it's to be applicable to all groups in therein, or a group's parameters
if it's to be specific to that group.

In both of these places the @code{download score rule} can take one of
three forms:

@enumerate
@item
Score rule

This has the same syntax as a normal Gnus score file except only a
subset of scoring keywords are available as mentioned above.

example:

@itemize @bullet
@item
Category specification

@lisp
(("from"
       ("Lars Ingebrigtsen" 1000000 nil s))
("lines"
       (500 -100 nil <)))
@end lisp

@item
Group/Topic Parameter specification

@lisp
(agent-score ("from"
                   ("Lars Ingebrigtsen" 1000000 nil s))
             ("lines"
                   (500 -100 nil <)))
@end lisp

Again, note the omission of the outermost parenthesis here.
@end itemize

@item
Agent score file

These score files must @emph{only} contain the permitted scoring
keywords stated above.

example:

@itemize @bullet
@item
Category specification

@lisp
("~/News/agent.SCORE")
@end lisp

or perhaps

@lisp
("~/News/agent.SCORE" "~/News/agent.group.SCORE")
@end lisp

@item
Group Parameter specification

@lisp
(agent-score "~/News/agent.SCORE")
@end lisp

Additional score files can be specified as above.  Need I say anything
about parenthesis?
@end itemize

@item
Use @code{normal} score files

If you don't want to maintain two sets of scoring rules for a group, and
your desired @code{downloading} criteria for a group are the same as your
@code{reading} criteria then you can tell the agent to refer to your
@code{normal} score files when deciding what to download.

These directives in either the category definition or a group's
parameters will cause the agent to read in all the applicable score
files for a group, @emph{filtering out} those sections that do not
relate to one of the permitted subset of scoring keywords.

@itemize @bullet
@item
Category Specification

@lisp
file
@end lisp

@item
Group Parameter specification

@lisp
(agent-score . file)
@end lisp
@end itemize
@end enumerate

@node Category Buffer
@subsubsection Category Buffer

You'd normally do all category maintenance from the category buffer.
When you enter it for the first time (with the @kbd{J c} command from
the group buffer), you'll only see the @code{default} category.

The following commands are available in this buffer:

@table @kbd
@item q
@kindex q (Category)
@findex gnus-category-exit
Return to the group buffer (@code{gnus-category-exit}).

@item e
@kindex e (Category)
@findex gnus-category-customize-category
Use a customization buffer to set all of the selected category's
parameters at one time (@code{gnus-category-customize-category}).

@item k
@kindex k (Category)
@findex gnus-category-kill
Kill the current category (@code{gnus-category-kill}).

@item c
@kindex c (Category)
@findex gnus-category-copy
Copy the current category (@code{gnus-category-copy}).

@item a
@kindex a (Category)
@findex gnus-category-add
Add a new category (@code{gnus-category-add}).

@item p
@kindex p (Category)
@findex gnus-category-edit-predicate
Edit the predicate of the current category
(@code{gnus-category-edit-predicate}).

@item g
@kindex g (Category)
@findex gnus-category-edit-groups
Edit the list of groups belonging to the current category
(@code{gnus-category-edit-groups}).

@item s
@kindex s (Category)
@findex gnus-category-edit-score
Edit the download score rule of the current category
(@code{gnus-category-edit-score}).

@item l
@kindex l (Category)
@findex gnus-category-list
List all the categories (@code{gnus-category-list}).
@end table


@node Category Variables
@subsubsection Category Variables

@table @code
@item gnus-category-mode-hook
@vindex gnus-category-mode-hook
Hook run in category buffers.

@item gnus-category-line-format
@vindex gnus-category-line-format
Format of the lines in the category buffer (@pxref{Formatting
Variables}).  Valid elements are:

@table @samp
@item c
The name of the category.

@item g
The number of groups in the category.
@end table

@item gnus-category-mode-line-format
@vindex gnus-category-mode-line-format
Format of the category mode line (@pxref{Mode Line Formatting}).

@item gnus-agent-short-article
@vindex gnus-agent-short-article
Articles that have fewer lines than this are short.  Default 100.

@item gnus-agent-long-article
@vindex gnus-agent-long-article
Articles that have more lines than this are long.  Default 200.

@item gnus-agent-low-score
@vindex gnus-agent-low-score
Articles that have a score lower than this have a low score.  Default
0.

@item gnus-agent-high-score
@vindex gnus-agent-high-score
Articles that have a score higher than this have a high score.  Default
0.

@item gnus-agent-expire-days
@vindex gnus-agent-expire-days
The number of days that a @samp{read} article must stay in the agent's
local disk before becoming eligible for expiration (While the name is
the same, this doesn't mean expiring the article on the server.  It
just means deleting the local copy of the article).  What is also
important to understand is that the counter starts with the time the
article was written to the local disk and not the time the article was
read.
Default 7.

@item gnus-agent-enable-expiration
@vindex gnus-agent-enable-expiration
Determines whether articles in a group are, by default, expired or
retained indefinitely.  The default is @code{ENABLE} which means that
you'll have to disable expiration when desired.  On the other hand,
you could set this to @code{DISABLE}.  In that case, you would then
have to enable expiration in selected groups.

@end table


@node Agent Commands
@subsection Agent Commands
@findex gnus-agent-toggle-plugged
@kindex J j (Agent)

All the Gnus Agent commands are on the @kbd{J} submap.  The @kbd{J j}
(@code{gnus-agent-toggle-plugged}) command works in all modes, and
toggles the plugged/unplugged state of the Gnus Agent.


@menu
* Group Agent Commands::        Configure groups and fetch their contents.
* Summary Agent Commands::      Manually select then fetch specific articles.
* Server Agent Commands::       Select the servers that are supported by the agent.
@end menu




@node Group Agent Commands
@subsubsection Group Agent Commands

@table @kbd
@item J u
@kindex J u (Agent Group)
@findex gnus-agent-fetch-groups
Fetch all eligible articles in the current group
(@code{gnus-agent-fetch-groups}).

@item J c
@kindex J c (Agent Group)
@findex gnus-enter-category-buffer
Enter the Agent category buffer (@code{gnus-enter-category-buffer}).

@item J s
@kindex J s (Agent Group)
@findex gnus-agent-fetch-session
Fetch all eligible articles in all groups
(@code{gnus-agent-fetch-session}).

@item J S
@kindex J S (Agent Group)
@findex gnus-group-send-queue
Send all sendable messages in the queue group
(@code{gnus-group-send-queue}).  @xref{Drafts}.

@item J a
@kindex J a (Agent Group)
@findex gnus-agent-add-group
Add the current group to an Agent category
(@code{gnus-agent-add-group}).  This command understands the
process/prefix convention (@pxref{Process/Prefix}).

@item J r
@kindex J r (Agent Group)
@findex gnus-agent-remove-group
Remove the current group from its category, if any
(@code{gnus-agent-remove-group}).  This command understands the
process/prefix convention (@pxref{Process/Prefix}).

@item J Y
@kindex J Y (Agent Group)
@findex gnus-agent-synchronize-flags
Synchronize flags changed while unplugged with remote server, if any.


@end table


@node Summary Agent Commands
@subsubsection Summary Agent Commands

@table @kbd
@item J #
@kindex J # (Agent Summary)
@findex gnus-agent-mark-article
Mark the article for downloading (@code{gnus-agent-mark-article}).

@item J M-#
@kindex J M-# (Agent Summary)
@findex gnus-agent-unmark-article
Remove the downloading mark from the article
(@code{gnus-agent-unmark-article}).

@cindex %
@item @@
@kindex @@ (Agent Summary)
@findex gnus-agent-toggle-mark
Toggle whether to download the article
(@code{gnus-agent-toggle-mark}).  The download mark is @samp{%} by
default.

@item J c
@kindex J c (Agent Summary)
@findex gnus-agent-catchup
Mark all articles as read (@code{gnus-agent-catchup}) that are neither cached, downloaded, nor downloadable.

@item J S
@kindex J S (Agent Summary)
@findex gnus-agent-fetch-group
Download all eligible (@pxref{Agent Categories}) articles in this group.
(@code{gnus-agent-fetch-group}).

@item J s
@kindex J s (Agent Summary)
@findex gnus-agent-fetch-series
Download all processable articles in this group.
(@code{gnus-agent-fetch-series}).

@item J u
@kindex J u (Agent Summary)
@findex gnus-agent-summary-fetch-group
Download all downloadable articles in the current group
(@code{gnus-agent-summary-fetch-group}).

@end table


@node Server Agent Commands
@subsubsection Server Agent Commands

@table @kbd
@item J a
@kindex J a (Agent Server)
@findex gnus-agent-add-server
Add the current server to the list of servers covered by the Gnus Agent
(@code{gnus-agent-add-server}).

@item J r
@kindex J r (Agent Server)
@findex gnus-agent-remove-server
Remove the current server from the list of servers covered by the Gnus
Agent (@code{gnus-agent-remove-server}).

@end table


@node Agent Visuals
@subsection Agent Visuals

If you open a summary while unplugged and, Gnus knows from the group's
active range that there are more articles than the headers currently
stored in the Agent, you may see some articles whose subject looks
something like @samp{[Undownloaded article #####]}.  These are
placeholders for the missing headers.  Aside from setting a mark,
there is not much that can be done with one of these placeholders.
When Gnus finally gets a chance to fetch the group's headers, the
placeholders will automatically be replaced by the actual headers.
You can configure the summary buffer's maneuvering to skip over the
placeholders if you care (See @code{gnus-auto-goto-ignores}).

While it may be obvious to all, the only headers and articles
available while unplugged are those headers and articles that were
fetched into the Agent while previously plugged.  To put it another
way, "If you forget to fetch something while plugged, you might have a
less than satisfying unplugged session".  For this reason, the Agent
adds two visual effects to your summary buffer.  These effects display
the download status of each article so that you always know which
articles will be available when unplugged.

The first visual effect is the @samp{%O} spec.  If you customize
@code{gnus-summary-line-format} to include this specifier, you will add
a single character field that indicates an article's download status.
Articles that have been fetched into either the Agent or the Cache,
will display @code{gnus-downloaded-mark} (defaults to @samp{+}).  All
other articles will display @code{gnus-undownloaded-mark} (defaults to
@samp{-}).  If you open a group that has not been agentized, a space
(@samp{ }) will be displayed.

The second visual effect are the undownloaded faces.  The faces, there
are three indicating the article's score (low, normal, high), seem to
result in a love/hate response from many Gnus users.  The problem is
that the face selection is controlled by a list of condition tests and
face names (See @code{gnus-summary-highlight}).  Each condition is
tested in the order in which it appears in the list so early
conditions have precedence over later conditions.  All of this means
that, if you tick an undownloaded article, the article will continue
to be displayed in the undownloaded face rather than the ticked face.

If you use the Agent as a cache (to avoid downloading the same article
each time you visit it or to minimize your connection time), the
undownloaded face will probably seem like a good idea.  The reason
being that you do all of our work (marking, reading, deleting) with
downloaded articles so the normal faces always appear.

For occasional Agent users, the undownloaded faces may appear to be an
absolutely horrible idea.  The issue being that, since most of their
articles have not been fetched into the Agent, most of the normal
faces will be obscured by the undownloaded faces.  If this is your
situation, you have two choices available.  First, you can completely
disable the undownload faces by customizing
@code{gnus-summary-highlight} to delete the three cons-cells that
refer to the @code{gnus-summary-*-undownloaded-face} faces.  Second, if
you prefer to take a more fine-grained approach, you may set the
@code{agent-disable-undownloaded-faces} group parameter to t.  This
parameter, like all other agent parameters, may be set on an Agent
Category (@pxref{Agent Categories}), a Group Topic (@pxref{Topic
Parameters}), or an individual group (@pxref{Group Parameters}).

@node Agent as Cache
@subsection Agent as Cache

When Gnus is plugged, it is not efficient to download headers or
articles from the server again, if they are already stored in the
Agent.  So, Gnus normally only downloads headers once, and stores them
in the Agent.  These headers are later used when generating the summary
buffer, regardless of whether you are plugged or unplugged.  Articles
are not cached in the Agent by default though (that would potentially
consume lots of disk space), but if you have already downloaded an
article into the Agent, Gnus will not download the article from the
server again but use the locally stored copy instead.

If you so desire, you can configure the agent (see @code{gnus-agent-cache}
@pxref{Agent Variables}) to always download headers and articles while
plugged.  Gnus will almost certainly be slower, but it will be kept
synchronized with the server.  That last point probably won't make any
sense if you are using a nntp or nnimap back end.

@node Agent Expiry
@subsection Agent Expiry

@vindex gnus-agent-expire-days
@findex gnus-agent-expire
@kindex M-x gnus-agent-expire
@kindex M-x gnus-agent-expire-group
@findex gnus-agent-expire-group
@cindex agent expiry
@cindex Gnus agent expiry
@cindex expiry

The Agent back end, @code{nnagent}, doesn't handle expiry.  Well, at
least it doesn't handle it like other back ends.  Instead, there are
special @code{gnus-agent-expire} and @code{gnus-agent-expire-group}
commands that will expire all read articles that are older than
@code{gnus-agent-expire-days} days.  They can be run whenever you feel
that you're running out of space.  Neither are particularly fast or
efficient, and it's not a particularly good idea to interrupt them (with
@kbd{C-g} or anything else) once you've started one of them.

Note that other functions, e.g. @code{gnus-request-expire-articles},
might run @code{gnus-agent-expire} for you to keep the agent
synchronized with the group.

The agent parameter @code{agent-enable-expiration} may be used to
prevent expiration in selected groups.

@vindex gnus-agent-expire-all
If @code{gnus-agent-expire-all} is non-@code{nil}, the agent
expiration commands will expire all articles---unread, read, ticked
and dormant.  If @code{nil} (which is the default), only read articles
are eligible for expiry, and unread, ticked and dormant articles will
be kept indefinitely.

If you find that some articles eligible for expiry are never expired,
perhaps some Gnus Agent files are corrupted.  There's are special
commands, @code{gnus-agent-regenerate} and
@code{gnus-agent-regenerate-group}, to fix possible problems.

@node Agent Regeneration
@subsection Agent Regeneration

@cindex agent regeneration
@cindex Gnus agent regeneration
@cindex regeneration

The local data structures used by @code{nnagent} may become corrupted
due to certain exceptional conditions.  When this happens,
@code{nnagent} functionality may degrade or even fail.  The solution
to this problem is to repair the local data structures by removing all
internal inconsistencies.

For example, if your connection to your server is lost while
downloaded articles into the agent, the local data structures will not
know about articles successfully downloaded prior to the connection
failure.  Running @code{gnus-agent-regenerate} or
@code{gnus-agent-regenerate-group} will update the data structures
such that you don't need to download these articles a second time.

@findex gnus-agent-regenerate
@kindex M-x gnus-agent-regenerate
The command @code{gnus-agent-regenerate} will perform
@code{gnus-agent-regenerate-group} on every agentized group.  While
you can run @code{gnus-agent-regenerate} in any buffer, it is strongly
recommended that you first close all summary buffers.

@findex gnus-agent-regenerate-group
@kindex M-x gnus-agent-regenerate-group
The command @code{gnus-agent-regenerate-group} uses the local copies
of individual articles to repair the local @acronym{NOV}(header) database.  It
then updates the internal data structures that document which articles
are stored locally.  An optional argument will mark articles in the
agent as unread.

@node Agent and IMAP
@subsection Agent and IMAP

The Agent works with any Gnus back end, including nnimap.  However,
since there are some conceptual differences between @acronym{NNTP} and
@acronym{IMAP}, this section (should) provide you with some information to
make Gnus Agent work smoother as a @acronym{IMAP} Disconnected Mode client.

The first thing to keep in mind is that all flags (read, ticked, etc)
are kept on the @acronym{IMAP} server, rather than in @file{.newsrc} as is the
case for nntp.  Thus Gnus need to remember flag changes when
disconnected, and synchronize these flags when you plug back in.

Gnus keeps track of flag changes when reading nnimap groups under the
Agent.  When you plug back in, Gnus will check if you have any changed
any flags and ask if you wish to synchronize these with the server.
The behavior is customizable by @code{gnus-agent-synchronize-flags}.

@vindex gnus-agent-synchronize-flags
If @code{gnus-agent-synchronize-flags} is @code{nil}, the Agent will
never automatically synchronize flags.  If it is @code{ask}, which is
the default, the Agent will check if you made any changes and if so
ask if you wish to synchronize these when you re-connect.  If it has
any other value, all flags will be synchronized automatically.

If you do not wish to synchronize flags automatically when you
re-connect, you can do it manually with the
@code{gnus-agent-synchronize-flags} command that is bound to @kbd{J Y}
in the group buffer.

Some things are currently not implemented in the Agent that you'd might
expect from a disconnected @acronym{IMAP} client, including:

@itemize @bullet

@item
Copying/moving articles into nnimap groups when unplugged.

@item
Creating/deleting nnimap groups when unplugged.

@end itemize

Technical note: the synchronization algorithm does not work by ``pushing''
all local flags to the server, but rather incrementally update the
server view of flags by changing only those flags that were changed by
the user.  Thus, if you set one flag on an article, quit the group and
re-select the group and remove the flag; the flag will be set and
removed from the server when you ``synchronize''.  The queued flag
operations can be found in the per-server @code{flags} file in the Agent
directory.  It's emptied when you synchronize flags.


@node Outgoing Messages
@subsection Outgoing Messages

When Gnus is unplugged, all outgoing messages (both mail and news) are
stored in the draft group ``queue'' (@pxref{Drafts}).  You can view
them there after posting, and edit them at will.

When Gnus is plugged again, you can send the messages either from the
draft group with the special commands available there, or you can use
the @kbd{J S} command in the group buffer to send all the sendable
messages in the draft group.



@node Agent Variables
@subsection Agent Variables

@table @code
@item gnus-agent-directory
@vindex gnus-agent-directory
Where the Gnus Agent will store its files.  The default is
@file{~/News/agent/}.

@item gnus-agent-handle-level
@vindex gnus-agent-handle-level
Groups on levels (@pxref{Group Levels}) higher than this variable will
be ignored by the Agent.  The default is @code{gnus-level-subscribed},
which means that only subscribed group will be considered by the Agent
by default.

@item gnus-agent-plugged-hook
@vindex gnus-agent-plugged-hook
Hook run when connecting to the network.

@item gnus-agent-unplugged-hook
@vindex gnus-agent-unplugged-hook
Hook run when disconnecting from the network.

@item gnus-agent-fetched-hook
@vindex gnus-agent-fetched-hook
Hook run when finished fetching articles.

@item gnus-agent-cache
@vindex gnus-agent-cache
Variable to control whether use the locally stored @acronym{NOV} and
articles when plugged, e.g. essentially using the Agent as a cache.
The default is non-@code{nil}, which means to use the Agent as a cache.

@item gnus-agent-go-online
@vindex gnus-agent-go-online
If @code{gnus-agent-go-online} is @code{nil}, the Agent will never
automatically switch offline servers into online status.  If it is
@code{ask}, the default, the Agent will ask if you wish to switch
offline servers into online status when you re-connect.  If it has any
other value, all offline servers will be automatically switched into
online status.

@item gnus-agent-mark-unread-after-downloaded
@vindex gnus-agent-mark-unread-after-downloaded
If @code{gnus-agent-mark-unread-after-downloaded} is non-@code{nil},
mark articles as unread after downloading.  This is usually a safe
thing to do as the newly downloaded article has obviously not been
read.  The default is t.

@item gnus-agent-consider-all-articles
@vindex gnus-agent-consider-all-articles
If @code{gnus-agent-consider-all-articles} is non-@code{nil}, the
agent will fetch all missing headers.  When @code{nil}, the agent will
fetch only new headers.  The default is @code{nil}.

@item gnus-agent-max-fetch-size
@vindex gnus-agent-max-fetch-size
The agent fetches articles into a temporary buffer prior to parsing
them into individual files.  To avoid exceeding the max. buffer size,
the agent alternates between fetching and parsing until all articles
have been fetched.  @code{gnus-agent-max-fetch-size} provides a size
limit to control how often the cycling occurs.  A large value improves
performance.  A small value minimizes the time lost should the
connection be lost while fetching (You may need to run
@code{gnus-agent-regenerate-group} to update the group's state.
However, all articles parsed prior to loosing the connection will be
available while unplugged).  The default is 10M so it is unusual to
see any cycling.

@item gnus-server-unopen-status
@vindex gnus-server-unopen-status
Perhaps not an Agent variable, but closely related to the Agent, this
variable says what will happen if Gnus cannot open a server.  If the
Agent is enabled, the default, @code{nil}, makes Gnus ask the user
whether to deny the server or whether to unplug the agent.  If the
Agent is disabled, Gnus always simply deny the server.  Other choices
for this variable include @code{denied} and @code{offline} the latter
is only valid if the Agent is used.

@item gnus-auto-goto-ignores
@vindex gnus-auto-goto-ignores
Another variable that isn't an Agent variable, yet so closely related
that most will look for it here, this variable tells the summary
buffer how to maneuver around undownloaded (only headers stored in the
agent) and unfetched (neither article nor headers stored) articles.

The legal values are @code{nil} (maneuver to any article),
@code{undownloaded} (maneuvering while unplugged ignores articles that
have not been fetched), @code{always-undownloaded} (maneuvering always
ignores articles that have not been fetched), @code{unfetched}
(maneuvering ignores articles whose headers have not been fetched).

@end table


@node Example Setup
@subsection Example Setup

If you don't want to read this manual, and you have a fairly standard
setup, you may be able to use something like the following as your
@file{~/.gnus.el} file to get started.

@lisp
;;; @r{Define how Gnus is to fetch news.  We do this over @acronym{NNTP}}
;;; @r{from your ISP's server.}
(setq gnus-select-method '(nntp "news.your-isp.com"))

;;; @r{Define how Gnus is to read your mail.  We read mail from}
;;; @r{your ISP's @acronym{POP} server.}
(setq mail-sources '((pop :server "pop.your-isp.com")))

;;; @r{Say how Gnus is to store the mail.  We use nnml groups.}
(setq gnus-secondary-select-methods '((nnml "")))

;;; @r{Make Gnus into an offline newsreader.}
;;; (gnus-agentize) ; @r{The obsolete setting.}
;;; (setq gnus-agent t) ; @r{Now the default.}
@end lisp

That should be it, basically.  Put that in your @file{~/.gnus.el} file,
edit to suit your needs, start up PPP (or whatever), and type @kbd{M-x
gnus}.

If this is the first time you've run Gnus, you will be subscribed
automatically to a few default newsgroups.  You'll probably want to
subscribe to more groups, and to do that, you have to query the
@acronym{NNTP} server for a complete list of groups with the @kbd{A A}
command.  This usually takes quite a while, but you only have to do it
once.

After reading and parsing a while, you'll be presented with a list of
groups.  Subscribe to the ones you want to read with the @kbd{u}
command.  @kbd{l} to make all the killed groups disappear after you've
subscribe to all the groups you want to read.  (@kbd{A k} will bring
back all the killed groups.)

You can now read the groups at once, or you can download the articles
with the @kbd{J s} command.  And then read the rest of this manual to
find out which of the other gazillion things you want to customize.


@node Batching Agents
@subsection Batching Agents
@findex gnus-agent-batch

Having the Gnus Agent fetch articles (and post whatever messages you've
written) is quite easy once you've gotten things set up properly.  The
following shell script will do everything that is necessary:

You can run a complete batch command from the command line with the
following incantation:

@example
#!/bin/sh
emacs -batch -l ~/.emacs -f -l ~/.gnus.el gnus-agent-batch >/dev/null 2>&1
@end example


@node Agent Caveats
@subsection Agent Caveats

The Gnus Agent doesn't seem to work like most other offline
newsreaders.  Here are some common questions that some imaginary people
may ask:

@table @dfn
@item If I read an article while plugged, do they get entered into the Agent?

@strong{No}.  If you want this behaviour, add
@code{gnus-agent-fetch-selected-article} to
@code{gnus-select-article-hook}.

@item If I read an article while plugged, and the article already exists in
the Agent, will it get downloaded once more?

@strong{No}, unless @code{gnus-agent-cache} is @code{nil}.

@end table

In short, when Gnus is unplugged, it only looks into the locally stored
articles; when it's plugged, it talks to your ISP and may also use the
locally stored articles.


@node Scoring
@chapter Scoring
@cindex scoring

Other people use @dfn{kill files}, but we here at Gnus Towers like
scoring better than killing, so we'd rather switch than fight.  They do
something completely different as well, so sit up straight and pay
attention!

@vindex gnus-summary-mark-below
All articles have a default score (@code{gnus-summary-default-score}),
which is 0 by default.  This score may be raised or lowered either
interactively or by score files.  Articles that have a score lower than
@code{gnus-summary-mark-below} are marked as read.

Gnus will read any @dfn{score files} that apply to the current group
before generating the summary buffer.

There are several commands in the summary buffer that insert score
entries based on the current article.  You can, for instance, ask Gnus to
lower or increase the score of all articles with a certain subject.

There are two sorts of scoring entries: Permanent and temporary.
Temporary score entries are self-expiring entries.  Any entries that are
temporary and have not been used for, say, a week, will be removed
silently to help keep the sizes of the score files down.

@menu
* Summary Score Commands::      Adding score entries for the current group.
* Group Score Commands::        General score commands.
* Score Variables::             Customize your scoring.  (My, what terminology).
* Score File Format::           What a score file may contain.
* Score File Editing::          You can edit score files by hand as well.
* Adaptive Scoring::            Big Sister Gnus knows what you read.
* Home Score File::             How to say where new score entries are to go.
* Followups To Yourself::       Having Gnus notice when people answer you.
* Scoring On Other Headers::    Scoring on non-standard headers.
* Scoring Tips::                How to score effectively.
* Reverse Scoring::             That problem child of old is not problem.
* Global Score Files::          Earth-spanning, ear-splitting score files.
* Kill Files::                  They are still here, but they can be ignored.
* Converting Kill Files::       Translating kill files to score files.
* GroupLens::                   Getting predictions on what you like to read.
* Advanced Scoring::            Using logical expressions to build score rules.
* Score Decays::                It can be useful to let scores wither away.
@end menu


@node Summary Score Commands
@section Summary Score Commands
@cindex score commands

The score commands that alter score entries do not actually modify real
score files.  That would be too inefficient.  Gnus maintains a cache of
previously loaded score files, one of which is considered the
@dfn{current score file alist}.  The score commands simply insert
entries into this list, and upon group exit, this list is saved.

The current score file is by default the group's local score file, even
if no such score file actually exists.  To insert score commands into
some other score file (e.g. @file{all.SCORE}), you must first make this
score file the current one.

General score commands that don't actually change the score file:

@table @kbd

@item V s
@kindex V s (Summary)
@findex gnus-summary-set-score
Set the score of the current article (@code{gnus-summary-set-score}).

@item V S
@kindex V S (Summary)
@findex gnus-summary-current-score
Display the score of the current article
(@code{gnus-summary-current-score}).

@item V t
@kindex V t (Summary)
@findex gnus-score-find-trace
Display all score rules that have been used on the current article
(@code{gnus-score-find-trace}).  In the @code{*Score Trace*} buffer, you
can use @kbd{q} to quit.  @kbd{e} edits the corresponding score file.
When point is on a string within the match element, @kbd{e} will try to
bring you to this string in the score file.

@item V w
@kindex V w (Summary)
@findex gnus-score-find-favourite-words
List words used in scoring (@code{gnus-score-find-favourite-words}).

@item V R
@kindex V R (Summary)
@findex gnus-summary-rescore
Run the current summary through the scoring process
(@code{gnus-summary-rescore}).  This might be useful if you're playing
around with your score files behind Gnus' back and want to see the
effect you're having.

@item V c
@kindex V c (Summary)
@findex gnus-score-change-score-file
Make a different score file the current
(@code{gnus-score-change-score-file}).

@item V e
@kindex V e (Summary)
@findex gnus-score-edit-current-scores
Edit the current score file (@code{gnus-score-edit-current-scores}).
You will be popped into a @code{gnus-score-mode} buffer (@pxref{Score
File Editing}).

@item V f
@kindex V f (Summary)
@findex gnus-score-edit-file
Edit a score file and make this score file the current one
(@code{gnus-score-edit-file}).

@item V F
@kindex V F (Summary)
@findex gnus-score-flush-cache
Flush the score cache (@code{gnus-score-flush-cache}).  This is useful
after editing score files.

@item V C
@kindex V C (Summary)
@findex gnus-score-customize
Customize a score file in a visually pleasing manner
(@code{gnus-score-customize}).

@end table

The rest of these commands modify the local score file.

@table @kbd

@item V m
@kindex V m (Summary)
@findex gnus-score-set-mark-below
Prompt for a score, and mark all articles with a score below this as
read (@code{gnus-score-set-mark-below}).

@item V x
@kindex V x (Summary)
@findex gnus-score-set-expunge-below
Prompt for a score, and add a score rule to the current score file to
expunge all articles below this score
(@code{gnus-score-set-expunge-below}).
@end table

The keystrokes for actually making score entries follow a very regular
pattern, so there's no need to list all the commands.  (Hundreds of
them.)

@findex gnus-summary-increase-score
@findex gnus-summary-lower-score

@enumerate
@item
The first key is either @kbd{I} (upper case i) for increasing the score
or @kbd{L} for lowering the score.
@item
The second key says what header you want to score on.  The following
keys are available:
@table @kbd

@item a
Score on the author name.

@item s
Score on the subject line.

@item x
Score on the @code{Xref} line---i.e., the cross-posting line.

@item r
Score on the @code{References} line.

@item d
Score on the date.

@item l
Score on the number of lines.

@item i
Score on the @code{Message-ID} header.

@item e
Score on an ``extra'' header, that is, one of those in gnus-extra-headers,
if your @acronym{NNTP} server tracks additional header data in overviews.

@item f
Score on followups---this matches the author name, and adds scores to
the followups to this author.  (Using this key leads to the creation of
@file{ADAPT} files.)

@item b
Score on the body.

@item h
Score on the head.

@item t
Score on thread.  (Using this key leads to the creation of @file{ADAPT}
files.)

@end table

@item
The third key is the match type.  Which match types are valid depends on
what headers you are scoring on.

@table @code

@item strings

@table @kbd

@item e
Exact matching.

@item s
Substring matching.

@item f
Fuzzy matching (@pxref{Fuzzy Matching}).

@item r
Regexp matching
@end table

@item date
@table @kbd

@item b
Before date.

@item a
After date.

@item n
This date.
@end table

@item number
@table @kbd

@item <
Less than number.

@item =
Equal to number.

@item >
Greater than number.
@end table
@end table

@item
The fourth and usually final key says whether this is a temporary (i.e.,
expiring) score entry, or a permanent (i.e., non-expiring) score entry,
or whether it is to be done immediately, without adding to the score
file.
@table @kbd

@item t
Temporary score entry.

@item p
Permanent score entry.

@item i
Immediately scoring.
@end table

@item
If you are scoring on `e' (extra) headers, you will then be prompted for
the header name on which you wish to score.  This must be a header named
in gnus-extra-headers, and @samp{TAB} completion is available.

@end enumerate

So, let's say you want to increase the score on the current author with
exact matching permanently: @kbd{I a e p}.  If you want to lower the
score based on the subject line, using substring matching, and make a
temporary score entry: @kbd{L s s t}.  Pretty easy.

To make things a bit more complicated, there are shortcuts.  If you use
a capital letter on either the second or third keys, Gnus will use
defaults for the remaining one or two keystrokes.  The defaults are
``substring'' and ``temporary''.  So @kbd{I A} is the same as @kbd{I a s
t}, and @kbd{I a R} is the same as @kbd{I a r t}.

These functions take both the numerical prefix and the symbolic prefix
(@pxref{Symbolic Prefixes}).  A numerical prefix says how much to lower
(or increase) the score of the article.  A symbolic prefix of @code{a}
says to use the @file{all.SCORE} file for the command instead of the
current score file.

@vindex gnus-score-mimic-keymap
The @code{gnus-score-mimic-keymap} says whether these commands will
pretend they are keymaps or not.


@node Group Score Commands
@section Group Score Commands
@cindex group score commands

There aren't many of these as yet, I'm afraid.

@table @kbd

@item W f
@kindex W f (Group)
@findex gnus-score-flush-cache
Gnus maintains a cache of score alists to avoid having to reload them
all the time.  This command will flush the cache
(@code{gnus-score-flush-cache}).

@end table

You can do scoring from the command line by saying something like:

@findex gnus-batch-score
@cindex batch scoring
@example
$ emacs -batch -l ~/.emacs -l ~/.gnus.el -f gnus-batch-score
@end example


@node Score Variables
@section Score Variables
@cindex score variables

@table @code

@item gnus-use-scoring
@vindex gnus-use-scoring
If @code{nil}, Gnus will not check for score files, and will not, in
general, do any score-related work.  This is @code{t} by default.

@item gnus-kill-killed
@vindex gnus-kill-killed
If this variable is @code{nil}, Gnus will never apply score files to
articles that have already been through the kill process.  While this
may save you lots of time, it also means that if you apply a kill file
to a group, and then change the kill file and want to run it over you
group again to kill more articles, it won't work.  You have to set this
variable to @code{t} to do that.  (It is @code{t} by default.)

@item gnus-kill-files-directory
@vindex gnus-kill-files-directory
All kill and score files will be stored in this directory, which is
initialized from the @env{SAVEDIR} environment variable by default.
This is @file{~/News/} by default.

@item gnus-score-file-suffix
@vindex gnus-score-file-suffix
Suffix to add to the group name to arrive at the score file name
(@file{SCORE} by default.)

@item gnus-score-uncacheable-files
@vindex gnus-score-uncacheable-files
@cindex score cache
All score files are normally cached to avoid excessive re-loading of
score files.  However, if this might make your Emacs grow big and
bloated, so this regexp can be used to weed out score files unlikely
to be needed again.  It would be a bad idea to deny caching of
@file{all.SCORE}, while it might be a good idea to not cache
@file{comp.infosystems.www.authoring.misc.ADAPT}.  In fact, this
variable is @samp{ADAPT$} by default, so no adaptive score files will
be cached.

@item gnus-save-score
@vindex gnus-save-score
If you have really complicated score files, and do lots of batch
scoring, then you might set this variable to @code{t}.  This will make
Gnus save the scores into the @file{.newsrc.eld} file.

If you do not set this to @code{t}, then manual scores (like those set
with @kbd{V s} (@code{gnus-summary-set-score})) will not be preserved
across group visits.

@item gnus-score-interactive-default-score
@vindex gnus-score-interactive-default-score
Score used by all the interactive raise/lower commands to raise/lower
score with.  Default is 1000, which may seem excessive, but this is to
ensure that the adaptive scoring scheme gets enough room to play with.
We don't want the small changes from the adaptive scoring to overwrite
manually entered data.

@item gnus-summary-default-score
@vindex gnus-summary-default-score
Default score of an article, which is 0 by default.

@item gnus-summary-expunge-below
@vindex gnus-summary-expunge-below
Don't display the summary lines of articles that have scores lower than
this variable.  This is @code{nil} by default, which means that no
articles will be hidden.  This variable is local to the summary buffers,
and has to be set from @code{gnus-summary-mode-hook}.

@item gnus-score-over-mark
@vindex gnus-score-over-mark
Mark (in the third column) used for articles with a score over the
default.  Default is @samp{+}.

@item gnus-score-below-mark
@vindex gnus-score-below-mark
Mark (in the third column) used for articles with a score below the
default.  Default is @samp{-}.

@item gnus-score-find-score-files-function
@vindex gnus-score-find-score-files-function
Function used to find score files for the current group.  This function
is called with the name of the group as the argument.

Predefined functions available are:
@table @code

@item gnus-score-find-single
@findex gnus-score-find-single
Only apply the group's own score file.

@item gnus-score-find-bnews
@findex gnus-score-find-bnews
Apply all score files that match, using bnews syntax.  This is the
default.  If the current group is @samp{gnu.emacs.gnus}, for instance,
@file{all.emacs.all.SCORE}, @file{not.alt.all.SCORE} and
@file{gnu.all.SCORE} would all apply.  In short, the instances of
@samp{all} in the score file names are translated into @samp{.*}, and
then a regexp match is done.

This means that if you have some score entries that you want to apply to
all groups, then you put those entries in the @file{all.SCORE} file.

The score files are applied in a semi-random order, although Gnus will
try to apply the more general score files before the more specific score
files.  It does this by looking at the number of elements in the score
file names---discarding the @samp{all} elements.

@item gnus-score-find-hierarchical
@findex gnus-score-find-hierarchical
Apply all score files from all the parent groups.  This means that you
can't have score files like @file{all.SCORE}, but you can have
@file{SCORE}, @file{comp.SCORE} and @file{comp.emacs.SCORE} for each
server.

@end table
This variable can also be a list of functions.  In that case, all
these functions will be called with the group name as argument, and
all the returned lists of score files will be applied.  These
functions can also return lists of lists of score alists directly.  In
that case, the functions that return these non-file score alists
should probably be placed before the ``real'' score file functions, to
ensure that the last score file returned is the local score file.
Phu.

For example, to do hierarchical scoring but use a non-server-specific
overall score file, you could use the value
@example
(list (lambda (group) ("all.SCORE"))
      'gnus-score-find-hierarchical)
@end example

@item gnus-score-expiry-days
@vindex gnus-score-expiry-days
This variable says how many days should pass before an unused score file
entry is expired.  If this variable is @code{nil}, no score file entries
are expired.  It's 7 by default.

@item gnus-update-score-entry-dates
@vindex gnus-update-score-entry-dates
If this variable is non-@code{nil}, temporary score entries that have
been triggered (matched) will have their dates updated.  (This is how Gnus
controls expiry---all non-matched-entries will become too old while
matched entries will stay fresh and young.)  However, if you set this
variable to @code{nil}, even matched entries will grow old and will
have to face that oh-so grim reaper.

@item gnus-score-after-write-file-function
@vindex gnus-score-after-write-file-function
Function called with the name of the score file just written.

@item gnus-score-thread-simplify
@vindex gnus-score-thread-simplify
If this variable is non-@code{nil}, article subjects will be
simplified for subject scoring purposes in the same manner as with
threading---according to the current value of
@code{gnus-simplify-subject-functions}.  If the scoring entry uses
@code{substring} or @code{exact} matching, the match will also be
simplified in this manner.

@end table


@node Score File Format
@section Score File Format
@cindex score file format

A score file is an @code{emacs-lisp} file that normally contains just a
single form.  Casual users are not expected to edit these files;
everything can be changed from the summary buffer.

Anyway, if you'd like to dig into it yourself, here's an example:

@lisp
(("from"
  ("Lars Ingebrigtsen" -10000)
  ("Per Abrahamsen")
  ("larsi\\|lmi" -50000 nil R))
 ("subject"
  ("Ding is Badd" nil 728373))
 ("xref"
  ("alt.politics" -1000 728372 s))
 ("lines"
  (2 -100 nil <))
 (mark 0)
 (expunge -1000)
 (mark-and-expunge -10)
 (read-only nil)
 (orphan -10)
 (adapt t)
 (files "/hom/larsi/News/gnu.SCORE")
 (exclude-files "all.SCORE")
 (local (gnus-newsgroup-auto-expire t)
        (gnus-summary-make-false-root empty))
 (eval (ding)))
@end lisp

This example demonstrates most score file elements.  @xref{Advanced
Scoring}, for a different approach.

Even though this looks much like Lisp code, nothing here is actually
@code{eval}ed.  The Lisp reader is used to read this form, though, so it
has to be valid syntactically, if not semantically.

Six keys are supported by this alist:

@table @code

@item STRING
If the key is a string, it is the name of the header to perform the
match on.  Scoring can only be performed on these eight headers:
@code{From}, @code{Subject}, @code{References}, @code{Message-ID},
@code{Xref}, @code{Lines}, @code{Chars} and @code{Date}.  In addition to
these headers, there are three strings to tell Gnus to fetch the entire
article and do the match on larger parts of the article: @code{Body}
will perform the match on the body of the article, @code{Head} will
perform the match on the head of the article, and @code{All} will
perform the match on the entire article.  Note that using any of these
last three keys will slow down group entry @emph{considerably}.  The
final ``header'' you can score on is @code{Followup}.  These score
entries will result in new score entries being added for all follow-ups
to articles that matches these score entries.

Following this key is an arbitrary number of score entries, where each
score entry has one to four elements.
@enumerate

@item
The first element is the @dfn{match element}.  On most headers this will
be a string, but on the Lines and Chars headers, this must be an
integer.

@item
If the second element is present, it should be a number---the @dfn{score
element}.  This number should be an integer in the neginf to posinf
interval.  This number is added to the score of the article if the match
is successful.  If this element is not present, the
@code{gnus-score-interactive-default-score} number will be used
instead.  This is 1000 by default.

@item
If the third element is present, it should be a number---the @dfn{date
element}.  This date says when the last time this score entry matched,
which provides a mechanism for expiring the score entries.  It this
element is not present, the score entry is permanent.  The date is
represented by the number of days since December 31, 1 BCE.

@item
If the fourth element is present, it should be a symbol---the @dfn{type
element}.  This element specifies what function should be used to see
whether this score entry matches the article.  What match types that can
be used depends on what header you wish to perform the match on.
@table @dfn

@item From, Subject, References, Xref, Message-ID
For most header types, there are the @code{r} and @code{R} (regexp), as
well as @code{s} and @code{S} (substring) types, and @code{e} and
@code{E} (exact match), and @code{w} (word match) types.  If this
element is not present, Gnus will assume that substring matching should
be used.  @code{R}, @code{S}, and @code{E} differ from the others in
that the matches will be done in a case-sensitive manner.  All these
one-letter types are really just abbreviations for the @code{regexp},
@code{string}, @code{exact}, and @code{word} types, which you can use
instead, if you feel like.

@item Extra
Just as for the standard string overview headers, if you are using
gnus-extra-headers, you can score on these headers' values.  In this
case, there is a 5th element in the score entry, being the name of the
header to be scored.  The following entry is useful in your
@file{all.SCORE} file in case of spam attacks from a single origin host,
if your @acronym{NNTP} server tracks NNTP-Posting-Host in overviews:

@lisp
("111.222.333.444" -1000 nil s "NNTP-Posting-Host")
@end lisp

@item Lines, Chars
These two headers use different match types: @code{<}, @code{>},
@code{=}, @code{>=} and @code{<=}.

These predicates are true if

@example
(PREDICATE HEADER MATCH)
@end example

evaluates to non-@code{nil}.  For instance, the advanced match
@code{("lines" 4 <)} (@pxref{Advanced Scoring}) will result in the
following form:

@lisp
(< header-value 4)
@end lisp

Or to put it another way: When using @code{<} on @code{Lines} with 4 as
the match, we get the score added if the article has less than 4 lines.
(It's easy to get confused and think it's the other way around.  But
it's not.  I think.)

When matching on @code{Lines}, be careful because some back ends (like
@code{nndir}) do not generate @code{Lines} header, so every article ends
up being marked as having 0 lines.  This can lead to strange results if
you happen to lower score of the articles with few lines.

@item Date
For the Date header we have three kinda silly match types:
@code{before}, @code{at} and @code{after}.  I can't really imagine this
ever being useful, but, like, it would feel kinda silly not to provide
this function.  Just in case.  You never know.  Better safe than sorry.
Once burnt, twice shy.  Don't judge a book by its cover.  Never not have
sex on a first date.  (I have been told that at least one person, and I
quote, ``found this function indispensable'', however.)

@cindex ISO8601
@cindex date
A more useful match type is @code{regexp}.  With it, you can match the
date string using a regular expression.  The date is normalized to
ISO8601 compact format first---@var{YYYYMMDD}@code{T}@var{HHMMSS}.  If
you want to match all articles that have been posted on April 1st in
every year, you could use @samp{....0401.........} as a match string,
for instance.  (Note that the date is kept in its original time zone, so
this will match articles that were posted when it was April 1st where
the article was posted from.  Time zones are such wholesome fun for the
whole family, eh?)

@item Head, Body, All
These three match keys use the same match types as the @code{From} (etc)
header uses.

@item Followup
This match key is somewhat special, in that it will match the
@code{From} header, and affect the score of not only the matching
articles, but also all followups to the matching articles.  This allows
you e.g. increase the score of followups to your own articles, or
decrease the score of followups to the articles of some known
trouble-maker.  Uses the same match types as the @code{From} header
uses.  (Using this match key will lead to creation of @file{ADAPT}
files.)

@item Thread
This match key works along the same lines as the @code{Followup} match
key.  If you say that you want to score on a (sub-)thread started by an
article with a @code{Message-ID} @var{x}, then you add a @samp{thread}
match.  This will add a new @samp{thread} match for each article that
has @var{x} in its @code{References} header.  (These new @samp{thread}
matches will use the @code{Message-ID}s of these matching articles.)
This will ensure that you can raise/lower the score of an entire thread,
even though some articles in the thread may not have complete
@code{References} headers.  Note that using this may lead to
undeterministic scores of the articles in the thread.  (Using this match
key will lead to creation of @file{ADAPT} files.)
@end table
@end enumerate

@cindex score file atoms
@item mark
The value of this entry should be a number.  Any articles with a score
lower than this number will be marked as read.

@item expunge
The value of this entry should be a number.  Any articles with a score
lower than this number will be removed from the summary buffer.

@item mark-and-expunge
The value of this entry should be a number.  Any articles with a score
lower than this number will be marked as read and removed from the
summary buffer.

@item thread-mark-and-expunge
The value of this entry should be a number.  All articles that belong to
a thread that has a total score below this number will be marked as read
and removed from the summary buffer.  @code{gnus-thread-score-function}
says how to compute the total score for a thread.

@item files
The value of this entry should be any number of file names.  These files
are assumed to be score files as well, and will be loaded the same way
this one was.

@item exclude-files
The clue of this entry should be any number of files.  These files will
not be loaded, even though they would normally be so, for some reason or
other.

@item eval
The value of this entry will be @code{eval}el.  This element will be
ignored when handling global score files.

@item read-only
Read-only score files will not be updated or saved.  Global score files
should feature this atom (@pxref{Global Score Files}).  (Note:
@dfn{Global} here really means @dfn{global}; not your personal
apply-to-all-groups score files.)

@item orphan
The value of this entry should be a number.  Articles that do not have
parents will get this number added to their scores.  Imagine you follow
some high-volume newsgroup, like @samp{comp.lang.c}.  Most likely you
will only follow a few of the threads, also want to see any new threads.

You can do this with the following two score file entries:

@example
        (orphan -500)
        (mark-and-expunge -100)
@end example

When you enter the group the first time, you will only see the new
threads.  You then raise the score of the threads that you find
interesting (with @kbd{I T} or @kbd{I S}), and ignore (@kbd{C y}) the
rest.  Next time you enter the group, you will see new articles in the
interesting threads, plus any new threads.

I.e.---the orphan score atom is for high-volume groups where a few
interesting threads which can't be found automatically by ordinary
scoring rules exist.

@item adapt
This entry controls the adaptive scoring.  If it is @code{t}, the
default adaptive scoring rules will be used.  If it is @code{ignore}, no
adaptive scoring will be performed on this group.  If it is a list, this
list will be used as the adaptive scoring rules.  If it isn't present,
or is something other than @code{t} or @code{ignore}, the default
adaptive scoring rules will be used.  If you want to use adaptive
scoring on most groups, you'd set @code{gnus-use-adaptive-scoring} to
@code{t}, and insert an @code{(adapt ignore)} in the groups where you do
not want adaptive scoring.  If you only want adaptive scoring in a few
groups, you'd set @code{gnus-use-adaptive-scoring} to @code{nil}, and
insert @code{(adapt t)} in the score files of the groups where you want
it.

@item adapt-file
All adaptive score entries will go to the file named by this entry.  It
will also be applied when entering the group.  This atom might be handy
if you want to adapt on several groups at once, using the same adaptive
file for a number of groups.

@item local
@cindex local variables
The value of this entry should be a list of @code{(@var{var}
@var{value})} pairs.  Each @var{var} will be made buffer-local to the
current summary buffer, and set to the value specified.  This is a
convenient, if somewhat strange, way of setting variables in some
groups if you don't like hooks much.  Note that the @var{value} won't
be evaluated.
@end table


@node Score File Editing
@section Score File Editing

You normally enter all scoring commands from the summary buffer, but you
might feel the urge to edit them by hand as well, so we've supplied you
with a mode for that.

It's simply a slightly customized @code{emacs-lisp} mode, with these
additional commands:

@table @kbd

@item C-c C-c
@kindex C-c C-c (Score)
@findex gnus-score-edit-done
Save the changes you have made and return to the summary buffer
(@code{gnus-score-edit-done}).

@item C-c C-d
@kindex C-c C-d (Score)
@findex gnus-score-edit-insert-date
Insert the current date in numerical format
(@code{gnus-score-edit-insert-date}).  This is really the day number, if
you were wondering.

@item C-c C-p
@kindex C-c C-p (Score)
@findex gnus-score-pretty-print
The adaptive score files are saved in an unformatted fashion.  If you
intend to read one of these files, you want to @dfn{pretty print} it
first.  This command (@code{gnus-score-pretty-print}) does that for
you.

@end table

Type @kbd{M-x gnus-score-mode} to use this mode.

@vindex gnus-score-mode-hook
@code{gnus-score-menu-hook} is run in score mode buffers.

In the summary buffer you can use commands like @kbd{V f} and @kbd{V
e} to begin editing score files.


@node Adaptive Scoring
@section Adaptive Scoring
@cindex adaptive scoring

If all this scoring is getting you down, Gnus has a way of making it all
happen automatically---as if by magic.  Or rather, as if by artificial
stupidity, to be precise.

@vindex gnus-use-adaptive-scoring
When you read an article, or mark an article as read, or kill an
article, you leave marks behind.  On exit from the group, Gnus can sniff
these marks and add score elements depending on what marks it finds.
You turn on this ability by setting @code{gnus-use-adaptive-scoring} to
@code{t} or @code{(line)}.  If you want score adaptively on separate
words appearing in the subjects, you should set this variable to
@code{(word)}.  If you want to use both adaptive methods, set this
variable to @code{(word line)}.

@vindex gnus-default-adaptive-score-alist
To give you complete control over the scoring process, you can customize
the @code{gnus-default-adaptive-score-alist} variable.  For instance, it
might look something like this:

@lisp
(setq gnus-default-adaptive-score-alist
  '((gnus-unread-mark)
    (gnus-ticked-mark (from 4))
    (gnus-dormant-mark (from 5))
    (gnus-del-mark (from -4) (subject -1))
    (gnus-read-mark (from 4) (subject 2))
    (gnus-expirable-mark (from -1) (subject -1))
    (gnus-killed-mark (from -1) (subject -3))
    (gnus-kill-file-mark)
    (gnus-ancient-mark)
    (gnus-low-score-mark)
    (gnus-catchup-mark (from -1) (subject -1))))
@end lisp

As you see, each element in this alist has a mark as a key (either a
variable name or a ``real'' mark---a character).  Following this key is
a arbitrary number of header/score pairs.  If there are no header/score
pairs following the key, no adaptive scoring will be done on articles
that have that key as the article mark.  For instance, articles with
@code{gnus-unread-mark} in the example above will not get adaptive score
entries.

Each article can have only one mark, so just a single of these rules
will be applied to each article.

To take @code{gnus-del-mark} as an example---this alist says that all
articles that have that mark (i.e., are marked with @samp{e}) will have a
score entry added to lower based on the @code{From} header by -4, and
lowered by @code{Subject} by -1.  Change this to fit your prejudices.

If you have marked 10 articles with the same subject with
@code{gnus-del-mark}, the rule for that mark will be applied ten times.
That means that that subject will get a score of ten times -1, which
should be, unless I'm much mistaken, -10.

If you have auto-expirable (mail) groups (@pxref{Expiring Mail}), all
the read articles will be marked with the @samp{E} mark.  This'll
probably make adaptive scoring slightly impossible, so auto-expiring and
adaptive scoring doesn't really mix very well.

The headers you can score on are @code{from}, @code{subject},
@code{message-id}, @code{references}, @code{xref}, @code{lines},
@code{chars} and @code{date}.  In addition, you can score on
@code{followup}, which will create an adaptive score entry that matches
on the @code{References} header using the @code{Message-ID} of the
current article, thereby matching the following thread.

If you use this scheme, you should set the score file atom @code{mark}
to something small---like -300, perhaps, to avoid having small random
changes result in articles getting marked as read.

After using adaptive scoring for a week or so, Gnus should start to
become properly trained and enhance the authors you like best, and kill
the authors you like least, without you having to say so explicitly.

You can control what groups the adaptive scoring is to be performed on
by using the score files (@pxref{Score File Format}).  This will also
let you use different rules in different groups.

@vindex gnus-adaptive-file-suffix
The adaptive score entries will be put into a file where the name is the
group name with @code{gnus-adaptive-file-suffix} appended.  The default
is @file{ADAPT}.

@vindex gnus-score-exact-adapt-limit
When doing adaptive scoring, substring or fuzzy matching would probably
give you the best results in most cases.  However, if the header one
matches is short, the possibility for false positives is great, so if
the length of the match is less than
@code{gnus-score-exact-adapt-limit}, exact matching will be used.  If
this variable is @code{nil}, exact matching will always be used to avoid
this problem.

@vindex gnus-default-adaptive-word-score-alist
As mentioned above, you can adapt either on individual words or entire
headers.  If you adapt on words, the
@code{gnus-default-adaptive-word-score-alist} variable says what score
each instance of a word should add given a mark.

@lisp
(setq gnus-default-adaptive-word-score-alist
      `((,gnus-read-mark . 30)
        (,gnus-catchup-mark . -10)
        (,gnus-killed-mark . -20)
        (,gnus-del-mark . -15)))
@end lisp

This is the default value.  If you have adaption on words enabled, every
word that appears in subjects of articles marked with
@code{gnus-read-mark} will result in a score rule that increase the
score with 30 points.

@vindex gnus-default-ignored-adaptive-words
@vindex gnus-ignored-adaptive-words
Words that appear in the @code{gnus-default-ignored-adaptive-words} list
will be ignored.  If you wish to add more words to be ignored, use the
@code{gnus-ignored-adaptive-words} list instead.

@vindex gnus-adaptive-word-length-limit
Some may feel that short words shouldn't count when doing adaptive
scoring.  If so, you may set @code{gnus-adaptive-word-length-limit} to
an integer.  Words shorter than this number will be ignored.  This
variable defaults to @code{nil}.

@vindex gnus-adaptive-word-syntax-table
When the scoring is done, @code{gnus-adaptive-word-syntax-table} is the
syntax table in effect.  It is similar to the standard syntax table, but
it considers numbers to be non-word-constituent characters.

@vindex gnus-adaptive-word-minimum
If @code{gnus-adaptive-word-minimum} is set to a number, the adaptive
word scoring process will never bring down the score of an article to
below this number.  The default is @code{nil}.

@vindex gnus-adaptive-word-no-group-words
If @code{gnus-adaptive-word-no-group-words} is set to @code{t}, gnus
won't adaptively word score any of the words in the group name.  Useful
for groups like @samp{comp.editors.emacs}, where most of the subject
lines contain the word @samp{emacs}.

After using this scheme for a while, it might be nice to write a
@code{gnus-psychoanalyze-user} command to go through the rules and see
what words you like and what words you don't like.  Or perhaps not.

Note that the adaptive word scoring thing is highly experimental and is
likely to change in the future.  Initial impressions seem to indicate
that it's totally useless as it stands.  Some more work (involving more
rigorous statistical methods) will have to be done to make this useful.


@node Home Score File
@section Home Score File

The score file where new score file entries will go is called the
@dfn{home score file}.  This is normally (and by default) the score file
for the group itself.  For instance, the home score file for
@samp{gnu.emacs.gnus} is @file{gnu.emacs.gnus.SCORE}.

However, this may not be what you want.  It is often convenient to share
a common home score file among many groups---all @samp{emacs} groups
could perhaps use the same home score file.

@vindex gnus-home-score-file
The variable that controls this is @code{gnus-home-score-file}.  It can
be:

@enumerate
@item
A string.  Then this file will be used as the home score file for all
groups.

@item
A function.  The result of this function will be used as the home score
file.  The function will be called with the name of the group as the
parameter.

@item
A list.  The elements in this list can be:

@enumerate
@item
@code{(@var{regexp} @var{file-name})}.  If the @var{regexp} matches the
group name, the @var{file-name} will be used as the home score file.

@item
A function.  If the function returns non-@code{nil}, the result will
be used as the home score file.

@item
A string.  Use the string as the home score file.
@end enumerate

The list will be traversed from the beginning towards the end looking
for matches.

@end enumerate

So, if you want to use just a single score file, you could say:

@lisp
(setq gnus-home-score-file
      "my-total-score-file.SCORE")
@end lisp

If you want to use @file{gnu.SCORE} for all @samp{gnu} groups and
@file{rec.SCORE} for all @samp{rec} groups (and so on), you can say:

@findex gnus-hierarchial-home-score-file
@lisp
(setq gnus-home-score-file
      'gnus-hierarchial-home-score-file)
@end lisp

This is a ready-made function provided for your convenience.
Other functions include

@table @code
@item gnus-current-home-score-file
@findex gnus-current-home-score-file
Return the ``current'' regular score file.  This will make scoring
commands add entry to the ``innermost'' matching score file.

@end table

If you want to have one score file for the @samp{emacs} groups and
another for the @samp{comp} groups, while letting all other groups use
their own home score files:

@lisp
(setq gnus-home-score-file
      ;; @r{All groups that match the regexp @code{"\\.emacs"}}
      '(("\\.emacs" "emacs.SCORE")
        ;; @r{All the comp groups in one score file}
        ("^comp" "comp.SCORE")))
@end lisp

@vindex gnus-home-adapt-file
@code{gnus-home-adapt-file} works exactly the same way as
@code{gnus-home-score-file}, but says what the home adaptive score file
is instead.  All new adaptive file entries will go into the file
specified by this variable, and the same syntax is allowed.

In addition to using @code{gnus-home-score-file} and
@code{gnus-home-adapt-file}, you can also use group parameters
(@pxref{Group Parameters}) and topic parameters (@pxref{Topic
Parameters}) to achieve much the same.  Group and topic parameters take
precedence over this variable.


@node Followups To Yourself
@section Followups To Yourself

Gnus offers two commands for picking out the @code{Message-ID} header in
the current buffer.  Gnus will then add a score rule that scores using
this @code{Message-ID} on the @code{References} header of other
articles.  This will, in effect, increase the score of all articles that
respond to the article in the current buffer.  Quite useful if you want
to easily note when people answer what you've said.

@table @code

@item gnus-score-followup-article
@findex gnus-score-followup-article
This will add a score to articles that directly follow up your own
article.

@item gnus-score-followup-thread
@findex gnus-score-followup-thread
This will add a score to all articles that appear in a thread ``below''
your own article.
@end table

@vindex message-sent-hook
These two functions are both primarily meant to be used in hooks like
@code{message-sent-hook}, like this:
@lisp
(add-hook 'message-sent-hook 'gnus-score-followup-thread)
@end lisp


If you look closely at your own @code{Message-ID}, you'll notice that
the first two or three characters are always the same.  Here's two of
mine:

@example
<x6u3u47icf.fsf@@eyesore.no>
<x6sp9o7ibw.fsf@@eyesore.no>
@end example

So ``my'' ident on this machine is @samp{x6}.  This can be
exploited---the following rule will raise the score on all followups to
myself:

@lisp
("references"
 ("<x6[0-9a-z]+\\.fsf\\(_-_\\)?@@.*eyesore\\.no>"
  1000 nil r))
@end lisp

Whether it's the first two or first three characters that are ``yours''
is system-dependent.


@node Scoring On Other Headers
@section Scoring On Other Headers
@cindex scoring on other headers

Gnus is quite fast when scoring the ``traditional''
headers---@samp{From}, @samp{Subject} and so on.  However, scoring
other headers requires writing a @code{head} scoring rule, which means
that Gnus has to request every single article from the back end to find
matches.  This takes a long time in big groups.

Now, there's not much you can do about this for news groups, but for
mail groups, you have greater control.  In @ref{To From Newsgroups},
it's explained in greater detail what this mechanism does, but here's
a cookbook example for @code{nnml} on how to allow scoring on the
@samp{To} and @samp{Cc} headers.

Put the following in your @file{~/.gnus.el} file.

@lisp
(setq gnus-extra-headers '(To Cc Newsgroups Keywords)
      nnmail-extra-headers gnus-extra-headers)
@end lisp

Restart Gnus and rebuild your @code{nnml} overview files with the
@kbd{M-x nnml-generate-nov-databases} command.  This will take a long
time if you have much mail.

Now you can score on @samp{To} and @samp{Cc} as ``extra headers'' like
so: @kbd{I e s p To RET <your name> RET}.

See?  Simple.


@node Scoring Tips
@section Scoring Tips
@cindex scoring tips

@table @dfn

@item Crossposts
@cindex crossposts
@cindex scoring crossposts
If you want to lower the score of crossposts, the line to match on is
the @code{Xref} header.
@lisp
("xref" (" talk.politics.misc:" -1000))
@end lisp

@item Multiple crossposts
If you want to lower the score of articles that have been crossposted to
more than, say, 3 groups:
@lisp
("xref"
  ("[^:\n]+:[0-9]+ +[^:\n]+:[0-9]+ +[^:\n]+:[0-9]+"
   -1000 nil r))
@end lisp

@item Matching on the body
This is generally not a very good idea---it takes a very long time.
Gnus actually has to fetch each individual article from the server.  But
you might want to anyway, I guess.  Even though there are three match
keys (@code{Head}, @code{Body} and @code{All}), you should choose one
and stick with it in each score file.  If you use any two, each article
will be fetched @emph{twice}.  If you want to match a bit on the
@code{Head} and a bit on the @code{Body}, just use @code{All} for all
the matches.

@item Marking as read
You will probably want to mark articles that have scores below a certain
number as read.  This is most easily achieved by putting the following
in your @file{all.SCORE} file:
@lisp
((mark -100))
@end lisp
You may also consider doing something similar with @code{expunge}.

@item Negated character classes
If you say stuff like @code{[^abcd]*}, you may get unexpected results.
That will match newlines, which might lead to, well, The Unknown.  Say
@code{[^abcd\n]*} instead.
@end table


@node Reverse Scoring
@section Reverse Scoring
@cindex reverse scoring

If you want to keep just articles that have @samp{Sex with Emacs} in the
subject header, and expunge all other articles, you could put something
like this in your score file:

@lisp
(("subject"
  ("Sex with Emacs" 2))
 (mark 1)
 (expunge 1))
@end lisp

So, you raise all articles that match @samp{Sex with Emacs} and mark the
rest as read, and expunge them to boot.


@node Global Score Files
@section Global Score Files
@cindex global score files

Sure, other newsreaders have ``global kill files''.  These are usually
nothing more than a single kill file that applies to all groups, stored
in the user's home directory.  Bah!  Puny, weak newsreaders!

What I'm talking about here are Global Score Files.  Score files from
all over the world, from users everywhere, uniting all nations in one
big, happy score file union!  Ange-score!  New and untested!

@vindex gnus-global-score-files
All you have to do to use other people's score files is to set the
@code{gnus-global-score-files} variable.  One entry for each score file,
or each score file directory.  Gnus will decide by itself what score
files are applicable to which group.

To use the score file
@file{/ftp@@ftp.gnus.org:/pub/larsi/ding/score/soc.motss.SCORE} and
all score files in the @file{/ftp@@ftp.some-where:/pub/score} directory,
say this:

@lisp
(setq gnus-global-score-files
      '("/ftp@@ftp.gnus.org:/pub/larsi/ding/score/soc.motss.SCORE"
        "/ftp@@ftp.some-where:/pub/score/"))
@end lisp

@findex gnus-score-search-global-directories
@noindent
Simple, eh?  Directory names must end with a @samp{/}.  These
directories are typically scanned only once during each Gnus session.
If you feel the need to manually re-scan the remote directories, you can
use the @code{gnus-score-search-global-directories} command.

Note that, at present, using this option will slow down group entry
somewhat.  (That is---a lot.)

If you want to start maintaining score files for other people to use,
just put your score file up for anonymous ftp and announce it to the
world.  Become a retro-moderator!  Participate in the retro-moderator
wars sure to ensue, where retro-moderators battle it out for the
sympathy of the people, luring them to use their score files on false
premises!  Yay!  The net is saved!

Here are some tips for the would-be retro-moderator, off the top of my
head:

@itemize @bullet

@item
Articles heavily crossposted are probably junk.
@item
To lower a single inappropriate article, lower by @code{Message-ID}.
@item
Particularly brilliant authors can be raised on a permanent basis.
@item
Authors that repeatedly post off-charter for the group can safely be
lowered out of existence.
@item
Set the @code{mark} and @code{expunge} atoms to obliterate the nastiest
articles completely.

@item
Use expiring score entries to keep the size of the file down.  You
should probably have a long expiry period, though, as some sites keep
old articles for a long time.
@end itemize

@dots{} I wonder whether other newsreaders will support global score files
in the future.  @emph{Snicker}.  Yup, any day now, newsreaders like Blue
Wave, xrn and 1stReader are bound to implement scoring.  Should we start
holding our breath yet?


@node Kill Files
@section Kill Files
@cindex kill files

Gnus still supports those pesky old kill files.  In fact, the kill file
entries can now be expiring, which is something I wrote before Daniel
Quinlan thought of doing score files, so I've left the code in there.

In short, kill processing is a lot slower (and I do mean @emph{a lot})
than score processing, so it might be a good idea to rewrite your kill
files into score files.

Anyway, a kill file is a normal @code{emacs-lisp} file.  You can put any
forms into this file, which means that you can use kill files as some
sort of primitive hook function to be run on group entry, even though
that isn't a very good idea.

Normal kill files look like this:

@lisp
(gnus-kill "From" "Lars Ingebrigtsen")
(gnus-kill "Subject" "ding")
(gnus-expunge "X")
@end lisp

This will mark every article written by me as read, and remove the
marked articles from the summary buffer.  Very useful, you'll agree.

Other programs use a totally different kill file syntax.  If Gnus
encounters what looks like a @code{rn} kill file, it will take a stab at
interpreting it.

Two summary functions for editing a @sc{gnus} kill file:

@table @kbd

@item M-k
@kindex M-k (Summary)
@findex gnus-summary-edit-local-kill
Edit this group's kill file (@code{gnus-summary-edit-local-kill}).

@item M-K
@kindex M-K (Summary)
@findex gnus-summary-edit-global-kill
Edit the general kill file (@code{gnus-summary-edit-global-kill}).
@end table

Two group mode functions for editing the kill files:

@table @kbd

@item M-k
@kindex M-k (Group)
@findex gnus-group-edit-local-kill
Edit this group's kill file (@code{gnus-group-edit-local-kill}).

@item M-K
@kindex M-K (Group)
@findex gnus-group-edit-global-kill
Edit the general kill file (@code{gnus-group-edit-global-kill}).
@end table

Kill file variables:

@table @code
@item gnus-kill-file-name
@vindex gnus-kill-file-name
A kill file for the group @samp{soc.motss} is normally called
@file{soc.motss.KILL}.  The suffix appended to the group name to get
this file name is detailed by the @code{gnus-kill-file-name} variable.
The ``global'' kill file (not in the score file sense of ``global'', of
course) is just called @file{KILL}.

@vindex gnus-kill-save-kill-file
@item gnus-kill-save-kill-file
If this variable is non-@code{nil}, Gnus will save the
kill file after processing, which is necessary if you use expiring
kills.

@item gnus-apply-kill-hook
@vindex gnus-apply-kill-hook
@findex gnus-apply-kill-file-unless-scored
@findex gnus-apply-kill-file
A hook called to apply kill files to a group.  It is
@code{(gnus-apply-kill-file)} by default.  If you want to ignore the
kill file if you have a score file for the same group, you can set this
hook to @code{(gnus-apply-kill-file-unless-scored)}.  If you don't want
kill files to be processed, you should set this variable to @code{nil}.

@item gnus-kill-file-mode-hook
@vindex gnus-kill-file-mode-hook
A hook called in kill-file mode buffers.

@end table


@node Converting Kill Files
@section Converting Kill Files
@cindex kill files
@cindex converting kill files

If you have loads of old kill files, you may want to convert them into
score files.  If they are ``regular'', you can use
the @file{gnus-kill-to-score.el} package; if not, you'll have to do it
by hand.

The kill to score conversion package isn't included in Gnus by default.
You can fetch it from
@uref{http://www.stud.ifi.uio.no/~larsi/ding-various/gnus-kill-to-score.el}.

If your old kill files are very complex---if they contain more
non-@code{gnus-kill} forms than not, you'll have to convert them by
hand.  Or just let them be as they are.  Gnus will still use them as
before.


@node GroupLens
@section GroupLens
@cindex GroupLens

@sc{Note:} Unfortunately the GroupLens system seems to have shut down,
so this section is mostly of historical interest.

@uref{http://www.cs.umn.edu/Research/GroupLens/, GroupLens} is a
collaborative filtering system that helps you work together with other
people to find the quality news articles out of the huge volume of
news articles generated every day.

To accomplish this the GroupLens system combines your opinions about
articles you have already read with the opinions of others who have done
likewise and gives you a personalized prediction for each unread news
article.  Think of GroupLens as a matchmaker.  GroupLens watches how you
rate articles, and finds other people that rate articles the same way.
Once it has found some people you agree with it tells you, in the form
of a prediction, what they thought of the article.  You can use this
prediction to help you decide whether or not you want to read the
article.

@menu
* Using GroupLens::             How to make Gnus use GroupLens.
* Rating Articles::             Letting GroupLens know how you rate articles.
* Displaying Predictions::      Displaying predictions given by GroupLens.
* GroupLens Variables::         Customizing GroupLens.
@end menu


@node Using GroupLens
@subsection Using GroupLens

To use GroupLens you must register a pseudonym with your local
@uref{http://www.cs.umn.edu/Research/GroupLens/bbb.html, Better Bit
Bureau (BBB)} is the only better bit in town at the moment.

Once you have registered you'll need to set a couple of variables.

@table @code

@item gnus-use-grouplens
@vindex gnus-use-grouplens
Setting this variable to a non-@code{nil} value will make Gnus hook into
all the relevant GroupLens functions.

@item grouplens-pseudonym
@vindex grouplens-pseudonym
This variable should be set to the pseudonym you got when registering
with the Better Bit Bureau.

@item grouplens-newsgroups
@vindex grouplens-newsgroups
A list of groups that you want to get GroupLens predictions for.

@end table

That's the minimum of what you need to get up and running with GroupLens.
Once you've registered, GroupLens will start giving you scores for
articles based on the average of what other people think.  But, to get
the real benefit of GroupLens you need to start rating articles
yourself.  Then the scores GroupLens gives you will be personalized for
you, based on how the people you usually agree with have already rated.


@node Rating Articles
@subsection Rating Articles

In GroupLens, an article is rated on a scale from 1 to 5, inclusive.
Where 1 means something like this article is a waste of bandwidth and 5
means that the article was really good.  The basic question to ask
yourself is, ``on a scale from 1 to 5 would I like to see more articles
like this one?''

There are four ways to enter a rating for an article in GroupLens.

@table @kbd

@item r
@kindex r (GroupLens)
@findex bbb-summary-rate-article
This function will prompt you for a rating on a scale of one to five.

@item k
@kindex k (GroupLens)
@findex grouplens-score-thread
This function will prompt you for a rating, and rate all the articles in
the thread.  This is really useful for some of those long running giant
threads in rec.humor.

@end table

The next two commands, @kbd{n} and @kbd{,} take a numerical prefix to be
the score of the article you're reading.

@table @kbd

@item 1-5 n
@kindex n (GroupLens)
@findex grouplens-next-unread-article
Rate the article and go to the next unread article.

@item 1-5 ,
@kindex , (GroupLens)
@findex grouplens-best-unread-article
Rate the article and go to the next unread article with the highest score.

@end table

If you want to give the current article a score of 4 and then go to the
next article, just type @kbd{4 n}.


@node Displaying Predictions
@subsection Displaying Predictions

GroupLens makes a prediction for you about how much you will like a
news article.  The predictions from GroupLens are on a scale from 1 to
5, where 1 is the worst and 5 is the best.  You can use the predictions
from GroupLens in one of three ways controlled by the variable
@code{gnus-grouplens-override-scoring}.

@vindex gnus-grouplens-override-scoring
There are three ways to display predictions in grouplens.  You may
choose to have the GroupLens scores contribute to, or override the
regular Gnus scoring mechanism.  override is the default; however, some
people prefer to see the Gnus scores plus the grouplens scores.  To get
the separate scoring behavior you need to set
@code{gnus-grouplens-override-scoring} to @code{'separate}.  To have the
GroupLens predictions combined with the grouplens scores set it to
@code{'override} and to combine the scores set
@code{gnus-grouplens-override-scoring} to @code{'combine}.  When you use
the combine option you will also want to set the values for
@code{grouplens-prediction-offset} and
@code{grouplens-score-scale-factor}.

@vindex grouplens-prediction-display
In either case, GroupLens gives you a few choices for how you would like
to see your predictions displayed.  The display of predictions is
controlled by the @code{grouplens-prediction-display} variable.

The following are valid values for that variable.

@table @code
@item prediction-spot
The higher the prediction, the further to the right an @samp{*} is
displayed.

@item confidence-interval
A numeric confidence interval.

@item prediction-bar
The higher the prediction, the longer the bar.

@item confidence-bar
Numerical confidence.

@item confidence-spot
The spot gets bigger with more confidence.

@item prediction-num
Plain-old numeric value.

@item confidence-plus-minus
Prediction +/- confidence.

@end table


@node GroupLens Variables
@subsection GroupLens Variables

@table @code

@item gnus-summary-grouplens-line-format
The summary line format used in GroupLens-enhanced summary buffers.  It
accepts the same specs as the normal summary line format (@pxref{Summary
Buffer Lines}).  The default is @samp{%U%R%z%l%I%(%[%4L: %-23,23n%]%)
%s\n}.

@item grouplens-bbb-host
Host running the bbbd server.  @samp{grouplens.cs.umn.edu} is the
default.

@item grouplens-bbb-port
Port of the host running the bbbd server.  The default is 9000.

@item grouplens-score-offset
Offset the prediction by this value.  In other words, subtract the
prediction value by this number to arrive at the effective score.  The
default is 0.

@item grouplens-score-scale-factor
This variable allows the user to magnify the effect of GroupLens scores.
The scale factor is applied after the offset.  The default is 1.

@end table


@node Advanced Scoring
@section Advanced Scoring

Scoring on Subjects and From headers is nice enough, but what if you're
really interested in what a person has to say only when she's talking
about a particular subject?  Or what if you really don't want to
read what person A has to say when she's following up to person B, but
want to read what she says when she's following up to person C?

By using advanced scoring rules you may create arbitrarily complex
scoring patterns.

@menu
* Advanced Scoring Syntax::     A definition.
* Advanced Scoring Examples::   What they look like.
* Advanced Scoring Tips::       Getting the most out of it.
@end menu


@node Advanced Scoring Syntax
@subsection Advanced Scoring Syntax

Ordinary scoring rules have a string as the first element in the rule.
Advanced scoring rules have a list as the first element.  The second
element is the score to be applied if the first element evaluated to a
non-@code{nil} value.

These lists may consist of three logical operators, one redirection
operator, and various match operators.

Logical operators:

@table @code
@item &
@itemx and
This logical operator will evaluate each of its arguments until it finds
one that evaluates to @code{false}, and then it'll stop.  If all arguments
evaluate to @code{true} values, then this operator will return
@code{true}.

@item |
@itemx or
This logical operator will evaluate each of its arguments until it finds
one that evaluates to @code{true}.  If no arguments are @code{true},
then this operator will return @code{false}.

@item !
@itemx not
@itemx ¬
This logical operator only takes a single argument.  It returns the
logical negation of the value of its argument.

@end table

There is an @dfn{indirection operator} that will make its arguments
apply to the ancestors of the current article being scored.  For
instance, @code{1-} will make score rules apply to the parent of the
current article.  @code{2-} will make score rules apply to the
grandparent of the current article.  Alternatively, you can write
@code{^^}, where the number of @code{^}s (carets) says how far back into
the ancestry you want to go.

Finally, we have the match operators.  These are the ones that do the
real work.  Match operators are header name strings followed by a match
and a match type.  A typical match operator looks like @samp{("from"
"Lars Ingebrigtsen" s)}.  The header names are the same as when using
simple scoring, and the match types are also the same.


@node Advanced Scoring Examples
@subsection Advanced Scoring Examples

Please note that the following examples are score file rules.  To
make a complete score file from them, surround them with another pair
of parentheses.

Let's say you want to increase the score of articles written by Lars
when he's talking about Gnus:

@example
@group
((&
  ("from" "Lars Ingebrigtsen")
  ("subject" "Gnus"))
 1000)
@end group
@end example

Quite simple, huh?

When he writes long articles, he sometimes has something nice to say:

@example
((&
  ("from" "Lars Ingebrigtsen")
  (|
   ("subject" "Gnus")
   ("lines" 100 >)))
 1000)
@end example

However, when he responds to things written by Reig Eigil Logge, you
really don't want to read what he's written:

@example
((&
  ("from" "Lars Ingebrigtsen")
  (1- ("from" "Reig Eigir Logge")))
 -100000)
@end example

Everybody that follows up Redmondo when he writes about disappearing
socks should have their scores raised, but only when they talk about
white socks.  However, when Lars talks about socks, it's usually not
very interesting:

@example
((&
  (1-
   (&
    ("from" "redmondo@@.*no" r)
    ("body" "disappearing.*socks" t)))
  (! ("from" "Lars Ingebrigtsen"))
  ("body" "white.*socks"))
 1000)
@end example

The possibilities are endless.


@node Advanced Scoring Tips
@subsection Advanced Scoring Tips

The @code{&} and @code{|} logical operators do short-circuit logic.
That is, they stop processing their arguments when it's clear what the
result of the operation will be.  For instance, if one of the arguments
of an @code{&} evaluates to @code{false}, there's no point in evaluating
the rest of the arguments.  This means that you should put slow matches
(@samp{body}, @samp{header}) last and quick matches (@samp{from},
@samp{subject}) first.

The indirection arguments (@code{1-} and so on) will make their
arguments work on previous generations of the thread.  If you say
something like:

@example
...
(1-
 (1-
  ("from" "lars")))
...
@end example

Then that means "score on the from header of the grandparent of the
current article".  An indirection is quite fast, but it's better to say:

@example
(1-
 (&
  ("from" "Lars")
  ("subject" "Gnus")))
@end example

than it is to say:

@example
(&
 (1- ("from" "Lars"))
 (1- ("subject" "Gnus")))
@end example


@node Score Decays
@section Score Decays
@cindex score decays
@cindex decays

You may find that your scores have a tendency to grow without
bounds, especially if you're using adaptive scoring.  If scores get too
big, they lose all meaning---they simply max out and it's difficult to
use them in any sensible way.

@vindex gnus-decay-scores
@findex gnus-decay-score
@vindex gnus-decay-score-function
Gnus provides a mechanism for decaying scores to help with this problem.
When score files are loaded and @code{gnus-decay-scores} is
non-@code{nil}, Gnus will run the score files through the decaying
mechanism thereby lowering the scores of all non-permanent score rules.
The decay itself if performed by the @code{gnus-decay-score-function}
function, which is @code{gnus-decay-score} by default.  Here's the
definition of that function:

@lisp
(defun gnus-decay-score (score)
  "Decay SCORE.
This is done according to `gnus-score-decay-constant'
and `gnus-score-decay-scale'."
  (floor
   (- score
      (* (if (< score 0) 1 -1)
         (min (abs score)
              (max gnus-score-decay-constant
                   (* (abs score)
                      gnus-score-decay-scale)))))))
@end lisp

@vindex gnus-score-decay-scale
@vindex gnus-score-decay-constant
@code{gnus-score-decay-constant} is 3 by default and
@code{gnus-score-decay-scale} is 0.05.  This should cause the following:

@enumerate
@item
Scores between -3 and 3 will be set to 0 when this function is called.

@item
Scores with magnitudes between 3 and 60 will be shrunk by 3.

@item
Scores with magnitudes greater than 60 will be shrunk by 5% of the
score.
@end enumerate

If you don't like this decay function, write your own.  It is called
with the score to be decayed as its only parameter, and it should return
the new score, which should be an integer.

Gnus will try to decay scores once a day.  If you haven't run Gnus for
four days, Gnus will decay the scores four times, for instance.

@iftex
@iflatex
@chapter Message
@include message.texi
@chapter Emacs MIME
@include emacs-mime.texi
@chapter Sieve
@include sieve.texi
@c @chapter PGG
@c @include pgg.texi
@end iflatex
@end iftex

@node Various
@chapter Various

@menu
* Process/Prefix::              A convention used by many treatment commands.
* Interactive::                 Making Gnus ask you many questions.
* Symbolic Prefixes::           How to supply some Gnus functions with options.
* Formatting Variables::        You can specify what buffers should look like.
* Window Layout::               Configuring the Gnus buffer windows.
* Faces and Fonts::             How to change how faces look.
* Compilation::                 How to speed Gnus up.
* Mode Lines::                  Displaying information in the mode lines.
* Highlighting and Menus::      Making buffers look all nice and cozy.
* Buttons::                     Get tendinitis in ten easy steps!
* Daemons::                     Gnus can do things behind your back.
* NoCeM::                       How to avoid spam and other fatty foods.
* Undo::                        Some actions can be undone.
* Predicate Specifiers::        Specifying predicates.
* Moderation::                  What to do if you're a moderator.
* Image Enhancements::          Modern versions of Emacs/XEmacs can display images.
* Fuzzy Matching::              What's the big fuzz?
* Thwarting Email Spam::        A how-to on avoiding unsolicited commercial email.
* Various Various::             Things that are really various.
@end menu


@node Process/Prefix
@section Process/Prefix
@cindex process/prefix convention

Many functions, among them functions for moving, decoding and saving
articles, use what is known as the @dfn{Process/Prefix convention}.

This is a method for figuring out what articles the user wants the
command to be performed on.

It goes like this:

If the numeric prefix is N, perform the operation on the next N
articles, starting with the current one.  If the numeric prefix is
negative, perform the operation on the previous N articles, starting
with the current one.

@vindex transient-mark-mode
If @code{transient-mark-mode} in non-@code{nil} and the region is
active, all articles in the region will be worked upon.

If there is no numeric prefix, but some articles are marked with the
process mark, perform the operation on the articles marked with
the process mark.

If there is neither a numeric prefix nor any articles marked with the
process mark, just perform the operation on the current article.

Quite simple, really, but it needs to be made clear so that surprises
are avoided.

Commands that react to the process mark will push the current list of
process marked articles onto a stack and will then clear all process
marked articles.  You can restore the previous configuration with the
@kbd{M P y} command (@pxref{Setting Process Marks}).

@vindex gnus-summary-goto-unread
One thing that seems to shock & horrify lots of people is that, for
instance, @kbd{3 d} does exactly the same as @kbd{d} @kbd{d} @kbd{d}.
Since each @kbd{d} (which marks the current article as read) by default
goes to the next unread article after marking, this means that @kbd{3 d}
will mark the next three unread articles as read, no matter what the
summary buffer looks like.  Set @code{gnus-summary-goto-unread} to
@code{nil} for a more straightforward action.

Many commands do not use the process/prefix convention.  All commands
that do explicitly say so in this manual.  To apply the process/prefix
convention to commands that do not use it, you can use the @kbd{M-&}
command.  For instance, to mark all the articles in the group as
expirable, you could say @kbd{M P b M-& E}.


@node Interactive
@section Interactive
@cindex interaction

@table @code

@item gnus-novice-user
@vindex gnus-novice-user
If this variable is non-@code{nil}, you are either a newcomer to the
World of Usenet, or you are very cautious, which is a nice thing to be,
really.  You will be given questions of the type ``Are you sure you want
to do this?'' before doing anything dangerous.  This is @code{t} by
default.

@item gnus-expert-user
@vindex gnus-expert-user
If this variable is non-@code{nil}, you will seldom be asked any
questions by Gnus.  It will simply assume you know what you're doing, no
matter how strange.

@item gnus-interactive-catchup
@vindex gnus-interactive-catchup
Require confirmation before catching up a group if non-@code{nil}.  It
is @code{t} by default.

@item gnus-interactive-exit
@vindex gnus-interactive-exit
Require confirmation before exiting Gnus.  This variable is @code{t} by
default.
@end table


@node Symbolic Prefixes
@section Symbolic Prefixes
@cindex symbolic prefixes

Quite a lot of Emacs commands react to the (numeric) prefix.  For
instance, @kbd{C-u 4 C-f} moves point four characters forward, and
@kbd{C-u 9 0 0 I s s p} adds a permanent @code{Subject} substring score
rule of 900 to the current article.

This is all nice and well, but what if you want to give a command some
additional information?  Well, what most commands do is interpret the
``raw'' prefix in some special way.  @kbd{C-u 0 C-x C-s} means that one
doesn't want a backup file to be created when saving the current buffer,
for instance.  But what if you want to save without making a backup
file, and you want Emacs to flash lights and play a nice tune at the
same time?  You can't, and you're probably perfectly happy that way.

@kindex M-i (Summary)
@findex gnus-symbolic-argument
I'm not, so I've added a second prefix---the @dfn{symbolic prefix}.  The
prefix key is @kbd{M-i} (@code{gnus-symbolic-argument}), and the next
character typed in is the value.  You can stack as many @kbd{M-i}
prefixes as you want.  @kbd{M-i a C-M-u} means ``feed the @kbd{C-M-u}
command the symbolic prefix @code{a}''.  @kbd{M-i a M-i b C-M-u} means
``feed the @kbd{C-M-u} command the symbolic prefixes @code{a} and
@code{b}''.  You get the drift.

Typing in symbolic prefixes to commands that don't accept them doesn't
hurt, but it doesn't do any good either.  Currently not many Gnus
functions make use of the symbolic prefix.

If you're interested in how Gnus implements this, @pxref{Extended
Interactive}.


@node Formatting Variables
@section Formatting Variables
@cindex formatting variables

Throughout this manual you've probably noticed lots of variables called
things like @code{gnus-group-line-format} and
@code{gnus-summary-mode-line-format}.  These control how Gnus is to
output lines in the various buffers.  There's quite a lot of them.
Fortunately, they all use the same syntax, so there's not that much to
be annoyed by.

Here's an example format spec (from the group buffer): @samp{%M%S%5y:
%(%g%)\n}.  We see that it is indeed extremely ugly, and that there are
lots of percentages everywhere.

@menu
* Formatting Basics::           A formatting variable is basically a format string.
* Mode Line Formatting::        Some rules about mode line formatting variables.
* Advanced Formatting::         Modifying output in various ways.
* User-Defined Specs::          Having Gnus call your own functions.
* Formatting Fonts::            Making the formatting look colorful and nice.
* Positioning Point::           Moving point to a position after an operation.
* Tabulation::                  Tabulating your output.
* Wide Characters::             Dealing with wide characters.
@end menu

Currently Gnus uses the following formatting variables:
@code{gnus-group-line-format}, @code{gnus-summary-line-format},
@code{gnus-server-line-format}, @code{gnus-topic-line-format},
@code{gnus-group-mode-line-format},
@code{gnus-summary-mode-line-format},
@code{gnus-article-mode-line-format},
@code{gnus-server-mode-line-format}, and
@code{gnus-summary-pick-line-format}.

All these format variables can also be arbitrary elisp forms.  In that
case, they will be @code{eval}ed to insert the required lines.

@kindex M-x gnus-update-format
@findex gnus-update-format
Gnus includes a command to help you while creating your own format
specs.  @kbd{M-x gnus-update-format} will @code{eval} the current form,
update the spec in question and pop you to a buffer where you can
examine the resulting Lisp code to be run to generate the line.



@node Formatting Basics
@subsection Formatting Basics

Each @samp{%} element will be replaced by some string or other when the
buffer in question is generated.  @samp{%5y} means ``insert the @samp{y}
spec, and pad with spaces to get a 5-character field''.

As with normal C and Emacs Lisp formatting strings, the numerical
modifier between the @samp{%} and the formatting type character will
@dfn{pad} the output so that it is always at least that long.
@samp{%5y} will make the field always (at least) five characters wide by
padding with spaces to the left.  If you say @samp{%-5y}, it will pad to
the right instead.

You may also wish to limit the length of the field to protect against
particularly wide values.  For that you can say @samp{%4,6y}, which
means that the field will never be more than 6 characters wide and never
less than 4 characters wide.

Also Gnus supports some extended format specifications, such as
@samp{%&user-date;}.


@node Mode Line Formatting
@subsection Mode Line Formatting

Mode line formatting variables (e.g.,
@code{gnus-summary-mode-line-format}) follow the same rules as other,
buffer line oriented formatting variables (@pxref{Formatting Basics})
with the following two differences:

@enumerate

@item
There must be no newline (@samp{\n}) at the end.

@item
The special @samp{%%b} spec can be used to display the buffer name.
Well, it's no spec at all, really---@samp{%%} is just a way to quote
@samp{%} to allow it to pass through the formatting machinery unmangled,
so that Emacs receives @samp{%b}, which is something the Emacs mode line
display interprets to mean ``show the buffer name''.  For a full list of
mode line specs Emacs understands, see the documentation of the
@code{mode-line-format} variable.

@end enumerate


@node Advanced Formatting
@subsection Advanced Formatting

It is frequently useful to post-process the fields in some way.
Padding, limiting, cutting off parts and suppressing certain values can
be achieved by using @dfn{tilde modifiers}.  A typical tilde spec might
look like @samp{%~(cut 3)~(ignore "0")y}.

These are the valid modifiers:

@table @code
@item pad
@itemx pad-left
Pad the field to the left with spaces until it reaches the required
length.

@item pad-right
Pad the field to the right with spaces until it reaches the required
length.

@item max
@itemx max-left
Cut off characters from the left until it reaches the specified length.

@item max-right
Cut off characters from the right until it reaches the specified
length.

@item cut
@itemx cut-left
Cut off the specified number of characters from the left.

@item cut-right
Cut off the specified number of characters from the right.

@item ignore
Return an empty string if the field is equal to the specified value.

@item form
Use the specified form as the field value when the @samp{@@} spec is
used.

Here's an example:

@lisp
"~(form (current-time-string))@@"
@end lisp

@end table

Let's take an example.  The @samp{%o} spec in the summary mode lines
will return a date in compact ISO8601 format---@samp{19960809T230410}.
This is quite a mouthful, so we want to shave off the century number and
the time, leaving us with a six-character date.  That would be
@samp{%~(cut-left 2)~(max-right 6)~(pad 6)o}.  (Cutting is done before
maxing, and we need the padding to ensure that the date is never less
than 6 characters to make it look nice in columns.)

Ignoring is done first; then cutting; then maxing; and then as the very
last operation, padding.

@vindex gnus-compile-user-specs
If @code{gnus-compile-user-specs} is set to @code{nil} (@code{t} by
default) with your strong personality, and use a lots of these advanced
thingies, you'll find that Gnus gets quite slow.  This can be helped
enormously by running @kbd{M-x gnus-compile} when you are satisfied with
the look of your lines.
@xref{Compilation}.


@node User-Defined Specs
@subsection User-Defined Specs

All the specs allow for inserting user defined specifiers---@samp{u}.
The next character in the format string should be a letter.  Gnus
will call the function @code{gnus-user-format-function-}@samp{X}, where
@samp{X} is the letter following @samp{%u}.  The function will be passed
a single parameter---what the parameter means depends on what buffer
it's being called from.  The function should return a string, which will
be inserted into the buffer just like information from any other
specifier.  This function may also be called with dummy values, so it
should protect against that.

Also Gnus supports extended user-defined specs, such as @samp{%u&foo;}.
Gnus will call the function @code{gnus-user-format-function-}@samp{foo}.

You can also use tilde modifiers (@pxref{Advanced Formatting} to achieve
much the same without defining new functions.  Here's an example:
@samp{%~(form (count-lines (point-min) (point)))@@}.  The form
given here will be evaluated to yield the current line number, and then
inserted.


@node Formatting Fonts
@subsection Formatting Fonts

There are specs for highlighting, and these are shared by all the format
variables.  Text inside the @samp{%(} and @samp{%)} specifiers will get
the special @code{mouse-face} property set, which means that it will be
highlighted (with @code{gnus-mouse-face}) when you put the mouse pointer
over it.

Text inside the @samp{%@{} and @samp{%@}} specifiers will have their
normal faces set using @code{gnus-face-0}, which is @code{bold} by
default.  If you say @samp{%1@{}, you'll get @code{gnus-face-1} instead,
and so on.  Create as many faces as you wish.  The same goes for the
@code{mouse-face} specs---you can say @samp{%3(hello%)} to have
@samp{hello} mouse-highlighted with @code{gnus-mouse-face-3}.

Text inside the @samp{%<<} and @samp{%>>} specifiers will get the
special @code{balloon-help} property set to
@code{gnus-balloon-face-0}.  If you say @samp{%1<<}, you'll get
@code{gnus-balloon-face-1} and so on.  The @code{gnus-balloon-face-*}
variables should be either strings or symbols naming functions that
return a string.  When the mouse passes over text with this property
set, a balloon window will appear and display the string.  Please
refer to @ref{Tooltips, ,Tooltips, emacs, The Emacs Manual},
(in GNU Emacs) or the doc string of @code{balloon-help-mode} (in
XEmacs) for more information on this.  (For technical reasons, the
guillemets have been approximated as @samp{<<} and @samp{>>} in this
paragraph.)

Here's an alternative recipe for the group buffer:

@lisp
;; @r{Create three face types.}
(setq gnus-face-1 'bold)
(setq gnus-face-3 'italic)

;; @r{We want the article count to be in}
;; @r{a bold and green face.  So we create}
;; @r{a new face called @code{my-green-bold}.}
(copy-face 'bold 'my-green-bold)
;; @r{Set the color.}
(set-face-foreground 'my-green-bold "ForestGreen")
(setq gnus-face-2 'my-green-bold)

;; @r{Set the new & fancy format.}
(setq gnus-group-line-format
      "%M%S%3@{%5y%@}%2[:%] %(%1@{%g%@}%)\n")
@end lisp

I'm sure you'll be able to use this scheme to create totally unreadable
and extremely vulgar displays.  Have fun!

Note that the @samp{%(} specs (and friends) do not make any sense on the
mode-line variables.

@node Positioning Point
@subsection Positioning Point

Gnus usually moves point to a pre-defined place on each line in most
buffers.  By default, point move to the first colon character on the
line.  You can customize this behaviour in three different ways.

You can move the colon character to somewhere else on the line.

@findex gnus-goto-colon
You can redefine the function that moves the point to the colon.  The
function is called @code{gnus-goto-colon}.

But perhaps the most convenient way to deal with this, if you don't want
to have a colon in your line, is to use the @samp{%*} specifier.  If you
put a @samp{%*} somewhere in your format line definition, Gnus will
place point there.


@node Tabulation
@subsection Tabulation

You can usually line up your displays by padding and cutting your
strings.  However, when combining various strings of different size, it
can often be more convenient to just output the strings, and then worry
about lining up the following text afterwards.

To do that, Gnus supplies tabulator specs---@samp{%=}.  There are two
different types---@dfn{hard tabulators} and @dfn{soft tabulators}.

@samp{%50=} will insert space characters to pad the line up to column
50.  If the text is already past column 50, nothing will be inserted.
This is the soft tabulator.

@samp{%-50=} will insert space characters to pad the line up to column
50.  If the text is already past column 50, the excess text past column
50 will be removed.  This is the hard tabulator.


@node Wide Characters
@subsection Wide Characters

Fixed width fonts in most countries have characters of the same width.
Some countries, however, use Latin characters mixed with wider
characters---most notable East Asian countries.

The problem is that when formatting, Gnus assumes that if a string is 10
characters wide, it'll be 10 Latin characters wide on the screen.  In
these countries, that's not true.

@vindex gnus-use-correct-string-widths
To help fix this, you can set @code{gnus-use-correct-string-widths} to
@code{t}.  This makes buffer generation slower, but the results will be
prettier.  The default value under XEmacs is @code{t} but @code{nil}
for Emacs.


@node Window Layout
@section Window Layout
@cindex window layout

No, there's nothing here about X, so be quiet.

@vindex gnus-use-full-window
If @code{gnus-use-full-window} non-@code{nil}, Gnus will delete all
other windows and occupy the entire Emacs screen by itself.  It is
@code{t} by default.

Setting this variable to @code{nil} kinda works, but there are
glitches.  Use at your own peril.

@vindex gnus-buffer-configuration
@code{gnus-buffer-configuration} describes how much space each Gnus
buffer should be given.  Here's an excerpt of this variable:

@lisp
((group (vertical 1.0 (group 1.0 point)
                      (if gnus-carpal (group-carpal 4))))
 (article (vertical 1.0 (summary 0.25 point)
                        (article 1.0))))
@end lisp

This is an alist.  The @dfn{key} is a symbol that names some action or
other.  For instance, when displaying the group buffer, the window
configuration function will use @code{group} as the key.  A full list of
possible names is listed below.

The @dfn{value} (i.e., the @dfn{split}) says how much space each buffer
should occupy.  To take the @code{article} split as an example -

@lisp
(article (vertical 1.0 (summary 0.25 point)
                       (article 1.0)))
@end lisp

This @dfn{split} says that the summary buffer should occupy 25% of upper
half of the screen, and that it is placed over the article buffer.  As
you may have noticed, 100% + 25% is actually 125% (yup, I saw y'all
reaching for that calculator there).  However, the special number
@code{1.0} is used to signal that this buffer should soak up all the
rest of the space available after the rest of the buffers have taken
whatever they need.  There should be only one buffer with the @code{1.0}
size spec per split.

Point will be put in the buffer that has the optional third element
@code{point}.  In a @code{frame} split, the last subsplit having a leaf
split where the tag @code{frame-focus} is a member (i.e. is the third or
fourth element in the list, depending on whether the @code{point} tag is
present) gets focus.

Here's a more complicated example:

@lisp
(article (vertical 1.0 (group 4)
                       (summary 0.25 point)
                       (if gnus-carpal (summary-carpal 4))
                       (article 1.0)))
@end lisp

If the size spec is an integer instead of a floating point number,
then that number will be used to say how many lines a buffer should
occupy, not a percentage.

If the @dfn{split} looks like something that can be @code{eval}ed (to be
precise---if the @code{car} of the split is a function or a subr), this
split will be @code{eval}ed.  If the result is non-@code{nil}, it will
be used as a split.  This means that there will be three buffers if
@code{gnus-carpal} is @code{nil}, and four buffers if @code{gnus-carpal}
is non-@code{nil}.

Not complicated enough for you?  Well, try this on for size:

@lisp
(article (horizontal 1.0
             (vertical 0.5
                 (group 1.0)
                 (gnus-carpal 4))
             (vertical 1.0
                 (summary 0.25 point)
                 (summary-carpal 4)
                 (article 1.0))))
@end lisp

Whoops.  Two buffers with the mystery 100% tag.  And what's that
@code{horizontal} thingie?

If the first element in one of the split is @code{horizontal}, Gnus will
split the window horizontally, giving you two windows side-by-side.
Inside each of these strips you may carry on all you like in the normal
fashion.  The number following @code{horizontal} says what percentage of
the screen is to be given to this strip.

For each split, there @emph{must} be one element that has the 100% tag.
The splitting is never accurate, and this buffer will eat any leftover
lines from the splits.

To be slightly more formal, here's a definition of what a valid split
may look like:

@example
@group
split      = frame | horizontal | vertical | buffer | form
frame      = "(frame " size *split ")"
horizontal = "(horizontal " size *split ")"
vertical   = "(vertical " size *split ")"
buffer     = "(" buf-name " " size *[ "point" ] *[ "frame-focus"] ")"
size       = number | frame-params
buf-name   = group | article | summary ...
@end group
@end example

The limitations are that the @code{frame} split can only appear as the
top-level split.  @var{form} should be an Emacs Lisp form that should
return a valid split.  We see that each split is fully recursive, and
may contain any number of @code{vertical} and @code{horizontal} splits.

@vindex gnus-window-min-width
@vindex gnus-window-min-height
@cindex window height
@cindex window width
Finding the right sizes can be a bit complicated.  No window may be less
than @code{gnus-window-min-height} (default 1) characters high, and all
windows must be at least @code{gnus-window-min-width} (default 1)
characters wide.  Gnus will try to enforce this before applying the
splits.  If you want to use the normal Emacs window width/height limit,
you can just set these two variables to @code{nil}.

If you're not familiar with Emacs terminology, @code{horizontal} and
@code{vertical} splits may work the opposite way of what you'd expect.
Windows inside a @code{horizontal} split are shown side-by-side, and
windows within a @code{vertical} split are shown above each other.

@findex gnus-configure-frame
If you want to experiment with window placement, a good tip is to call
@code{gnus-configure-frame} directly with a split.  This is the function
that does all the real work when splitting buffers.  Below is a pretty
nonsensical configuration with 5 windows; two for the group buffer and
three for the article buffer.  (I said it was nonsensical.)  If you
@code{eval} the statement below, you can get an idea of how that would
look straight away, without going through the normal Gnus channels.
Play with it until you're satisfied, and then use
@code{gnus-add-configuration} to add your new creation to the buffer
configuration list.

@lisp
(gnus-configure-frame
 '(horizontal 1.0
    (vertical 10
      (group 1.0)
      (article 0.3 point))
    (vertical 1.0
      (article 1.0)
      (horizontal 4
        (group 1.0)
        (article 10)))))
@end lisp

You might want to have several frames as well.  No prob---just use the
@code{frame} split:

@lisp
(gnus-configure-frame
 '(frame 1.0
         (vertical 1.0
                   (summary 0.25 point frame-focus)
                   (article 1.0))
         (vertical ((height . 5) (width . 15)
                    (user-position . t)
                    (left . -1) (top . 1))
                   (picon 1.0))))

@end lisp

This split will result in the familiar summary/article window
configuration in the first (or ``main'') frame, while a small additional
frame will be created where picons will be shown.  As you can see,
instead of the normal @code{1.0} top-level spec, each additional split
should have a frame parameter alist as the size spec.
@xref{Frame Parameters, , Frame Parameters, elisp, The GNU Emacs Lisp
Reference Manual}.  Under XEmacs, a frame property list will be
accepted, too---for instance, @code{(height 5 width 15 left -1 top 1)}
is such a plist.
The list of all possible keys for @code{gnus-buffer-configuration} can
be found in its default value.

Note that the @code{message} key is used for both
@code{gnus-group-mail} and @code{gnus-summary-mail-other-window}.  If
it is desirable to distinguish between the two, something like this
might be used:

@lisp
(message (horizontal 1.0
                     (vertical 1.0 (message 1.0 point))
                     (vertical 0.24
                               (if (buffer-live-p gnus-summary-buffer)
                                   '(summary 0.5))
                               (group 1.0))))
@end lisp

One common desire for a multiple frame split is to have a separate frame
for composing mail and news while leaving the original frame intact.  To
accomplish that, something like the following can be done:

@lisp
(message
  (frame 1.0
         (if (not (buffer-live-p gnus-summary-buffer))
             (car (cdr (assoc 'group gnus-buffer-configuration)))
           (car (cdr (assoc 'summary gnus-buffer-configuration))))
         (vertical ((user-position . t) (top . 1) (left . 1)
                    (name . "Message"))
                   (message 1.0 point))))
@end lisp

@findex gnus-add-configuration
Since the @code{gnus-buffer-configuration} variable is so long and
complicated, there's a function you can use to ease changing the config
of a single setting: @code{gnus-add-configuration}.  If, for instance,
you want to change the @code{article} setting, you could say:

@lisp
(gnus-add-configuration
 '(article (vertical 1.0
               (group 4)
               (summary .25 point)
               (article 1.0))))
@end lisp

You'd typically stick these @code{gnus-add-configuration} calls in your
@file{~/.gnus.el} file or in some startup hook---they should be run after
Gnus has been loaded.

@vindex gnus-always-force-window-configuration
If all windows mentioned in the configuration are already visible, Gnus
won't change the window configuration.  If you always want to force the
``right'' window configuration, you can set
@code{gnus-always-force-window-configuration} to non-@code{nil}.

If you're using tree displays (@pxref{Tree Display}), and the tree
window is displayed vertically next to another window, you may also want
to fiddle with @code{gnus-tree-minimize-window} to avoid having the
windows resized.

@subsection Example Window Configurations

@itemize @bullet
@item
Narrow left hand side occupied by group buffer.  Right hand side split
between summary buffer (top one-sixth) and article buffer (bottom).

@ifinfo
@example
+---+---------+
| G | Summary |
| r +---------+
| o |         |
| u | Article |
| p |         |
+---+---------+
@end example
@end ifinfo

@lisp
(gnus-add-configuration
 '(article
   (horizontal 1.0
               (vertical 25 (group 1.0))
               (vertical 1.0
                         (summary 0.16 point)
                         (article 1.0)))))

(gnus-add-configuration
 '(summary
   (horizontal 1.0
               (vertical 25 (group 1.0))
               (vertical 1.0 (summary 1.0 point)))))
@end lisp

@end itemize


@node Faces and Fonts
@section Faces and Fonts
@cindex faces
@cindex fonts
@cindex colors

Fiddling with fonts and faces used to be very difficult, but these days
it is very simple.  You simply say @kbd{M-x customize-face}, pick out
the face you want to alter, and alter it via the standard Customize
interface.


@node Compilation
@section Compilation
@cindex compilation
@cindex byte-compilation

@findex gnus-compile

Remember all those line format specification variables?
@code{gnus-summary-line-format}, @code{gnus-group-line-format}, and so
on.  By default, T-gnus will use the byte-compiled codes of these
variables and we can keep a slow-down to a minimum.  However, if you set
@code{gnus-compile-user-specs} to @code{nil} (@code{t} by default),
unfortunately, changing them will mean a quite significant slow-down.
(The default values of these variables have byte-compiled functions
associated with them, while the user-generated versions do not, of
course.)

To help with this, you can run @kbd{M-x gnus-compile} after you've
fiddled around with the variables and feel that you're (kind of)
satisfied.  This will result in the new specs being byte-compiled, and
you'll get top speed again.  Note that T-gnus will not save these
compiled specs in the @file{.newsrc.eld} file.

@table @code
@item gnus-compile-user-specs
@vindex gnus-compile-user-specs
If it is non-nil, the user-defined format specs will be byte-compiled
automatically.  The default value of this variable is @code{t}.  It has
an effect on the values of @code{gnus-*-line-format-spec}.
@end table


@node Mode Lines
@section Mode Lines
@cindex mode lines

@vindex gnus-updated-mode-lines
@code{gnus-updated-mode-lines} says what buffers should keep their mode
lines updated.  It is a list of symbols.  Supported symbols include
@code{group}, @code{article}, @code{summary}, @code{server},
@code{browse}, and @code{tree}.  If the corresponding symbol is present,
Gnus will keep that mode line updated with information that may be
pertinent.  If this variable is @code{nil}, screen refresh may be
quicker.

@cindex display-time

@vindex gnus-mode-non-string-length
By default, Gnus displays information on the current article in the mode
lines of the summary and article buffers.  The information Gnus wishes
to display (e.g. the subject of the article) is often longer than the
mode lines, and therefore have to be cut off at some point.  The
@code{gnus-mode-non-string-length} variable says how long the other
elements on the line is (i.e., the non-info part).  If you put
additional elements on the mode line (e.g. a clock), you should modify
this variable:

@c Hook written by Francesco Potorti` <pot@cnuce.cnr.it>
@lisp
(add-hook 'display-time-hook
          (lambda () (setq gnus-mode-non-string-length
                           (+ 21
                              (if line-number-mode 5 0)
                              (if column-number-mode 4 0)
                              (length display-time-string)))))
@end lisp

If this variable is @code{nil} (which is the default), the mode line
strings won't be chopped off, and they won't be padded either.  Note
that the default is unlikely to be desirable, as even the percentage
complete in the buffer may be crowded off the mode line; the user should
configure this variable appropriately for her configuration.


@node Highlighting and Menus
@section Highlighting and Menus
@cindex visual
@cindex highlighting
@cindex menus

@vindex gnus-visual
The @code{gnus-visual} variable controls most of the Gnus-prettifying
aspects.  If @code{nil}, Gnus won't attempt to create menus or use fancy
colors or fonts.  This will also inhibit loading the @file{gnus-vis.el}
file.

This variable can be a list of visual properties that are enabled.  The
following elements are valid, and are all included by default:

@table @code
@item group-highlight
Do highlights in the group buffer.
@item summary-highlight
Do highlights in the summary buffer.
@item article-highlight
Do highlights in the article buffer.
@item highlight
Turn on highlighting in all buffers.
@item group-menu
Create menus in the group buffer.
@item summary-menu
Create menus in the summary buffers.
@item article-menu
Create menus in the article buffer.
@item browse-menu
Create menus in the browse buffer.
@item server-menu
Create menus in the server buffer.
@item score-menu
Create menus in the score buffers.
@item menu
Create menus in all buffers.
@end table

So if you only want highlighting in the article buffer and menus in all
buffers, you could say something like:

@lisp
(setq gnus-visual '(article-highlight menu))
@end lisp

If you want highlighting only and no menus whatsoever, you'd say:

@lisp
(setq gnus-visual '(highlight))
@end lisp

If @code{gnus-visual} is @code{t}, highlighting and menus will be used
in all Gnus buffers.

Other general variables that influence the look of all buffers include:

@table @code
@item gnus-mouse-face
@vindex gnus-mouse-face
This is the face (i.e., font) used for mouse highlighting in Gnus.  No
mouse highlights will be done if @code{gnus-visual} is @code{nil}.

@end table

There are hooks associated with the creation of all the different menus:

@table @code

@item gnus-article-menu-hook
@vindex gnus-article-menu-hook
Hook called after creating the article mode menu.

@item gnus-group-menu-hook
@vindex gnus-group-menu-hook
Hook called after creating the group mode menu.

@item gnus-summary-menu-hook
@vindex gnus-summary-menu-hook
Hook called after creating the summary mode menu.

@item gnus-server-menu-hook
@vindex gnus-server-menu-hook
Hook called after creating the server mode menu.

@item gnus-browse-menu-hook
@vindex gnus-browse-menu-hook
Hook called after creating the browse mode menu.

@item gnus-score-menu-hook
@vindex gnus-score-menu-hook
Hook called after creating the score mode menu.

@end table


@node Buttons
@section Buttons
@cindex buttons
@cindex mouse
@cindex click

Those new-fangled @dfn{mouse} contraptions is very popular with the
young, hep kids who don't want to learn the proper way to do things
these days.  Why, I remember way back in the summer of '89, when I was
using Emacs on a Tops 20 system.  Three hundred users on one single
machine, and every user was running Simula compilers.  Bah!

Right.

@vindex gnus-carpal
Well, you can make Gnus display bufferfuls of buttons you can click to
do anything by setting @code{gnus-carpal} to @code{t}.  Pretty simple,
really.  Tell the chiropractor I sent you.


@table @code

@item gnus-carpal-mode-hook
@vindex gnus-carpal-mode-hook
Hook run in all carpal mode buffers.

@item gnus-carpal-button-face
@vindex gnus-carpal-button-face
Face used on buttons.

@item gnus-carpal-header-face
@vindex gnus-carpal-header-face
Face used on carpal buffer headers.

@item gnus-carpal-group-buffer-buttons
@vindex gnus-carpal-group-buffer-buttons
Buttons in the group buffer.

@item gnus-carpal-summary-buffer-buttons
@vindex gnus-carpal-summary-buffer-buttons
Buttons in the summary buffer.

@item gnus-carpal-server-buffer-buttons
@vindex gnus-carpal-server-buffer-buttons
Buttons in the server buffer.

@item gnus-carpal-browse-buffer-buttons
@vindex gnus-carpal-browse-buffer-buttons
Buttons in the browse buffer.
@end table

All the @code{buttons} variables are lists.  The elements in these list
are either cons cells where the @code{car} contains a text to be displayed and
the @code{cdr} contains a function symbol, or a simple string.


@node Daemons
@section Daemons
@cindex demons
@cindex daemons

Gnus, being larger than any program ever written (allegedly), does lots
of strange stuff that you may wish to have done while you're not
present.  For instance, you may want it to check for new mail once in a
while.  Or you may want it to close down all connections to all servers
when you leave Emacs idle.  And stuff like that.

Gnus will let you do stuff like that by defining various
@dfn{handlers}.  Each handler consists of three elements:  A
@var{function}, a @var{time}, and an @var{idle} parameter.

Here's an example of a handler that closes connections when Emacs has
been idle for thirty minutes:

@lisp
(gnus-demon-close-connections nil 30)
@end lisp

Here's a handler that scans for @acronym{PGP} headers every hour when
Emacs is idle:

@lisp
(gnus-demon-scan-pgp 60 t)
@end lisp

This @var{time} parameter and that @var{idle} parameter work together
in a strange, but wonderful fashion.  Basically, if @var{idle} is
@code{nil}, then the function will be called every @var{time} minutes.

If @var{idle} is @code{t}, then the function will be called after
@var{time} minutes only if Emacs is idle.  So if Emacs is never idle,
the function will never be called.  But once Emacs goes idle, the
function will be called every @var{time} minutes.

If @var{idle} is a number and @var{time} is a number, the function will
be called every @var{time} minutes only when Emacs has been idle for
@var{idle} minutes.

If @var{idle} is a number and @var{time} is @code{nil}, the function
will be called once every time Emacs has been idle for @var{idle}
minutes.

And if @var{time} is a string, it should look like @samp{07:31}, and
the function will then be called once every day somewhere near that
time.  Modified by the @var{idle} parameter, of course.

@vindex gnus-demon-timestep
(When I say ``minute'' here, I really mean @code{gnus-demon-timestep}
seconds.  This is 60 by default.  If you change that variable,
all the timings in the handlers will be affected.)

So, if you want to add a handler, you could put something like this in
your @file{~/.gnus.el} file:

@findex gnus-demon-add-handler
@lisp
(gnus-demon-add-handler 'gnus-demon-close-connections 30 t)
@end lisp

@findex gnus-demon-add-nocem
@findex gnus-demon-add-scanmail
@findex gnus-demon-add-rescan
@findex gnus-demon-add-scan-timestamps
@findex gnus-demon-add-disconnection
Some ready-made functions to do this have been created:
@code{gnus-demon-add-nocem}, @code{gnus-demon-add-disconnection},
@code{gnus-demon-add-nntp-close-connection},
@code{gnus-demon-add-scan-timestamps}, @code{gnus-demon-add-rescan}, and
@code{gnus-demon-add-scanmail}.  Just put those functions in your
@file{~/.gnus.el} if you want those abilities.

@findex gnus-demon-init
@findex gnus-demon-cancel
@vindex gnus-demon-handlers
If you add handlers to @code{gnus-demon-handlers} directly, you should
run @code{gnus-demon-init} to make the changes take hold.  To cancel all
daemons, you can use the @code{gnus-demon-cancel} function.

Note that adding daemons can be pretty naughty if you over do it.  Adding
functions that scan all news and mail from all servers every two seconds
is a sure-fire way of getting booted off any respectable system.  So
behave.


@node NoCeM
@section NoCeM
@cindex nocem
@cindex spam

@dfn{Spamming} is posting the same article lots and lots of times.
Spamming is bad.  Spamming is evil.

Spamming is usually canceled within a day or so by various anti-spamming
agencies.  These agencies usually also send out @dfn{NoCeM} messages.
NoCeM is pronounced ``no see-'em'', and means what the name
implies---these are messages that make the offending articles, like, go
away.

What use are these NoCeM messages if the articles are canceled anyway?
Some sites do not honor cancel messages and some sites just honor cancels
from a select few people.  Then you may wish to make use of the NoCeM
messages, which are distributed in the @samp{alt.nocem.misc} newsgroup.

Gnus can read and parse the messages in this group automatically, and
this will make spam disappear.

There are some variables to customize, of course:

@table @code
@item gnus-use-nocem
@vindex gnus-use-nocem
Set this variable to @code{t} to set the ball rolling.  It is @code{nil}
by default.

@item gnus-nocem-groups
@vindex gnus-nocem-groups
Gnus will look for NoCeM messages in the groups in this list.  The
default is
@lisp
("news.lists.filters" "news.admin.net-abuse.bulletins"
 "alt.nocem.misc" "news.admin.net-abuse.announce")
@end lisp

@item gnus-nocem-issuers
@vindex gnus-nocem-issuers
There are many people issuing NoCeM messages.  This list says what
people you want to listen to.  The default is
@lisp
("Automoose-1" "clewis@@ferret.ocunix.on.ca"
 "cosmo.roadkill" "SpamHippo" "hweede@@snafu.de")
@end lisp
fine, upstanding citizens all of them.

Known despammers that you can put in this list are listed at@*
@uref{http://www.xs4all.nl/~rosalind/nocemreg/nocemreg.html}.

You do not have to heed NoCeM messages from all these people---just the
ones you want to listen to.  You also don't have to accept all NoCeM
messages from the people you like.  Each NoCeM message has a @dfn{type}
header that gives the message a (more or less, usually less) rigorous
definition.  Common types are @samp{spam}, @samp{spew}, @samp{mmf},
@samp{binary}, and @samp{troll}.  To specify this, you have to use
@code{(@var{issuer} @var{conditions} @dots{})} elements in the list.
Each condition is either a string (which is a regexp that matches types
you want to use) or a list on the form @code{(not @var{string})}, where
@var{string} is a regexp that matches types you don't want to use.

For instance, if you want all NoCeM messages from Chris Lewis except his
@samp{troll} messages, you'd say:

@lisp
("clewis@@ferret.ocunix.on.ca" ".*" (not "troll"))
@end lisp

On the other hand, if you just want nothing but his @samp{spam} and
@samp{spew} messages, you'd say:

@lisp
("clewis@@ferret.ocunix.on.ca" (not ".*") "spew" "spam")
@end lisp

The specs are applied left-to-right.


@item gnus-nocem-verifyer
@vindex gnus-nocem-verifyer
@findex mc-verify
This should be a function for verifying that the NoCeM issuer is who she
says she is.  The default is @code{mc-verify}, which is a Mailcrypt
function.  If this is too slow and you don't care for verification
(which may be dangerous), you can set this variable to @code{nil}.

If you want signed NoCeM messages to be verified and unsigned messages
not to be verified (but used anyway), you could do something like:

@lisp
(setq gnus-nocem-verifyer 'my-gnus-mc-verify)

(defun my-gnus-mc-verify ()
  (not (eq 'forged
           (ignore-errors
             (if (mc-verify)
                 t
               'forged)))))
@end lisp

This might be dangerous, though.

@item gnus-nocem-directory
@vindex gnus-nocem-directory
This is where Gnus will store its NoCeM cache files.  The default is@*
@file{~/News/NoCeM/}.

@item gnus-nocem-expiry-wait
@vindex gnus-nocem-expiry-wait
The number of days before removing old NoCeM entries from the cache.
The default is 15.  If you make it shorter Gnus will be faster, but you
might then see old spam.

@item gnus-nocem-check-from
@vindex gnus-nocem-check-from
Non-@code{nil} means check for valid issuers in message bodies.
Otherwise don't bother fetching articles unless their author matches a
valid issuer; that is much faster if you are selective about the
issuers.

@item gnus-nocem-check-article-limit
@vindex gnus-nocem-check-article-limit
If non-@code{nil}, the maximum number of articles to check in any NoCeM
group.  NoCeM groups can be huge and very slow to process.

@end table

Using NoCeM could potentially be a memory hog.  If you have many living
(i. e., subscribed or unsubscribed groups), your Emacs process will grow
big.  If this is a problem, you should kill off all (or most) of your
unsubscribed groups (@pxref{Subscription Commands}).


@node Undo
@section Undo
@cindex undo

It is very useful to be able to undo actions one has done.  In normal
Emacs buffers, it's easy enough---you just push the @code{undo} button.
In Gnus buffers, however, it isn't that simple.

The things Gnus displays in its buffer is of no value whatsoever to
Gnus---it's all just data designed to look nice to the user.
Killing a group in the group buffer with @kbd{C-k} makes the line
disappear, but that's just a side-effect of the real action---the
removal of the group in question from the internal Gnus structures.
Undoing something like that can't be done by the normal Emacs
@code{undo} function.

Gnus tries to remedy this somewhat by keeping track of what the user
does and coming up with actions that would reverse the actions the user
takes.  When the user then presses the @code{undo} key, Gnus will run
the code to reverse the previous action, or the previous actions.
However, not all actions are easily reversible, so Gnus currently offers
a few key functions to be undoable.  These include killing groups,
yanking groups, and changing the list of read articles of groups.
That's it, really.  More functions may be added in the future, but each
added function means an increase in data to be stored, so Gnus will
never be totally undoable.

@findex gnus-undo-mode
@vindex gnus-use-undo
@findex gnus-undo
The undoability is provided by the @code{gnus-undo-mode} minor mode.  It
is used if @code{gnus-use-undo} is non-@code{nil}, which is the
default.  The @kbd{C-M-_} key performs the @code{gnus-undo}
command, which should feel kinda like the normal Emacs @code{undo}
command.


@node Predicate Specifiers
@section Predicate Specifiers
@cindex predicate specifiers

Some Gnus variables are @dfn{predicate specifiers}.  This is a special
form that allows flexible specification of predicates without having
to type all that much.

These specifiers are lists consisting of functions, symbols and lists.

Here's an example:

@lisp
(or gnus-article-unseen-p
    gnus-article-unread-p)
@end lisp

The available symbols are @code{or}, @code{and} and @code{not}.  The
functions all take one parameter.

@findex gnus-make-predicate
Internally, Gnus calls @code{gnus-make-predicate} on these specifiers
to create a function that can be called.  This input parameter to this
function will be passed along to all the functions in the predicate
specifier.


@node Moderation
@section Moderation
@cindex moderation

If you are a moderator, you can use the @file{gnus-mdrtn.el} package.
It is not included in the standard Gnus package.  Write a mail to
@samp{larsi@@gnus.org} and state what group you moderate, and you'll
get a copy.

The moderation package is implemented as a minor mode for summary
buffers.  Put

@lisp
(add-hook 'gnus-summary-mode-hook 'gnus-moderate)
@end lisp

in your @file{~/.gnus.el} file.

If you are the moderator of @samp{rec.zoofle}, this is how it's
supposed to work:

@enumerate
@item
You split your incoming mail by matching on
@samp{Newsgroups:.*rec.zoofle}, which will put all the to-be-posted
articles in some mail group---for instance, @samp{nnml:rec.zoofle}.

@item
You enter that group once in a while and post articles using the @kbd{e}
(edit-and-post) or @kbd{s} (just send unedited) commands.

@item
If, while reading the @samp{rec.zoofle} newsgroup, you happen upon some
articles that weren't approved by you, you can cancel them with the
@kbd{c} command.
@end enumerate

To use moderation mode in these two groups, say:

@lisp
(setq gnus-moderated-list
      "^nnml:rec.zoofle$\\|^rec.zoofle$")
@end lisp


@node Image Enhancements
@section Image Enhancements

XEmacs, as well as Emacs 21@footnote{Emacs 21 on MS Windows doesn't
support images yet.}, is able to display pictures and stuff, so Gnus has
taken advantage of that.

@menu
* X-Face::                      Display a funky, teensy black-and-white image.
* Face::                        Display a funkier, teensier colored image.
* Smileys::                     Show all those happy faces the way they were meant to be shown.
* Picons::                      How to display pictures of what you're reading.
* XVarious::                    Other XEmacsy Gnusey variables.
@end menu


@node X-Face
@subsection X-Face
@cindex x-face

@code{X-Face} headers describe a 48x48 pixel black-and-white (1 bit
depth) image that's supposed to represent the author of the message.
It seems to be supported by an ever-growing number of mail and news
readers.

@cindex x-face
@findex gnus-article-display-x-face
@vindex gnus-article-x-face-command
@vindex gnus-article-x-face-too-ugly
@iftex
@iflatex
\include{xface}
@end iflatex
@end iftex
@c @anchor{X-Face}

Decoding an @code{X-Face} header either requires an Emacs that has
@samp{compface} support (which most XEmacs versions has), or that you
have @samp{compface} installed on your system.  If either is true,
Gnus will default to displaying @code{X-Face} headers.

The variable that controls this is the
@code{gnus-article-x-face-command} variable.  If this variable is a
string, this string will be executed in a sub-shell.  If it is a
function, this function will be called with the face as the argument.
If the @code{gnus-article-x-face-too-ugly} (which is a regexp) matches
the @code{From} header, the face will not be shown.

The default action under Emacs 20 is to fork off the @code{display}
program@footnote{@code{display} is from the ImageMagick package.  For
the @code{uncompface} and @code{icontopbm} programs look for a package
like @code{compface} or @code{faces-xface} on a GNU/Linux system.}  to
view the face.

Under XEmacs or Emacs 21+ with suitable image support, the default
action is to display the face before the @code{From} header.  (It's
nicer if XEmacs has been compiled with @code{X-Face} support---that
will make display somewhat faster.  If there's no native @code{X-Face}
support, Gnus will try to convert the @code{X-Face} header using
external programs from the @code{pbmplus} package and
friends.@footnote{On a GNU/Linux system look for packages with names
like @code{netpbm}, @code{libgr-progs} and @code{compface}.})

(Note: @code{x-face} is used in the variable/function names, not
@code{xface}).

Gnus provides a few convenience functions and variables to allow
easier insertion of X-Face headers in outgoing messages.

@findex gnus-random-x-face
@vindex gnus-convert-pbm-to-x-face-command
@vindex gnus-x-face-directory
@code{gnus-random-x-face} goes through all the @samp{pbm} files in
@code{gnus-x-face-directory} and picks one at random, and then
converts it to the X-Face format by using the
@code{gnus-convert-pbm-to-x-face-command} shell command.  The
@samp{pbm} files should be 48x48 pixels big.  It returns the X-Face
header data as a string.

@findex gnus-insert-random-x-face-header
@code{gnus-insert-random-x-face-header} calls
@code{gnus-random-x-face} and inserts a @samp{X-Face} header with the
randomly generated data.

@findex gnus-x-face-from-file
@vindex gnus-convert-image-to-x-face-command
@code{gnus-x-face-from-file} takes a GIF file as the parameter, and then
converts the file to X-Face format by using the
@code{gnus-convert-image-to-x-face-command} shell command.

Here's how you would typically use the first function.  Put something
like the following in your @file{~/.gnus.el} file:

@lisp
(setq message-required-news-headers
      (nconc message-required-news-headers
             (list '(X-Face . gnus-random-x-face))))
@end lisp

Using the last function would be something like this:

@lisp
(setq message-required-news-headers
      (nconc message-required-news-headers
             (list '(X-Face . (lambda ()
                                (gnus-x-face-from-file
                                 "~/My-face.gif"))))))
@end lisp


@node Face
@subsection Face
@cindex face

@c #### FIXME: faces and x-faces'implementations should really be harmonized.

@code{Face} headers are essentially a funkier version of @code{X-Face}
ones. They describe a 48x48 pixel colored image that's supposed to
represent the author of the message.

@cindex face
@findex gnus-article-display-face
The contents of a @code{Face} header must be a base64 encoded PNG image.
See @uref{http://quimby.gnus.org/circus/face/} for the precise
specifications.

Gnus provides a few convenience functions and variables to allow
easier insertion of Face headers in outgoing messages.

@findex gnus-convert-png-to-face
@code{gnus-convert-png-to-face} takes a 48x48 PNG image, no longer than
726 bytes long, and converts it to a face.

@findex gnus-face-from-file
@vindex gnus-convert-image-to-face-command
@code{gnus-face-from-file} takes a JPEG file as the parameter, and then
converts the file to Face format by using the
@code{gnus-convert-image-to-face-command} shell command.

Here's how you would typically use this function. Put something like the
following in your @file{~/.gnus.el} file:

@lisp
(setq message-required-news-headers
      (nconc message-required-news-headers
             (list '(Face . (lambda ()
                              (gnus-face-from-file "~/face.jpg"))))))
@end lisp


@node Smileys
@subsection Smileys
@cindex smileys

@iftex
@iflatex
\gnusfig{-3cm}{0.5cm}{\epsfig{figure=ps/BigFace,height=20cm}}
\input{smiley}
@end iflatex
@end iftex

@dfn{Smiley} is a package separate from Gnus, but since Gnus is
currently the only package that uses Smiley, it is documented here.

In short---to use Smiley in Gnus, put the following in your
@file{~/.gnus.el} file:

@lisp
(setq gnus-treat-display-smileys t)
@end lisp

Smiley maps text smiley faces---@samp{:-)}, @samp{8-)}, @samp{:-(} and
the like---to pictures and displays those instead of the text smiley
faces.  The conversion is controlled by a list of regexps that matches
text and maps that to file names.

@vindex smiley-regexp-alist
The alist used is specified by the @code{smiley-regexp-alist}
variable.  The first item in each element is the regexp to be matched;
the second element is the regexp match group that is to be replaced by
the picture; and the third element is the name of the file to be
displayed.

The following variables customize where Smiley will look for these
files:

@table @code

@item smiley-data-directory
@vindex smiley-data-directory
Where Smiley will look for smiley faces files.

@item gnus-smiley-file-types
@vindex gnus-smiley-file-types
List of suffixes on smiley file names to try.

@end table


@node Picons
@subsection Picons

@iftex
@iflatex
\include{picons}
@end iflatex
@end iftex

So@dots{}  You want to slow down your news reader even more!  This is a
good way to do so.  It's also a great way to impress people staring
over your shoulder as you read news.

What are Picons?  To quote directly from the Picons Web site:

@iftex
@iflatex
\margindex{}
@end iflatex
@end iftex

@quotation
@dfn{Picons} is short for ``personal icons''.  They're small,
constrained images used to represent users and domains on the net,
organized into databases so that the appropriate image for a given
e-mail address can be found.  Besides users and domains, there are picon
databases for Usenet newsgroups and weather forecasts.  The picons are
in either monochrome @code{XBM} format or color @code{XPM} and
@code{GIF} formats.
@end quotation

@vindex gnus-picon-databases
For instructions on obtaining and installing the picons databases,
point your Web browser at
@uref{http://www.cs.indiana.edu/picons/ftp/index.html}.

If you are using Debian GNU/Linux, saying @samp{apt-get install
picons.*} will install the picons where Gnus can find them.

To enable displaying picons, simply make sure that
@code{gnus-picon-databases} points to the directory containing the
Picons databases.

The following variables offer control over where things are located.

@table @code

@item gnus-picon-databases
@vindex gnus-picon-databases
The location of the picons database.  This is a list of directories
containing the @file{news}, @file{domains}, @file{users} (and so on)
subdirectories.  Defaults to @code{("/usr/lib/picon"
"/usr/local/faces")}.

@item gnus-picon-news-directories
@vindex gnus-picon-news-directories
List of subdirectories to search in @code{gnus-picon-databases} for
newsgroups faces.  @code{("news")} is the default.

@item gnus-picon-user-directories
@vindex gnus-picon-user-directories
List of subdirectories to search in @code{gnus-picon-databases} for user
faces.  @code{("users" "usenix" "local" "misc")} is the default.

@item gnus-picon-domain-directories
@vindex gnus-picon-domain-directories
List of subdirectories to search in @code{gnus-picon-databases} for
domain name faces.  Defaults to @code{("domains")}.  Some people may
want to add @samp{"unknown"} to this list.

@item gnus-picon-file-types
@vindex gnus-picon-file-types
Ordered list of suffixes on picon file names to try.  Defaults to
@code{("xpm" "gif" "xbm")} minus those not built-in your Emacs.

@end table


@node XVarious
@subsection Various XEmacs Variables

@table @code
@item gnus-xmas-glyph-directory
@vindex gnus-xmas-glyph-directory
This is where Gnus will look for pictures.  Gnus will normally
auto-detect this directory, but you may set it manually if you have an
unusual directory structure.

@item gnus-xmas-logo-color-alist
@vindex gnus-xmas-logo-color-alist
This is an alist where the key is a type symbol and the values are the
foreground and background color of the splash page glyph.

@item gnus-xmas-logo-color-style
@vindex gnus-xmas-logo-color-style
This is the key used to look up the color in the alist described above.
Valid values include @code{flame}, @code{pine}, @code{moss},
@code{irish}, @code{sky}, @code{tin}, @code{velvet}, @code{grape},
@code{labia}, @code{berry}, @code{neutral}, and @code{september}.

@item gnus-xmas-modeline-glyph
@vindex gnus-xmas-modeline-glyph
A glyph displayed in all Gnus mode lines.  It is a tiny gnu head by
default.

@end table

@subsubsection Toolbar

@table @code

@item gnus-use-toolbar
@vindex gnus-use-toolbar
If @code{nil}, don't display toolbars.  If non-@code{nil}, it should be
one of @code{default-toolbar}, @code{top-toolbar}, @code{bottom-toolbar},
@code{right-toolbar}, or @code{left-toolbar}.

@item gnus-group-toolbar
@vindex gnus-group-toolbar
The toolbar in the group buffer.

@item gnus-summary-toolbar
@vindex gnus-summary-toolbar
The toolbar in the summary buffer.

@item gnus-summary-mail-toolbar
@vindex gnus-summary-mail-toolbar
The toolbar in the summary buffer of mail groups.

@end table

@iftex
@iflatex
\margindex{}
@end iflatex
@end iftex


@node Fuzzy Matching
@section Fuzzy Matching
@cindex fuzzy matching

Gnus provides @dfn{fuzzy matching} of @code{Subject} lines when doing
things like scoring, thread gathering and thread comparison.

As opposed to regular expression matching, fuzzy matching is very fuzzy.
It's so fuzzy that there's not even a definition of what @dfn{fuzziness}
means, and the implementation has changed over time.

Basically, it tries to remove all noise from lines before comparing.
@samp{Re: }, parenthetical remarks, white space, and so on, are filtered
out of the strings before comparing the results.  This often leads to
adequate results---even when faced with strings generated by text
manglers masquerading as newsreaders.


@node Thwarting Email Spam
@section Thwarting Email Spam
@cindex email spam
@cindex spam
@cindex UCE
@cindex unsolicited commercial email

In these last days of the Usenet, commercial vultures are hanging about
and grepping through news like crazy to find email addresses they can
foist off their scams and products to.  As a reaction to this, many
people have started putting nonsense addresses into their @code{From}
lines.  I think this is counterproductive---it makes it difficult for
people to send you legitimate mail in response to things you write, as
well as making it difficult to see who wrote what.  This rewriting may
perhaps be a bigger menace than the unsolicited commercial email itself
in the end.

The biggest problem I have with email spam is that it comes in under
false pretenses.  I press @kbd{g} and Gnus merrily informs me that I
have 10 new emails.  I say ``Golly gee!  Happy is me!'' and select the
mail group, only to find two pyramid schemes, seven advertisements
(``New!  Miracle tonic for growing full, lustrous hair on your toes!'')
and one mail asking me to repent and find some god.

This is annoying.  Here's what you can do about it.

@menu
* The problem of spam::         Some background, and some solutions
* Anti-Spam Basics::            Simple steps to reduce the amount of spam.
* SpamAssassin::                How to use external anti-spam tools.
* Hashcash::                    Reduce spam by burning CPU time.
* Filtering Spam Using The Spam ELisp Package::
* Filtering Spam Using Statistics with spam-stat::
@end menu

@node The problem of spam
@subsection The problem of spam
@cindex email spam
@cindex spam filtering approaches
@cindex filtering approaches, spam
@cindex UCE
@cindex unsolicited commercial email

First, some background on spam.

If you have access to e-mail, you are familiar with spam (technically
termed @acronym{UCE}, Unsolicited Commercial E-mail).  Simply put, it exists
because e-mail delivery is very cheap compared to paper mail, so only
a very small percentage of people need to respond to an UCE to make it
worthwhile to the advertiser.  Ironically, one of the most common
spams is the one offering a database of e-mail addresses for further
spamming.  Senders of spam are usually called @emph{spammers}, but terms like
@emph{vermin}, @emph{scum}, and @emph{morons} are in common use as well.

Spam comes from a wide variety of sources.  It is simply impossible to
dispose of all spam without discarding useful messages.  A good
example is the TMDA system, which requires senders
unknown to you to confirm themselves as legitimate senders before
their e-mail can reach you.  Without getting into the technical side
of TMDA, a downside is clearly that e-mail from legitimate sources may
be discarded if those sources can't or won't confirm themselves
through the TMDA system.  Another problem with TMDA is that it
requires its users to have a basic understanding of e-mail delivery
and processing.

The simplest approach to filtering spam is filtering.  If you get 200
spam messages per day from @samp{random-address@@vmadmin.com}, you
block @samp{vmadmin.com}.  If you get 200 messages about
@samp{VIAGRA}, you discard all messages with @samp{VIAGRA} in the
message.  This, unfortunately, is a great way to discard legitimate
e-mail.  For instance, the very informative and useful RISKS digest
has been blocked by overzealous mail filters because it
@strong{contained} words that were common in spam messages.
Nevertheless, in isolated cases, with great care, direct filtering of
mail can be useful.

Another approach to filtering e-mail is the distributed spam
processing, for instance DCC implements such a system.  In essence,
@var{N} systems around the world agree that a machine @var{X} in
China, Ghana, or California is sending out spam e-mail, and these
@var{N} systems enter @var{X} or the spam e-mail from @var{X} into
a database.  The criteria for spam detection vary---it may be the
number of messages sent, the content of the messages, and so on.  When
a user of the distributed processing system wants to find out if a
message is spam, he consults one of those @var{N} systems.

Distributed spam processing works very well against spammers that send
a large number of messages at once, but it requires the user to set up
fairly complicated checks.  There are commercial and free distributed
spam processing systems.  Distributed spam processing has its risks as
well.  For instance legitimate e-mail senders have been accused of
sending spam, and their web sites have been shut down for some time
because of the incident.

The statistical approach to spam filtering is also popular.  It is
based on a statistical analysis of previous spam messages.  Usually
the analysis is a simple word frequency count, with perhaps pairs of
words or 3-word combinations thrown into the mix.  Statistical
analysis of spam works very well in most of the cases, but it can
classify legitimate e-mail as spam in some cases.  It takes time to
run the analysis, the full message must be analyzed, and the user has
to store the database of spam analyses.

@node Anti-Spam Basics
@subsection Anti-Spam Basics
@cindex email spam
@cindex spam
@cindex UCE
@cindex unsolicited commercial email

One way of dealing with spam is having Gnus split out all spam into a
@samp{spam} mail group (@pxref{Splitting Mail}).

First, pick one (1) valid mail address that you can be reached at, and
put it in your @code{From} header of all your news articles.  (I've
chosen @samp{larsi@@trym.ifi.uio.no}, but for many addresses on the form
@samp{larsi+usenet@@ifi.uio.no} will be a better choice.  Ask your
sysadmin whether your sendmail installation accepts keywords in the local
part of the mail address.)

@lisp
(setq message-default-news-headers
      "From: Lars Magne Ingebrigtsen <larsi@@trym.ifi.uio.no>\n")
@end lisp

Then put the following split rule in @code{nnmail-split-fancy}
(@pxref{Fancy Mail Splitting}):

@lisp
(
 ...
 (to "larsi@@trym.ifi.uio.no"
      (| ("subject" "re:.*" "misc")
         ("references" ".*@@.*" "misc")
         "spam"))
 ...
)
@end lisp

This says that all mail to this address is suspect, but if it has a
@code{Subject} that starts with a @samp{Re:} or has a @code{References}
header, it's probably ok.  All the rest goes to the @samp{spam} group.
(This idea probably comes from Tim Pierce.)

In addition, many mail spammers talk directly to your @acronym{SMTP} server
and do not include your email address explicitly in the @code{To}
header.  Why they do this is unknown---perhaps it's to thwart this
thwarting scheme?  In any case, this is trivial to deal with---you just
put anything not addressed to you in the @samp{spam} group by ending
your fancy split rule in this way:

@lisp
(
 ...
 (to "larsi" "misc")
 "spam")
@end lisp

In my experience, this will sort virtually everything into the right
group.  You still have to check the @samp{spam} group from time to time to
check for legitimate mail, though.  If you feel like being a good net
citizen, you can even send off complaints to the proper authorities on
each unsolicited commercial email---at your leisure.

This works for me.  It allows people an easy way to contact me (they can
just press @kbd{r} in the usual way), and I'm not bothered at all with
spam.  It's a win-win situation.  Forging @code{From} headers to point
to non-existent domains is yucky, in my opinion.



@node SpamAssassin
@subsection SpamAssassin, Vipul's Razor, DCC, etc
@cindex SpamAssassin
@cindex Vipul's Razor
@cindex DCC

The days where the hints in the previous section was sufficient in
avoiding spam are coming to an end.  There are many tools out there
that claim to reduce the amount of spam you get.  This section could
easily become outdated fast, as new products replace old, but
fortunately most of these tools seem to have similar interfaces.  Even
though this section will use SpamAssassin as an example, it should be
easy to adapt it to most other tools.

If the tool you are using is not installed on the mail server, you
need to invoke it yourself.  Ideas on how to use the
@code{:postscript} mail source parameter (@pxref{Mail Source
Specifiers}) follow.

@lisp
(setq mail-sources
      '((file :prescript "formail -bs spamassassin < /var/mail/%u")
        (pop :user "jrl"
             :server "pophost"
             :postscript "mv %t /tmp/foo; formail -bs spamc < /tmp/foo > %t")))
@end lisp

Once you manage to process your incoming spool somehow, thus making
the mail contain e.g.@: a header indicating it is spam, you are ready to
filter it out.  Using normal split methods (@pxref{Splitting Mail}):

@lisp
(setq nnmail-split-methods '(("spam"  "^X-Spam-Flag: YES")
                             ...))
@end lisp

Or using fancy split methods (@pxref{Fancy Mail Splitting}):

@lisp
(setq nnmail-split-methods 'nnmail-split-fancy
      nnmail-split-fancy '(| ("X-Spam-Flag" "YES" "spam")
                             ...))
@end lisp

Some people might not like the idea of piping the mail through various
programs using a @code{:prescript} (if some program is buggy, you
might lose all mail).  If you are one of them, another solution is to
call the external tools during splitting.  Example fancy split method:

@lisp
(setq nnmail-split-fancy '(| (: kevin-spamassassin)
                             ...))
(defun kevin-spamassassin ()
  (save-excursion
    (widen)
    (if (eq 1 (call-process-region (point-min) (point-max)
                                   "spamc" nil nil nil "-c"))
        "spam")))
@end lisp

Note that with the nnimap backend, message bodies will not be
downloaded by default.  You need to set
@code{nnimap-split-download-body} to t to do that (@pxref{Splitting in
IMAP}).

That is about it.  As some spam is likely to get through anyway, you
might want to have a nifty function to call when you happen to read
spam.  And here is the nifty function:

@lisp
 (defun my-gnus-raze-spam ()
  "Submit SPAM to Vipul's Razor, then mark it as expirable."
  (interactive)
  (gnus-summary-show-raw-article)
  (gnus-summary-save-in-pipe "razor-report -f -d")
  (gnus-summary-mark-as-expirable 1))
@end lisp

@node Hashcash
@subsection Hashcash
@cindex hashcash

A novel technique to fight spam is to require senders to do something
costly for each message they send.  This has the obvious drawback that
you cannot rely on everyone in the world using this technique,
since it is not part of the Internet standards, but it may be useful
in smaller communities.

While the tools in the previous section work well in practice, they
work only because the tools are constantly maintained and updated as
new form of spam appears.  This means that a small percentage of spam
will always get through.  It also means that somewhere, someone needs
to read lots of spam to update these tools.  Hashcash avoids that, but
instead requires that everyone you communicate with supports the
scheme.  You can view the two approaches as pragmatic vs dogmatic.
The approaches have their own advantages and disadvantages, but as
often in the real world, a combination of them is stronger than either
one of them separately.

@cindex X-Hashcash
The ``something costly'' is to burn CPU time, more specifically to
compute a hash collision up to a certain number of bits.  The
resulting hashcash cookie is inserted in a @samp{X-Hashcash:}
header.  For more details, and for the external application
@code{hashcash} you need to install to use this feature, see
@uref{http://www.cypherspace.org/~adam/hashcash/}.  Even more
information can be found at @uref{http://www.camram.org/}.

If you wish to call hashcash for each message you send, say something
like:

@lisp
(require 'hashcash)
(add-hook 'message-send-hook 'mail-add-payment)
@end lisp

The @file{hashcash.el} library can be found in the Gnus development
contrib directory or at
@uref{http://users.actrix.gen.nz/mycroft/hashcash.el}.

You will need to set up some additional variables as well:

@table @code

@item hashcash-default-payment
@vindex hashcash-default-payment
This variable indicates the default number of bits the hash collision
should consist of.  By default this is 0, meaning nothing will be
done.  Suggested useful values include 17 to 29.

@item hashcash-payment-alist
@vindex hashcash-payment-alist
Some receivers may require you to spend burn more CPU time than the
default.  This variable contains a list of @samp{(@var{addr}
@var{amount})} cells, where @var{addr} is the receiver (email address
or newsgroup) and @var{amount} is the number of bits in the collision
that is needed.  It can also contain @samp{(@var{addr} @var{string}
@var{amount})} cells, where the @var{string} is the string to use
(normally the email address or newsgroup name is used).

@item hashcash
@vindex hashcash
Where the @code{hashcash} binary is installed.

@end table

Currently there is no built in functionality in Gnus to verify
hashcash cookies, it is expected that this is performed by your hand
customized mail filtering scripts.  Improvements in this area would be
a useful contribution, however.

@node Filtering Spam Using The Spam ELisp Package
@subsection Filtering Spam Using The Spam ELisp Package
@cindex spam filtering
@cindex spam

The idea behind @file{spam.el} is to have a control center for spam detection
and filtering in Gnus.  To that end, @file{spam.el} does two things: it
filters incoming mail, and it analyzes mail known to be spam or ham.
@dfn{Ham} is the name used throughout @file{spam.el} to indicate
non-spam messages.

First of all, you @strong{must} run the function
@code{spam-initialize} to autoload @code{spam.el} and to install the
@code{spam.el} hooks:

@example
(spam-initialize)
@end example

So, what happens when you load @file{spam.el}?  

You get the following keyboard commands:

@table @kbd

@item M-d
@itemx M s x
@itemx S x
@kindex M-d
@kindex S x
@kindex M s x
@findex gnus-summary-mark-as-spam
@code{gnus-summary-mark-as-spam}.

Mark current article as spam, showing it with the @samp{$} mark.
Whenever you see a spam article, make sure to mark its summary line
with @kbd{M-d} before leaving the group.  This is done automatically
for unread articles in @emph{spam} groups.

@item M s t
@itemx S t
@kindex M s t
@kindex S t
@findex spam-bogofilter-score
@code{spam-bogofilter-score}.

You must have Bogofilter installed for that command to work properly.

@xref{Bogofilter}.

@end table

Also, when you load @file{spam.el}, you will be able to customize its
variables.  Try @code{customize-group} on the @samp{spam} variable
group.

@vindex gnus-spam-process-newsgroups
The concepts of ham processors and spam processors are very important.
Ham processors and spam processors for a group can be set with the
@code{spam-process} group parameter, or the
@code{gnus-spam-process-newsgroups} variable.  Ham processors take
mail known to be non-spam (@emph{ham}) and process it in some way so
that later similar mail will also be considered non-spam.  Spam
processors take mail known to be spam and process it so similar spam
will be detected later.

@vindex gnus-spam-newsgroup-contents
Gnus learns from the spam you get.  You have to collect your spam in
one or more spam groups, and set or customize the variable
@code{spam-junk-mailgroups} as appropriate.  You can also declare
groups to contain spam by setting their group parameter
@code{spam-contents} to @code{gnus-group-spam-classification-spam}, or
by customizing the corresponding variable
@code{gnus-spam-newsgroup-contents}.  The @code{spam-contents} group
parameter and the @code{gnus-spam-newsgroup-contents} variable can
also be used to declare groups as @emph{ham} groups if you set their
classification to @code{gnus-group-spam-classification-ham}.  If
groups are not classified by means of @code{spam-junk-mailgroups},
@code{spam-contents}, or @code{gnus-spam-newsgroup-contents}, they are
considered @emph{unclassified}.  All groups are unclassified by
default.

@vindex gnus-spam-mark
@cindex $
In spam groups, all messages are considered to be spam by default:
they get the @samp{$} mark (@code{gnus-spam-mark}) when you enter the
group.  If you have seen a message, had it marked as spam, then
unmarked it, it won't be marked as spam when you enter the group
thereafter.  You can disable that behavior, so all unread messages
will get the @samp{$} mark, if you set the
@code{spam-mark-only-unseen-as-spam} parameter to @code{nil}.  You
should remove the @samp{$} mark when you are in the group summary
buffer for every message that is not spam after all.  To remove the
@samp{$} mark, you can use @kbd{M-u} to ``unread'' the article, or
@kbd{d} for declaring it read the non-spam way.  When you leave a
group, all spam-marked (@samp{$}) articles are sent to a spam
processor which will study them as spam samples.

Messages may also be deleted in various other ways, and unless
@code{ham-marks} group parameter gets overridden below, marks @samp{R}
and @samp{r} for default read or explicit delete, marks @samp{X} and
@samp{K} for automatic or explicit kills, as well as mark @samp{Y} for
low scores, are all considered to be associated with articles which
are not spam.  This assumption might be false, in particular if you
use kill files or score files as means for detecting genuine spam, you
should then adjust the @code{ham-marks} group parameter.

@defvar ham-marks
You can customize this group or topic parameter to be the list of
marks you want to consider ham.  By default, the list contains the
deleted, read, killed, kill-filed, and low-score marks.
@end defvar

@defvar spam-marks
You can customize this group or topic parameter to be the list of
marks you want to consider spam.  By default, the list contains only
the spam mark.
@end defvar

When you leave @emph{any} group, regardless of its
@code{spam-contents} classification, all spam-marked articles are sent
to a spam processor, which will study these as spam samples.  If you
explicit kill a lot, you might sometimes end up with articles marked
@samp{K} which you never saw, and which might accidentally contain
spam.  Best is to make sure that real spam is marked with @samp{$},
and nothing else.

@vindex gnus-ham-process-destinations
When you leave a @emph{spam} group, all spam-marked articles are
marked as expired after processing with the spam processor.  This is
not done for @emph{unclassified} or @emph{ham} groups.  Also, any
@strong{ham} articles in a spam group will be moved to a location
determined by either the @code{ham-process-destination} group
parameter or a match in the @code{gnus-ham-process-destinations}
variable, which is a list of regular expressions matched with group
names (it's easiest to customize this variable with
@code{customize-variable gnus-ham-process-destinations}).  The ultimate
location is a group name.  If the @code{ham-process-destination}
parameter is not set, ham articles are left in place.  If the
@code{spam-mark-ham-unread-before-move-from-spam-group} parameter is
set, the ham articles are marked as unread before being moved.

When you leave a @emph{ham} group, all ham-marked articles are sent to
a ham processor, which will study these as non-spam samples.

@vindex spam-process-ham-in-spam-groups
By default the variable @code{spam-process-ham-in-spam-groups} is
@code{nil}.  Set it to @code{t} if you want ham found in spam groups
to be processed.  Normally this is not done, you are expected instead
to send your ham to a ham group and process it there.

@vindex spam-process-ham-in-nonham-groups
By default the variable @code{spam-process-ham-in-nonham-groups} is
@code{nil}.  Set it to @code{t} if you want ham found in non-ham (spam
or unclassified) groups to be processed.  Normally this is not done,
you are expected instead to send your ham to a ham group and process
it there.

@vindex gnus-spam-process-destinations
When you leave a @emph{ham} or @emph{unclassified} group, all
@strong{spam} articles are moved to a location determined by either
the @code{spam-process-destination} group parameter or a match in the
@code{gnus-spam-process-destinations} variable, which is a list of
regular expressions matched with group names (it's easiest to
customize this variable with @code{customize-variable
gnus-spam-process-destinations}).  The ultimate location is a group
name.  If the @code{spam-process-destination} parameter is not set,
the spam articles are only expired.

To use the @file{spam.el} facilities for incoming mail filtering, you
must add the following to your fancy split list
@code{nnmail-split-fancy} or @code{nnimap-split-fancy}:

@example
(: spam-split)
@end example

Note that the fancy split may be called @code{nnmail-split-fancy} or
@code{nnimap-split-fancy}, depending on whether you use the nnmail or
nnimap back ends to retrieve your mail.

The @code{spam-split} function will process incoming mail and send the
mail considered to be spam into the group name given by the variable
@code{spam-split-group}.  By default that group name is @samp{spam},
but you can customize @code{spam-split-group}.

You can also give @code{spam-split} a parameter,
e.g. @samp{'spam-use-regex-headers} or @samp{"maybe-spam"}.  Why is
this useful?

Take these split rules (with @code{spam-use-regex-headers} and
@code{spam-use-blackholes} set):

@example
 nnimap-split-fancy '(|
                      (any "ding" "ding")
                      (: spam-split)
                      ;; default mailbox
                      "mail")
@end example

Now, the problem is that you want all ding messages to make it to the
ding folder.  But that will let obvious spam (for example, spam
detected by SpamAssassin, and @code{spam-use-regex-headers}) through,
when it's sent to the ding list.  On the other hand, some messages to
the ding list are from a mail server in the blackhole list, so the
invocation of @code{spam-split} can't be before the ding rule.

You can let SpamAssassin headers supersede ding rules, but all other
@code{spam-split} rules (including a second invocation of the
regex-headers check) will be after the ding rule:

@example
 nnimap-split-fancy '(|
;;; all spam detected by spam-use-regex-headers goes to "regex-spam"
                      (: spam-split "regex-spam" 'spam-use-regex-headers)
                      (any "ding" "ding")
;;; all other spam detected by spam-split goes to spam-split-group
                      (: spam-split)
                      ;; default mailbox
                      "mail")
@end example

Basically, this lets you invoke specific @code{spam-split} checks
depending on your particular needs, and to target the results of those
checks to a particular spam group.  You don't have to throw all mail
into all the spam tests.  Another reason why this is nice is that
messages to mailing lists you have rules for don't have to have
resource-intensive blackhole checks performed on them.  You could also
specify different spam checks for your nnmail split vs. your nnimap
split.  Go crazy.

You still have to have specific checks such as
@code{spam-use-regex-headers} set to @code{t}, even if you specifically
invoke @code{spam-split} with the check.  The reason is that when
loading @file{spam.el}, some conditional loading is done depending on
what @code{spam-use-xyz} variables you have set.

@emph{Note for IMAP users}

The boolean variable @code{nnimap-split-download-body} needs to be
set, if you want to split based on the whole message instead of just
the headers.  By default, the nnimap back end will only retrieve the
message headers.  If you use @code{spam-check-bogofilter},
@code{spam-check-ifile}, or @code{spam-check-stat} (the splitters that
can benefit from the full message body), you should set this variable.
It is not set by default because it will slow @acronym{IMAP} down, and
that is not an appropriate decision to make on behalf of the user.

@xref{Splitting in IMAP}.

@emph{TODO: Currently, spam.el only supports insertion of articles
into a back end.  There is no way to tell spam.el that an article is no
longer spam or ham.}

@emph{TODO: spam.el needs to provide a uniform way of training all the
statistical databases.  Some have that functionality built-in, others
don't.}

The following are the methods you can use to control the behavior of
@code{spam-split} and their corresponding spam and ham processors:

@menu
* Blacklists and Whitelists::
* BBDB Whitelists::
* Gmane Spam Reporting::
* Anti-spam Hashcash Payments::
* Blackholes::
* Regular Expressions Header Matching::
* Bogofilter::
* ifile spam filtering::
* spam-stat spam filtering::
* SpamOracle::
* Extending the spam elisp package::
@end menu

@node Blacklists and Whitelists
@subsubsection Blacklists and Whitelists
@cindex spam filtering
@cindex whitelists, spam filtering
@cindex blacklists, spam filtering
@cindex spam

@defvar spam-use-blacklist

Set this variable to @code{t} if you want to use blacklists when
splitting incoming mail.  Messages whose senders are in the blacklist
will be sent to the @code{spam-split-group}.  This is an explicit
filter, meaning that it acts only on mail senders @emph{declared} to
be spammers.

@end defvar

@defvar spam-use-whitelist

Set this variable to @code{t} if you want to use whitelists when
splitting incoming mail.  Messages whose senders are not in the
whitelist will be sent to the next spam-split rule.  This is an
explicit filter, meaning that unless someone is in the whitelist, their
messages are not assumed to be spam or ham.

@end defvar

@defvar spam-use-whitelist-exclusive

Set this variable to @code{t} if you want to use whitelists as an
implicit filter, meaning that every message will be considered spam
unless the sender is in the whitelist.  Use with care.

@end defvar

@defvar gnus-group-spam-exit-processor-blacklist

Add this symbol to a group's @code{spam-process} parameter by
customizing the group parameters or the
@code{gnus-spam-process-newsgroups} variable.  When this symbol is
added to a group's @code{spam-process} parameter, the senders of
spam-marked articles will be added to the blacklist.

@end defvar

@defvar gnus-group-ham-exit-processor-whitelist

Add this symbol to a group's @code{spam-process} parameter by
customizing the group parameters or the
@code{gnus-spam-process-newsgroups} variable.  When this symbol is
added to a group's @code{spam-process} parameter, the senders of
ham-marked articles in @emph{ham} groups will be added to the
whitelist.  Note that this ham processor has no effect in @emph{spam}
or @emph{unclassified} groups.

@end defvar

Blacklists are lists of regular expressions matching addresses you
consider to be spam senders.  For instance, to block mail from any
sender at @samp{vmadmin.com}, you can put @samp{vmadmin.com} in your
blacklist.  You start out with an empty blacklist.  Blacklist entries
use the Emacs regular expression syntax.

Conversely, whitelists tell Gnus what addresses are considered
legitimate.  All messages from whitelisted addresses are considered
non-spam.  Also see @ref{BBDB Whitelists}.  Whitelist entries use the
Emacs regular expression syntax.

The blacklist and whitelist file locations can be customized with the
@code{spam-directory} variable (@file{~/News/spam} by default), or
the @code{spam-whitelist} and @code{spam-blacklist} variables
directly.  The whitelist and blacklist files will by default be in the
@code{spam-directory} directory, named @file{whitelist} and
@file{blacklist} respectively.

@node BBDB Whitelists
@subsubsection BBDB Whitelists
@cindex spam filtering
@cindex BBDB whitelists, spam filtering
@cindex BBDB, spam filtering
@cindex spam

@defvar spam-use-BBDB

Analogous to @code{spam-use-whitelist} (@pxref{Blacklists and
Whitelists}), but uses the BBDB as the source of whitelisted
addresses, without regular expressions.  You must have the BBDB loaded
for @code{spam-use-BBDB} to work properly.  Messages whose senders are
not in the BBDB will be sent to the next spam-split rule.  This is an
explicit filter, meaning that unless someone is in the BBDB, their
messages are not assumed to be spam or ham.

@end defvar

@defvar spam-use-BBDB-exclusive

Set this variable to @code{t} if you want to use the BBDB as an
implicit filter, meaning that every message will be considered spam
unless the sender is in the BBDB.  Use with care.  Only sender
addresses in the BBDB will be allowed through; all others will be
classified as spammers.

@end defvar

@defvar gnus-group-ham-exit-processor-BBDB

Add this symbol to a group's @code{spam-process} parameter by
customizing the group parameters or the
@code{gnus-spam-process-newsgroups} variable.  When this symbol is
added to a group's @code{spam-process} parameter, the senders of
ham-marked articles in @emph{ham} groups will be added to the
BBDB.  Note that this ham processor has no effect in @emph{spam}
or @emph{unclassified} groups.

@end defvar

@node Gmane Spam Reporting
@subsubsection Gmane Spam Reporting
@cindex spam reporting
@cindex Gmane, spam reporting
@cindex Gmane, spam reporting
@cindex spam

@defvar gnus-group-spam-exit-processor-report-gmane

Add this symbol to a group's @code{spam-process} parameter by
customizing the group parameters or the
@code{gnus-spam-process-newsgroups} variable.  When this symbol is
added to a group's @code{spam-process} parameter, the spam-marked
articles groups will be reported to the Gmane administrators via a
HTTP request.

Gmane can be found at @uref{http://gmane.org}.

@end defvar

@defvar spam-report-gmane-use-article-number

This variable is @code{t} by default.  Set it to @code{nil} if you are
running your own news server, for instance, and the local article
numbers don't correspond to the Gmane article numbers.  When
@code{spam-report-gmane-use-article-number} is @code{nil},
@code{spam-report.el} will use the @code{X-Report-Spam} header that
Gmane provides.

@end defvar

@node Anti-spam Hashcash Payments
@subsubsection Anti-spam Hashcash Payments
@cindex spam filtering
@cindex hashcash, spam filtering
@cindex spam

@defvar spam-use-hashcash

Similar to @code{spam-use-whitelist} (@pxref{Blacklists and
Whitelists}), but uses hashcash tokens for whitelisting messages
instead of the sender address.  You must have the @code{hashcash.el}
package loaded for @code{spam-use-hashcash} to work properly.
Messages without a hashcash payment token will be sent to the next
spam-split rule.  This is an explicit filter, meaning that unless a
hashcash token is found, the messages are not assumed to be spam or
ham.

@end defvar

@node Blackholes
@subsubsection Blackholes
@cindex spam filtering
@cindex blackholes, spam filtering
@cindex spam

@defvar spam-use-blackholes

This option is disabled by default.  You can let Gnus consult the
blackhole-type distributed spam processing systems (DCC, for instance)
when you set this option.  The variable @code{spam-blackhole-servers}
holds the list of blackhole servers Gnus will consult.  The current
list is fairly comprehensive, but make sure to let us know if it
contains outdated servers.

The blackhole check uses the @code{dig.el} package, but you can tell
@file{spam.el} to use @code{dns.el} instead for better performance if
you set @code{spam-use-dig} to @code{nil}.  It is not recommended at
this time to set @code{spam-use-dig} to @code{nil} despite the
possible performance improvements, because some users may be unable to
use it, but you can try it and see if it works for you.

@end defvar

@defvar spam-blackhole-servers

The list of servers to consult for blackhole checks.

@end defvar

@defvar spam-blackhole-good-server-regex

A regular expression for IPs that should not be checked against the
blackhole server list.  When set to @code{nil}, it has no effect.

@end defvar

@defvar spam-use-dig

Use the @code{dig.el} package instead of the @code{dns.el} package.
The default setting of @code{t} is recommended.

@end defvar

Blackhole checks are done only on incoming mail.  There is no spam or
ham processor for blackholes.

@node Regular Expressions Header Matching
@subsubsection Regular Expressions Header Matching
@cindex spam filtering
@cindex regular expressions header matching, spam filtering
@cindex spam

@defvar spam-use-regex-headers

This option is disabled by default.  You can let Gnus check the
message headers against lists of regular expressions when you set this
option.  The variables @code{spam-regex-headers-spam} and
@code{spam-regex-headers-ham} hold the list of regular expressions.
Gnus will check against the message headers to determine if the
message is spam or ham, respectively.

@end defvar

@defvar spam-regex-headers-spam

The list of regular expressions that, when matched in the headers of
the message, positively identify it as spam.

@end defvar

@defvar spam-regex-headers-ham

The list of regular expressions that, when matched in the headers of
the message, positively identify it as ham.

@end defvar

Regular expression header checks are done only on incoming mail.
There is no specific spam or ham processor for regular expressions.

@node Bogofilter
@subsubsection Bogofilter
@cindex spam filtering
@cindex bogofilter, spam filtering
@cindex spam

@defvar spam-use-bogofilter

Set this variable if you want @code{spam-split} to use Eric Raymond's
speedy Bogofilter.

With a minimum of care for associating the @samp{$} mark for spam
articles only, Bogofilter training all gets fairly automatic.  You
should do this until you get a few hundreds of articles in each
category, spam or not.  The command @kbd{S t} in summary mode, either
for debugging or for curiosity, shows the @emph{spamicity} score of
the current article (between 0.0 and 1.0).

Bogofilter determines if a message is spam based on a specific
threshold.  That threshold can be customized, consult the Bogofilter
documentation.

If the @code{bogofilter} executable is not in your path, Bogofilter
processing will be turned off.

You should not enable this if you use @code{spam-use-bogofilter-headers}.

@end defvar

@defvar spam-use-bogofilter-headers

Set this variable if you want @code{spam-split} to use Eric Raymond's
speedy Bogofilter, looking only at the message headers.  It works
similarly to @code{spam-use-bogofilter}, but the @code{X-Bogosity} header
must be in the message already.  Normally you would do this with a
procmail recipe or something similar; consult the Bogofilter
installation documents for details.

You should not enable this if you use @code{spam-use-bogofilter}.

@end defvar

@defvar gnus-group-spam-exit-processor-bogofilter
Add this symbol to a group's @code{spam-process} parameter by
customizing the group parameters or the
@code{gnus-spam-process-newsgroups} variable.  When this symbol is
added to a group's @code{spam-process} parameter, spam-marked articles
will be added to the Bogofilter spam database.
@end defvar

@defvar gnus-group-ham-exit-processor-bogofilter
Add this symbol to a group's @code{spam-process} parameter by
customizing the group parameters or the
@code{gnus-spam-process-newsgroups} variable.  When this symbol is
added to a group's @code{spam-process} parameter, the ham-marked
articles in @emph{ham} groups will be added to the Bogofilter database
of non-spam messages.  Note that this ham processor has no effect in
@emph{spam} or @emph{unclassified} groups.
@end defvar

@defvar spam-bogofilter-database-directory

This is the directory where Bogofilter will store its databases.  It
is not specified by default, so Bogofilter will use its own default
database directory.

@end defvar

The Bogofilter mail classifier is similar to @command{ifile} in intent and
purpose.  A ham and a spam processor are provided, plus the
@code{spam-use-bogofilter} and @code{spam-use-bogofilter-headers}
variables to indicate to spam-split that Bogofilter should either be
used, or has already been used on the article.  The 0.9.2.1 version of
Bogofilter was used to test this functionality.

@node ifile spam filtering
@subsubsection ifile spam filtering
@cindex spam filtering
@cindex ifile, spam filtering
@cindex spam

@defvar spam-use-ifile

Enable this variable if you want @code{spam-split} to use @command{ifile}, a
statistical analyzer similar to Bogofilter.

@end defvar

@defvar spam-ifile-all-categories

Enable this variable if you want @code{spam-use-ifile} to give you all
the ifile categories, not just spam/non-spam.  If you use this, make
sure you train ifile as described in its documentation.

@end defvar

@defvar spam-ifile-spam-category

This is the category of spam messages as far as ifile is concerned.
The actual string used is irrelevant, but you probably want to leave
the default value of @samp{spam}.
@end defvar

@defvar spam-ifile-database-path

This is the filename for the ifile database.  It is not specified by
default, so ifile will use its own default database name.

@end defvar

The ifile mail classifier is similar to Bogofilter in intent and
purpose.  A ham and a spam processor are provided, plus the
@code{spam-use-ifile} variable to indicate to spam-split that ifile
should be used.  The 1.2.1 version of ifile was used to test this
functionality.

@node spam-stat spam filtering
@subsubsection spam-stat spam filtering
@cindex spam filtering
@cindex spam-stat, spam filtering
@cindex spam-stat
@cindex spam

@xref{Filtering Spam Using Statistics with spam-stat}.

@defvar spam-use-stat

Enable this variable if you want @code{spam-split} to use
spam-stat.el, an Emacs Lisp statistical analyzer.

@end defvar

@defvar gnus-group-spam-exit-processor-stat
Add this symbol to a group's @code{spam-process} parameter by
customizing the group parameters or the
@code{gnus-spam-process-newsgroups} variable.  When this symbol is
added to a group's @code{spam-process} parameter, the spam-marked
articles will be added to the spam-stat database of spam messages.
@end defvar

@defvar gnus-group-ham-exit-processor-stat
Add this symbol to a group's @code{spam-process} parameter by
customizing the group parameters or the
@code{gnus-spam-process-newsgroups} variable.  When this symbol is
added to a group's @code{spam-process} parameter, the ham-marked
articles in @emph{ham} groups will be added to the spam-stat database
of non-spam messages.  Note that this ham processor has no effect in
@emph{spam} or @emph{unclassified} groups.
@end defvar

This enables @file{spam.el} to cooperate with @file{spam-stat.el}.
@file{spam-stat.el} provides an internal (Lisp-only) spam database,
which unlike ifile or Bogofilter does not require external programs.
A spam and a ham processor, and the @code{spam-use-stat} variable for
@code{spam-split} are provided.

@node SpamOracle
@subsubsection Using SpamOracle with Gnus
@cindex spam filtering
@cindex SpamOracle
@cindex spam

An easy way to filter out spam is to use SpamOracle.  SpamOracle is an
statistical mail filtering tool written by Xavier Leroy and needs to be
installed separately.

There are several ways to use SpamOracle with Gnus.  In all cases, your
mail is piped through SpamOracle in its @emph{mark} mode.  SpamOracle will
then enter an @samp{X-Spam} header indicating whether it regards the
mail as a spam mail or not.

One possibility is to run SpamOracle as a @code{:prescript} from the
@xref{Mail Source Specifiers}, (@pxref{SpamAssassin}).  This method has
the advantage that the user can see the @emph{X-Spam} headers.

The easiest method is to make @file{spam.el} (@pxref{Filtering Spam
Using The Spam ELisp Package}) call SpamOracle.

@vindex spam-use-spamoracle
To enable SpamOracle usage by @file{spam.el}, set the variable
@code{spam-use-spamoracle} to @code{t} and configure the
@code{nnmail-split-fancy} or @code{nnimap-split-fancy} as described in
the section @xref{Filtering Spam Using The Spam ELisp Package}.  In
this example the @samp{INBOX} of an nnimap server is filtered using
SpamOracle.  Mails recognized as spam mails will be moved to
@code{spam-split-group}, @samp{Junk} in this case.  Ham messages stay
in @samp{INBOX}:

@example
(setq spam-use-spamoracle t
      spam-split-group "Junk"
      nnimap-split-inbox '("INBOX")
      nnimap-split-rule 'nnimap-split-fancy
      nnimap-split-fancy '(| (: spam-split) "INBOX"))
@end example

@defvar spam-use-spamoracle
Set to @code{t} if you want Gnus to enable spam filtering using
SpamOracle.
@end defvar

@defvar spam-spamoracle-binary
Gnus uses the SpamOracle binary called @file{spamoracle} found in the
user's PATH.  Using the variable @code{spam-spamoracle-binary}, this
can be customized.
@end defvar

@defvar spam-spamoracle-database
By default, SpamOracle uses the file @file{~/.spamoracle.db} as a database to
store its analyses.  This is controlled by the variable
@code{spam-spamoracle-database} which defaults to @code{nil}.  That means
the default SpamOracle database will be used.  In case you want your
database to live somewhere special, set
@code{spam-spamoracle-database} to this path.
@end defvar

SpamOracle employs a statistical algorithm to determine whether a
message is spam or ham.  In order to get good results, meaning few
false hits or misses, SpamOracle needs training.  SpamOracle learns the
characteristics of your spam mails.  Using the @emph{add} mode
(training mode) one has to feed good (ham) and spam mails to
SpamOracle.  This can be done by pressing @kbd{|} in the Summary buffer
and pipe the mail to a SpamOracle process or using @file{spam.el}'s
spam- and ham-processors, which is much more convenient.  For a
detailed description of spam- and ham-processors, @xref{Filtering Spam
Using The Spam ELisp Package}.

@defvar gnus-group-spam-exit-processor-spamoracle
Add this symbol to a group's @code{spam-process} parameter by
customizing the group parameter or the
@code{gnus-spam-process-newsgroups} variable.  When this symbol is added
to a group's @code{spam-process} parameter, spam-marked articles will be
sent to SpamOracle as spam samples.
@end defvar

@defvar gnus-group-ham-exit-processor-spamoracle
Add this symbol to a group's @code{spam-process} parameter by
customizing the group parameter or the
@code{gnus-spam-process-newsgroups} variable.  When this symbol is added
to a grup's @code{spam-process} parameter, the ham-marked articles in
@emph{ham} groups will be sent to the SpamOracle as samples of ham
messages.  Note that this ham processor has no effect in @emph{spam} or
@emph{unclassified} groups.
@end defvar

@emph{Example:} These are the Group Parameters of an group that has been
classified as a ham group, meaning that it should only contain ham
messages.
@example
 ((spam-contents gnus-group-spam-classification-ham)
  (spam-process
   (gnus-group-spam-exit-processor-spamoracle)))
@end example
For this group the @code{gnus-group-spam-exit-processor-spamoracle} is
installed.  If the group contains spam message (e.g. because SpamOracle
has not had enough sample messages yet) and the user marks some
messages as spam messages, these messages will be processed by
@code{gnus-group-spam-exit-processor-spamoracle}.  This processor sends
the messages to SpamOracle as new samples for spam.

@node Extending the spam elisp package
@subsubsection Extending the spam elisp package
@cindex spam filtering
@cindex spam elisp package, extending
@cindex extending the spam elisp package

Say you want to add a new back end called blackbox.  For filtering
incoming mail, provide the following:

@enumerate

@item
code

@lisp
(defvar spam-use-blackbox nil
  "True if blackbox should be used.")
@end lisp

Add
@example
    (spam-use-blackbox   . spam-check-blackbox)
@end example
to @code{spam-list-of-checks}.

@item
functionality

Write the @code{spam-check-blackbox} function.  It should return
@samp{nil} or @code{spam-split-group}.  See the existing
@code{spam-check-*} functions for examples of what you can do.

Make sure to add @code{spam-use-blackbox} to
@code{spam-list-of-statistical-checks} if Blackbox is a statistical
mail analyzer that needs the full message body to operate.

@end enumerate

For processing spam and ham messages, provide the following:

@enumerate

@item
code

Note you don't have to provide a spam or a ham processor.  Only
provide them if Blackbox supports spam or ham processing.

@lisp
(defvar gnus-group-spam-exit-processor-blackbox "blackbox"
  "The Blackbox summary exit spam processor.
Only applicable to spam groups.")

(defvar gnus-group-ham-exit-processor-blackbox "blackbox"
  "The whitelist summary exit ham processor.
Only applicable to non-spam (unclassified and ham) groups.")

@end lisp

@item
functionality

@lisp
(defun spam-blackbox-register-spam-routine ()
  (spam-generic-register-routine
   ;; @r{the spam function}
   (lambda (article)
     (let ((from (spam-fetch-field-from-fast article)))
       (when (stringp from)
           (blackbox-do-something-with-this-spammer from))))
   ;; @r{the ham function}
   nil))

(defun spam-blackbox-register-ham-routine ()
  (spam-generic-register-routine
   ;; @r{the spam function}
   nil
   ;; @r{the ham function}
   (lambda (article)
     (let ((from (spam-fetch-field-from-fast article)))
       (when (stringp from)
           (blackbox-do-something-with-this-ham-sender from))))))
@end lisp

Write the @code{blackbox-do-something-with-this-ham-sender} and
@code{blackbox-do-something-with-this-spammer} functions.  You can add
more complex code than fetching the message sender, but keep in mind
that retrieving the whole message takes significantly longer than the
sender through @code{spam-fetch-field-from-fast}, because the message
senders are kept in memory by Gnus.

@end enumerate


@node Filtering Spam Using Statistics with spam-stat
@subsection Filtering Spam Using Statistics with spam-stat
@cindex Paul Graham
@cindex Graham, Paul
@cindex naive Bayesian spam filtering
@cindex Bayesian spam filtering, naive
@cindex spam filtering, naive Bayesian

Paul Graham has written an excellent essay about spam filtering using
statistics: @uref{http://www.paulgraham.com/spam.html,A Plan for
Spam}.  In it he describes the inherent deficiency of rule-based
filtering as used by SpamAssassin, for example: Somebody has to write
the rules, and everybody else has to install these rules.  You are
always late.  It would be much better, he argues, to filter mail based
on whether it somehow resembles spam or non-spam.  One way to measure
this is word distribution.  He then goes on to describe a solution
that checks whether a new mail resembles any of your other spam mails
or not.

The basic idea is this:  Create a two collections of your mail, one
with spam, one with non-spam.  Count how often each word appears in
either collection, weight this by the total number of mails in the
collections, and store this information in a dictionary.  For every
word in a new mail, determine its probability to belong to a spam or a
non-spam mail.  Use the 15 most conspicuous words, compute the total
probability of the mail being spam.  If this probability is higher
than a certain threshold, the mail is considered to be spam.

Gnus supports this kind of filtering.  But it needs some setting up.
First, you need two collections of your mail, one with spam, one with
non-spam.  Then you need to create a dictionary using these two
collections, and save it.  And last but not least, you need to use
this dictionary in your fancy mail splitting rules.

@menu
* Creating a spam-stat dictionary::
* Splitting mail using spam-stat::
* Low-level interface to the spam-stat dictionary::
@end menu

@node Creating a spam-stat dictionary
@subsubsection Creating a spam-stat dictionary

Before you can begin to filter spam based on statistics, you must
create these statistics based on two mail collections, one with spam,
one with non-spam.  These statistics are then stored in a dictionary
for later use.  In order for these statistics to be meaningful, you
need several hundred emails in both collections.

Gnus currently supports only the nnml back end for automated dictionary
creation.  The nnml back end stores all mails in a directory, one file
per mail.  Use the following:

@defun spam-stat-process-spam-directory
Create spam statistics for every file in this directory.  Every file
is treated as one spam mail.
@end defun

@defun spam-stat-process-non-spam-directory
Create non-spam statistics for every file in this directory.  Every
file is treated as one non-spam mail.
@end defun

Usually you would call @code{spam-stat-process-spam-directory} on a
directory such as @file{~/Mail/mail/spam} (this usually corresponds
the the group @samp{nnml:mail.spam}), and you would call
@code{spam-stat-process-non-spam-directory} on a directory such as
@file{~/Mail/mail/misc} (this usually corresponds the the group
@samp{nnml:mail.misc}).

When you are using @acronym{IMAP}, you won't have the mails available
locally, so that will not work.  One solution is to use the Gnus Agent
to cache the articles.  Then you can use directories such as
@file{"~/News/agent/nnimap/mail.yourisp.com/personal_spam"} for
@code{spam-stat-process-spam-directory}.  @xref{Agent as Cache}.

@defvar spam-stat
This variable holds the hash-table with all the statistics---the
dictionary we have been talking about.  For every word in either
collection, this hash-table stores a vector describing how often the
word appeared in spam and often it appeared in non-spam mails.
@end defvar

If you want to regenerate the statistics from scratch, you need to
reset the dictionary.

@defun spam-stat-reset
Reset the @code{spam-stat} hash-table, deleting all the statistics.
@end defun

When you are done, you must save the dictionary.  The dictionary may
be rather large.  If you will not update the dictionary incrementally
(instead, you will recreate it once a month, for example), then you
can reduce the size of the dictionary by deleting all words that did
not appear often enough or that do not clearly belong to only spam or
only non-spam mails.

@defun spam-stat-reduce-size
Reduce the size of the dictionary.  Use this only if you do not want
to update the dictionary incrementally.
@end defun

@defun spam-stat-save
Save the dictionary.
@end defun

@defvar spam-stat-file
The filename used to store the dictionary.  This defaults to
@file{~/.spam-stat.el}.
@end defvar

@node Splitting mail using spam-stat
@subsubsection Splitting mail using spam-stat

In order to use @code{spam-stat} to split your mail, you need to add the
following to your @file{~/.gnus.el} file:

@lisp
(require 'spam-stat)
(spam-stat-load)
@end lisp

This will load the necessary Gnus code, and the dictionary you
created.

Next, you need to adapt your fancy splitting rules:  You need to
determine how to use @code{spam-stat}.  The following examples are for
the nnml back end.  Using the nnimap back end works just as well.  Just
use @code{nnimap-split-fancy} instead of @code{nnmail-split-fancy}.

In the simplest case, you only have two groups, @samp{mail.misc} and
@samp{mail.spam}.  The following expression says that mail is either
spam or it should go into @samp{mail.misc}.  If it is spam, then
@code{spam-stat-split-fancy} will return @samp{mail.spam}.

@lisp
(setq nnmail-split-fancy
      `(| (: spam-stat-split-fancy)
          "mail.misc"))
@end lisp

@defvar spam-stat-split-fancy-spam-group
The group to use for spam.  Default is @samp{mail.spam}.
@end defvar

If you also filter mail with specific subjects into other groups, use
the following expression.  Only mails not matching the regular
expression are considered potential spam.

@lisp
(setq nnmail-split-fancy
      `(| ("Subject" "\\bspam-stat\\b" "mail.emacs")
          (: spam-stat-split-fancy)
          "mail.misc"))
@end lisp

If you want to filter for spam first, then you must be careful when
creating the dictionary.  Note that @code{spam-stat-split-fancy} must
consider both mails in @samp{mail.emacs} and in @samp{mail.misc} as
non-spam, therefore both should be in your collection of non-spam
mails, when creating the dictionary!

@lisp
(setq nnmail-split-fancy
      `(| (: spam-stat-split-fancy)
          ("Subject" "\\bspam-stat\\b" "mail.emacs")
          "mail.misc"))
@end lisp

You can combine this with traditional filtering.  Here, we move all
HTML-only mails into the @samp{mail.spam.filtered} group.  Note that since
@code{spam-stat-split-fancy} will never see them, the mails in
@samp{mail.spam.filtered} should be neither in your collection of spam mails,
nor in your collection of non-spam mails, when creating the
dictionary!

@lisp
(setq nnmail-split-fancy
      `(| ("Content-Type" "text/html" "mail.spam.filtered")
          (: spam-stat-split-fancy)
          ("Subject" "\\bspam-stat\\b" "mail.emacs")
          "mail.misc"))
@end lisp


@node Low-level interface to the spam-stat dictionary
@subsubsection Low-level interface to the spam-stat dictionary

The main interface to using @code{spam-stat}, are the following functions:

@defun spam-stat-buffer-is-spam
Called in a buffer, that buffer is considered to be a new spam mail.
Use this for new mail that has not been processed before.
@end defun

@defun spam-stat-buffer-is-no-spam
Called in a buffer, that buffer is considered to be a new non-spam
mail.  Use this for new mail that has not been processed before.
@end defun

@defun spam-stat-buffer-change-to-spam
Called in a buffer, that buffer is no longer considered to be normal
mail but spam.  Use this to change the status of a mail that has
already been processed as non-spam.
@end defun

@defun spam-stat-buffer-change-to-non-spam
Called in a buffer, that buffer is no longer considered to be spam but
normal mail.  Use this to change the status of a mail that has already
been processed as spam.
@end defun

@defun spam-stat-save
Save the hash table to the file.  The filename used is stored in the
variable @code{spam-stat-file}.
@end defun

@defun spam-stat-load
Load the hash table from a file.  The filename used is stored in the
variable @code{spam-stat-file}.
@end defun

@defun spam-stat-score-word
Return the spam score for a word.
@end defun

@defun spam-stat-score-buffer
Return the spam score for a buffer.
@end defun

@defun spam-stat-split-fancy
Use this function for fancy mail splitting.  Add the rule @samp{(:
spam-stat-split-fancy)} to @code{nnmail-split-fancy}
@end defun

Make sure you load the dictionary before using it.  This requires the
following in your @file{~/.gnus.el} file:

@lisp
(require 'spam-stat)
(spam-stat-load)
@end lisp

Typical test will involve calls to the following functions:

@smallexample
Reset: (setq spam-stat (make-hash-table :test 'equal))
Learn spam: (spam-stat-process-spam-directory "~/Mail/mail/spam")
Learn non-spam: (spam-stat-process-non-spam-directory "~/Mail/mail/misc")
Save table: (spam-stat-save)
File size: (nth 7 (file-attributes spam-stat-file))
Number of words: (hash-table-count spam-stat)
Test spam: (spam-stat-test-directory "~/Mail/mail/spam")
Test non-spam: (spam-stat-test-directory "~/Mail/mail/misc")
Reduce table size: (spam-stat-reduce-size)
Save table: (spam-stat-save)
File size: (nth 7 (file-attributes spam-stat-file))
Number of words: (hash-table-count spam-stat)
Test spam: (spam-stat-test-directory "~/Mail/mail/spam")
Test non-spam: (spam-stat-test-directory "~/Mail/mail/misc")
@end smallexample

Here is how you would create your dictionary:

@smallexample
Reset: (setq spam-stat (make-hash-table :test 'equal))
Learn spam: (spam-stat-process-spam-directory "~/Mail/mail/spam")
Learn non-spam: (spam-stat-process-non-spam-directory "~/Mail/mail/misc")
Repeat for any other non-spam group you need...
Reduce table size: (spam-stat-reduce-size)
Save table: (spam-stat-save)
@end smallexample

@node Various Various
@section Various Various
@cindex mode lines
@cindex highlights

@table @code

@item gnus-home-directory
@vindex gnus-home-directory
All Gnus file and directory variables will be initialized from this
variable, which defaults to @file{~/}.

@item gnus-directory
@vindex gnus-directory
Most Gnus storage file and directory variables will be initialized from
this variable, which defaults to the @env{SAVEDIR} environment
variable, or @file{~/News/} if that variable isn't set.

Note that gnus is mostly loaded when the @file{.gnus.el} file is read.
This means that other directory variables that are initialized from this
variable won't be set properly if you set this variable in
@file{.gnus.el}.  Set this variable in @file{.emacs} instead.

@item gnus-default-directory
@vindex gnus-default-directory
Not related to the above variable at all---this variable says what the
default directory of all Gnus buffers should be.  If you issue commands
like @kbd{C-x C-f}, the prompt you'll get starts in the current buffer's
default directory.  If this variable is @code{nil} (which is the
default), the default directory will be the default directory of the
buffer you were in when you started Gnus.

@item gnus-verbose
@vindex gnus-verbose
This variable is an integer between zero and ten.  The higher the value,
the more messages will be displayed.  If this variable is zero, Gnus
will never flash any messages, if it is seven (which is the default),
most important messages will be shown, and if it is ten, Gnus won't ever
shut up, but will flash so many messages it will make your head swim.

@item gnus-verbose-backends
@vindex gnus-verbose-backends
This variable works the same way as @code{gnus-verbose}, but it applies
to the Gnus back ends instead of Gnus proper.

@item nnheader-max-head-length
@vindex nnheader-max-head-length
When the back ends read straight heads of articles, they all try to read
as little as possible.  This variable (default 4096) specifies
the absolute max length the back ends will try to read before giving up
on finding a separator line between the head and the body.  If this
variable is @code{nil}, there is no upper read bound.  If it is
@code{t}, the back ends won't try to read the articles piece by piece,
but read the entire articles.  This makes sense with some versions of
@code{ange-ftp} or @code{efs}.

@item nnheader-head-chop-length
@vindex nnheader-head-chop-length
This variable (default 2048) says how big a piece of each article to
read when doing the operation described above.

@item nnheader-file-name-translation-alist
@vindex nnheader-file-name-translation-alist
@cindex file names
@cindex invalid characters in file names
@cindex characters in file names
This is an alist that says how to translate characters in file names.
For instance, if @samp{:} is invalid as a file character in file names
on your system (you OS/2 user you), you could say something like:

@lisp
@group
(setq nnheader-file-name-translation-alist
      '((?: . ?_)))
@end group
@end lisp

In fact, this is the default value for this variable on OS/2 and MS
Windows (phooey) systems.

@item gnus-hidden-properties
@vindex gnus-hidden-properties
This is a list of properties to use to hide ``invisible'' text.  It is
@code{(invisible t intangible t)} by default on most systems, which
makes invisible text invisible and intangible.

@item gnus-parse-headers-hook
@vindex gnus-parse-headers-hook
A hook called before parsing headers.  It can be used, for instance, to
gather statistics on the headers fetched, or perhaps you'd like to prune
some headers.  I don't see why you'd want that, though.

@item gnus-shell-command-separator
@vindex gnus-shell-command-separator
String used to separate two shell commands.  The default is @samp{;}.

@item gnus-invalid-group-regexp
@vindex gnus-invalid-group-regexp

Regexp to match ``invalid'' group names when querying user for a group
name.  The default value catches some @strong{really} invalid group
names who could possibly mess up Gnus internally (like allowing
@samp{:} in a group name, which is normally used to delimit method and
group).

@acronym{IMAP} users might want to allow @samp{/} in group names though.


@end table

@node The End
@chapter The End

Well, that's the manual---you can get on with your life now.  Keep in
touch.  Say hello to your cats from me.

My @strong{ghod}---I just can't stand goodbyes.  Sniffle.

Ol' Charles Reznikoff said it pretty well, so I leave the floor to him:

@quotation
@strong{Te Deum}

@sp 1
Not because of victories @*
I sing,@*
having none,@*
but for the common sunshine,@*
the breeze,@*
the largess of the spring.

@sp 1
Not for victory@*
but for the day's work done@*
as well as I was able;@*
not for a seat upon the dais@*
but at the common table.@*
@end quotation


@node Appendices
@chapter Appendices

@menu
* XEmacs::                      Requirements for installing under XEmacs.
* History::                     How Gnus got where it is today.
* On Writing Manuals::          Why this is not a beginner's guide.
* Terminology::                 We use really difficult, like, words here.
* Customization::               Tailoring Gnus to your needs.
* Troubleshooting::             What you might try if things do not work.
* Gnus Reference Guide::        Rilly, rilly technical stuff.
* Emacs for Heathens::          A short introduction to Emacsian terms.
* Frequently Asked Questions::  The Gnus FAQ
@end menu


@node XEmacs
@section XEmacs
@cindex XEmacs
@cindex installing under XEmacs

XEmacs is distributed as a collection of packages.  You should install
whatever packages the Gnus XEmacs package requires.  The current
requirements are @samp{gnus}, @samp{w3}, @samp{mh-e},
@samp{mailcrypt}, @samp{rmail}, @samp{eterm}, @samp{mail-lib},
@samp{xemacs-base}, @samp{sh-script} and @samp{fsf-compat}.  The
@samp{misc-games} package is required for Morse decoding.


@node History
@section History

@cindex history
@sc{gnus} was written by Masanobu @sc{Umeda}.  When autumn crept up in
'94, Lars Magne Ingebrigtsen grew bored and decided to rewrite Gnus.

If you want to investigate the person responsible for this outrage,
you can point your (feh!) web browser to
@uref{http://quimby.gnus.org/}.  This is also the primary
distribution point for the new and spiffy versions of Gnus, and is
known as The Site That Destroys Newsrcs And Drives People Mad.

During the first extended alpha period of development, the new Gnus was
called ``(ding) Gnus''.  @dfn{(ding)} is, of course, short for
@dfn{ding is not Gnus}, which is a total and utter lie, but who cares?
(Besides, the ``Gnus'' in this abbreviation should probably be
pronounced ``news'' as @sc{Umeda} intended, which makes it a more
appropriate name, don't you think?)

In any case, after spending all that energy on coming up with a new and
spunky name, we decided that the name was @emph{too} spunky, so we
renamed it back again to ``Gnus''.  But in mixed case.  ``Gnus'' vs.
``@sc{gnus}''.  New vs. old.

@menu
* Gnus Versions::               What Gnus versions have been released.
* Other Gnus Versions::         Other Gnus versions that also have been released.
* Why?::                        What's the point of Gnus?
* Compatibility::               Just how compatible is Gnus with @sc{gnus}?
* Conformity::                  Gnus tries to conform to all standards.
* Emacsen::                     Gnus can be run on a few modern Emacsen.
* Gnus Development::            How Gnus is developed.
* Contributors::                Oodles of people.
* New Features::                Pointers to some of the new stuff in Gnus.
@end menu


@node Gnus Versions
@subsection Gnus Versions
@cindex ding Gnus
@cindex September Gnus
@cindex Red Gnus
@cindex Quassia Gnus
@cindex Pterodactyl Gnus
@cindex Oort Gnus
@cindex No Gnus
@cindex Gnus versions

The first ``proper'' release of Gnus 5 was done in November 1995 when it
was included in the Emacs 19.30 distribution (132 (ding) Gnus releases
plus 15 Gnus 5.0 releases).

In May 1996 the next Gnus generation (aka. ``September Gnus'' (after 99
releases)) was released under the name ``Gnus 5.2'' (40 releases).

On July 28th 1996 work on Red Gnus was begun, and it was released on
January 25th 1997 (after 84 releases) as ``Gnus 5.4'' (67 releases).

On September 13th 1997, Quassia Gnus was started and lasted 37 releases.
If was released as ``Gnus 5.6'' on March 8th 1998 (46 releases).

Gnus 5.6 begat Pterodactyl Gnus on August 29th 1998 and was released as
``Gnus 5.8'' (after 99 releases and a CVS repository) on December 3rd
1999.

On the 26th of October 2000, Oort Gnus was begun.

If you happen upon a version of Gnus that has a prefixed name --
``(ding) Gnus'', ``September Gnus'', ``Red Gnus'', ``Quassia Gnus'',
``Pterodactyl Gnus'', ``Oort Gnus'' -- don't panic.  Don't let it know
that you're frightened.  Back away.  Slowly.  Whatever you do, don't
run.  Walk away, calmly, until you're out of its reach.  Find a proper
released version of Gnus and snuggle up to that instead.


@node Other Gnus Versions
@subsection Other Gnus Versions
@cindex Semi-gnus

In addition to the versions of Gnus which have had their releases
coordinated by Lars, one major development has been Semi-gnus from
Japan.  It's based on a library called @acronym{SEMI}, which provides
@acronym{MIME} capabilities.

These Gnusae are based mainly on Gnus 5.6 and Pterodactyl Gnus.
Collectively, they are called ``Semi-gnus'', and different strains are
called T-gnus, ET-gnus, Nana-gnus and Chaos.  These provide powerful
@acronym{MIME} and multilingualization things, especially important for
Japanese users.


@node Why?
@subsection Why?

What's the point of Gnus?

I want to provide a ``rad'', ``happening'', ``way cool'' and ``hep''
newsreader, that lets you do anything you can think of.  That was my
original motivation, but while working on Gnus, it has become clear to
me that this generation of newsreaders really belong in the stone age.
Newsreaders haven't developed much since the infancy of the net.  If the
volume continues to rise with the current rate of increase, all current
newsreaders will be pretty much useless.  How do you deal with
newsgroups that have thousands of new articles each day?  How do you
keep track of millions of people who post?

Gnus offers no real solutions to these questions, but I would very much
like to see Gnus being used as a testing ground for new methods of
reading and fetching news.  Expanding on @sc{Umeda}-san's wise decision
to separate the newsreader from the back ends, Gnus now offers a simple
interface for anybody who wants to write new back ends for fetching mail
and news from different sources.  I have added hooks for customizations
everywhere I could imagine it being useful.  By doing so, I'm inviting
every one of you to explore and invent.

May Gnus never be complete.  @kbd{C-u 100 M-x all-hail-emacs} and
@kbd{C-u 100 M-x all-hail-xemacs}.


@node Compatibility
@subsection Compatibility

@cindex compatibility
Gnus was designed to be fully compatible with @sc{gnus}.  Almost all key
bindings have been kept.  More key bindings have been added, of course,
but only in one or two obscure cases have old bindings been changed.

Our motto is:
@quotation
@cartouche
@center In a cloud bones of steel.
@end cartouche
@end quotation

All commands have kept their names.  Some internal functions have changed
their names.

The @code{gnus-uu} package has changed drastically.  @xref{Decoding
Articles}.

One major compatibility question is the presence of several summary
buffers.  All variables relevant while reading a group are
buffer-local to the summary buffer they belong in.  Although many
important variables have their values copied into their global
counterparts whenever a command is executed in the summary buffer, this
change might lead to incorrect values being used unless you are careful.

All code that relies on knowledge of @sc{gnus} internals will probably
fail.  To take two examples: Sorting @code{gnus-newsrc-alist} (or
changing it in any way, as a matter of fact) is strictly verboten.  Gnus
maintains a hash table that points to the entries in this alist (which
speeds up many functions), and changing the alist directly will lead to
peculiar results.

@cindex hilit19
@cindex highlighting
Old hilit19 code does not work at all.  In fact, you should probably
remove all hilit code from all Gnus hooks
(@code{gnus-group-prepare-hook} and @code{gnus-summary-prepare-hook}).
Gnus provides various integrated functions for highlighting.  These are
faster and more accurate.  To make life easier for everybody, Gnus will
by default remove all hilit calls from all hilit hooks.  Uncleanliness!
Away!

Packages like @code{expire-kill} will no longer work.  As a matter of
fact, you should probably remove all old @sc{gnus} packages (and other
code) when you start using Gnus.  More likely than not, Gnus already
does what you have written code to make @sc{gnus} do.  (Snicker.)

Even though old methods of doing things are still supported, only the
new methods are documented in this manual.  If you detect a new method of
doing something while reading this manual, that does not mean you have
to stop doing it the old way.

Gnus understands all @sc{gnus} startup files.

@kindex M-x gnus-bug
@findex gnus-bug
@cindex reporting bugs
@cindex bugs
Overall, a casual user who hasn't written much code that depends on
@sc{gnus} internals should suffer no problems.  If problems occur,
please let me know by issuing that magic command @kbd{M-x gnus-bug}.

@vindex gnus-bug-create-help-buffer
If you are in the habit of sending bug reports @emph{very} often, you
may find the helpful help buffer annoying after a while.  If so, set
@code{gnus-bug-create-help-buffer} to @code{nil} to avoid having it pop
up at you.


@node Conformity
@subsection Conformity

No rebels without a clue here, ma'am.  We conform to all standards known
to (wo)man.  Except for those standards and/or conventions we disagree
with, of course.

@table @strong

@item RFC (2)822
@cindex RFC 822
@cindex RFC 2822
There are no known breaches of this standard.

@item RFC 1036
@cindex RFC 1036
There are no known breaches of this standard, either.

@item Son-of-RFC 1036
@cindex Son-of-RFC 1036
We do have some breaches to this one.

@table @emph

@item X-Newsreader
@itemx User-Agent
These are considered to be ``vanity headers'', while I consider them
to be consumer information.  After seeing so many badly formatted
articles coming from @code{tin} and @code{Netscape} I know not to use
either of those for posting articles.  I would not have known that if
it wasn't for the @code{X-Newsreader} header.
@end table

@item USEFOR
@cindex USEFOR
USEFOR is an IETF working group writing a successor to RFC 1036, based
on Son-of-RFC 1036.  They have produced a number of drafts proposing
various changes to the format of news articles.  The Gnus towers will
look into implementing the changes when the draft is accepted as an RFC.

@item MIME - RFC 2045-2049 etc
@cindex @acronym{MIME}
All the various @acronym{MIME} RFCs are supported.

@item Disposition Notifications - RFC 2298
Message Mode is able to request notifications from the receiver.

@item PGP - RFC 1991 and RFC 2440
@cindex RFC 1991
@cindex RFC 2440
RFC 1991 is the original @acronym{PGP} message specification,
published as an informational RFC.  RFC 2440 was the follow-up, now
called Open PGP, and put on the Standards Track.  Both document a
non-@acronym{MIME} aware @acronym{PGP} format.  Gnus supports both
encoding (signing and encryption) and decoding (verification and
decryption).

@item PGP/MIME - RFC 2015/3156
RFC 2015 (superseded by 3156 which references RFC 2440 instead of RFC
1991) describes the @acronym{MIME}-wrapping around the RF 1991/2440 format.
Gnus supports both encoding and decoding.

@item S/MIME - RFC 2633
RFC 2633 describes the @acronym{S/MIME} format.

@item IMAP - RFC 1730/2060, RFC 2195, RFC 2086, RFC 2359, RFC 2595, RFC 1731
RFC 1730 is @acronym{IMAP} version 4, updated somewhat by RFC 2060
(@acronym{IMAP} 4 revision 1).  RFC 2195 describes CRAM-MD5
authentication for @acronym{IMAP}.  RFC 2086 describes access control
lists (ACLs) for @acronym{IMAP}.  RFC 2359 describes a @acronym{IMAP}
protocol enhancement.  RFC 2595 describes the proper @acronym{TLS}
integration (STARTTLS) with @acronym{IMAP}.  RFC 1731 describes the
GSSAPI/Kerberos4 mechanisms for @acronym{IMAP}.

@end table

If you ever notice Gnus acting non-compliant with regards to the texts
mentioned above, don't hesitate to drop a note to Gnus Towers and let us
know.


@node Emacsen
@subsection Emacsen
@cindex Emacsen
@cindex XEmacs
@cindex Mule
@cindex Emacs

Gnus should work on:

@itemize @bullet

@item
Emacs 20.3 and up.

@item
XEmacs 21.1.1 and up.

@end itemize

This Gnus version will absolutely not work on any Emacsen older than
that.  Not reliably, at least.  Older versions of Gnus may work on older
Emacs versions.  However, T-gnus does support ``Mule 2.3 based on Emacs
19.34'' and possibly the versions of XEmacs prior to 21.1.1, e.g. 20.4.
See the file ``README'' in the T-gnus distribution for more details.

There are some vague differences between Gnus on the various
platforms---XEmacs features more graphics (a logo and a toolbar)---but
other than that, things should look pretty much the same under all
Emacsen.


@node Gnus Development
@subsection Gnus Development

Gnus is developed in a two-phased cycle.  The first phase involves much
discussion on the @samp{ding@@gnus.org} mailing list, where people
propose changes and new features, post patches and new back ends.  This
phase is called the @dfn{alpha} phase, since the Gnusae released in this
phase are @dfn{alpha releases}, or (perhaps more commonly in other
circles) @dfn{snapshots}.  During this phase, Gnus is assumed to be
unstable and should not be used by casual users.  Gnus alpha releases
have names like ``Red Gnus'' and ``Quassia Gnus''.

After futzing around for 50-100 alpha releases, Gnus is declared
@dfn{frozen}, and only bug fixes are applied.  Gnus loses the prefix,
and is called things like ``Gnus 5.6.32'' instead.  Normal people are
supposed to be able to use these, and these are mostly discussed on the
@samp{gnu.emacs.gnus} newsgroup.

@cindex Incoming*
@vindex mail-source-delete-incoming
Some variable defaults differ between alpha Gnusae and released Gnusae.
In particular, @code{mail-source-delete-incoming} defaults to @code{nil} in
alpha Gnusae and @code{t} in released Gnusae.  This is to prevent
lossage of mail if an alpha release hiccups while handling the mail.

The division of discussion between the ding mailing list and the Gnus
newsgroup is not purely based on publicity concerns.  It's true that
having people write about the horrible things that an alpha Gnus release
can do (sometimes) in a public forum may scare people off, but more
importantly, talking about new experimental features that have been
introduced may confuse casual users.  New features are frequently
introduced, fiddled with, and judged to be found wanting, and then
either discarded or totally rewritten.  People reading the mailing list
usually keep up with these rapid changes, while people on the newsgroup
can't be assumed to do so.



@node Contributors
@subsection Contributors
@cindex contributors

The new Gnus version couldn't have been done without the help of all the
people on the (ding) mailing list.  Every day for over a year I have
gotten billions of nice bug reports from them, filling me with joy,
every single one of them.  Smooches.  The people on the list have been
tried beyond endurance, what with my ``oh, that's a neat idea <type
type>, yup, I'll release it right away <ship off> no wait, that doesn't
work at all <type type>, yup, I'll ship that one off right away <ship
off> no, wait, that absolutely does not work'' policy for releases.
Micro$oft---bah.  Amateurs.  I'm @emph{much} worse.  (Or is that
``worser''? ``much worser''?  ``worsest''?)

I would like to take this opportunity to thank the Academy for@dots{}  oops,
wrong show.

@itemize @bullet

@item
Masanobu @sc{Umeda}---the writer of the original @sc{gnus}.

@item
Shenghuo Zhu---uudecode.el, mm-uu.el, rfc1843.el, webmail.el,
nnwarchive and many, many other things connected with @acronym{MIME} and
other types of en/decoding, as well as general bug fixing, new
functionality and stuff.

@item
Per Abrahamsen---custom, scoring, highlighting and @sc{soup} code (as
well as numerous other things).

@item
Luis Fernandes---design and graphics.

@item
Joe Reiss---creator of the smiley faces.

@item
Justin Sheehy---the @acronym{FAQ} maintainer.

@item
Erik Naggum---help, ideas, support, code and stuff.

@item
Wes Hardaker---@file{gnus-picon.el} and the manual section on
@dfn{picons} (@pxref{Picons}).

@item
Kim-Minh Kaplan---further work on the picon code.

@item
Brad Miller---@file{gnus-gl.el} and the GroupLens manual section
(@pxref{GroupLens}).

@item
Sudish Joseph---innumerable bug fixes.

@item
Ilja Weis---@file{gnus-topic.el}.

@item
Steven L. Baur---lots and lots and lots of bugs detections and fixes.

@item
Vladimir Alexiev---the refcard and reference booklets.

@item
Felix Lee & Jamie Zawinski---I stole some pieces from the XGnus
distribution by Felix Lee and JWZ.

@item
Scott Byer---@file{nnfolder.el} enhancements & rewrite.

@item
Peter Mutsaers---orphan article scoring code.

@item
Ken Raeburn---POP mail support.

@item
Hallvard B Furuseth---various bits and pieces, especially dealing with
.newsrc files.

@item
Brian Edmonds---@file{gnus-bbdb.el}.

@item
David Moore---rewrite of @file{nnvirtual.el} and many other things.

@item
Kevin Davidson---came up with the name @dfn{ding}, so blame him.

@item
François Pinard---many, many interesting and thorough bug reports, as
well as autoconf support.

@end itemize

This manual was proof-read by Adrian Aichner, with Ricardo Nassif, Mark
Borges, and Jost Krieger proof-reading parts of the manual.

The following people have contributed many patches and suggestions:

Christopher Davis,
Andrew Eskilsson,
Kai Grossjohann,
Kevin Greiner,
Jesper Harder,
Paul Jarc,
Simon Josefsson,
David Kågedal,
Richard Pieri,
Fabrice Popineau,
Daniel Quinlan,
Michael Shields,
Reiner Steib,
Jason L. Tibbitts, III,
Jack Vinson,
Katsumi Yamaoka, @c Yamaoka
and
Teodor Zlatanov.

Also thanks to the following for patches and stuff:

Jari Aalto,
Adrian Aichner,
Vladimir Alexiev,
Russ Allbery,
Peter Arius,
Matt Armstrong,
Marc Auslander,
Miles Bader,
Alexei V. Barantsev,
Frank Bennett,
Robert Bihlmeyer,
Chris Bone,
Mark Borges,
Mark Boyns,
Lance A. Brown,
Rob Browning,
Kees de Bruin,
Martin Buchholz,
Joe Buehler,
Kevin Buhr,
Alastair Burt,
Joao Cachopo,
Zlatko Calusic,
Massimo Campostrini,
Castor,
David Charlap,
Dan Christensen,
Kevin Christian,
Jae-you Chung, @c ?
James H. Cloos, Jr.,
Laura Conrad,
Michael R. Cook,
Glenn Coombs,
Andrew J. Cosgriff,
Neil Crellin,
Frank D. Cringle,
Geoffrey T. Dairiki,
Andre Deparade,
Ulrik Dickow,
Dave Disser,
Rui-Tao Dong, @c ?
Joev Dubach,
Michael Welsh Duggan,
Dave Edmondson,
Paul Eggert,
Mark W. Eichin,
Karl Eichwalder,
Enami Tsugutomo, @c Enami
Michael Ernst,
Luc Van Eycken,
Sam Falkner,
Nelson Jose dos Santos Ferreira,
Sigbjorn Finne,
Sven Fischer,
Paul Fisher,
Decklin Foster,
Gary D. Foster,
Paul Franklin,
Guy Geens,
Arne Georg Gleditsch,
David S. Goldberg,
Michelangelo Grigni,
Dale Hagglund,
D. Hall,
Magnus Hammerin,
Kenichi Handa, @c Handa
Raja R. Harinath,
Yoshiki Hayashi, @c Hayashi
P. E. Jareth Hein,
Hisashige Kenji, @c Hisashige
Scott Hofmann,
Marc Horowitz,
Gunnar Horrigmo,
Richard Hoskins,
Brad Howes,
Miguel de Icaza,
François Felix Ingrand,
Tatsuya Ichikawa, @c Ichikawa
Ishikawa Ichiro, @c Ishikawa
Lee Iverson,
Iwamuro Motonori, @c Iwamuro
Rajappa Iyer,
Andreas Jaeger,
Adam P. Jenkins,
Randell Jesup,
Fred Johansen,
Gareth Jones,
Greg Klanderman,
Karl Kleinpaste,
Michael Klingbeil,
Peter Skov Knudsen,
Shuhei Kobayashi, @c Kobayashi
Petr Konecny,
Koseki Yoshinori, @c Koseki
Thor Kristoffersen,
Jens Lautenbacher,
Martin Larose,
Seokchan Lee, @c Lee
Joerg Lenneis,
Carsten Leonhardt,
James LewisMoss,
Christian Limpach,
Markus Linnala,
Dave Love,
Mike McEwan,
Tonny Madsen,
Shlomo Mahlab,
Nat Makarevitch,
Istvan Marko,
David Martin,
Jason R. Mastaler,
Gordon Matzigkeit,
Timo Metzemakers,
Richard Mlynarik,
Lantz Moore,
Morioka Tomohiko, @c Morioka
Erik Toubro Nielsen,
Hrvoje Niksic,
Andy Norman,
Fred Oberhauser,
C. R. Oldham,
Alexandre Oliva,
Ken Olstad,
Masaharu Onishi, @c Onishi
Hideki Ono, @c Ono
Ettore Perazzoli,
William Perry,
Stephen Peters,
Jens-Ulrik Holger Petersen,
Ulrich Pfeifer,
Matt Pharr,
Andy Piper,
John McClary Prevost,
Bill Pringlemeir,
Mike Pullen,
Jim Radford,
Colin Rafferty,
Lasse Rasinen,
Lars Balker Rasmussen,
Joe Reiss,
Renaud Rioboo,
Roland B. Roberts,
Bart Robinson,
Christian von Roques,
Markus Rost,
Jason Rumney,
Wolfgang Rupprecht,
Jay Sachs,
Dewey M. Sasser,
Conrad Sauerwald,
Loren Schall,
Dan Schmidt,
Ralph Schleicher,
Philippe Schnoebelen,
Andreas Schwab,
Randal L. Schwartz,
Danny Siu,
Matt Simmons,
Paul D. Smith,
Jeff Sparkes,
Toby Speight,
Michael Sperber,
Darren Stalder,
Richard Stallman,
Greg Stark,
Sam Steingold,
Paul Stevenson,
Jonas Steverud,
Paul Stodghill,
Kiyokazu Suto, @c Suto
Kurt Swanson,
Samuel Tardieu,
Teddy,
Chuck Thompson,
Tozawa Akihiko, @c Tozawa
Philippe Troin,
James Troup,
Trung Tran-Duc,
Jack Twilley,
Aaron M. Ucko,
Aki Vehtari,
Didier Verna,
Vladimir Volovich,
Jan Vroonhof,
Stefan Waldherr,
Pete Ware,
Barry A. Warsaw,
Christoph Wedler,
Joe Wells,
Lee Willis,
and
Lloyd Zusman.


For a full overview of what each person has done, the ChangeLogs
included in the Gnus alpha distributions should give ample reading
(550kB and counting).

Apologies to everybody that I've forgotten, of which there are many, I'm
sure.

Gee, that's quite a list of people.  I guess that must mean that there
actually are people who are using Gnus.  Who'd'a thunk it!


@node New Features
@subsection New Features
@cindex new features

@menu
* ding Gnus::                   New things in Gnus 5.0/5.1, the first new Gnus.
* September Gnus::              The Thing Formally Known As Gnus 5.2/5.3.
* Red Gnus::                    Third time best---Gnus 5.4/5.5.
* Quassia Gnus::                Two times two is four, or Gnus 5.6/5.7.
* Pterodactyl Gnus::            Pentad also starts with P, AKA Gnus 5.8/5.9.
* Oort Gnus::                   It's big.  It's far out.  Gnus 5.10.
@end menu

These lists are, of course, just @emph{short} overviews of the
@emph{most} important new features.  No, really.  There are tons more.
Yes, we have feeping creaturism in full effect.

@node ding Gnus
@subsubsection (ding) Gnus

New features in Gnus 5.0/5.1:

@itemize @bullet

@item
The look of all buffers can be changed by setting format-like variables
(@pxref{Group Buffer Format} and @pxref{Summary Buffer Format}).

@item
Local spool and several @acronym{NNTP} servers can be used at once
(@pxref{Select Methods}).

@item
You can combine groups into virtual groups (@pxref{Virtual Groups}).

@item
You can read a number of different mail formats (@pxref{Getting Mail}).
All the mail back ends implement a convenient mail expiry scheme
(@pxref{Expiring Mail}).

@item
Gnus can use various strategies for gathering threads that have lost
their roots (thereby gathering loose sub-threads into one thread) or it
can go back and retrieve enough headers to build a complete thread
(@pxref{Customizing Threading}).

@item
Killed groups can be displayed in the group buffer, and you can read
them as well (@pxref{Listing Groups}).

@item
Gnus can do partial group updates---you do not have to retrieve the
entire active file just to check for new articles in a few groups
(@pxref{The Active File}).

@item
Gnus implements a sliding scale of subscribedness to groups
(@pxref{Group Levels}).

@item
You can score articles according to any number of criteria
(@pxref{Scoring}).  You can even get Gnus to find out how to score
articles for you (@pxref{Adaptive Scoring}).

@item
Gnus maintains a dribble buffer that is auto-saved the normal Emacs
manner, so it should be difficult to lose much data on what you have
read if your machine should go down (@pxref{Auto Save}).

@item
Gnus now has its own startup file (@file{~/.gnus.el}) to avoid
cluttering up the @file{.emacs} file.

@item
You can set the process mark on both groups and articles and perform
operations on all the marked items (@pxref{Process/Prefix}).

@item
You can grep through a subset of groups and create a group from the
results (@pxref{Kibozed Groups}).

@item
You can list subsets of groups according to, well, anything
(@pxref{Listing Groups}).

@item
You can browse foreign servers and subscribe to groups from those
servers (@pxref{Browse Foreign Server}).

@item
Gnus can fetch articles, asynchronously, on a second connection to the
server (@pxref{Asynchronous Fetching}).

@item
You can cache articles locally (@pxref{Article Caching}).

@item
The uudecode functions have been expanded and generalized
(@pxref{Decoding Articles}).

@item
You can still post uuencoded articles, which was a little-known feature
of @sc{gnus}' past (@pxref{Uuencoding and Posting}).

@item
Fetching parents (and other articles) now actually works without
glitches (@pxref{Finding the Parent}).

@item
Gnus can fetch @acronym{FAQ}s and group descriptions (@pxref{Group Information}).

@item
Digests (and other files) can be used as the basis for groups
(@pxref{Document Groups}).

@item
Articles can be highlighted and customized (@pxref{Customizing
Articles}).

@item
URLs and other external references can be buttonized (@pxref{Article
Buttons}).

@item
You can do lots of strange stuff with the Gnus window & frame
configuration (@pxref{Window Layout}).

@item
You can click on buttons instead of using the keyboard
(@pxref{Buttons}).

@end itemize


@node September Gnus
@subsubsection September Gnus

@iftex
@iflatex
\gnusfig{-28cm}{0cm}{\epsfig{figure=ps/september,height=20cm}}
@end iflatex
@end iftex

New features in Gnus 5.2/5.3:

@itemize @bullet

@item
A new message composition mode is used.  All old customization variables
for @code{mail-mode}, @code{rnews-reply-mode} and @code{gnus-msg} are
now obsolete.

@item
Gnus is now able to generate @dfn{sparse} threads---threads where
missing articles are represented by empty nodes (@pxref{Customizing
Threading}).

@lisp
(setq gnus-build-sparse-threads 'some)
@end lisp

@item
Outgoing articles are stored on a special archive server
(@pxref{Archived Messages}).

@item
Partial thread regeneration now happens when articles are
referred.

@item
Gnus can make use of GroupLens predictions (@pxref{GroupLens}).

@item
Picons (personal icons) can be displayed under XEmacs (@pxref{Picons}).

@item
A @code{trn}-like tree buffer can be displayed (@pxref{Tree Display}).

@lisp
(setq gnus-use-trees t)
@end lisp

@item
An @code{nn}-like pick-and-read minor mode is available for the summary
buffers (@pxref{Pick and Read}).

@lisp
(add-hook 'gnus-summary-mode-hook 'gnus-pick-mode)
@end lisp

@item
In binary groups you can use a special binary minor mode (@pxref{Binary
Groups}).

@item
Groups can be grouped in a folding topic hierarchy (@pxref{Group
Topics}).

@lisp
(add-hook 'gnus-group-mode-hook 'gnus-topic-mode)
@end lisp

@item
Gnus can re-send and bounce mail (@pxref{Summary Mail Commands}).

@item
Groups can now have a score, and bubbling based on entry frequency
is possible (@pxref{Group Score}).

@lisp
(add-hook 'gnus-summary-exit-hook 'gnus-summary-bubble-group)
@end lisp

@item
Groups can be process-marked, and commands can be performed on
groups of groups (@pxref{Marking Groups}).

@item
Caching is possible in virtual groups.

@item
@code{nndoc} now understands all kinds of digests, mail boxes, rnews
news batches, ClariNet briefs collections, and just about everything
else (@pxref{Document Groups}).

@item
Gnus has a new back end (@code{nnsoup}) to create/read SOUP packets
(@pxref{SOUP}).

@item
The Gnus cache is much faster.

@item
Groups can be sorted according to many criteria (@pxref{Sorting
Groups}).

@item
New group parameters have been introduced to set list-addresses and
expiry times (@pxref{Group Parameters}).

@item
All formatting specs allow specifying faces to be used
(@pxref{Formatting Fonts}).

@item
There are several more commands for setting/removing/acting on process
marked articles on the @kbd{M P} submap (@pxref{Setting Process Marks}).

@item
The summary buffer can be limited to show parts of the available
articles based on a wide range of criteria.  These commands have been
bound to keys on the @kbd{/} submap (@pxref{Limiting}).

@item
Articles can be made persistent with the @kbd{*} command
(@pxref{Persistent Articles}).

@item
All functions for hiding article elements are now toggles.

@item
Article headers can be buttonized (@pxref{Article Washing}).

@item
All mail back ends support fetching articles by @code{Message-ID}.

@item
Duplicate mail can now be treated properly (@pxref{Duplicates}).

@item
All summary mode commands are available directly from the article
buffer (@pxref{Article Keymap}).

@item
Frames can be part of @code{gnus-buffer-configuration} (@pxref{Window
Layout}).

@item
Mail can be re-scanned by a daemonic process (@pxref{Daemons}).
@iftex
@iflatex
\marginpar[\mbox{}\hfill\epsfig{figure=ps/fseptember,height=5cm}]{\epsfig{figure=ps/fseptember,height=5cm}}
@end iflatex
@end iftex

@item
Gnus can make use of NoCeM files to weed out spam (@pxref{NoCeM}).

@lisp
(setq gnus-use-nocem t)
@end lisp

@item
Groups can be made permanently visible (@pxref{Listing Groups}).

@lisp
(setq gnus-permanently-visible-groups "^nnml:")
@end lisp

@item
Many new hooks have been introduced to make customizing easier.

@item
Gnus respects the @code{Mail-Copies-To} header.

@item
Threads can be gathered by looking at the @code{References} header
(@pxref{Customizing Threading}).

@lisp
(setq gnus-summary-thread-gathering-function
      'gnus-gather-threads-by-references)
@end lisp

@item
Read articles can be stored in a special backlog buffer to avoid
refetching (@pxref{Article Backlog}).

@lisp
(setq gnus-keep-backlog 50)
@end lisp

@item
A clean copy of the current article is always stored in a separate
buffer to allow easier treatment.

@item
Gnus can suggest where to save articles (@pxref{Saving Articles}).

@item
Gnus doesn't have to do as much prompting when saving (@pxref{Saving
Articles}).

@lisp
(setq gnus-prompt-before-saving t)
@end lisp

@item
@code{gnus-uu} can view decoded files asynchronously while fetching
articles (@pxref{Other Decode Variables}).

@lisp
(setq gnus-uu-grabbed-file-functions 'gnus-uu-grab-view)
@end lisp

@item
Filling in the article buffer now works properly on cited text
(@pxref{Article Washing}).

@item
Hiding cited text adds buttons to toggle hiding, and how much
cited text to hide is now customizable (@pxref{Article Hiding}).

@lisp
(setq gnus-cited-lines-visible 2)
@end lisp

@item
Boring headers can be hidden (@pxref{Article Hiding}).

@item
Default scoring values can now be set from the menu bar.

@item
Further syntax checking of outgoing articles have been added.

@end itemize


@node Red Gnus
@subsubsection Red Gnus

New features in Gnus 5.4/5.5:

@iftex
@iflatex
\gnusfig{-5.5cm}{-4cm}{\epsfig{figure=ps/red,height=20cm}}
@end iflatex
@end iftex

@itemize @bullet

@item
@file{nntp.el} has been totally rewritten in an asynchronous fashion.

@item
Article prefetching functionality has been moved up into
Gnus (@pxref{Asynchronous Fetching}).

@item
Scoring can now be performed with logical operators like @code{and},
@code{or}, @code{not}, and parent redirection (@pxref{Advanced
Scoring}).

@item
Article washing status can be displayed in the
article mode line (@pxref{Misc Article}).

@item
@file{gnus.el} has been split into many smaller files.

@item
Suppression of duplicate articles based on Message-ID can be done
(@pxref{Duplicate Suppression}).

@lisp
(setq gnus-suppress-duplicates t)
@end lisp

@item
New variables for specifying what score and adapt files are to be
considered home score and adapt files (@pxref{Home Score File}) have
been added.

@item
@code{nndoc} was rewritten to be easily extendable (@pxref{Document
Server Internals}).

@item
Groups can inherit group parameters from parent topics (@pxref{Topic
Parameters}).

@item
Article editing has been revamped and is now actually usable.

@item
Signatures can be recognized in more intelligent fashions
(@pxref{Article Signature}).

@item
Summary pick mode has been made to look more @code{nn}-like.  Line
numbers are displayed and the @kbd{.} command can be used to pick
articles (@code{Pick and Read}).

@item
Commands for moving the @file{.newsrc.eld} from one server to
another have been added (@pxref{Changing Servers}).

@item
There's a way now to specify that ``uninteresting'' fields be suppressed
when generating lines in buffers (@pxref{Advanced Formatting}).

@item
Several commands in the group buffer can be undone with @kbd{C-M-_}
(@pxref{Undo}).

@item
Scoring can be done on words using the new score type @code{w}
(@pxref{Score File Format}).

@item
Adaptive scoring can be done on a Subject word-by-word basis
(@pxref{Adaptive Scoring}).

@lisp
(setq gnus-use-adaptive-scoring '(word))
@end lisp

@item
Scores can be decayed (@pxref{Score Decays}).

@lisp
(setq gnus-decay-scores t)
@end lisp

@item
Scoring can be performed using a regexp on the Date header.  The Date is
normalized to compact ISO 8601 format first (@pxref{Score File Format}).

@item
A new command has been added to remove all data on articles from
the native server (@pxref{Changing Servers}).

@item
A new command for reading collections of documents
(@code{nndoc} with @code{nnvirtual} on top) has been added---@kbd{C-M-d}
(@pxref{Really Various Summary Commands}).

@item
Process mark sets can be pushed and popped (@pxref{Setting Process
Marks}).

@item
A new mail-to-news back end makes it possible to post even when the @acronym{NNTP}
server doesn't allow posting (@pxref{Mail-To-News Gateways}).

@item
A new back end for reading searches from Web search engines
(@dfn{DejaNews}, @dfn{Alta Vista}, @dfn{InReference}) has been added
(@pxref{Web Searches}).

@item
Groups inside topics can now be sorted using the standard sorting
functions, and each topic can be sorted independently (@pxref{Topic
Sorting}).

@item
Subsets of the groups can be sorted independently (@code{Sorting
Groups}).

@item
Cached articles can be pulled into the groups (@pxref{Summary Generation
Commands}).
@iftex
@iflatex
\marginpar[\mbox{}\hfill\epsfig{figure=ps/fred,width=3cm}]{\epsfig{figure=ps/fred,width=3cm}}
@end iflatex
@end iftex

@item
Score files are now applied in a more reliable order (@pxref{Score
Variables}).

@item
Reports on where mail messages end up can be generated (@pxref{Splitting
Mail}).

@item
More hooks and functions have been added to remove junk from incoming
mail before saving the mail (@pxref{Washing Mail}).

@item
Emphasized text can be properly fontisized:

@end itemize


@node Quassia Gnus
@subsubsection Quassia Gnus

New features in Gnus 5.6:

@itemize @bullet

@item
New functionality for using Gnus as an offline newsreader has been
added.  A plethora of new commands and modes have been added.
@xref{Gnus Unplugged}, for the full story.

@item
The @code{nndraft} back end has returned, but works differently than
before.  All Message buffers are now also articles in the @code{nndraft}
group, which is created automatically.

@item
@code{gnus-alter-header-function} can now be used to alter header
values.

@item
@code{gnus-summary-goto-article} now accept Message-ID's.

@item
A new Message command for deleting text in the body of a message
outside the region: @kbd{C-c C-v}.

@item
You can now post to component group in @code{nnvirtual} groups with
@kbd{C-u C-c C-c}.

@item
 @code{nntp-rlogin-program}---new variable to ease customization.

@item
@code{C-u C-c C-c} in @code{gnus-article-edit-mode} will now inhibit
re-highlighting of the article buffer.

@item
New element in @code{gnus-boring-article-headers}---@code{long-to}.

@item
@kbd{M-i} symbolic prefix command.  @xref{Symbolic Prefixes}, for
details.

@item
@kbd{L} and @kbd{I} in the summary buffer now take the symbolic prefix
@kbd{a} to add the score rule to the @file{all.SCORE} file.

@item
@code{gnus-simplify-subject-functions} variable to allow greater
control over simplification.

@item
@kbd{A T}---new command for fetching the current thread.

@item
@kbd{/ T}---new command for including the current thread in the
limit.

@item
@kbd{M-RET} is a new Message command for breaking cited text.

@item
@samp{\\1}-expressions are now valid in @code{nnmail-split-methods}.

@item
The @code{custom-face-lookup} function has been removed.
If you used this function in your initialization files, you must
rewrite them to use @code{face-spec-set} instead.

@item
Canceling now uses the current select method.  Symbolic prefix
@kbd{a} forces normal posting method.

@item
New command to translate M******** sm*rtq**t*s into proper
text---@kbd{W d}.

@item
For easier debugging of @code{nntp}, you can set
@code{nntp-record-commands} to a non-@code{nil} value.

@item
@code{nntp} now uses @file{~/.authinfo}, a @file{.netrc}-like file, for
controlling where and how to send @sc{authinfo} to @acronym{NNTP} servers.

@item
A command for editing group parameters from the summary buffer
has been added.

@item
A history of where mails have been split is available.

@item
A new article date command has been added---@code{article-date-iso8601}.

@item
Subjects can be simplified when threading by setting
@code{gnus-score-thread-simplify}.

@item
A new function for citing in Message has been
added---@code{message-cite-original-without-signature}.

@item
@code{article-strip-all-blank-lines}---new article command.

@item
A new Message command to kill to the end of the article has
been added.

@item
A minimum adaptive score can be specified by using the
@code{gnus-adaptive-word-minimum} variable.

@item
The ``lapsed date'' article header can be kept continually
updated by the @code{gnus-start-date-timer} command.

@item
Web listserv archives can be read with the @code{nnlistserv} back end.

@item
Old dejanews archives can now be read by @code{nnweb}.

@end itemize

@node Pterodactyl Gnus
@subsubsection Pterodactyl Gnus

New features in Gnus 5.8:

@itemize @bullet

@item
The mail-fetching functions have changed.  See the manual for the
many details.  In particular, all procmail fetching variables are gone.

If you used procmail like in

@lisp
(setq nnmail-use-procmail t)
(setq nnmail-spool-file 'procmail)
(setq nnmail-procmail-directory "~/mail/incoming/")
(setq nnmail-procmail-suffix "\\.in")
@end lisp

this now has changed to

@lisp
(setq mail-sources
      '((directory :path "~/mail/incoming/"
                   :suffix ".in")))
@end lisp

@xref{Mail Source Specifiers}.

@item
Gnus is now a @acronym{MIME}-capable reader.  This affects many parts of
Gnus, and adds a slew of new commands.  See the manual for details.

@item
Gnus has also been multilingualized.  This also affects too
many parts of Gnus to summarize here, and adds many new variables.

@item
@code{gnus-auto-select-first} can now be a function to be
called to position point.

@item
The user can now decide which extra headers should be included in
summary buffers and @acronym{NOV} files.

@item
@code{gnus-article-display-hook} has been removed.  Instead, a number
of variables starting with @code{gnus-treat-} have been added.

@item
The Gnus posting styles have been redone again and now works in a
subtly different manner.

@item
New web-based back ends have been added: @code{nnslashdot},
@code{nnwarchive} and @code{nnultimate}.  nnweb has been revamped,
again, to keep up with ever-changing layouts.

@item
Gnus can now read @acronym{IMAP} mail via @code{nnimap}.

@end itemize

@node Oort Gnus
@subsubsection Oort Gnus
@cindex Oort Gnus

New features in Gnus 5.10:

@itemize @bullet

@item
The revised Gnus @acronym{FAQ} is included in the manual,
@xref{Frequently Asked Questions}.

@item
Upgrading from previous (stable) version if you have used Oort.

If you have tried Oort (the unstable Gnus branch leading to this
release) but went back to a stable version, be careful when upgrading to
this version.  In particular, you will probably want to remove all
@file{.marks} (nnml) and @file{.mrk} (nnfolder) files, so that flags are
read from your @file{.newsrc.eld} instead of from the
@file{.marks}/@file{.mrk} file where this release store flags.  See a
later entry for more information about marks.  Note that downgrading
isn't save in general.

@item
Article Buttons

More buttons for URLs, mail addresses, Message-IDs, Info links, man
pages and Emacs or Gnus related references.  @xref{Article Buttons}.  The
variables @code{gnus-button-@var{*}-level} can be used to control the
appearance of all article buttons.  @xref{Article Button Levels}.

@item
Dired integration

@code{gnus-dired-minor-mode} installs key bindings in dired buffers to send
a file as an attachment (@kbd{C-c C-a}), open a file using the appropriate
mailcap entry (@kbd{C-c C-l}), and print a file using the mailcap entry
(@kbd{C-c P}).  It is enabled with
@lisp
(add-hook 'dired-mode-hook 'turn-on-gnus-dired-mode)
@end lisp

@item
Gnus can display RSS newsfeeds as a newsgroup.  @xref{RSS}.

@item
Single-part yenc encoded attachments can be decoded.

@item
Picons

The picons code has been reimplemented to work in GNU Emacs---some of
the previous options have been removed or renamed.

Picons are small ``personal icons'' representing users, domain and
newsgroups, which can be displayed in the Article buffer.
@xref{Picons}.

@item
If the new option @code{gnus-treat-body-boundary} is non-@code{nil}, a
boundary line is drawn at the end of the headers.

@item
Retrieval of charters and control messages

There are new commands for fetching newsgroup charters (@kbd{H c}) and
control messages (@kbd{H C}).

@item
Delayed articles

You can delay the sending of a message with @kbd{C-c C-j} in the Message
buffer.  The messages are delivered at specified time.  This is useful
for sending yourself reminders.  @xref{Delayed Articles}.

@item
If @code{auto-compression-mode} is enabled, attachments are automatically
decompressed when activated.

@item
If the new option @code{nnml-use-compressed-files} is non-@code{nil},
the nnml back end allows compressed message files.

@item
Signed article headers (X-PGP-Sig) can be verified with @kbd{W p}.

@item
The Summary Buffer uses an arrow in the fringe to indicate the current
article.  Use @code{(setq gnus-summary-display-arrow nil)} to disable it.

@item
Warn about email replies to news

Do you often find yourself replying to news by email by mistake?  Then
the new option @code{gnus-confirm-mail-reply-to-news} is just the thing for
you.

@item
If the new option @code{gnus-summary-display-while-building} is
non-@code{nil}, the summary buffer is shown and updated as it's being
built.

@item
The new @code{recent} mark @samp{.} indicates newly arrived messages (as
opposed to old but unread messages).

@item
The new option @code{gnus-gcc-mark-as-read} automatically marks
Gcc articles as read.

@item
The nndoc back end now supports mailman digests and exim bounces.

@item
Gnus supports RFC 2369 mailing list headers, and adds a number of
related commands in mailing list groups.  @xref{Mailing List}.

@item
The Date header can be displayed in a format that can be read aloud
in English.  @xref{Article Date}.

@item
The envelope sender address can be customized when using Sendmail.
@xref{Mail Variables, Mail Variables,, message, Message Manual}.

@item
diffs are automatically highlighted in groups matching
@code{mm-uu-diff-groups-regexp}

@item
@acronym{TLS} wrapper shipped with Gnus

@acronym{TLS}/@acronym{SSL} is now supported in @acronym{IMAP} and
@acronym{NNTP} via @file{tls.el} and GNUTLS.  The old
@acronym{TLS}/@acronym{SSL} support via (external third party)
@file{ssl.el} and OpenSSL still works.

@item
New @file{make.bat} for compiling and installing Gnus under MS Windows

Use @file{make.bat} if you want to install Gnus under MS Windows, the
first argument to the batch-program should be the directory where
@file{xemacs.exe} respectively @file{emacs.exe} is located, iff you want
to install Gnus after compiling it, give @file{make.bat} @code{/copy} as
the second parameter.

@file{make.bat} has been rewritten from scratch, it now features
automatic recognition of XEmacs and GNU Emacs, generates
@file{gnus-load.el}, checks if errors occur while compilation and
generation of info files and reports them at the end of the build
process.  It now uses @code{makeinfo} if it is available and falls
back to @file{infohack.el} otherwise.  @file{make.bat} should now
install all files which are necessary to run Gnus and be generally a
complete replacement for the @code{configure; make; make install}
cycle used under Unix systems.

The new @file{make.bat} makes @file{make-x.bat} superfluous, so it has
been removed.

@item
Support for non-@acronym{ASCII} domain names

Message supports non-@acronym{ASCII} domain names in From:, To: and
Cc: and will query you whether to perform encoding when you try to
send a message.  The variable @code{message-use-idna} controls this.
Gnus will also decode non-@acronym{ASCII} domain names in From:, To:
and Cc: when you view a message.  The variable @code{gnus-use-idna}
controls this.

@item
Better handling of Microsoft citation styles

Gnus now tries to recognize the mangled header block that some Microsoft
mailers use to indicate that the rest of the message is a citation, even
though it is not quoted in any way.  The variable
@code{gnus-cite-unsightly-citation-regexp} matches the start of these
citations.

@item
@code{gnus-article-skip-boring}

If you set @code{gnus-article-skip-boring} to @code{t}, then Gnus will
not scroll down to show you a page that contains only boring text,
which by default means cited text and signature.  You can customize
what is skippable using @code{gnus-article-boring-faces}.

This feature is especially useful if you read many articles that
consist of a little new content at the top with a long, untrimmed
message cited below.

@item
The format spec @code{%C} for positioning point has changed to @code{%*}.

@item
The new variable @code{gnus-parameters} can be used to set group parameters.

Earlier this was done only via @kbd{G p} (or @kbd{G c}), which stored
the parameters in @file{~/.newsrc.eld}, but via this variable you can
enjoy the powers of customize, and simplified backups since you set the
variable in @file{~/.emacs} instead of @file{~/.newsrc.eld}.  The
variable maps regular expressions matching group names to group
parameters, a'la:
@lisp
(setq gnus-parameters
      '(("mail\\..*"
         (gnus-show-threads nil)
         (gnus-use-scoring nil))
        ("^nnimap:\\(foo.bar\\)$"
         (to-group . "\\1"))))
@end lisp

@item
Smileys (@samp{:-)}, @samp{;-)} etc) are now iconized for Emacs too.

Put @code{(setq gnus-treat-display-smileys nil)} in @file{~/.emacs} to
disable it.

@item
Gnus no longer generate the Sender: header automatically.

Earlier it was generated iff the user configurable email address was
different from the Gnus guessed default user address.  As the guessing
algorithm is rarely correct these days, and (more controversially) the
only use of the Sender: header was to check if you are entitled to
cancel/supersede news (which is now solved by Cancel Locks instead,
see another entry), generation of the header has been disabled by
default.  See the variables @code{message-required-headers},
@code{message-required-news-headers}, and
@code{message-required-mail-headers}.

@item
Features from third party @file{message-utils.el} added to @file{message.el}.

Message now asks if you wish to remove @samp{(was: <old subject>)} from
subject lines (see @code{message-subject-trailing-was-query}).  @kbd{C-c
M-m} and @kbd{C-c M-f} inserts markers indicating included text.
@kbd{C-c C-f a} adds a X-No-Archive: header.  @kbd{C-c C-f x} inserts
appropriate headers and a note in the body for cross-postings and
followups (see the variables @code{message-cross-post-@var{*}}).

@item
References and X-Draft-Headers are no longer generated when you start
composing messages and @code{message-generate-headers-first} is
@code{nil}.

@item
Improved anti-spam features.

Gnus is now able to take out spam from your mail and news streams
using a wide variety of programs and filter rules.  Among the supported
methods are RBL blocklists, bogofilter and white/blacklists.  Hooks
for easy use of external packages such as SpamAssassin and Hashcash
are also new.  @xref{Thwarting Email Spam}.

@item
Easy inclusion of X-Faces headers.

@item
Face headers handling.

@item
In the summary buffer, the new command @kbd{/ N} inserts new messages
and @kbd{/ o} inserts old messages.

@item
Gnus decodes morse encoded messages if you press @kbd{W m}.

@item
Unread count correct in nnimap groups.

The estimated number of unread articles in the group buffer should now
be correct for nnimap groups.  This is achieved by calling
@code{nnimap-fixup-unread-after-getting-new-news} from the
@code{gnus-setup-news-hook} (called on startup) and
@code{gnus-after-getting-new-news-hook}. (called after getting new
mail).  If you have modified those variables from the default, you may
want to add @code{nnimap-fixup-unread-after-getting-new-news} again.  If
you were happy with the estimate and want to save some (minimal) time
when getting new mail, remove the function.

@item
Group Carbon Copy (GCC) quoting

To support groups that contains SPC and other weird characters, groups
are quoted before they are placed in the Gcc: header.  This means
variables such as @code{gnus-message-archive-group} should no longer
contain quote characters to make groups containing SPC work.  Also, if
you are using the string @samp{nnml:foo, nnml:bar} (indicating Gcc
into two groups) you must change it to return the list
@code{("nnml:foo" "nnml:bar")}, otherwise the Gcc: line will be quoted
incorrectly.  Note that returning the string @samp{nnml:foo, nnml:bar}
was incorrect earlier, it just didn't generate any problems since it
was inserted directly.

@item
@file{~/News/overview/} not used.

As a result of the following change, the @file{~/News/overview/}
directory is not used any more.  You can safely delete the entire
hierarchy.

@item
@code{gnus-agent}

The Gnus Agent has seen a major updated and is now enabled by default,
and all nntp and nnimap servers from @code{gnus-select-method} and
@code{gnus-secondary-select-method} are agentized by default.  Earlier
only the server in @code{gnus-select-method} was agentized by the
default, and the agent was disabled by default.  When the agent is
enabled, headers are now also retrieved from the Agent cache instead
of the back ends when possible.  Earlier this only happened in the
unplugged state.  You can enroll or remove servers with @kbd{J a} and
@kbd{J r} in the server buffer.  Gnus will not download articles into
the Agent cache, unless you instruct it to do so, though, by using
@kbd{J u} or @kbd{J s} from the Group buffer.  You revert to the old
behaviour of having the Agent disabled with @code{(setq gnus-agent
nil)}.  Note that putting @code{(gnus-agentize)} in @file{~/.gnus.el}
is not needed any more.

@item
@code{gnus-summary-line-format}

The default value changed to @samp{%U%R%z%I%(%[%4L: %-23,23f%]%)
%s\n}.  Moreover @code{gnus-extra-headers},
@code{nnmail-extra-headers} and @code{gnus-ignored-from-addresses}
changed their default so that the users name will be replaced by the
recipient's name or the group name posting to for @acronym{NNTP}
groups.

@item
@file{deuglify.el} (@code{gnus-article-outlook-deuglify-article})

A new file from Raymond Scholz @email{rscholz@@zonix.de} for deuglifying
broken Outlook (Express) articles.

@item
@code{(require 'gnus-load)}

If you use a stand-alone Gnus distribution, you'd better add
@code{(require 'gnus-load)} into your @file{~/.emacs} after adding the Gnus
lisp directory into load-path.

File @file{gnus-load.el} contains autoload commands, functions and variables,
some of which may not be included in distributions of Emacsen.

@item
@code{gnus-slave-unplugged}

A new command which starts Gnus offline in slave mode.

@item
@code{message-insinuate-rmail}

Adding @code{(message-insinuate-rmail)} and @code{(setq
mail-user-agent 'gnus-user-agent)} in @file{.emacs} convinces Rmail to
compose, reply and forward messages in message-mode, where you can
enjoy the power of @acronym{MML}.

@item
@code{message-minibuffer-local-map}

The line below enables BBDB in resending a message:
@lisp
(define-key message-minibuffer-local-map [(tab)]
  'bbdb-complete-name)
@end lisp

@item
Externalizing and deleting of attachments.

If @code{gnus-gcc-externalize-attachments} or
@code{message-fcc-externalize-attachments} is non-@code{nil}, attach
local files as external parts.

The command @code{gnus-mime-save-part-and-strip} (bound to @kbd{C-o}
on @acronym{MIME} buttons) saves a part and replaces the part with an
external one.  @code{gnus-mime-delete-part} (bound to @kbd{d} on
@acronym{MIME} buttons) removes a part.  It works only on back ends
that support editing.

@item
@code{gnus-default-charset}

The default value is determined from the
@code{current-language-environment} variable, instead of
@code{iso-8859-1}.  Also the @samp{.*} item in
@code{gnus-group-charset-alist} is removed.

@item
@code{gnus-posting-styles}

Add a new format of match like
@lisp
((header "to" "larsi.*org")
 (Organization "Somewhere, Inc."))
@end lisp
The old format like the lines below is obsolete, but still accepted.
@lisp
(header "to" "larsi.*org"
        (Organization "Somewhere, Inc."))
@end lisp

@item
@code{message-ignored-news-headers} and @code{message-ignored-mail-headers}

@samp{X-Draft-From} and @samp{X-Gnus-Agent-Meta-Information} have been
added into these two variables.  If you customized those, perhaps you
need add those two headers too.

@item
Gnus reads the @acronym{NOV} and articles in the Agent if plugged.

If one reads an article while plugged, and the article already exists
in the Agent, it won't get downloaded once more.  @code{(setq
gnus-agent-cache nil)} reverts to the old behavior.

@item
Gnus supports the ``format=flowed'' (RFC 2646) parameter.  On
composing messages, it is enabled by @code{use-hard-newlines}.
Decoding format=flowed was present but not documented in earlier
versions.

@item
Gnus supports the generation of RFC 2298 Disposition Notification requests.

This is invoked with the @kbd{C-c M-n} key binding from message mode.

@item
Gnus supports Maildir groups.

Gnus includes a new back end @file{nnmaildir.el}.  @xref{Maildir}.

@item
Printing capabilities are enhanced.

Gnus supports Muttprint natively with @kbd{O P} from the Summary and
Article buffers.  Also, each individual @acronym{MIME} part can be
printed using @kbd{p} on the @acronym{MIME} button.

@item
Message supports the Importance: (RFC 2156) header.

In the message buffer, @kbd{C-c C-f C-i} or @kbd{C-c C-u} cycles through
the valid values.

@item
Gnus supports Cancel Locks in News.

This means a header @samp{Cancel-Lock} is inserted in news posting.  It is
used to determine if you wrote an article or not (for canceling and
superseding).  Gnus generates a random password string the first time
you post a message, and saves it in your @file{~/.emacs} using the Custom
system.  While the variable is called @code{canlock-password}, it is not
security sensitive data.  Publishing your canlock string on the web
will not allow anyone to be able to anything she could not already do.
The behaviour can be changed by customizing @code{message-insert-canlock}.

@item
Gnus supports server-side mail filtering using Sieve.

Sieve rules can be added as Group Parameters for groups, and the
complete Sieve script is generated using @kbd{D g} from the Group
buffer, and then uploaded to the server using @kbd{C-c C-l} in the
generated Sieve buffer.  @xref{Sieve Commands}, and the new Sieve
manual @ref{Top, , Top, sieve, Emacs Sieve}.

@item
Extended format specs.

Format spec @samp{%&user-date;} is added into
@code{gnus-summary-line-format-alist}.  Also, user defined extended
format specs are supported.  The extended format specs look like
@samp{%u&foo;}, which invokes function
@code{gnus-user-format-function-@var{foo}}.  Because @samp{&} is used as the
escape character, old user defined format @samp{%u&} is no longer supported.

@item
@kbd{/ *} (@code{gnus-summary-limit-include-cached}) is rewritten.

It was aliased to @kbd{Y c}
(@code{gnus-summary-insert-cached-articles}).  The new function filters
out other articles.

@item Some limiting commands accept a @kbd{C-u} prefix to negate the match.

If @kbd{C-u} is used on subject, author or extra headers, i.e., @kbd{/
s}, @kbd{/ a}, and @kbd{/ x}
(@code{gnus-summary-limit-to-@{subject,author,extra@}}) respectively, the
result will be to display all articles that do not match the expression.

@item
Group names are treated as UTF-8 by default.

This is supposedly what USEFOR wanted to migrate to.  See
@code{gnus-group-name-charset-group-alist} and
@code{gnus-group-name-charset-method-alist} for customization.

@item
The nnml and nnfolder back ends store marks for each groups.

This makes it possible to take backup of nnml/nnfolder servers/groups
separately of @file{~/.newsrc.eld}, while preserving marks.  It also
makes it possible to share articles and marks between users (without
sharing the @file{~/.newsrc.eld} file) within e.g. a department.  It
works by storing the marks stored in @file{~/.newsrc.eld} in a per-group
file @file{.marks} (for nnml) and @file{@var{groupname}.mrk} (for
nnfolder, named @var{groupname}).  If the nnml/nnfolder is moved to
another machine, Gnus will automatically use the @file{.marks} or
@file{.mrk} file instead of the information in @file{~/.newsrc.eld}.
The new server variables @code{nnml-marks-is-evil} and
@code{nnfolder-marks-is-evil} can be used to disable this feature.

@item
The menu bar item (in Group and Summary buffer) named ``Misc'' has
been renamed to ``Gnus''.

@item
The menu bar item (in Message mode) named ``@acronym{MML}'' has been
renamed to ``Attachments''.  Note that this menu also contains security
related stuff, like signing and encryption (@pxref{Security, Security,,
message, Message Manual}).

@item
@code{gnus-group-charset-alist} and
@code{gnus-group-ignored-charsets-alist}.

The regexps in these variables are compared with full group names
instead of real group names in 5.8.  Users who customize these
variables should change those regexps accordingly.  For example:
@lisp
("^han\\>" euc-kr) -> ("\\(^\\|:\\)han\\>" euc-kr)
@end lisp

@item
Gnus supports @acronym{PGP} (RFC 1991/2440), @acronym{PGP/MIME} (RFC
2015/3156) and @acronym{S/MIME} (RFC 2630-2633).

It needs an external @acronym{S/MIME} and OpenPGP implementation, but no
additional Lisp libraries.  This add several menu items to the
Attachments menu, and @kbd{C-c RET} key bindings, when composing
messages.  This also obsoletes @code{gnus-article-hide-pgp-hook}.

@item
Gnus inlines external parts (message/external).

@item
@acronym{MML} (Mime compose) prefix changed from @kbd{M-m} to @kbd{C-c
C-m}.

This change was made to avoid conflict with the standard binding of
@code{back-to-indentation}, which is also useful in message mode.

@item
The default for @code{message-forward-show-mml} changed to symbol @code{best}.

The behaviour for the @code{best} value is to show @acronym{MML} (i.e.,
convert to @acronym{MIME}) when appropriate.  @acronym{MML} will not be
used when forwarding signed or encrypted messages, as the conversion
invalidate the digital signature.
@end itemize

@iftex

@page
@node The Manual
@section The Manual
@cindex colophon
@cindex manual

This manual was generated from a TeXinfo file and then run through
either @code{texi2dvi}
@iflatex
or my own home-brewed TeXinfo to \LaTeX\ transformer,
and then run through @code{latex} and @code{dvips}
@end iflatex
to get what you hold in your hands now.

The following conventions have been used:

@enumerate

@item
This is a @samp{string}

@item
This is a @kbd{keystroke}

@item
This is a @file{file}

@item
This is a @code{symbol}

@end enumerate

So if I were to say ``set @code{flargnoze} to @samp{yes}'', that would
mean:

@lisp
(setq flargnoze "yes")
@end lisp

If I say ``set @code{flumphel} to @code{yes}'', that would mean:

@lisp
(setq flumphel 'yes)
@end lisp

@samp{yes} and @code{yes} are two @emph{very} different things---don't
ever get them confused.

@iflatex
@c @head
Of course, everything in this manual is of vital interest, so you should
read it all.  Several times.  However, if you feel like skimming the
manual, look for that gnu head you should see in the margin over
there---it means that what's being discussed is of more importance than
the rest of the stuff.  (On the other hand, if everything is infinitely
important, how can anything be more important than that?  Just one more
of the mysteries of this world, I guess.)
@end iflatex

@end iftex


@node On Writing Manuals
@section On Writing Manuals

I guess most manuals are written after-the-fact; documenting a program
that's already there.  This is not how this manual is written.  When
implementing something, I write the manual entry for that something
straight away.  I then see that it's difficult to explain the
functionality, so I write how it's supposed to be, and then I change the
implementation.  Writing the documentation and writing the code goes
hand in hand.

This, of course, means that this manual has no, or little, flow.  It
documents absolutely everything in Gnus, but often not where you're
looking for it.  It is a reference manual, and not a guide to how to get
started with Gnus.

That would be a totally different book, that should be written using the
reference manual as source material.  It would look quite differently.


@page
@node Terminology
@section Terminology

@cindex terminology
@table @dfn

@item news
@cindex news
This is what you are supposed to use this thing for---reading news.
News is generally fetched from a nearby @acronym{NNTP} server, and is
generally publicly available to everybody.  If you post news, the entire
world is likely to read just what you have written, and they'll all
snigger mischievously.  Behind your back.

@item mail
@cindex mail
Everything that's delivered to you personally is mail.  Some news/mail
readers (like Gnus) blur the distinction between mail and news, but
there is a difference.  Mail is private.  News is public.  Mailing is
not posting, and replying is not following up.

@item reply
@cindex reply
Send a mail to the person who has written what you are reading.

@item follow up
@cindex follow up
Post an article to the current newsgroup responding to the article you
are reading.

@item back end
@cindex back end
Gnus considers mail and news to be mostly the same, really.  The only
difference is how to access the actual articles.  News articles are
commonly fetched via the protocol @acronym{NNTP}, whereas mail
messages could be read from a file on the local disk.  The internal
architecture of Gnus thus comprises a ``front end'' and a number of
``back ends''.  Internally, when you enter a group (by hitting
@key{RET}, say), you thereby invoke a function in the front end in
Gnus.  The front end then ``talks'' to a back end and says things like
``Give me the list of articles in the foo group'' or ``Show me article
number 4711''.

So a back end mainly defines either a protocol (the @code{nntp} back
end accesses news via @acronym{NNTP}, the @code{nnimap} back end
accesses mail via @acronym{IMAP}) or a file format and directory
layout (the @code{nnspool} back end accesses news via the common
``spool directory'' format, the @code{nnml} back end access mail via a
file format and directory layout that's quite similar).

Gnus does not handle the underlying media, so to speak---this is all
done by the back ends.  A back end is a collection of functions to
access the articles.

However, sometimes the term ``back end'' is also used where ``server''
would have been more appropriate.  And then there is the term ``select
method'' which can mean either.  The Gnus terminology can be quite
confusing.

@item native
@cindex native
Gnus will always use one method (and back end) as the @dfn{native}, or
default, way of getting news.

@item foreign
@cindex foreign
You can also have any number of foreign groups active at the same time.
These are groups that use non-native non-secondary back ends for getting
news.

@item secondary
@cindex secondary
Secondary back ends are somewhere half-way between being native and being
foreign, but they mostly act like they are native.

@item article
@cindex article
A message that has been posted as news.

@item mail message
@cindex mail message
A message that has been mailed.

@item message
@cindex message
A mail message or news article

@item head
@cindex head
The top part of a message, where administrative information (etc.) is
put.

@item body
@cindex body
The rest of an article.  Everything not in the head is in the
body.

@item header
@cindex header
A line from the head of an article.

@item headers
@cindex headers
A collection of such lines, or a collection of heads.  Or even a
collection of @acronym{NOV} lines.

@item @acronym{NOV}
@cindex @acronym{NOV}
When Gnus enters a group, it asks the back end for the headers of all
unread articles in the group.  Most servers support the News OverView
format, which is more compact and much faster to read and parse than the
normal @sc{head} format.

@item level
@cindex levels
Each group is subscribed at some @dfn{level} or other (1-9).  The ones
that have a lower level are ``more'' subscribed than the groups with a
higher level.  In fact, groups on levels 1-5 are considered
@dfn{subscribed}; 6-7 are @dfn{unsubscribed}; 8 are @dfn{zombies}; and 9
are @dfn{killed}.  Commands for listing groups and scanning for new
articles will all use the numeric prefix as @dfn{working level}.

@item killed groups
@cindex killed groups
No information on killed groups is stored or updated, which makes killed
groups much easier to handle than subscribed groups.

@item zombie groups
@cindex zombie groups
Just like killed groups, only slightly less dead.

@item active file
@cindex active file
The news server has to keep track of what articles it carries, and what
groups exist.  All this information in stored in the active file, which
is rather large, as you might surmise.

@item bogus groups
@cindex bogus groups
A group that exists in the @file{.newsrc} file, but isn't known to the
server (i.e.,  it isn't in the active file), is a @emph{bogus group}.
This means that the group probably doesn't exist (any more).

@item activating
@cindex activating groups
The act of asking the server for info on a group and computing the
number of unread articles is called @dfn{activating the group}.
Un-activated groups are listed with @samp{*} in the group buffer.

@item server
@cindex server
A machine one can connect to and get news (or mail) from.

@item select method
@cindex select method
A structure that specifies the back end, the server and the virtual
server settings.

@item virtual server
@cindex virtual server
A named select method.  Since a select method defines all there is to
know about connecting to a (physical) server, taking the thing as a
whole is a virtual server.

@item washing
@cindex washing
Taking a buffer and running it through a filter of some sort.  The
result will (more often than not) be cleaner and more pleasing than the
original.

@item ephemeral groups
@cindex ephemeral groups
@cindex temporary groups
Most groups store data on what articles you have read.  @dfn{Ephemeral}
groups are groups that will have no data stored---when you exit the
group, it'll disappear into the aether.

@item solid groups
@cindex solid groups
This is the opposite of ephemeral groups.  All groups listed in the
group buffer are solid groups.

@item sparse articles
@cindex sparse articles
These are article placeholders shown in the summary buffer when
@code{gnus-build-sparse-threads} has been switched on.

@item threading
@cindex threading
To put responses to articles directly after the articles they respond
to---in a hierarchical fashion.

@item root
@cindex root
@cindex thread root
The first article in a thread is the root.  It is the ancestor of all
articles in the thread.

@item parent
@cindex parent
An article that has responses.

@item child
@cindex child
An article that responds to a different article---its parent.

@item digest
@cindex digest
A collection of messages in one file.  The most common digest format is
specified by RFC 1153.

@item splitting
@cindex splitting, terminolgy
@cindex mail sorting
@cindex mail filtering (splitting)
The action of sorting your emails according to certain rules. Sometimes
incorrectly called mail filtering.

@end table


@page
@node Customization
@section Customization
@cindex general customization

All variables are properly documented elsewhere in this manual.  This
section is designed to give general pointers on how to customize Gnus
for some quite common situations.

@menu
* Slow/Expensive Connection::   You run a local Emacs and get the news elsewhere.
* Slow Terminal Connection::    You run a remote Emacs.
* Little Disk Space::           You feel that having large setup files is icky.
* Slow Machine::                You feel like buying a faster machine.
@end menu


@node Slow/Expensive Connection
@subsection Slow/Expensive NNTP Connection

If you run Emacs on a machine locally, and get your news from a machine
over some very thin strings, you want to cut down on the amount of data
Gnus has to get from the @acronym{NNTP} server.

@table @code

@item gnus-read-active-file
Set this to @code{nil}, which will inhibit Gnus from requesting the
entire active file from the server.  This file is often v.  large.  You
also have to set @code{gnus-check-new-newsgroups} and
@code{gnus-check-bogus-newsgroups} to @code{nil} to make sure that Gnus
doesn't suddenly decide to fetch the active file anyway.

@item gnus-nov-is-evil
This one has to be @code{nil}.  If not, grabbing article headers from
the @acronym{NNTP} server will not be very fast.  Not all @acronym{NNTP} servers
support @sc{xover}; Gnus will detect this by itself.
@end table


@node Slow Terminal Connection
@subsection Slow Terminal Connection

Let's say you use your home computer for dialing up the system that runs
Emacs and Gnus.  If your modem is slow, you want to reduce (as much as
possible) the amount of data sent over the wires.

@table @code

@item gnus-auto-center-summary
Set this to @code{nil} to inhibit Gnus from re-centering the summary
buffer all the time.  If it is @code{vertical}, do only vertical
re-centering.  If it is neither @code{nil} nor @code{vertical}, do both
horizontal and vertical recentering.

@item gnus-visible-headers
Cut down on the headers included in the articles to the
minimum.  You can, in fact, make do without them altogether---most of the
useful data is in the summary buffer, anyway.  Set this variable to
@samp{^NEVVVVER} or @samp{From:}, or whatever you feel you need.

Set this hook to all the available hiding commands:
@lisp
(setq gnus-treat-hide-headers 'head
      gnus-treat-hide-signature t
      gnus-treat-hide-citation t)
@end lisp

@item gnus-use-full-window
By setting this to @code{nil}, you can make all the windows smaller.
While this doesn't really cut down much generally, it means that you
have to see smaller portions of articles before deciding that you didn't
want to read them anyway.

@item gnus-thread-hide-subtree
If this is non-@code{nil}, all threads in the summary buffer will be
hidden initially.


@item gnus-updated-mode-lines
If this is @code{nil}, Gnus will not put information in the buffer mode
lines, which might save some time.
@end table


@node Little Disk Space
@subsection Little Disk Space
@cindex disk space

The startup files can get rather large, so you may want to cut their
sizes a bit if you are running out of space.

@table @code

@item gnus-save-newsrc-file
If this is @code{nil}, Gnus will never save @file{.newsrc}---it will
only save @file{.newsrc.eld}.  This means that you will not be able to
use any other newsreaders than Gnus.  This variable is @code{t} by
default.

@item gnus-read-newsrc-file
If this is @code{nil}, Gnus will never read @file{.newsrc}---it will
only read @file{.newsrc.eld}.  This means that you will not be able to
use any other newsreaders than Gnus.  This variable is @code{t} by
default.

@item gnus-save-killed-list
If this is @code{nil}, Gnus will not save the list of dead groups.  You
should also set @code{gnus-check-new-newsgroups} to @code{ask-server}
and @code{gnus-check-bogus-newsgroups} to @code{nil} if you set this
variable to @code{nil}.  This variable is @code{t} by default.

@end table


@node Slow Machine
@subsection Slow Machine
@cindex slow machine

If you have a slow machine, or are just really impatient, there are a
few things you can do to make Gnus run faster.

Set @code{gnus-check-new-newsgroups} and
@code{gnus-check-bogus-newsgroups} to @code{nil} to make startup faster.

Set @code{gnus-show-threads}, @code{gnus-use-cross-reference} and
@code{gnus-nov-is-evil} to @code{nil} to make entering and exiting the
summary buffer faster.


@page
@node Troubleshooting
@section Troubleshooting
@cindex troubleshooting

Gnus works @emph{so} well straight out of the box---I can't imagine any
problems, really.

Ahem.

@enumerate

@item
Make sure your computer is switched on.

@item
Make sure that you really load the current Gnus version.  If you have
been running @sc{gnus}, you need to exit Emacs and start it up again before
Gnus will work.

@item
Try doing an @kbd{M-x gnus-version}.  If you get something that looks
like @samp{T-gnus 6.16.* (based on Gnus v5.10.*; for SEMI 1.1*, FLIM
1.1*)} you have the right files loaded.  If, on the other hand, you get
something like @samp{NNTP 3.x} or @samp{nntp flee}, you have some old
@file{.el} files lying around.  Delete these.

@item
Read the help group (@kbd{G h} in the group buffer) for a
@acronym{FAQ} and a how-to.

@item
@vindex max-lisp-eval-depth
Gnus works on many recursive structures, and in some extreme (and very
rare) cases Gnus may recurse down ``too deeply'' and Emacs will beep at
you.  If this happens to you, set @code{max-lisp-eval-depth} to 500 or
something like that.
@end enumerate

If all else fails, report the problem as a bug.

@cindex bugs
@cindex reporting bugs

@kindex M-x gnus-bug
@findex gnus-bug
If you find a bug in Gnus, you can report it with the @kbd{M-x gnus-bug}
command.  @kbd{M-x set-variable RET debug-on-error RET t RET}, and send
me the backtrace.  I will fix bugs, but I can only fix them if you send
me a precise description as to how to reproduce the bug.

You really can never be too detailed in a bug report.  Always use the
@kbd{M-x gnus-bug} command when you make bug reports, even if it creates
a 10Kb mail each time you use it, and even if you have sent me your
environment 500 times before.  I don't care.  I want the full info each
time.

It is also important to remember that I have no memory whatsoever.  If
you send a bug report, and I send you a reply, and then you just send
back ``No, it's not! Moron!'', I will have no idea what you are
insulting me about.  Always over-explain everything.  It's much easier
for all of us---if I don't have all the information I need, I will just
mail you and ask for more info, and everything takes more time.

If the problem you're seeing is very visual, and you can't quite explain
it, copy the Emacs window to a file (with @code{xwd}, for instance), put
it somewhere it can be reached, and include the URL of the picture in
the bug report.

@cindex patches
If you would like to contribute a patch to fix bugs or make
improvements, please produce the patch using @samp{diff -u}.

@cindex edebug
If you want to debug your problem further before reporting, possibly
in order to solve the problem yourself and send a patch, you can use
edebug.  Debugging Lisp code is documented in the Elisp manual
(@pxref{Debugging, , Debugging Lisp Programs, elisp, The GNU Emacs
Lisp Reference Manual}).  To get you started with edebug, consider if
you discover some weird behaviour when pressing @kbd{c}, the first
step is to do @kbd{C-h k c} and click on the hyperlink (Emacs only) in
the documentation buffer that leads you to the function definition,
then press @kbd{M-x edebug-defun RET} with point inside that function,
return to Gnus and press @kbd{c} to invoke the code.  You will be
placed in the lisp buffer and can single step using @kbd{SPC} and
evaluate expressions using @kbd{M-:} or inspect variables using
@kbd{C-h v}, abort execution with @kbd{q}, and resume execution with
@kbd{c} or @kbd{g}.

@cindex elp
@cindex profile
@cindex slow
Sometimes, a problem do not directly generate an elisp error but
manifests itself by causing Gnus to be very slow.  In these cases, you
can use @kbd{M-x toggle-debug-on-quit} and press @kbd{C-g} when things are
slow, and then try to analyze the backtrace (repeating the procedure
helps isolating the real problem areas).

A fancier approach is to use the elisp profiler, ELP.  The profiler is
(or should be) fully documented elsewhere, but to get you started
there are a few steps that need to be followed.  First, instrument the
part of Gnus you are interested in for profiling, e.g. @kbd{M-x
elp-instrument-package RET gnus} or @kbd{M-x elp-instrument-package
RET message}.  Then perform the operation that is slow and press
@kbd{M-x elp-results}.  You will then see which operations that takes
time, and can debug them further.  If the entire operation takes much
longer than the time spent in the slowest function in the profiler
output, you probably profiled the wrong part of Gnus.  To reset
profiling statistics, use @kbd{M-x elp-reset-all}.  @kbd{M-x
elp-restore-all} is supposed to remove profiling, but given the
complexities and dynamic code generation in Gnus, it might not always
work perfectly.

@cindex gnu.emacs.gnus
@cindex ding mailing list
If you just need help, you are better off asking on
@samp{gnu.emacs.gnus}.  I'm not very helpful.  You can also ask on
@email{ding@@gnus.org, the ding mailing list}.  Write to
@email{ding-request@@gnus.org} to subscribe.


@page
@node Gnus Reference Guide
@section Gnus Reference Guide

It is my hope that other people will figure out smart stuff that Gnus
can do, and that other people will write those smart things as well.  To
facilitate that I thought it would be a good idea to describe the inner
workings of Gnus.  And some of the not-so-inner workings, while I'm at
it.

You can never expect the internals of a program not to change, but I
will be defining (in some details) the interface between Gnus and its
back ends (this is written in stone), the format of the score files
(ditto), data structures (some are less likely to change than others)
and general methods of operation.

@menu
* Gnus Utility Functions::      Common functions and variable to use.
* Back End Interface::          How Gnus communicates with the servers.
* Score File Syntax::           A BNF definition of the score file standard.
* Headers::                     How Gnus stores headers internally.
* Ranges::                      A handy format for storing mucho numbers.
* Group Info::                  The group info format.
* Extended Interactive::        Symbolic prefixes and stuff.
* Emacs/XEmacs Code::           Gnus can be run under all modern Emacsen.
* Various File Formats::        Formats of files that Gnus use.
@end menu


@node Gnus Utility Functions
@subsection Gnus Utility Functions
@cindex Gnus utility functions
@cindex utility functions
@cindex functions
@cindex internal variables

When writing small functions to be run from hooks (and stuff), it's
vital to have access to the Gnus internal functions and variables.
Below is a list of the most common ones.

@table @code

@item gnus-newsgroup-name
@vindex gnus-newsgroup-name
This variable holds the name of the current newsgroup.

@item gnus-find-method-for-group
@findex gnus-find-method-for-group
A function that returns the select method for @var{group}.

@item gnus-group-real-name
@findex gnus-group-real-name
Takes a full (prefixed) Gnus group name, and returns the unprefixed
name.

@item gnus-group-prefixed-name
@findex gnus-group-prefixed-name
Takes an unprefixed group name and a select method, and returns the full
(prefixed) Gnus group name.

@item gnus-get-info
@findex gnus-get-info
Returns the group info list for @var{group}.

@item gnus-group-unread
@findex gnus-group-unread
The number of unread articles in @var{group}, or @code{t} if that is
unknown.

@item gnus-active
@findex gnus-active
The active entry for @var{group}.

@item gnus-set-active
@findex gnus-set-active
Set the active entry for @var{group}.

@item gnus-add-current-to-buffer-list
@findex gnus-add-current-to-buffer-list
Adds the current buffer to the list of buffers to be killed on Gnus
exit.

@item gnus-continuum-version
@findex gnus-continuum-version
Takes a Gnus version string as a parameter and returns a floating point
number.  Earlier versions will always get a lower number than later
versions.

@item gnus-group-read-only-p
@findex gnus-group-read-only-p
Says whether @var{group} is read-only or not.

@item gnus-news-group-p
@findex gnus-news-group-p
Says whether @var{group} came from a news back end.

@item gnus-ephemeral-group-p
@findex gnus-ephemeral-group-p
Says whether @var{group} is ephemeral or not.

@item gnus-server-to-method
@findex gnus-server-to-method
Returns the select method corresponding to @var{server}.

@item gnus-server-equal
@findex gnus-server-equal
Says whether two virtual servers are equal.

@item gnus-group-native-p
@findex gnus-group-native-p
Says whether @var{group} is native or not.

@item gnus-group-secondary-p
@findex gnus-group-secondary-p
Says whether @var{group} is secondary or not.

@item gnus-group-foreign-p
@findex gnus-group-foreign-p
Says whether @var{group} is foreign or not.

@item gnus-group-find-parameter
@findex gnus-group-find-parameter
Returns the parameter list of @var{group}.  If given a second parameter,
returns the value of that parameter for @var{group}.

@item gnus-group-set-parameter
@findex gnus-group-set-parameter
Takes three parameters; @var{group}, @var{parameter} and @var{value}.

@item gnus-narrow-to-body
@findex gnus-narrow-to-body
Narrows the current buffer to the body of the article.

@item gnus-check-backend-function
@findex gnus-check-backend-function
Takes two parameters, @var{function} and @var{group}.  If the back end
@var{group} comes from supports @var{function}, return non-@code{nil}.

@lisp
(gnus-check-backend-function "request-scan" "nnml:misc")
@result{} t
@end lisp

@item gnus-read-method
@findex gnus-read-method
Prompts the user for a select method.

@end table


@node Back End Interface
@subsection Back End Interface

Gnus doesn't know anything about @acronym{NNTP}, spools, mail or virtual
groups.  It only knows how to talk to @dfn{virtual servers}.  A virtual
server is a @dfn{back end} and some @dfn{back end variables}.  As examples
of the first, we have @code{nntp}, @code{nnspool} and @code{nnmbox}.  As
examples of the latter we have @code{nntp-port-number} and
@code{nnmbox-directory}.

When Gnus asks for information from a back end---say @code{nntp}---on
something, it will normally include a virtual server name in the
function parameters.  (If not, the back end should use the ``current''
virtual server.)  For instance, @code{nntp-request-list} takes a virtual
server as its only (optional) parameter.  If this virtual server hasn't
been opened, the function should fail.

Note that a virtual server name has no relation to some physical server
name.  Take this example:

@lisp
(nntp "odd-one"
      (nntp-address "ifi.uio.no")
      (nntp-port-number 4324))
@end lisp

Here the virtual server name is @samp{odd-one} while the name of
the physical server is @samp{ifi.uio.no}.

The back ends should be able to switch between several virtual servers.
The standard back ends implement this by keeping an alist of virtual
server environments that they pull down/push up when needed.

There are two groups of interface functions: @dfn{required functions},
which must be present, and @dfn{optional functions}, which Gnus will
always check for presence before attempting to call 'em.

All these functions are expected to return data in the buffer
@code{nntp-server-buffer} (@samp{ *nntpd*}), which is somewhat
unfortunately named, but we'll have to live with it.  When I talk about
@dfn{resulting data}, I always refer to the data in that buffer.  When I
talk about @dfn{return value}, I talk about the function value returned by
the function call.  Functions that fail should return @code{nil} as the
return value.

Some back ends could be said to be @dfn{server-forming} back ends, and
some might be said not to be.  The latter are back ends that generally
only operate on one group at a time, and have no concept of ``server''
---they have a group, and they deliver info on that group and nothing
more.

Gnus identifies each message by way of group name and article number.  A
few remarks about these article numbers might be useful.  First of all,
the numbers are positive integers.  Secondly, it is normally not
possible for later articles to ``re-use'' older article numbers without
confusing Gnus.  That is, if a group has ever contained a message
numbered 42, then no other message may get that number, or Gnus will get
mightily confused.@footnote{See the function
@code{nnchoke-request-update-info}, @ref{Optional Back End Functions}.}
Third, article numbers must be assigned in order of arrival in the
group; this is not necessarily the same as the date of the message.

The previous paragraph already mentions all the ``hard'' restrictions that
article numbers must fulfill.  But it seems that it might be useful to
assign @emph{consecutive} article numbers, for Gnus gets quite confused
if there are holes in the article numbering sequence.  However, due to
the ``no-reuse'' restriction, holes cannot be avoided altogether.  It's
also useful for the article numbers to start at 1 to avoid running out
of numbers as long as possible.

Note that by convention, back ends are named @code{nnsomething}, but
Gnus also comes with some @code{nnnotbackends}, such as
@file{nnheader.el}, @file{nnmail.el} and @file{nnoo.el}.

In the examples and definitions I will refer to the imaginary back end
@code{nnchoke}.

@cindex @code{nnchoke}

@menu
* Required Back End Functions::  Functions that must be implemented.
* Optional Back End Functions::  Functions that need not be implemented.
* Error Messaging::             How to get messages and report errors.
* Writing New Back Ends::       Extending old back ends.
* Hooking New Back Ends Into Gnus::  What has to be done on the Gnus end.
* Mail-like Back Ends::         Some tips on mail back ends.
@end menu


@node Required Back End Functions
@subsubsection Required Back End Functions

@table @code

@item (nnchoke-retrieve-headers ARTICLES &optional GROUP SERVER FETCH-OLD)

@var{articles} is either a range of article numbers or a list of
@code{Message-ID}s.  Current back ends do not fully support either---only
sequences (lists) of article numbers, and most back ends do not support
retrieval of @code{Message-ID}s.  But they should try for both.

The result data should either be HEADs or @acronym{NOV} lines, and the result
value should either be @code{headers} or @code{nov} to reflect this.
This might later be expanded to @code{various}, which will be a mixture
of HEADs and @acronym{NOV} lines, but this is currently not supported by Gnus.

If @var{fetch-old} is non-@code{nil} it says to try fetching ``extra
headers'', in some meaning of the word.  This is generally done by
fetching (at most) @var{fetch-old} extra headers less than the smallest
article number in @code{articles}, and filling the gaps as well.  The
presence of this parameter can be ignored if the back end finds it
cumbersome to follow the request.  If this is non-@code{nil} and not a
number, do maximum fetches.

Here's an example HEAD:

@example
221 1056 Article retrieved.
Path: ifi.uio.no!sturles
From: sturles@@ifi.uio.no (Sturle Sunde)
Newsgroups: ifi.discussion
Subject: Re: Something very droll
Date: 27 Oct 1994 14:02:57 +0100
Organization: Dept. of Informatics, University of Oslo, Norway
Lines: 26
Message-ID: <38o8e1$a0o@@holmenkollen.ifi.uio.no>
References: <38jdmq$4qu@@visbur.ifi.uio.no>
NNTP-Posting-Host: holmenkollen.ifi.uio.no
.
@end example

So a @code{headers} return value would imply that there's a number of
these in the data buffer.

Here's a BNF definition of such a buffer:

@example
headers        = *head
head           = error / valid-head
error-message  = [ "4" / "5" ] 2number " " <error message> eol
valid-head     = valid-message *header "." eol
valid-message  = "221 " <number> " Article retrieved." eol
header         = <text> eol
@end example

@cindex BNF
(The version of BNF used here is the one used in RFC822.)

If the return value is @code{nov}, the data buffer should contain
@dfn{network overview database} lines.  These are basically fields
separated by tabs.

@example
nov-buffer = *nov-line
nov-line   = field 7*8[ <TAB> field ] eol
field      = <text except TAB>
@end example

For a closer look at what should be in those fields,
@pxref{Headers}.


@item (nnchoke-open-server SERVER &optional DEFINITIONS)

@var{server} is here the virtual server name.  @var{definitions} is a
list of @code{(VARIABLE VALUE)} pairs that define this virtual server.

If the server can't be opened, no error should be signaled.  The back end
may then choose to refuse further attempts at connecting to this
server.  In fact, it should do so.

If the server is opened already, this function should return a
non-@code{nil} value.  There should be no data returned.


@item (nnchoke-close-server &optional SERVER)

Close connection to @var{server} and free all resources connected
to it.  Return @code{nil} if the server couldn't be closed for some
reason.

There should be no data returned.


@item (nnchoke-request-close)

Close connection to all servers and free all resources that the back end
have reserved.  All buffers that have been created by that back end
should be killed.  (Not the @code{nntp-server-buffer}, though.)  This
function is generally only called when Gnus is shutting down.

There should be no data returned.


@item (nnchoke-server-opened &optional SERVER)

If @var{server} is the current virtual server, and the connection to the
physical server is alive, then this function should return a
non-@code{nil} value.  This function should under no circumstances
attempt to reconnect to a server we have lost connection to.

There should be no data returned.


@item (nnchoke-status-message &optional SERVER)

This function should return the last error message from @var{server}.

There should be no data returned.


@item (nnchoke-request-article ARTICLE &optional GROUP SERVER TO-BUFFER)

The result data from this function should be the article specified by
@var{article}.  This might either be a @code{Message-ID} or a number.
It is optional whether to implement retrieval by @code{Message-ID}, but
it would be nice if that were possible.

If @var{to-buffer} is non-@code{nil}, the result data should be returned
in this buffer instead of the normal data buffer.  This is to make it
possible to avoid copying large amounts of data from one buffer to
another, while Gnus mainly requests articles to be inserted directly
into its article buffer.

If it is at all possible, this function should return a cons cell where
the @code{car} is the group name the article was fetched from, and the @code{cdr} is
the article number.  This will enable Gnus to find out what the real
group and article numbers are when fetching articles by
@code{Message-ID}.  If this isn't possible, @code{t} should be returned
on successful article retrieval.


@item (nnchoke-request-group GROUP &optional SERVER FAST)

Get data on @var{group}.  This function also has the side effect of
making @var{group} the current group.

If @var{fast}, don't bother to return useful data, just make @var{group}
the current group.

Here's an example of some result data and a definition of the same:

@example
211 56 1000 1059 ifi.discussion
@end example

The first number is the status, which should be 211.  Next is the
total number of articles in the group, the lowest article number, the
highest article number, and finally the group name.  Note that the total
number of articles may be less than one might think while just
considering the highest and lowest article numbers, but some articles
may have been canceled.  Gnus just discards the total-number, so
whether one should take the bother to generate it properly (if that is a
problem) is left as an exercise to the reader.  If the group contains no
articles, the lowest article number should be reported as 1 and the
highest as 0.

@example
group-status = [ error / info ] eol
error        = [ "4" / "5" ] 2<number> " " <Error message>
info         = "211 " 3* [ <number> " " ] <string>
@end example


@item (nnchoke-close-group GROUP &optional SERVER)

Close @var{group} and free any resources connected to it.  This will be
a no-op on most back ends.

There should be no data returned.


@item (nnchoke-request-list &optional SERVER)

Return a list of all groups available on @var{server}.  And that means
@emph{all}.

Here's an example from a server that only carries two groups:

@example
ifi.test 0000002200 0000002000 y
ifi.discussion 3324 3300 n
@end example

On each line we have a group name, then the highest article number in
that group, the lowest article number, and finally a flag.  If the group
contains no articles, the lowest article number should be reported as 1
and the highest as 0.

@example
active-file = *active-line
active-line = name " " <number> " " <number> " " flags eol
name        = <string>
flags       = "n" / "y" / "m" / "x" / "j" / "=" name
@end example

The flag says whether the group is read-only (@samp{n}), is moderated
(@samp{m}), is dead (@samp{x}), is aliased to some other group
(@samp{=other-group}) or none of the above (@samp{y}).


@item (nnchoke-request-post &optional SERVER)

This function should post the current buffer.  It might return whether
the posting was successful or not, but that's not required.  If, for
instance, the posting is done asynchronously, it has generally not been
completed by the time this function concludes.  In that case, this
function should set up some kind of sentinel to beep the user loud and
clear if the posting could not be completed.

There should be no result data from this function.

@end table


@node Optional Back End Functions
@subsubsection Optional Back End Functions

@table @code

@item (nnchoke-retrieve-groups GROUPS &optional SERVER)

@var{groups} is a list of groups, and this function should request data
on all those groups.  How it does it is of no concern to Gnus, but it
should attempt to do this in a speedy fashion.

The return value of this function can be either @code{active} or
@code{group}, which says what the format of the result data is.  The
former is in the same format as the data from
@code{nnchoke-request-list}, while the latter is a buffer full of lines
in the same format as @code{nnchoke-request-group} gives.

@example
group-buffer = *active-line / *group-status
@end example


@item (nnchoke-request-update-info GROUP INFO &optional SERVER)

A Gnus group info (@pxref{Group Info}) is handed to the back end for
alterations.  This comes in handy if the back end really carries all
the information (as is the case with virtual and imap groups).  This
function should destructively alter the info to suit its needs, and
should return a non-@code{nil} value.

There should be no result data from this function.


@item (nnchoke-request-type GROUP &optional ARTICLE)

When the user issues commands for ``sending news'' (@kbd{F} in the
summary buffer, for instance), Gnus has to know whether the article the
user is following up on is news or mail.  This function should return
@code{news} if @var{article} in @var{group} is news, @code{mail} if it
is mail and @code{unknown} if the type can't be decided.  (The
@var{article} parameter is necessary in @code{nnvirtual} groups which
might very well combine mail groups and news groups.)  Both @var{group}
and @var{article} may be @code{nil}.

There should be no result data from this function.


@item (nnchoke-request-set-mark GROUP ACTION &optional SERVER)

Set/remove/add marks on articles.  Normally Gnus handles the article
marks (such as read, ticked, expired etc) internally, and store them in
@file{~/.newsrc.eld}.  Some back ends (such as @acronym{IMAP}) however carry
all information about the articles on the server, so Gnus need to
propagate the mark information to the server.

@var{action} is a list of mark setting requests, having this format:

@example
(RANGE ACTION MARK)
@end example

@var{range} is a range of articles you wish to update marks on.
@var{action} is @code{add} or @code{del}, used to add marks or remove
marks (preserving all marks not mentioned).  @var{mark} is a list of
marks; where each mark is a symbol.  Currently used marks are
@code{read}, @code{tick}, @code{reply}, @code{expire}, @code{killed},
@code{dormant}, @code{save}, @code{download}, @code{unsend},
@code{forward} and @code{recent}, but your back end should, if
possible, not limit itself to these.

Given contradictory actions, the last action in the list should be the
effective one.  That is, if your action contains a request to add the
@code{tick} mark on article 1 and, later in the list, a request to
remove the mark on the same article, the mark should in fact be removed.

An example action list:

@example
(((5 12 30) 'del '(tick))
 ((10 . 90) 'add '(read expire))
 ((92 94) 'del '(read)))
@end example

The function should return a range of articles it wasn't able to set the
mark on (currently not used for anything).

There should be no result data from this function.

@item (nnchoke-request-update-mark GROUP ARTICLE MARK)

If the user tries to set a mark that the back end doesn't like, this
function may change the mark.  Gnus will use whatever this function
returns as the mark for @var{article} instead of the original
@var{mark}.  If the back end doesn't care, it must return the original
@var{mark}, and not @code{nil} or any other type of garbage.

The only use for this I can see is what @code{nnvirtual} does with
it---if a component group is auto-expirable, marking an article as read
in the virtual group should result in the article being marked as
expirable.

There should be no result data from this function.


@item (nnchoke-request-scan &optional GROUP SERVER)

This function may be called at any time (by Gnus or anything else) to
request that the back end check for incoming articles, in one way or
another.  A mail back end will typically read the spool file or query
the @acronym{POP} server when this function is invoked.  The
@var{group} doesn't have to be heeded---if the back end decides that
it is too much work just scanning for a single group, it may do a
total scan of all groups.  It would be nice, however, to keep things
local if that's practical.

There should be no result data from this function.


@item (nnchoke-request-group-description GROUP &optional SERVER)

The result data from this function should be a description of
@var{group}.

@example
description-line = name <TAB> description eol
name             = <string>
description      = <text>
@end example

@item (nnchoke-request-list-newsgroups &optional SERVER)

The result data from this function should be the description of all
groups available on the server.

@example
description-buffer = *description-line
@end example


@item (nnchoke-request-newgroups DATE &optional SERVER)

The result data from this function should be all groups that were
created after @samp{date}, which is in normal human-readable date format
(i.e., the date format used in mail and news headers, and returned by
the function @code{message-make-date} by default).  The data should be
in the active buffer format.

It is okay for this function to return ``too many'' groups; some back ends
might find it cheaper to return the full list of groups, rather than
just the new groups.  But don't do this for back ends with many groups.
Normally, if the user creates the groups herself, there won't be too
many groups, so @code{nnml} and the like are probably safe.  But for
back ends like @code{nntp}, where the groups have been created by the
server, it is quite likely that there can be many groups.


@item (nnchoke-request-create-group GROUP &optional SERVER)

This function should create an empty group with name @var{group}.

There should be no return data.


@item (nnchoke-request-expire-articles ARTICLES &optional GROUP SERVER FORCE)

This function should run the expiry process on all articles in the
@var{articles} range (which is currently a simple list of article
numbers.)  It is left up to the back end to decide how old articles
should be before they are removed by this function.  If @var{force} is
non-@code{nil}, all @var{articles} should be deleted, no matter how new
they are.

This function should return a list of articles that it did not/was not
able to delete.

There should be no result data returned.


@item (nnchoke-request-move-article ARTICLE GROUP SERVER ACCEPT-FORM &optional LAST)

This function should move @var{article} (which is a number) from
@var{group} by calling @var{accept-form}.

This function should ready the article in question for moving by
removing any header lines it has added to the article, and generally
should ``tidy up'' the article.  Then it should @code{eval}
@var{accept-form} in the buffer where the ``tidy'' article is.  This
will do the actual copying.  If this @code{eval} returns a
non-@code{nil} value, the article should be removed.

If @var{last} is @code{nil}, that means that there is a high likelihood
that there will be more requests issued shortly, so that allows some
optimizations.

The function should return a cons where the @code{car} is the group name and
the @code{cdr} is the article number that the article was entered as.

The group should exist before the back end is asked to accept the
article for that group.

There should be no data returned.


@item (nnchoke-request-accept-article GROUP &optional SERVER LAST)

This function takes the current buffer and inserts it into @var{group}.
If @var{last} in @code{nil}, that means that there will be more calls to
this function in short order.

The function should return a cons where the @code{car} is the group name and
the @code{cdr} is the article number that the article was entered as.

There should be no data returned.


@item (nnchoke-request-replace-article ARTICLE GROUP BUFFER)

This function should remove @var{article} (which is a number) from
@var{group} and insert @var{buffer} there instead.

There should be no data returned.


@item (nnchoke-request-delete-group GROUP FORCE &optional SERVER)

This function should delete @var{group}.  If @var{force}, it should
really delete all the articles in the group, and then delete the group
itself.  (If there is such a thing as ``the group itself''.)

There should be no data returned.


@item (nnchoke-request-rename-group GROUP NEW-NAME &optional SERVER)

This function should rename @var{group} into @var{new-name}.  All
articles in @var{group} should move to @var{new-name}.

There should be no data returned.

@end table


@node Error Messaging
@subsubsection Error Messaging

@findex nnheader-report
@findex nnheader-get-report
The back ends should use the function @code{nnheader-report} to report
error conditions---they should not raise errors when they aren't able to
perform a request.  The first argument to this function is the back end
symbol, and the rest are interpreted as arguments to @code{format} if
there are multiple of them, or just a string if there is one of them.
This function must always returns @code{nil}.

@lisp
(nnheader-report 'nnchoke "You did something totally bogus")

(nnheader-report 'nnchoke "Could not request group %s" group)
@end lisp

Gnus, in turn, will call @code{nnheader-get-report} when it gets a
@code{nil} back from a server, and this function returns the most
recently reported message for the back end in question.  This function
takes one argument---the server symbol.

Internally, these functions access @var{back-end}@code{-status-string},
so the @code{nnchoke} back end will have its error message stored in
@code{nnchoke-status-string}.


@node Writing New Back Ends
@subsubsection Writing New Back Ends

Many back ends are quite similar.  @code{nnml} is just like
@code{nnspool}, but it allows you to edit the articles on the server.
@code{nnmh} is just like @code{nnml}, but it doesn't use an active file,
and it doesn't maintain overview databases.  @code{nndir} is just like
@code{nnml}, but it has no concept of ``groups'', and it doesn't allow
editing articles.

It would make sense if it were possible to ``inherit'' functions from
back ends when writing new back ends.  And, indeed, you can do that if you
want to.  (You don't have to if you don't want to, of course.)

All the back ends declare their public variables and functions by using a
package called @code{nnoo}.

To inherit functions from other back ends (and allow other back ends to
inherit functions from the current back end), you should use the
following macros:

@table @code

@item nnoo-declare
This macro declares the first parameter to be a child of the subsequent
parameters.  For instance:

@lisp
(nnoo-declare nndir
  nnml nnmh)
@end lisp

@code{nndir} has declared here that it intends to inherit functions from
both @code{nnml} and @code{nnmh}.

@item defvoo
This macro is equivalent to @code{defvar}, but registers the variable as
a public server variable.  Most state-oriented variables should be
declared with @code{defvoo} instead of @code{defvar}.

In addition to the normal @code{defvar} parameters, it takes a list of
variables in the parent back ends to map the variable to when executing
a function in those back ends.

@lisp
(defvoo nndir-directory nil
  "Where nndir will look for groups."
  nnml-current-directory nnmh-current-directory)
@end lisp

This means that @code{nnml-current-directory} will be set to
@code{nndir-directory} when an @code{nnml} function is called on behalf
of @code{nndir}.  (The same with @code{nnmh}.)

@item nnoo-define-basics
This macro defines some common functions that almost all back ends should
have.

@lisp
(nnoo-define-basics nndir)
@end lisp

@item deffoo
This macro is just like @code{defun} and takes the same parameters.  In
addition to doing the normal @code{defun} things, it registers the
function as being public so that other back ends can inherit it.

@item nnoo-map-functions
This macro allows mapping of functions from the current back end to
functions from the parent back ends.

@lisp
(nnoo-map-functions nndir
  (nnml-retrieve-headers 0 nndir-current-group 0 0)
  (nnmh-request-article 0 nndir-current-group 0 0))
@end lisp

This means that when @code{nndir-retrieve-headers} is called, the first,
third, and fourth parameters will be passed on to
@code{nnml-retrieve-headers}, while the second parameter is set to the
value of @code{nndir-current-group}.

@item nnoo-import
This macro allows importing functions from back ends.  It should be the
last thing in the source file, since it will only define functions that
haven't already been defined.

@lisp
(nnoo-import nndir
  (nnmh
   nnmh-request-list
   nnmh-request-newgroups)
  (nnml))
@end lisp

This means that calls to @code{nndir-request-list} should just be passed
on to @code{nnmh-request-list}, while all public functions from
@code{nnml} that haven't been defined in @code{nndir} yet should be
defined now.

@end table

Below is a slightly shortened version of the @code{nndir} back end.

@lisp
;;; @r{nndir.el --- single directory newsgroup access for Gnus}
;; @r{Copyright (C) 1995,96 Free Software Foundation, Inc.}

;;; @r{Code:}

(require 'nnheader)
(require 'nnmh)
(require 'nnml)
(require 'nnoo)
(eval-when-compile (require 'cl))

(nnoo-declare nndir
  nnml nnmh)

(defvoo nndir-directory nil
  "Where nndir will look for groups."
  nnml-current-directory nnmh-current-directory)

(defvoo nndir-nov-is-evil nil
  "*Non-nil means that nndir will never retrieve NOV headers."
  nnml-nov-is-evil)

(defvoo nndir-current-group ""
  nil
  nnml-current-group nnmh-current-group)
(defvoo nndir-top-directory nil nil nnml-directory nnmh-directory)
(defvoo nndir-get-new-mail nil nil nnml-get-new-mail nnmh-get-new-mail)

(defvoo nndir-status-string "" nil nnmh-status-string)
(defconst nndir-version "nndir 1.0")

;;; @r{Interface functions.}

(nnoo-define-basics nndir)

(deffoo nndir-open-server (server &optional defs)
  (setq nndir-directory
        (or (cadr (assq 'nndir-directory defs))
            server))
  (unless (assq 'nndir-directory defs)
    (push `(nndir-directory ,server) defs))
  (push `(nndir-current-group
          ,(file-name-nondirectory
            (directory-file-name nndir-directory)))
        defs)
  (push `(nndir-top-directory
          ,(file-name-directory (directory-file-name nndir-directory)))
        defs)
  (nnoo-change-server 'nndir server defs))

(nnoo-map-functions nndir
  (nnml-retrieve-headers 0 nndir-current-group 0 0)
  (nnmh-request-article 0 nndir-current-group 0 0)
  (nnmh-request-group nndir-current-group 0 0)
  (nnmh-close-group nndir-current-group 0))

(nnoo-import nndir
  (nnmh
   nnmh-status-message
   nnmh-request-list
   nnmh-request-newgroups))

(provide 'nndir)
@end lisp


@node Hooking New Back Ends Into Gnus
@subsubsection Hooking New Back Ends Into Gnus

@vindex gnus-valid-select-methods
@findex gnus-declare-backend
Having Gnus start using your new back end is rather easy---you just
declare it with the @code{gnus-declare-backend} functions.  This will
enter the back end into the @code{gnus-valid-select-methods} variable.

@code{gnus-declare-backend} takes two parameters---the back end name and
an arbitrary number of @dfn{abilities}.

Here's an example:

@lisp
(gnus-declare-backend "nnchoke" 'mail 'respool 'address)
@end lisp

The above line would then go in the @file{nnchoke.el} file.

The abilities can be:

@table @code
@item mail
This is a mailish back end---followups should (probably) go via mail.
@item post
This is a newsish back end---followups should (probably) go via news.
@item post-mail
This back end supports both mail and news.
@item none
This is neither a post nor mail back end---it's something completely
different.
@item respool
It supports respooling---or rather, it is able to modify its source
articles and groups.
@item address
The name of the server should be in the virtual server name.  This is
true for almost all back ends.
@item prompt-address
The user should be prompted for an address when doing commands like
@kbd{B} in the group buffer.  This is true for back ends like
@code{nntp}, but not @code{nnmbox}, for instance.
@end table


@node Mail-like Back Ends
@subsubsection Mail-like Back Ends

One of the things that separate the mail back ends from the rest of the
back ends is the heavy dependence by most of the mail back ends on
common functions in @file{nnmail.el}.  For instance, here's the
definition of @code{nnml-request-scan}:

@lisp
(deffoo nnml-request-scan (&optional group server)
  (setq nnml-article-file-alist nil)
  (nnmail-get-new-mail 'nnml 'nnml-save-nov nnml-directory group))
@end lisp

It simply calls @code{nnmail-get-new-mail} with a few parameters,
and @code{nnmail} takes care of all the moving and splitting of the
mail.

This function takes four parameters.

@table @var
@item method
This should be a symbol to designate which back end is responsible for
the call.

@item exit-function
This function should be called after the splitting has been performed.

@item temp-directory
Where the temporary files should be stored.

@item group
This optional argument should be a group name if the splitting is to be
performed for one group only.
@end table

@code{nnmail-get-new-mail} will call @var{back-end}@code{-save-mail} to
save each article.  @var{back-end}@code{-active-number} will be called to
find the article number assigned to this article.

The function also uses the following variables:
@var{back-end}@code{-get-new-mail} (to see whether to get new mail for
this back end); and @var{back-end}@code{-group-alist} and
@var{back-end}@code{-active-file} to generate the new active file.
@var{back-end}@code{-group-alist} should be a group-active alist, like
this:

@example
(("a-group" (1 . 10))
 ("some-group" (34 . 39)))
@end example


@node Score File Syntax
@subsection Score File Syntax

Score files are meant to be easily parseable, but yet extremely
mallable.  It was decided that something that had the same read syntax
as an Emacs Lisp list would fit that spec.

Here's a typical score file:

@lisp
(("summary"
  ("win95" -10000 nil s)
  ("Gnus"))
 ("from"
  ("Lars" -1000))
 (mark -100))
@end lisp

BNF definition of a score file:

@example
score-file      = "" / "(" *element ")"
element         = rule / atom
rule            = string-rule / number-rule / date-rule
string-rule     = "(" quote string-header quote space *string-match ")"
number-rule     = "(" quote number-header quote space *number-match ")"
date-rule       = "(" quote date-header quote space *date-match ")"
quote           = <ascii 34>
string-header   = "subject" / "from" / "references" / "message-id" /
                  "xref" / "body" / "head" / "all" / "followup"
number-header   = "lines" / "chars"
date-header     = "date"
string-match    = "(" quote <string> quote [ "" / [ space score [ "" /
                  space date [ "" / [ space string-match-t ] ] ] ] ] ")"
score           = "nil" / <integer>
date            = "nil" / <natural number>
string-match-t  = "nil" / "s" / "substring" / "S" / "Substring" /
                  "r" / "regex" / "R" / "Regex" /
                  "e" / "exact" / "E" / "Exact" /
                  "f" / "fuzzy" / "F" / "Fuzzy"
number-match    = "(" <integer> [ "" / [ space score [ "" /
                  space date [ "" / [ space number-match-t ] ] ] ] ] ")"
number-match-t  = "nil" / "=" / "<" / ">" / ">=" / "<="
date-match      = "(" quote <string> quote [ "" / [ space score [ "" /
                  space date [ "" / [ space date-match-t ] ] ] ] ")"
date-match-t    = "nil" / "at" / "before" / "after"
atom            = "(" [ required-atom / optional-atom ] ")"
required-atom   = mark / expunge / mark-and-expunge / files /
                  exclude-files / read-only / touched
optional-atom   = adapt / local / eval
mark            = "mark" space nil-or-number
nil-or-number   = "nil" / <integer>
expunge         = "expunge" space nil-or-number
mark-and-expunge = "mark-and-expunge" space nil-or-number
files           = "files" *[ space <string> ]
exclude-files   = "exclude-files" *[ space <string> ]
read-only       = "read-only" [ space "nil" / space "t" ]
adapt        = "adapt" [ space "ignore" / space "t" / space adapt-rule ]
adapt-rule      = "(" *[ <string> *[ "(" <string> <integer> ")" ] ")"
local           = "local" *[ space "(" <string> space <form> ")" ]
eval            = "eval" space <form>
space           = *[ " " / <TAB> / <NEWLINE> ]
@end example

Any unrecognized elements in a score file should be ignored, but not
discarded.

As you can see, white space is needed, but the type and amount of white
space is irrelevant.  This means that formatting of the score file is
left up to the programmer---if it's simpler to just spew it all out on
one looong line, then that's ok.

The meaning of the various atoms are explained elsewhere in this
manual (@pxref{Score File Format}).


@node Headers
@subsection Headers

Internally Gnus uses a format for storing article headers that
corresponds to the @acronym{NOV} format in a mysterious fashion.  One could
almost suspect that the author looked at the @acronym{NOV} specification and
just shamelessly @emph{stole} the entire thing, and one would be right.

@dfn{Header} is a severely overloaded term.  ``Header'' is used in
RFC 1036 to talk about lines in the head of an article (e.g.,
@code{From}).  It is used by many people as a synonym for
``head''---``the header and the body''.  (That should be avoided, in my
opinion.)  And Gnus uses a format internally that it calls ``header'',
which is what I'm talking about here.  This is a 9-element vector,
basically, with each header (ouch) having one slot.

These slots are, in order: @code{number}, @code{subject}, @code{from},
@code{date}, @code{id}, @code{references}, @code{chars}, @code{lines},
@code{xref}, and @code{extra}.  There are macros for accessing and
setting these slots---they all have predictable names beginning with
@code{mail-header-} and @code{mail-header-set-}, respectively.

All these slots contain strings, except the @code{extra} slot, which
contains an alist of header/value pairs (@pxref{To From Newsgroups}).


@node Ranges
@subsection Ranges

@sc{gnus} introduced a concept that I found so useful that I've started
using it a lot and have elaborated on it greatly.

The question is simple: If you have a large amount of objects that are
identified by numbers (say, articles, to take a @emph{wild} example)
that you want to qualify as being ``included'', a normal sequence isn't
very useful.  (A 200,000 length sequence is a bit long-winded.)

The solution is as simple as the question: You just collapse the
sequence.

@example
(1 2 3 4 5 6 10 11 12)
@end example

is transformed into

@example
((1 . 6) (10 . 12))
@end example

To avoid having those nasty @samp{(13 . 13)} elements to denote a
lonesome object, a @samp{13} is a valid element:

@example
((1 . 6) 7 (10 . 12))
@end example

This means that comparing two ranges to find out whether they are equal
is slightly tricky:

@example
((1 . 5) 7 8 (10 . 12))
@end example

and

@example
((1 . 5) (7 . 8) (10 . 12))
@end example

are equal.  In fact, any non-descending list is a range:

@example
(1 2 3 4 5)
@end example

is a perfectly valid range, although a pretty long-winded one.  This is
also valid:

@example
(1 . 5)
@end example

and is equal to the previous range.

Here's a BNF definition of ranges.  Of course, one must remember the
semantic requirement that the numbers are non-descending.  (Any number
of repetition of the same number is allowed, but apt to disappear in
range handling.)

@example
range           = simple-range / normal-range
simple-range    = "(" number " . " number ")"
normal-range    = "(" start-contents ")"
contents        = "" / simple-range *[ " " contents ] /
                  number *[ " " contents ]
@end example

Gnus currently uses ranges to keep track of read articles and article
marks.  I plan on implementing a number of range operators in C if The
Powers That Be are willing to let me.  (I haven't asked yet, because I
need to do some more thinking on what operators I need to make life
totally range-based without ever having to convert back to normal
sequences.)


@node Group Info
@subsection Group Info

Gnus stores all permanent info on groups in a @dfn{group info} list.
This list is from three to six elements (or more) long and exhaustively
describes the group.

Here are two example group infos; one is a very simple group while the
second is a more complex one:

@example
("no.group" 5 ((1 . 54324)))

("nnml:my.mail" 3 ((1 . 5) 9 (20 . 55))
                ((tick (15 . 19)) (replied 3 6 (19 . 3)))
                (nnml "")
                ((auto-expire . t) (to-address . "ding@@gnus.org")))
@end example

The first element is the @dfn{group name}---as Gnus knows the group,
anyway.  The second element is the @dfn{subscription level}, which
normally is a small integer.  (It can also be the @dfn{rank}, which is a
cons cell where the @code{car} is the level and the @code{cdr} is the
score.)  The third element is a list of ranges of read articles.  The
fourth element is a list of lists of article marks of various kinds.
The fifth element is the select method (or virtual server, if you like).
The sixth element is a list of @dfn{group parameters}, which is what
this section is about.

Any of the last three elements may be missing if they are not required.
In fact, the vast majority of groups will normally only have the first
three elements, which saves quite a lot of cons cells.

Here's a BNF definition of the group info format:

@example
info          = "(" group space ralevel space read
                [ "" / [ space marks-list [ "" / [ space method [ "" /
                space parameters ] ] ] ] ] ")"
group         = quote <string> quote
ralevel       = rank / level
level         = <integer in the range of 1 to inf>
rank          = "(" level "." score ")"
score         = <integer in the range of 1 to inf>
read          = range
marks-lists   = nil / "(" *marks ")"
marks         = "(" <string> range ")"
method        = "(" <string> *elisp-forms ")"
parameters    = "(" *elisp-forms ")"
@end example

Actually that @samp{marks} rule is a fib.  A @samp{marks} is a
@samp{<string>} consed on to a @samp{range}, but that's a bitch to say
in pseudo-BNF.

If you have a Gnus info and want to access the elements, Gnus offers a
series of macros for getting/setting these elements.

@table @code
@item gnus-info-group
@itemx gnus-info-set-group
@findex gnus-info-group
@findex gnus-info-set-group
Get/set the group name.

@item gnus-info-rank
@itemx gnus-info-set-rank
@findex gnus-info-rank
@findex gnus-info-set-rank
Get/set the group rank (@pxref{Group Score}).

@item gnus-info-level
@itemx gnus-info-set-level
@findex gnus-info-level
@findex gnus-info-set-level
Get/set the group level.

@item gnus-info-score
@itemx gnus-info-set-score
@findex gnus-info-score
@findex gnus-info-set-score
Get/set the group score (@pxref{Group Score}).

@item gnus-info-read
@itemx gnus-info-set-read
@findex gnus-info-read
@findex gnus-info-set-read
Get/set the ranges of read articles.

@item gnus-info-marks
@itemx gnus-info-set-marks
@findex gnus-info-marks
@findex gnus-info-set-marks
Get/set the lists of ranges of marked articles.

@item gnus-info-method
@itemx gnus-info-set-method
@findex gnus-info-method
@findex gnus-info-set-method
Get/set the group select method.

@item gnus-info-params
@itemx gnus-info-set-params
@findex gnus-info-params
@findex gnus-info-set-params
Get/set the group parameters.
@end table

All the getter functions take one parameter---the info list.  The setter
functions take two parameters---the info list and the new value.

The last three elements in the group info aren't mandatory, so it may be
necessary to extend the group info before setting the element.  If this
is necessary, you can just pass on a non-@code{nil} third parameter to
the three final setter functions to have this happen automatically.


@node Extended Interactive
@subsection Extended Interactive
@cindex interactive
@findex gnus-interactive

Gnus extends the standard Emacs @code{interactive} specification
slightly to allow easy use of the symbolic prefix (@pxref{Symbolic
Prefixes}).  Here's an example of how this is used:

@lisp
(defun gnus-summary-increase-score (&optional score symp)
  (interactive (gnus-interactive "P\ny"))
  ...
  )
@end lisp

The best thing to do would have been to implement
@code{gnus-interactive} as a macro which would have returned an
@code{interactive} form, but this isn't possible since Emacs checks
whether a function is interactive or not by simply doing an @code{assq}
on the lambda form.  So, instead we have @code{gnus-interactive}
function that takes a string and returns values that are usable to
@code{interactive}.

This function accepts (almost) all normal @code{interactive} specs, but
adds a few more.

@table @samp
@item y
@vindex gnus-current-prefix-symbol
The current symbolic prefix---the @code{gnus-current-prefix-symbol}
variable.

@item Y
@vindex gnus-current-prefix-symbols
A list of the current symbolic prefixes---the
@code{gnus-current-prefix-symbol} variable.

@item A
The current article number---the @code{gnus-summary-article-number}
function.

@item H
The current article header---the @code{gnus-summary-article-header}
function.

@item g
The current group name---the @code{gnus-group-group-name}
function.

@end table


@node Emacs/XEmacs Code
@subsection Emacs/XEmacs Code
@cindex XEmacs
@cindex Emacsen

While Gnus runs under Emacs, XEmacs and Mule, I decided that one of the
platforms must be the primary one.  I chose Emacs.  Not because I don't
like XEmacs or Mule, but because it comes first alphabetically.

This means that Gnus will byte-compile under Emacs with nary a warning,
while XEmacs will pump out gigabytes of warnings while byte-compiling.
As I use byte-compilation warnings to help me root out trivial errors in
Gnus, that's very useful.

I've also consistently used Emacs function interfaces, but have used
Gnusey aliases for the functions.  To take an example:  Emacs defines a
@code{run-at-time} function while XEmacs defines a @code{start-itimer}
function.  I then define a function called @code{gnus-run-at-time} that
takes the same parameters as the Emacs @code{run-at-time}.  When running
Gnus under Emacs, the former function is just an alias for the latter.
However, when running under XEmacs, the former is an alias for the
following function:

@lisp
(defun gnus-xmas-run-at-time (time repeat function &rest args)
  (start-itimer
   "gnus-run-at-time"
   `(lambda ()
      (,function ,@@args))
   time repeat))
@end lisp

This sort of thing has been done for bunches of functions.  Gnus does
not redefine any native Emacs functions while running under XEmacs---it
does this @code{defalias} thing with Gnus equivalents instead.  Cleaner
all over.

In the cases where the XEmacs function interface was obviously cleaner,
I used it instead.  For example @code{gnus-region-active-p} is an alias
for @code{region-active-p} in XEmacs, whereas in Emacs it is a function.

Of course, I could have chosen XEmacs as my native platform and done
mapping functions the other way around.  But I didn't.  The performance
hit these indirections impose on Gnus under XEmacs should be slight.


@node Various File Formats
@subsection Various File Formats

@menu
* Active File Format::          Information on articles and groups available.
* Newsgroups File Format::      Group descriptions.
@end menu


@node Active File Format
@subsubsection Active File Format

The active file lists all groups available on the server in
question.  It also lists the highest and lowest current article numbers
in each group.

Here's an excerpt from a typical active file:

@example
soc.motss 296030 293865 y
alt.binaries.pictures.fractals 3922 3913 n
comp.sources.unix 1605 1593 m
comp.binaries.ibm.pc 5097 5089 y
no.general 1000 900 y
@end example

Here's a pseudo-BNF definition of this file:

@example
active      = *group-line
group-line  = group spc high-number spc low-number spc flag <NEWLINE>
group       = <non-white-space string>
spc         = " "
high-number = <non-negative integer>
low-number  = <positive integer>
flag        = "y" / "n" / "m" / "j" / "x" / "=" group
@end example

For a full description of this file, see the manual pages for
@samp{innd}, in particular @samp{active(5)}.


@node Newsgroups File Format
@subsubsection Newsgroups File Format

The newsgroups file lists groups along with their descriptions.  Not all
groups on the server have to be listed,  and not all groups in the file
have to exist on the server.  The file is meant purely as information to
the user.

The format is quite simple; a group name, a tab, and the description.
Here's the definition:

@example
newsgroups    = *line
line          = group tab description <NEWLINE>
group         = <non-white-space string>
tab           = <TAB>
description   = <string>
@end example


@page
@node Emacs for Heathens
@section Emacs for Heathens

Believe it or not, but some people who use Gnus haven't really used
Emacs much before they embarked on their journey on the Gnus Love Boat.
If you are one of those unfortunates whom ``@kbd{C-M-a}'', ``kill the
region'', and ``set @code{gnus-flargblossen} to an alist where the key
is a regexp that is used for matching on the group name'' are magical
phrases with little or no meaning, then this appendix is for you.  If
you are already familiar with Emacs, just ignore this and go fondle your
cat instead.

@menu
* Keystrokes::                  Entering text and executing commands.
* Emacs Lisp::                  The built-in Emacs programming language.
@end menu


@node Keystrokes
@subsection Keystrokes

@itemize @bullet
@item
Q: What is an experienced Emacs user?

@item
A: A person who wishes that the terminal had pedals.
@end itemize

Yes, when you use Emacs, you are apt to use the control key, the shift
key and the meta key a lot.  This is very annoying to some people
(notably @code{vi}le users), and the rest of us just love the hell out
of it.  Just give up and submit.  Emacs really does stand for
``Escape-Meta-Alt-Control-Shift'', and not ``Editing Macros'', as you
may have heard from other disreputable sources (like the Emacs author).

The shift keys are normally located near your pinky fingers, and are
normally used to get capital letters and stuff.  You probably use it all
the time.  The control key is normally marked ``CTRL'' or something like
that.  The meta key is, funnily enough, never marked as such on any
keyboard.  The one I'm currently at has a key that's marked ``Alt'',
which is the meta key on this keyboard.  It's usually located somewhere
to the left hand side of the keyboard, usually on the bottom row.

Now, us Emacs people don't say ``press the meta-control-m key'',
because that's just too inconvenient.  We say ``press the @kbd{C-M-m}
key''.  @kbd{M-} is the prefix that means ``meta'' and ``C-'' is the
prefix that means ``control''.  So ``press @kbd{C-k}'' means ``press
down the control key, and hold it down while you press @kbd{k}''.
``Press @kbd{C-M-k}'' means ``press down and hold down the meta key and
the control key and then press @kbd{k}''.  Simple, ay?

This is somewhat complicated by the fact that not all keyboards have a
meta key.  In that case you can use the ``escape'' key.  Then @kbd{M-k}
means ``press escape, release escape, press @kbd{k}''.  That's much more
work than if you have a meta key, so if that's the case, I respectfully
suggest you get a real keyboard with a meta key.  You can't live without
it.



@node Emacs Lisp
@subsection Emacs Lisp

Emacs is the King of Editors because it's really a Lisp interpreter.
Each and every key you tap runs some Emacs Lisp code snippet, and since
Emacs Lisp is an interpreted language, that means that you can configure
any key to run any arbitrary code.  You just, like, do it.

Gnus is written in Emacs Lisp, and is run as a bunch of interpreted
functions.  (These are byte-compiled for speed, but it's still
interpreted.)  If you decide that you don't like the way Gnus does
certain things, it's trivial to have it do something a different way.
(Well, at least if you know how to write Lisp code.)  However, that's
beyond the scope of this manual, so we are simply going to talk about
some common constructs that you normally use in your @file{.emacs} file
to customize Gnus.

If you want to set the variable @code{gnus-florgbnize} to four (4), you
write the following:

@lisp
(setq gnus-florgbnize 4)
@end lisp

This function (really ``special form'') @code{setq} is the one that can
set a variable to some value.  This is really all you need to know.  Now
you can go and fill your @file{.emacs} file with lots of these to change
how Gnus works.

If you have put that thing in your @file{.emacs} file, it will be read
and @code{eval}ed (which is lisp-ese for ``run'') the next time you
start Emacs.  If you want to change the variable right away, simply say
@kbd{C-x C-e} after the closing parenthesis.  That will @code{eval} the
previous ``form'', which is a simple @code{setq} statement here.

Go ahead---just try it, if you're located at your Emacs.  After you
@kbd{C-x C-e}, you will see @samp{4} appear in the echo area, which
is the return value of the form you @code{eval}ed.

Some pitfalls:

If the manual says ``set @code{gnus-read-active-file} to @code{some}'',
that means:

@lisp
(setq gnus-read-active-file 'some)
@end lisp

On the other hand, if the manual says ``set @code{gnus-nntp-server} to
@samp{nntp.ifi.uio.no}'', that means:

@lisp
(setq gnus-nntp-server "nntp.ifi.uio.no")
@end lisp

So be careful not to mix up strings (the latter) with symbols (the
former).  The manual is unambiguous, but it can be confusing.

@page
@include gnus-faq.texi

@node Index
@chapter Index
@printindex cp

@node Key Index
@chapter Key Index
@printindex ky

@summarycontents
@contents
@bye

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@end iflatex
@end iftex

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