@top Emacs MIME
This manual documents the libraries used to compose and display
-@sc{mime} messages.
+@acronym{MIME} messages.
This manual is directed at users who want to modify the behaviour of
-the @sc{mime} encoding/decoding process or want a more detailed
-picture of how the Emacs @sc{mime} library works, and people who want
-to write functions and commands that manipulate @sc{mime} elements.
+the @acronym{MIME} encoding/decoding process or want a more detailed
+picture of how the Emacs @acronym{MIME} library works, and people who want
+to write functions and commands that manipulate @acronym{MIME} elements.
-@sc{mime} is short for @dfn{Multipurpose Internet Mail Extensions}.
+@acronym{MIME} is short for @dfn{Multipurpose Internet Mail Extensions}.
This standard is documented in a number of RFCs; mainly RFC2045 (Format
of Internet Message Bodies), RFC2046 (Media Types), RFC2047 (Message
-Header Extensions for Non-ASCII Text), RFC2048 (Registration
+Header Extensions for Non-@acronym{ASCII} Text), RFC2048 (Registration
Procedures), RFC2049 (Conformance Criteria and Examples). It is highly
-recommended that anyone who intends writing @sc{mime}-compliant software
+recommended that anyone who intends writing @acronym{MIME}-compliant software
read at least RFC2045 and RFC2047.
@menu
* Decoding and Viewing:: A framework for decoding and viewing.
-* Composing:: MML; a language for describing @sc{mime} parts.
+* Composing:: MML; a language for describing @acronym{MIME} parts.
* Interface Functions:: An abstraction over the basic functions.
* Basic Functions:: Utility and basic parsing functions.
* Standards:: A summary of RFCs and working documents used.
@node Decoding and Viewing
@chapter Decoding and Viewing
-This chapter deals with decoding and viewing @sc{mime} messages on a
+This chapter deals with decoding and viewing @acronym{MIME} messages on a
higher level.
-The main idea is to first analyze a @sc{mime} article, and then allow
+The main idea is to first analyze a @acronym{MIME} article, and then allow
other programs to do things based on the list of @dfn{handles} that are
returned as a result of this analysis.
@menu
-* Dissection:: Analyzing a @sc{mime} message.
-* Non-MIME:: Analyzing a non-@sc{mime} message.
+* Dissection:: Analyzing a @acronym{MIME} message.
+* Non-MIME:: Analyzing a non-@acronym{MIME} message.
* Handles:: Handle manipulations.
* Display:: Displaying handles.
* Display Customization:: Variables that affect display.
@section Dissection
The @code{mm-dissect-buffer} is the function responsible for dissecting
-a @sc{mime} article. If given a multipart message, it will recursively
+a @acronym{MIME} article. If given a multipart message, it will recursively
descend the message, following the structure, and return a tree of
-@sc{mime} handles that describes the structure of the message.
+@acronym{MIME} handles that describes the structure of the message.
@node Non-MIME
@section Non-MIME
@vindex mm-uu-configure-list
-Gnus also understands some non-@sc{mime} attachments, such as
+Gnus also understands some non-@acronym{MIME} attachments, such as
postscript, uuencode, binhex, yenc, shar, forward, gnatsweb, pgp,
diff. Each of these features can be disabled by add an item into
@code{mm-uu-configure-list}. For example,
@item forward
@findex forward
-Non-@sc{mime} forwarded message.
+Non-@acronym{MIME} forwarded message.
@item gnatsweb
@findex gnatsweb
@item pgp-signed
@findex pgp-signed
-PGP signed clear text.
+@acronym{PGP} signed clear text.
@item pgp-encrypted
@findex pgp-encrypted
-PGP encrypted clear text.
+@acronym{PGP} encrypted clear text.
@item pgp-key
@findex pgp-key
-PGP public keys.
+@acronym{PGP} public keys.
@item emacs-sources
@findex emacs-sources
@node Handles
@section Handles
-A @sc{mime} handle is a list that fully describes a @sc{mime}
+A @acronym{MIME} handle is a list that fully describes a @acronym{MIME}
component.
The following macros can be used to access elements in a handle:
@table @code
@item mm-handle-buffer
@findex mm-handle-buffer
-Return the buffer that holds the contents of the undecoded @sc{mime}
+Return the buffer that holds the contents of the undecoded @acronym{MIME}
part.
@item mm-handle-type
@item mm-inlinable-p
@findex mm-inlinable-p
-Say whether a @sc{mime} type can be displayed inline.
+Say whether a @acronym{MIME} type can be displayed inline.
@item mm-automatic-display-p
@findex mm-automatic-display-p
-Say whether a @sc{mime} type should be displayed automatically.
+Say whether a @acronym{MIME} type should be displayed automatically.
@item mm-destroy-part
@findex mm-destroy-part
@item mm-inline-media-tests
@vindex mm-inline-media-tests
-This is an alist where the key is a @sc{mime} type, the second element
+This is an alist where the key is a @acronym{MIME} type, the second element
is a function to display the part @dfn{inline} (i.e., inside Emacs), and
the third element is a form to be @code{eval}ed to say whether the part
can be displayed inline.
@vindex mm-inlined-types
This, on the other hand, says what types are to be displayed inline, if
they satisfy the conditions set by the variable above. It's a list of
-@sc{mime} media types.
+@acronym{MIME} media types.
@item mm-automatic-display
@vindex mm-automatic-display
@item mm-attachment-override-types
@vindex mm-attachment-override-types
-Some @sc{mime} agents create parts that have a content-disposition of
+Some @acronym{MIME} agents create parts that have a content-disposition of
@samp{attachment}. This variable allows overriding that disposition and
displaying the part inline. (Note that the disposition is only
overridden if we are able to, and want to, display the part inline.)
@item mm-discouraged-alternatives
@vindex mm-discouraged-alternatives
-List of @sc{mime} types that are discouraged when viewing
+List of @acronym{MIME} types that are discouraged when viewing
@samp{multipart/alternative}. Viewing agents are supposed to view the
last possible part of a message, as that is supposed to be the richest.
However, users may prefer other types instead, and this list says what
@item mm-text-html-renderer
@vindex mm-text-html-renderer
-This selects the function used to render @sc{html}. The predefined
+This selects the function used to render @acronym{HTML}. The predefined
renderers are selected by the symbols @code{w3},
@code{w3m}@footnote{See @uref{http://emacs-w3m.namazu.org/} for more
information about emacs-w3m}, @code{links}, @code{lynx},
@code{w3m-standalone} or @code{html2text}. If @code{nil} use an
external viewer. You can also specify a function, which will be
-called with a @sc{mime} handle as the argument.
+called with a @acronym{MIME} handle as the argument.
@item mm-inline-text-html-with-images
@vindex mm-inline-text-html-with-images
-Some @sc{html} mails might have the trick of spammers using
+Some @acronym{HTML} mails might have the trick of spammers using
@samp{<img>} tags. It is likely to be intended to verify whether you
have read the mail. You can prevent your personal informations from
leaking by setting this option to @code{nil} (which is the default).
@item mm-w3m-safe-url-regexp
@vindex mm-w3m-safe-url-regexp
A regular expression that matches safe URL names, i.e. URLs that are
-unlikely to leak personal information when rendering @sc{html} email
-(the default value is @samp{\\`cid:}). If @code{nil} consider all
-URLs safe.
+unlikely to leak personal information when rendering @acronym{HTML}
+email (the default value is @samp{\\`cid:}). If @code{nil} consider
+all URLs safe.
@item mm-inline-text-html-with-w3m-keymap
@vindex mm-inline-text-html-with-w3m-keymap
@item mm-file-name-rewrite-functions
@vindex mm-file-name-rewrite-functions
-A list of functions used for rewriting file names of @sc{mime}
+A list of functions used for rewriting file names of @acronym{MIME}
parts. Each function is applied successively to the file name.
Ready-made functions include
@item mm-path-name-rewrite-functions
@vindex mm-path-name-rewrite-functions
-List of functions used for rewriting the full file names of @sc{mime}
+List of functions used for rewriting the full file names of @acronym{MIME}
parts. This is used when viewing parts externally, and is meant for
transforming the absolute name so that non-compliant programs can find
the file where it's saved.
(mm-insert-inline handle text)))
@end lisp
-We see that the function takes a @sc{mime} handle as its parameter. It
+We see that the function takes a @acronym{MIME} handle as its parameter. It
then goes to a temporary buffer, inserts the text of the part, does some
work on the text, stores the result, goes back to the buffer it was
called from and inserts the result.
@cindex MML
@cindex MIME Meta Language
-Creating a @sc{mime} message is boring and non-trivial. Therefore, a
+Creating a @acronym{MIME} message is boring and non-trivial. Therefore, a
library called @code{mml} has been defined that parses a language called
-MML (@sc{mime} Meta Language) and generates @sc{mime} messages.
+MML (@acronym{MIME} Meta Language) and generates @acronym{MIME} messages.
@findex mml-generate-mime
The main interface function is @code{mml-generate-mime}. It will
examine the contents of the current (narrowed-to) buffer and return a
-string containing the @sc{mime} message.
+string containing the @acronym{MIME} message.
@menu
* Simple MML Example:: An example MML document.
* MML Definition:: All valid MML elements.
* Advanced MML Example:: Another example MML document.
* Encoding Customization:: Variables that affect encoding.
-* Charset Translation:: How charsets are mapped from @sc{mule} to @sc{mime}.
-* Conversion:: Going from @sc{mime} to MML and vice versa.
+* Charset Translation:: How charsets are mapped from @sc{mule} to @acronym{MIME}.
+* Conversion:: Going from @acronym{MIME} to MML and vice versa.
* Flowed text:: Soft and hard newlines.
@end menu
The following parameters have meaning in MML; parameters that have no
meaning are ignored. The MML parameter names are the same as the
-@sc{mime} parameter names; the things in the parentheses say which
+@acronym{MIME} parameter names; the things in the parentheses say which
header it will be used in.
@table @samp
@item type
-The @sc{mime} type of the part (@code{Content-Type}).
+The @acronym{MIME} type of the part (@code{Content-Type}).
@item filename
Use the contents of the file in the body of the part
Who to encrypt/sign the part to. This field is used to override any
auto-detection based on the To/CC headers.
+@item sender
+Identity used to sign the part. This field is used to override the
+default key used.
+
@item size
The size (in octets) of the part (@code{Content-Disposition}).
<#/multipart>
@end example
-And this is the resulting @sc{mime} message:
+And this is the resulting @acronym{MIME} message:
@example
Content-Type: multipart/mixed; boundary="=-=-="
@item mm-body-charset-encoding-alist
@vindex mm-body-charset-encoding-alist
-Mapping from @sc{mime} charset to encoding to use. This variable is
+Mapping from @acronym{MIME} charset to encoding to use. This variable is
usually used except, e.g., when other requirements force a specific
encoding (digitally signed messages require 7bit encodings). The
default is
@item mm-content-transfer-encoding-defaults
@vindex mm-content-transfer-encoding-defaults
-Mapping from @sc{mime} types to encoding to use. This variable is usually
+Mapping from @acronym{MIME} types to encoding to use. This variable is usually
used except, e.g., when other requirements force a safer encoding
(digitally signed messages require 7bit encoding). Besides the normal
-@sc{mime} encodings, @code{qp-or-base64} may be used to indicate that for
+@acronym{MIME} encodings, @code{qp-or-base64} may be used to indicate that for
each case the most efficient of quoted-printable and base64 should be
used. You can override this setting on a per-message basis by using
the @code{encoding} MML tag (@pxref{MML Definition}).
@section Charset Translation
@cindex charsets
-During translation from MML to @sc{mime}, for each @sc{mime} part which
+During translation from MML to @acronym{MIME}, for each @acronym{MIME} part which
has been composed inside Emacs, an appropriate charset has to be chosen.
@vindex mail-parse-charset
If you are running a non-@sc{mule} Emacs, this process is simple: If the
-part contains any non-ASCII (8-bit) characters, the @sc{mime} charset
+part contains any non-@acronym{ASCII} (8-bit) characters, the @acronym{MIME} charset
given by @code{mail-parse-charset} (a symbol) is used. (Never set this
variable directly, though. If you want to change the default charset,
please consult the documentation of the package which you use to process
-@sc{mime} messages.
+@acronym{MIME} messages.
@xref{Various Message Variables, , Various Message Variables, message,
Message Manual}, for example.)
-If there are only ASCII characters, the @sc{mime} charset US-ASCII is
+If there are only @acronym{ASCII} characters, the @acronym{MIME} charset US-ASCII is
used, of course.
@cindex MULE
@vindex mm-mime-mule-charset-alist
Things are slightly more complicated when running Emacs with @sc{mule}
support. In this case, a list of the @sc{mule} charsets used in the
-part is obtained, and the @sc{mule} charsets are translated to @sc{mime}
+part is obtained, and the @sc{mule} charsets are translated to @acronym{MIME}
charsets by consulting the variable @code{mm-mime-mule-charset-alist}.
-If this results in a single @sc{mime} charset, this is used to encode
-the part. But if the resulting list of @sc{mime} charsets contains more
+If this results in a single @acronym{MIME} charset, this is used to encode
+the part. But if the resulting list of @acronym{MIME} charsets contains more
than one element, two things can happen: If it is possible to encode the
part via UTF-8, this charset is used. (For this, Emacs must support
the @code{utf-8} coding system, and the part must consist entirely of
characters which have Unicode counterparts.) If UTF-8 is not available
for some reason, the part is split into several ones, so that each one
-can be encoded with a single @sc{mime} charset. The part can only be
-split at line boundaries, though---if more than one @sc{mime} charset is
+can be encoded with a single @acronym{MIME} charset. The part can only be
+split at line boundaries, though---if more than one @acronym{MIME} charset is
required to encode a single line, it is not possible to encode the part.
When running Emacs with @sc{mule} support, the preferences for which
@section Conversion
@findex mime-to-mml
-A (multipart) @sc{mime} message can be converted to MML with the
+A (multipart) @acronym{MIME} message can be converted to MML with the
@code{mime-to-mml} function. It works on the message in the current
-buffer, and substitutes MML markup for @sc{mime} boundaries.
+buffer, and substitutes MML markup for @acronym{MIME} boundaries.
Non-textual parts do not have their contents in the buffer, but instead
have the contents in separate buffers that are referred to from the MML
tags.
@findex mml-to-mime
-An MML message can be converted back to @sc{mime} by the
+An MML message can be converted back to @acronym{MIME} by the
@code{mml-to-mime} function.
These functions are in certain senses ``lossy''---you will not get back
-an identical message if you run @sc{mime-to-mml} and then
-@sc{mml-to-mime}. Not only will trivial things like the order of the
+an identical message if you run @code{mime-to-mml} and then
+@code{mml-to-mime}. Not only will trivial things like the order of the
headers differ, but the contents of the headers may also be different.
For instance, the original message may use base64 encoding on text,
-while @sc{mml-to-mime} may decide to use quoted-printable encoding, and
+while @code{mml-to-mime} may decide to use quoted-printable encoding, and
so on.
In essence, however, these two functions should be the inverse of each
@section Flowed text
@cindex format=flowed
-The Emacs @sc{mime} library will respect the @code{use-hard-newlines}
+The Emacs @acronym{MIME} library will respect the @code{use-hard-newlines}
variable (@pxref{Hard and Soft Newlines, ,Hard and Soft Newlines,
emacs, Emacs Manual}) when encoding a message, and the
``format=flowed'' Content-Type parameter when decoding a message.
Standards change, and so programs have to change to fit in the new
mold. For instance, RFC2045 describes a syntax for the
-@code{Content-Type} header that only allows ASCII characters in the
+@code{Content-Type} header that only allows @acronym{ASCII} characters in the
parameter list. RFC2231 expands on RFC2045 syntax to provide a scheme
-for continuation headers and non-ASCII characters.
+for continuation headers and non-@acronym{ASCII} characters.
The traditional way to deal with this is just to update the library
functions to parse the new syntax. However, this is sometimes the wrong
library, one must choose between the old version of the library and the
new version of the library.
-The Emacs @sc{mime} library takes a different tack. It defines a
+The Emacs @acronym{MIME} library takes a different tack. It defines a
series of low-level libraries (@file{rfc2047.el}, @file{rfc2231.el}
and so on) that parses strictly according to the corresponding
standard. However, normal programs would not use the functions
@item mail-encode-encoded-word-region
@findex mail-encode-encoded-word-region
-Encode the non-ASCII words in the region. For instance,
+Encode the non-@acronym{ASCII} words in the region. For instance,
@samp{Naïve} is encoded as @samp{=?iso-8859-1?q?Na=EFve?=}.
@item mail-encode-encoded-word-buffer
@findex mail-encode-encoded-word-buffer
-Encode the non-ASCII words in the current buffer. This function is
+Encode the non-@acronym{ASCII} words in the current buffer. This function is
meant to be called narrowed to the headers of a message.
@item mail-encode-encoded-word-string
@node rfc2045
@section rfc2045
-RFC2045 is the ``main'' @sc{mime} document, and as such, one would
+RFC2045 is the ``main'' @acronym{MIME} document, and as such, one would
imagine that there would be a lot to implement. But there isn't, since
most of the implementation details are delegated to the subsequent
RFCs.
@node rfc2047
@section rfc2047
-RFC2047 (Message Header Extensions for Non-ASCII Text) specifies how
-non-ASCII text in headers are to be encoded. This is actually rather
+RFC2047 (Message Header Extensions for Non-@acronym{ASCII} Text) specifies how
+non-@acronym{ASCII} text in headers are to be encoded. This is actually rather
complicated, so a number of variables are necessary to tweak what this
library does.
@node time-date
@section time-date
-While not really a part of the @sc{mime} library, it is convenient to
+While not really a part of the @acronym{MIME} library, it is convenient to
document this library here. It deals with parsing @code{Date} headers
and manipulating time. (Not by using tesseracts, though, I'm sorry to
say.)
@cindex HZ
@cindex Chinese
-RFC1843 deals with mixing Chinese and ASCII characters in messages. In
-essence, RFC1843 switches between ASCII and Chinese by doing this:
+RFC1843 deals with mixing Chinese and @acronym{ASCII} characters in messages. In
+essence, RFC1843 switches between @acronym{ASCII} and Chinese by doing this:
@example
-This sentence is in ASCII.
+This sentence is in @acronym{ASCII}.
The next sentence is in GB.~@{<:Ky2;S@{#,NpJ)l6HK!#~@}Bye.
@end example
@node mailcap
@section mailcap
-The @file{~/.mailcap} file is parsed by most @sc{mime}-aware message
+The @file{~/.mailcap} file is parsed by most @acronym{MIME}-aware message
handlers and describes how elements are supposed to be displayed.
Here's an example file:
Parse the @file{~/.mailcap} file.
@item mailcap-mime-info
-Takes a @sc{mime} type as its argument and returns the matching viewer.
+Takes a @acronym{MIME} type as its argument and returns the matching viewer.
@end table
@node Standards
@chapter Standards
-The Emacs @sc{mime} library implements handling of various elements
+The Emacs @acronym{MIME} library implements handling of various elements
according to a (somewhat) large number of RFCs, drafts and standards
documents. This chapter lists the relevant ones. They can all be
fetched from @uref{http://quimby.gnus.org/notes/}.
Media Types
@item RFC2047
-Message Header Extensions for Non-ASCII Text
+Message Header Extensions for Non-@acronym{ASCII} Text
@item RFC2048
Registration Procedures
Conformance Criteria and Examples
@item RFC2231
-@sc{mime} Parameter Value and Encoded Word Extensions: Character Sets,
+@acronym{MIME} Parameter Value and Encoded Word Extensions: Character Sets,
Languages, and Continuations
@item RFC1843
HZ - A Data Format for Exchanging Files of Arbitrarily Mixed Chinese and
-ASCII characters
+@acronym{ASCII} characters
@item draft-ietf-drums-msg-fmt-05.txt
Draft for the successor of RFC822
@item RFC2112
-The @sc{mime} Multipart/Related Content-type
+The @acronym{MIME} Multipart/Related Content-type
@item RFC1892
The Multipart/Report Content Type for the Reporting of Mail System
projects / elisp / gnus.git- / blobdiff