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Emacs provides extensive help features which revolve around a single
character, `C-h'. `C-h' is a prefix key that is used only for
documentation-printing commands. The characters you can type after
`C-h' are called "help options". One help option is `C-h'; you use it
to ask for help about using `C-h'.
`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:
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:
You should type one of those characters.
Typing a third `C-h' displays a description of what the options mean;
Emacs still waits for you to type an option. To cancel, type `C-g'.
Here is a summary of the defined help commands.
`C-h a STRING RET'
Display a list of commands whose names contain STRING (`command-
Display a table of all key bindings currently in effect, with
local bindings of the current major mode first, followed by all
global bindings (`describe-bindings').
`C-h c KEY'
Print the name of the command that KEY runs (`describe-key-
briefly'). `c' is for `character'. For more extensive
information on KEY, use `C-h k'.
`C-h f FUNCTION RET'
Display documentation on the Lisp function named FUNCTION
(`describe-function'). Note that commands are Lisp functions, so
a command name may be used.
Run Info, the program for browsing documentation files (`info').
The complete Emacs manual is available online in Info.
`C-h k KEY'
Display name and documentation of the command KEY runs
Display a description of the last 100 characters you typed
Display documentation of the current major mode (`describe-mode').
Display documentation of Emacs changes, most recent first
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 (`describe-pointer').
Display current contents of the syntax table, plus an explanation
of what they mean (`describe-syntax').
Display the Emacs tutorial (`help-with-tutorial').
`C-h v VAR RET'
Display the documentation of the Lisp variable VAR (`describe-
`C-h w COMMAND RET'
Print which keys run the command named COMMAND (`where-is').
`M-x apropos REGEXP'
Show all symbols whose names contain matches for REGEXP.
Documentation for a Key
The most basic `C-h' options are `C-h c' (`describe-key-briefly')
and `C-h k'
(`describe-key'). `C-h c KEY' prints the name of the command that KEY
is bound to in the echo area. For example, `C-h c C-f' prints
`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 KEY does.
`C-h k KEY' is similar to `C-h c' but gives more information. It
displays the documentation string of the function KEY is bound to as
well as its name. KEY is a string or vector of events. When called
interactively, 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.
Help by Command or Variable Name
`C-h f' (`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 FUNCTION to get the documentation of a command that you know
by name. For example,
C-h f auto-fill-mode RET
displays the documentation for `auto-fill-mode'. Using `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 `M-x'. If the
variable `describe-function-show-arglist' is `t', `describe-function'
shows its arglist if the FUNCTION is not an autoload function.
`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
`(make-vector len)' and want to make sure you are using `make-vector'
properly, type `C-h f make-vector RET'. Because `C-h f' allows all
function names, not just command names, you may find that some of your
favorite abbreviations that work in `M-x' don't work in `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 RET, leaving the minibuffer empty, `C-h f' by default
describes the function called by the innermost Lisp expression in the
buffer around point, provided that that is a valid, defined Lisp
function name. For example, if point is located following the text
`(make-vector (car x)', the innermost list containing point is the one
starting with `(make-vector', so the default is to describe the
`C-h f' is often useful just to verify that you have the right
spelling for the function name. If `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 `C-g' to cancel the `C-h f' command
and continue editing.
`C-h w COMMAND RET' (`where-s') tells you what keys are bound to
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 `M-x' to call the command.
`C-h v' (`describe-variable') is like `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.
Show only symbols that are names of commands (`command-apropos').
`M-x apropos REGEXP'
Show all symbols whose names comtain matches for REGEXP.
It is possible to ask a question like, "What are the commands for
working with files?" To do this, type `C-h a file RET', which displays
a list of all command names that contain `file', such as `copy-file',
`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
`find-file' by typing `C-x C-f'. The `a' in `C-h a' stands for
`Apropos'; `C-h a' runs the Lisp function `command-apropos'.
Because `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 `C-h a
kill-backwards RET' doesn't reveal any commands, don't give up. Try
just `kill', or just `backwards', or just `back'. Be persistent.
Pretend you are playing Adventure. Also note that you can use a
regular expression as the argument (Note: Regexps.).
Here is a set of arguments to give to `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 `apropos' strings.
char, line, word, sentence, paragraph, region, page, sexp, list,
defun, buffer, screen, 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.
To list all Lisp symbols that contain a match for a regexp, not just
the ones that are defined as commands, use the command `M-x apropos'
instead of `C-h a'.
Other Help Commands
`C-h i' (`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 `h' after entering Info to run a
tutorial on using Info.
If something surprising happens, and you are not sure what commands
you typed, use `C-h l' (`view-lossage'). `C-h l' prints the last 100
command characters you typed. If you see commands you don't know, use
`C-h c' to find out what they do.
Emacs has several major modes. Each mode redefines a few keys and
makes a few other changes in how editing works. `C-h m'
(`describe-mode') prints documentation on the current major mode, which
normally describes all the commands that are changed in this mode.
`C-h b' (`describe-bindings') and `C-h s' (`describe-syntax')
present information about the current Emacs mode that is not covered by
`C-h m'. `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 (Note: Key Bindings.). `C-h s'
displays the contents of the syntax table with explanations of each
character's syntax (Note: Syntax.).
The other `C-h' options display various files of useful information.
`C-h C-w' (`describe-no-warranty') displays details on the complete
absence of warranty for GNU Emacs. `C-h n' (`view-emacs-news')
displays the file `emacs/etc/NEWS', which contains documentation on
Emacs changes arranged chronologically. `C-h t' (`help-with-tutorial')
displays the learn-by-doing Emacs tutorial. `C-h C-c'
(`describe-copying') displays the file `emacs/etc/COPYING', which tells
you the conditions you must obey in distributing copies of Emacs. `C-h
C-d' (`describe-distribution') displays another file named
`emacs/etc/DISTRIB', which tells you how you can order a copy of the
latest version of Emacs.
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