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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 that you can type after C-h are called help options. One help option is C-h; that is how you ask for help about using C-h.
C-h C-h prints a list of the possible help options, and then asks you to go ahead and type the option. It prompts with a string
A B C F I K L M N S T V W C-c C-d C-n C-w. Type C-h again for more help:
and you should type one of those characters.
Typing a third C-h displays a description of what the options mean; it still waits for you to type an option. To cancel, type C-g.
Here is a summary of the defined help commands.
command-apropos).
describe-bindings).
describe-key-briefly).
c is for `character'. For more extensive information on key,
use C-h k.
describe-function). Note that commands are Lisp functions, so
a command name may be used.
info).
The complete Emacs manual is available on-line in Info.
describe-key).
view-lossage).
describe-mode).
view-emacs-news).
describe-syntax).
help-with-tutorial).
describe-variable).
where-is).
The most basic C-h options are C-h c
(describe-key-briefly) and C-h k (describe-key).
C-h c key prints in the echo area the name of the command that
key is bound to. For example, C-h c C-f prints
`forward-char'. Since command names are chosen to describe what the
command does, this is a good way to get a very brief description of what
key does.
C-h k key is similar but gives more information. It displays the documentation string of the command key is bound to as well as its name. This is too big for the echo area, so a window is used for the display.
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 this to get
the documentation of a command that is known by name. For example,
C-h f auto-fill-mode RET
displays the documentation of auto-fill-mode. This is the only
way to see the documentation of a command that is not bound to any key
(one which you would normally call using M-x).
C-h f is also useful for Lisp functions that you are planning to
use in a Lisp program. For example, if you have just written the code
(make-vector len) and want to be sure that 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.
The function name for C-h f to describe has a default which is
used if you type RET leaving the minibuffer empty. The default is
the function called by the innermost Lisp expression in the buffer around
point, provided 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 that starts with
`(make-vector', so the default is to describe the function
make-vector.
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 tells you what you want to know, just type C-g to cancel the C-h f command and go on editing.
C-h w command RET tells you what keys are bound to command. It prints a list of the keys in the echo area. Alternatively, it says that the command is not on any keys, which implies that you must use M-x to call it.
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, but only if that is the name of a known Lisp
variable. See section Variables.
A more sophisticated sort of question to ask is, "What are the commands
for working with files?" For 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
appears a brief description of how to use the command, and what keys you
can currently invoke it with. For example, it would say 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 which 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, 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 (see section Syntax of Regular Expressions).
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
the standard Emacs commands. By giving you a feel for the naming
conventions, this set should also serve to aid you in developing 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.
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 in. If you see commands that you don't
know, you can use C-h c to find out what they do.
Emacs has several major modes, each of which 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 other information about the current
Emacs mode. C-h b displays a list of all the key bindings now
in effect; the local bindings of the current major mode first,
followed by the global bindings (see section Customizing Key Bindings). C-h s
displays the contents of the syntax table, with explanations of each
character's syntax (see section The Syntax Table).
The other C-h options display various files of useful
information. C-h C-w displays the full 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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