Help
****

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-
     apropos).

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 (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.

C-h i
     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 (describe-key).

C-h l
     Display a description of the last 100 characters you typed (view-lossage).

C-h m
     Display documentation of the current major mode (describe-mode).

C-h n
     Display documentation of Emacs changes, most recent first (view-emacs-news).

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 (describe-pointer).

C-h s
     Display current contents of the syntax table, plus an explanation of what they mean (describe-syntax).

C-h t
     Display the Emacs tutorial (help-with-tutorial).

C-h v VAR RET
     Display the documentation of the Lisp variable VAR (describe-
     variable).

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 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 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.  See Variables.

Apropos
=======

C-h a
     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 (see 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, 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.

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 (see Key Bindings).  C-h s displays the contents of the syntax table with explanations of each character's syntax (see 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 XEmacs.  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.