XEmacs 21.2-b1

[chise/xemacs-chise.git.1] / man / xemacs / help.texi

@node Help, Mark, M-x, Top
@chapter Help
@cindex help
@cindex self-documentation

  Emacs provides extensive help features which revolve around a single
character, @kbd{C-h}.  @kbd{C-h} is a prefix key that is used only for
documentation-printing commands.  The characters you can type after
@kbd{C-h} are called @dfn{help options}.  One help option is @kbd{C-h};
you use it to ask for help about using @kbd{C-h}.

  @kbd{C-h C-h} prints a list of the possible help options, and then asks
you to type the desired option.  It prompts with the string:

@smallexample
A, B, C, F, I, K, L, M, N, S, T, V, W, C-c, C-d, C-n, C-w or C-h for more help:
@end smallexample

@noindent
You should type one of those characters.

  Typing a third @kbd{C-h} displays a description of what the options mean;
Emacs still waits for you to type an option.  To cancel, type @kbd{C-g}.

  Here is a summary of the defined help commands.

@table @kbd
@item C-h a @var{string} @key{RET}
Display a list of commands whose names contain @var{string}
(@code{command-@*apropos}).@refill
@item C-h b
Display a table of all key bindings currently in effect, with local bindings of
the current major mode first, followed by all global bindings
(@code{describe-bindings}).
@item C-h c @var{key}
Print the name of the command that @var{key} runs (@code{describe-key-@*briefly}).
@kbd{c} is for `character'.  For more extensive information on @var{key},
use @kbd{C-h k}.
@item C-h f @var{function} @key{RET}
Display documentation on the Lisp function named @var{function}
(@code{describe-function}).  Note that commands are Lisp functions, so
a command name may be used.
@item C-h i
Run Info, the program for browsing documentation files (@code{info}).
The complete Emacs manual is available online in Info.
@item C-h k @var{key}
Display name and documentation of the command @var{key} runs (@code{describe-key}).
@item C-h l
Display a description of the last 100 characters you typed
(@code{view-lossage}).
@item C-h m
Display documentation of the current major mode (@code{describe-mode}).
@item C-h n
Display documentation of Emacs changes, most recent first
(@code{view-emacs-news}).
@item C-h p
Display a table of all mouse bindings currently in effect now, with
local bindings of the current major mode first, followed by all global bindings
(@code{describe-pointer}).
@item C-h s
Display current contents of the syntax table, plus an explanation of
what they mean (@code{describe-syntax}).
@item C-h t
Display the Emacs tutorial (@code{help-with-tutorial}).
@item C-h v @var{var} @key{RET}
Display the documentation of the Lisp variable @var{var}
(@code{describe-@*variable}).
@item C-h w @var{command} @key{RET}
Print which keys run the command named @var{command} (@code{where-is}).
@item M-x apropos @var{regexp}
Show all symbols whose names contain matches for @var{regexp}.
@end table

@section Documentation for a Key

@kindex C-h c
@findex describe-key-briefly
  The most basic @kbd{C-h} options are @kbd{C-h c}
(@code{describe-key-briefly}) and @kbd{C-h k}@*(@code{describe-key}).
@kbd{C-h c @var{key}} prints the name of the command that @var{key} is
bound to in the echo area.  For example, @kbd{C-h c C-f} prints
@samp{forward-char}.  Since command names are chosen to describe what
the command does, using this option is a good way to get a somewhat cryptic
description of what @var{key} does.@refill

@kindex C-h k
@findex describe-key
  @kbd{C-h k @var{key}} is similar to @kbd{C-h c} but gives more
information.  It displays the documentation string of the function
@var{key} is bound to as well as its name.  @var{key} is a string or
vector of events.  When called interactively, @var{key} may also be a menu
selection.  This information does not usually fit into the echo area, so a
window is used for the display.

@section Help by Command or Variable Name

@kindex C-h f
@findex describe-function
@vindex describe-function-show-arglist
  @kbd{C-h f} (@code{describe-function}) reads the name of a Lisp
function using the minibuffer, then displays that function's
documentation string in a window.  Since commands are Lisp functions,
you can use the argument @var{function} to get the documentation of a
command that you know by name.  For example,

@example
C-h f auto-fill-mode @key{RET}
@end example

@noindent
displays the documentation for @code{auto-fill-mode}. Using @kbd{C-h f}
is the only way to see the documentation of a command that is not bound
to any key, that is, a command you would normally call using @kbd{M-x}.
If the variable @code{describe-function-show-arglist} is @code{t},
@code{describe-function} shows its arglist if the @var{function} is not
an autoload function.

  @kbd{C-h f} is also useful for Lisp functions you are planning to
use in a Lisp program.  For example, if you have just written the code
@code{(make-vector len)} and want to make sure you are using
@code{make-vector} properly, type @kbd{C-h f make-vector @key{RET}}.  Because
@kbd{C-h f} allows all function names, not just command names, you may find
that some of your favorite abbreviations that work in @kbd{M-x} don't work
in @kbd{C-h f}.  An abbreviation may be unique among command names, yet fail
to be unique when other function names are allowed.


If you type @key{RET}, leaving the minibuffer empty, @kbd{C-h f} by
default describes the function called by the innermost Lisp expression
in the buffer around point, @i{provided} that that is a valid, defined Lisp
function name.  For example, if point is located following the text
@samp{(make-vector (car x)}, the innermost list containing point is the
one starting with @samp{(make-vector}, so the default is to describe
the function @code{make-vector}.

  @kbd{C-h f} is often useful just to verify that you have the right
spelling for the function name.  If @kbd{C-h f} mentions a default in the
prompt, you have typed the name of a defined Lisp function.  If that is
what you wanted to know, just type @kbd{C-g} to cancel the @kbd{C-h f}
command and continue editing.

@kindex C-h w
@findex where-is
  @kbd{C-h w @var{command} @key{RET}} (@code{where-s}) tells you what 
keys are bound to @var{command}.  It prints a list of the keys in the
echo area. Alternatively, it informs you that a command is not bound to 
any keys, which implies that you must use @kbd{M-x} to call the 
command.@refill

@kindex C-h v
@findex describe-variable
  @kbd{C-h v} (@code{describe-variable}) is like @kbd{C-h f} but
describes Lisp variables instead of Lisp functions.  Its default is the
Lisp symbol around or before point, if that is the name of a known Lisp
variable.  @xref{Variables}.@refill

@section Apropos

@kindex C-h a
@findex command-apropos
@cindex apropos 

@table @kbd
@item C-h a 
Show only symbols that are names of commands
(@code{command-apropos}).@refill

@item M-x apropos @var{regexp}
Show all symbols whose names comtain matches for @var{regexp}.
@end table

  It is possible to ask a question like, ``What are the commands for
working with files?''  To do this, type @kbd{C-h a file @key{RET}},
which displays a list of all command names that contain @samp{file},
such as @code{copy-file}, @code{find-file}, and so on.  With each
command name a brief description of its use and information on the keys
you can use to invoke it is displayed.  For example, you would be
informed that you can invoke @code{find-file} by typing @kbd{C-x C-f}.
The @kbd{a} in @kbd{C-h a} stands for `Apropos'; @kbd{C-h a} runs the
Lisp function @code{command-apropos}.@refill

  Because @kbd{C-h a} looks only for functions whose names contain the
string you specify, you must use ingenuity in choosing the string.  If
you are looking for commands for killing backwards and @kbd{C-h a
kill-backwards @key{RET}} doesn't reveal any commands, don't give up.
Try just @kbd{kill}, or just @kbd{backwards}, or just @kbd{back}.  Be
persistent.  Pretend you are playing Adventure.  Also note that you can
use a regular expression as the argument (@pxref{Regexps}).

  Here is a set of arguments to give to @kbd{C-h a} that covers many
classes of Emacs commands, since there are strong conventions for naming
standard Emacs commands.  By giving you a feeling for the naming
conventions, this set of arguments can also help you develop a
technique for picking @code{apropos} strings.

@quotation
char, line, word, sentence, paragraph, region, page, sexp, list, defun,
buffer, frame, window, file, dir, register, mode,
beginning, end, forward, backward, next, previous, up, down, search, goto,
kill, delete, mark, insert, yank, fill, indent, case,
change, set, what, list, find, view, describe.
@end quotation

@findex apropos
  To list all Lisp symbols that contain a match for a regexp, not just
the ones that are defined as commands, use the command @kbd{M-x apropos}
instead of @kbd{C-h a}.

@section Other Help Commands

@kindex C-h i
@findex info
  @kbd{C-h i} (@code{info}) runs the Info program, which is used for
browsing through structured documentation files.  The entire Emacs manual
is available within Info.  Eventually all the documentation of the GNU
system will be available.  Type @kbd{h} after entering Info to run
a tutorial on using Info.

@kindex C-h l
@findex view-lossage
  If something surprising happens, and you are not sure what commands you
typed, use @kbd{C-h l} (@code{view-lossage}).  @kbd{C-h l} prints the last
100 command characters you typed.  If you see commands you don't
know, use @kbd{C-h c} to find out what they do.

@kindex C-h m
@findex describe-mode
  Emacs has several major modes. Each mode redefines a few keys and
makes a few other changes in how editing works.  @kbd{C-h m}
(@code{describe-mode}) prints documentation on the current major mode,
which normally describes all the commands that are changed in this mode.

@kindex C-h b
@findex describe-bindings
  @kbd{C-h b} (@code{describe-bindings}) and @kbd{C-h s}
(@code{describe-syntax}) present information about the current Emacs
mode that is not covered by @kbd{C-h m}.  @kbd{C-h b} displays a list of
all key bindings currently in effect, with the local bindings of the current
major mode first, followed by the global bindings (@pxref{Key
Bindings}).  @kbd{C-h s} displays the contents of the syntax table with
explanations of each character's syntax (@pxref{Syntax}).@refill

@kindex C-h n
@findex view-emacs-news
@kindex C-h t
@findex help-with-tutorial
@kindex C-h C-c
@findex describe-copying
@kindex C-h C-d
@findex describe-distribution
@kindex C-h C-w
@findex describe-no-warranty
  The other @kbd{C-h} options display various files of useful
information.  @kbd{C-h C-w} (@code{describe-no-warranty}) displays
details on the complete absence of warranty for XEmacs.  @kbd{C-h n} 
(@code{view-emacs-news}) displays the file @file{emacs/etc/NEWS}, which 
contains documentation on Emacs changes arranged chronologically.  
@kbd{C-h t} (@code{help-with-tutorial}) displays the learn-by-doing
Emacs tutorial. @kbd{C-h C-c} (@code{describe-copying}) displays the file
@file{emacs/etc/COPYING}, which tells you the conditions you must obey
in distributing copies of Emacs.  @kbd{C-h C-d}
(@code{describe-distribution}) displays another file named
@file{emacs/etc/DISTRIB}, which tells you how you can order a copy of
the latest version of Emacs.@refill