Help
****

Emacs provides extensive help features accessible through a single character, C-h.  C-h is a prefix key that is used for commands that display documentation.  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.  To cancel, type C-g.  The function key F1 is equivalent to C-h.

C-h C-h (help-for-help) displays a list of the possible help options, each with a brief description.  Before you type a help option, you can use SPC or DEL to scroll through the list.

C-h or F1 means ``help'' in various other contexts as well.  After a prefix key, it displays a list of the alternatives that can follow the prefix key.  (A few prefix keys don't support C-h, because they define other meanings for it, but they all support F1.)

Most help buffers use a special major mode, Help mode, which lets you scroll conveniently with SPC and DEL.  It also offers hyperlinks to URLs and further help regarding cross-referenced names, Info nodes, customization buffers and the like.  See Help Mode.

If you are looking for a certain feature, but don't know where exactly it is documented, and aren't sure of the name of a related command or variable, we recommend trying these methods.  Usually it is best to start with an apropos command, then try searching the manual index, then finally look in the FAQ and the package keywords.

C-h a TOPIC RET
     This searches for commands whose names match TOPIC, which should be a list of words or a regular expression (see Regexps).  Browse the buffer that this command displays to find what you are looking for.  See Apropos.

M-x apropos RET TOPIC RET
     This works like C-h a, but it also searches for noninteractive functions and for variables.  See Apropos.

C-h d TOPIC RET
     This searches the documentation strings (the built-in short descriptions) of all variables and functions (not their names) for a match for TOPIC, a list or words or a regular expression. See Apropos.

C-h i d m emacs RET i TOPIC RET
     This looks up TOPIC in the indices of the Emacs on-line manual. If there are several matches, Emacs displays the first one.  You can then press , to move to other matches, until you find what you are looking for.

C-h i d m emacs RET s TOPIC RET
     Similar, but searches for TOPIC (which can be a regular expression) in the text of the manual rather than in its indices.

C-h C-f
     This brings up the Emacs FAQ.  You can use the Info commands to browse it.

C-h p
     Finally, you can try looking up a suitable package using keywords pertinent to the feature you need.  See Library Keywords.

To find the documentation of a key sequence or a menu item, type C-h K and then type that key sequence or select the menu item.  This looks up the description of the command invoked by the key or the menu in the appropriate manual (not necessarily the Emacs manual).  Likewise, use C-h F for reading documentation of a command.

Help Summary
============

Here is a summary of the Emacs interactive help commands. See Help Files, for other help commands that just display a pre-written file of information.

C-h a TOPIC RET
     Display a list of commands whose names match word list or regexp TOPIC (apropos-command).

C-h b
     Display a table of all key bindings in effect now, in this order: minor mode bindings, major mode bindings, and global bindings (describe-bindings).

C-h c KEY
     Show the name of the command that KEY runs (describe-key-briefly).  Here c stands for ``character.'' For more extensive information on KEY, use C-h k.

C-h d TOPIC RET
     Display a list of commands and variables whose documentation match word list or regexp TOPIC (apropos-documentation).

C-h e
     Display the *Messages* buffer (view-echo-area-messages).

C-h f FUNCTION RET
     Display documentation on the Lisp function named FUNCTION (describe-function).  Since commands are Lisp functions, a command name may be used.

C-h h
     Display the HELLO file, which shows examples of various character sets.

C-h i
     Run Info, the program for browsing documentation files (info). The complete Emacs manual is available on-line in Info.

C-h k KEY
     Display the name and documentation of the command that 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 p
     Find packages by topic keyword (finder-by-keyword).

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

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

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

C-h w COMMAND RET
     Show which keys run the command named COMMAND (where-is).

C-h C CODING RET
     Describe coding system CODING (describe-coding-system).

C-h C RET
     Describe the coding systems currently in use.

C-h I METHOD RET
     Describe an input method (describe-input-method).

C-h L LANGUAGE-ENV RET
     Display information on the character sets, coding systems, and input methods used for language environment LANGUAGE-ENV (describe-language-environment).

C-h F FUNCTION RET
     Enter Info and go to the node documenting the Emacs function FUNCTION (Info-goto-emacs-command-node).

C-h K KEY
     Enter Info and go to the node where the key sequence KEY is documented (Info-goto-emacs-key-command-node).

C-h S SYMBOL RET
     Display the Info documentation on symbol SYMBOL according to the programming language you are editing (info-lookup-symbol).

C-h .
     Display a help message associated with special text areas, such as links in *Help* buffers (display-local-help).

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 displays in the echo area the name of the command that KEY is bound to.  For example, C-h c C-f displays forward-char.  Since command names are chosen to describe what the commands do, 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 as well as its name. This is too big for the echo area, so a window is used for the display.

C-h c and C-h k work for any sort of key sequences, including function keys and mouse events.

C-h w COMMAND RET tells you what keys are bound to COMMAND.  It displays a list of the keys in the echo area.  If it says the command is not on any key, you must use M-x to run it. C-h w runs the command where-is.

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 this to get the documentation of a command that you know by name.  For example,

     C-h f auto-fill-mode RET

displays the documentation of auto-fill-mode.  This is the only way to get the documentation of a command that is not bound to any key (one which you would normally run 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 expression (make-vector len) and want to check 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 completion 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 default function name for C-h f to describe, if you type just RET, is the name of 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 name from the buffer as the default, that name must be defined as a Lisp function.  If that is all you want to know, just type C-g to cancel the C-h f command, then go on editing.

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 Variables.

Help buffers describing Emacs variables and functions normally have hyperlinks to the definition, if you have the source files installed. (see Hyperlinking.)  If you know Lisp (or C), this provides the ultimate documentation.  If you don't know Lisp, you should learn it. If you are just using Emacs, treating Emacs as an object (file), then you don't really love it.  For true intimacy with your editor, you need to read the source code.

Apropos
=======

A more sophisticated sort of question to ask is, ``What are the commands for working with files?''  To ask this question, type C-h a file RET, which displays a list of all command names that contain file, including 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 command apropos-command.  This command normally checks only commands (interactive functions); if you specify a prefix argument, it checks noninteractive functions as well.

Because C-h a looks only for commands matching the string you specify, you may not find what you want on the first try.  In that case, don't just give up.  You can give Apropos a list of words to search for.  When more than one word is specified, at least two of those words must be present for an item to match.  If you are looking for commands to kill a chunk of text before point, try C-h a kill back behind before RET.  For even greater flexibility, you can also supply a regular expression to Apropos (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 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, rect, buffer, frame, window, face, 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, default.

To list all user variables that match a word list or regexp, use the command M-x apropos-variable.  By default, this command shows only variables meant for user customization; if you specify a prefix argument, it checks all variables.

To list all Lisp symbols that contain a match for a word list or regexp, not just the ones that are defined as commands, use the command M-x apropos instead of C-h a.  This command does not check key bindings by default; specify a numeric argument if you want it to check them.

The apropos-documentation command is like apropos except that it searches documentation strings as well as symbol names for matches for the specified topic, a word list or regular expression.

The apropos-value command is like apropos except that it searches symbols' values for matches for the specified word list or regular expression.  This command does not check function definitions or property lists by default; specify a numeric argument if you want it to check them.

If the variable apropos-do-all is non-nil, the commands above all behave as if they had been given a prefix argument.

By default, Apropos lists the search results in alphabetical order. If the variable apropos-sort-by-scores is non-nil, Apropos tries to guess the relevance of each result, and displays the most relevant ones first.

By default, Apropos lists the search results for apropos-documentation in order of relevance. If the variable apropos-documentation-sort-by-scores is nil, Apropos will list documentation in alphabetical order.

If you want more information about a function definition, variable or symbol property listed in the Apropos buffer, you can click on it with Mouse-1 or Mouse-2, or move there and type RET.

Keyword Search for Lisp Libraries
=================================

The C-h p command lets you search the standard Emacs Lisp libraries by topic keywords.  Here is a partial list of keywords you can use:

abbrev  abbreviation handling, typing shortcuts, macros.
bib  code related to the bib bibliography processor.
c  support for the C language and related languages.
calendar  calendar and time management support.
comm  communications, networking, remote access to files.
convenience  convenience features for faster editing.
data  support for editing files of data.
docs  support for Emacs documentation.
emulations  emulations of other editors.
extensions  Emacs Lisp language extensions.
faces  support for multiple fonts.
files  support for editing and manipulating files.
frames  support for Emacs frames and window systems.
games  games, jokes and amusements.
hardware  support for interfacing with exotic hardware.
help  support for on-line help systems.
hypermedia  support for links between text or other media types.
i18n  internationalization and alternate character-set support.
internal  code for Emacs internals, build process, defaults.
languages  specialized modes for editing programming languages.
lisp  Lisp support, including Emacs Lisp.
local  code local to your site.
maint  maintenance aids for the Emacs development group.
mail  modes for electronic-mail handling.
matching  various sorts of searching and matching.
mouse  mouse support.
multimedia  images and sound support.
news  support for netnews reading and posting.
oop  support for object-oriented programming.
outlines  support for hierarchical outlining.
processes  process, subshell, compilation, and job control support.
terminals  support for terminal types.
tex  supporting code for the TeX formatter.
tools  programming tools.
unix  front-ends/assistants for, or emulators of, UNIX-like features.
wp  word processing.

Help for International Language Support
=======================================

You can use the command C-h L (describe-language-environment) to find out information about the support for a specific language environment.  See Language Environments.  This tells you which languages this language environment is useful for, and lists the character sets, coding systems, and input methods that go with it.  It also shows some sample text to illustrate scripts.

The command C-h h (view-hello-file) displays the file etc/HELLO, which shows how to say ``hello'' in many languages.

The command C-h I (describe-input-method) describes information about input methods---either a specified input method, or by default the input method in use.  See Input Methods.

The command C-h C (describe-coding-system) describes information about coding systems---either a specified coding system, or the ones currently in use.  See Coding Systems.

Help Mode Commands
==================

Help buffers provide the same commands as View mode (see Misc File Ops), plus a few special commands of their own.

SPC
     Scroll forward.

DEL
BS
     Scroll backward.  On some keyboards, this key is known as BS or backspace.

RET
     Follow a cross reference at point.

TAB
     Move point forward to the next cross reference.

S-TAB
     Move point back to the previous cross reference.

Mouse-1
Mouse-2
     Follow a cross reference that you click on.

When a function name (see Running Commands by Name) or variable name (see Variables) appears in the documentation, it normally appears inside paired single-quotes.  You can click on the name with Mouse-1 or Mouse-2, or move point there and type RET, to view the documentation of that command or variable.  Use C-c C-b to retrace your steps.

You can follow cross references to URLs (web pages) as well.  When you follow a cross reference that is a URL, the browse-url command is used to view the web page in a browser of your choosing. See Browse-URL.

There are convenient commands for moving point to cross references in the help text.  TAB (help-next-ref) moves point down to the next cross reference.  Use S-TAB to move point up to the previous cross reference (help-previous-ref).

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.

With a numeric argument, C-h i selects an Info buffer with the number appended to the default *info* buffer name (e.g. *info*<2>).  This is useful if you want to browse multiple Info manuals simultaneously.  If you specify just C-u as the prefix argument, C-h i prompts for the name of a documentation file.  This way, you can browse a file which doesn't have an entry in the top-level Info menu.  It is also handy when you need to get to the documentation quickly, and you know the exact name of the file.

There are two special help commands for accessing Emacs documentation through Info.  C-h F FUNCTION RET enters Info and goes straight to the documentation of the Emacs function FUNCTION.  C-h K KEY enters Info and goes straight to the documentation of the key KEY.  These two keys run the commands Info-goto-emacs-command-node and Info-goto-emacs-key-command-node.  You can use C-h K to find the documentation of a menu item: just select that menu item when C-h K prompts for a key.

C-h F and C-h K know about commands and keys described in manuals other than the Emacs manual.  Thus, they make it easier to find the documentation of commands and keys when you are not sure which manual describes them, like when using some specialized mode.

When editing a program, if you have an Info version of the manual for the programming language, you can use the command C-h S (info-lookup-symbol) to refer to the manual documentation for a symbol (keyword, function or variable).  The details of how this command works depend on the major mode.

If something surprising happens, and you are not sure what commands you typed, use C-h l (view-lossage).  C-h l displays 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.

To review messages that recently appeared in the echo area, use C-h e (view-echo-area-messages).  This displays the buffer *Messages*, where those messages are kept.

Emacs has numerous major modes, each of which redefines a few keys and makes a few other changes in how editing works.  C-h m (describe-mode) displays 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, showing the local bindings defined by the current minor modes first, then the local bindings defined by the current major mode, and finally 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).

You can get a similar list for a particular prefix key by typing C-h after the prefix key.  (There are a few prefix keys for which this does not work---those that provide their own bindings for C-h.  One of these is ESC, because ESC C-h is actually C-M-h, which marks a defun.)

Help Files
==========

The Emacs help commands described above display the state of data bases within Emacs.  Emacs has a few other help commands that display pre-written help files.  These commands all have the form C-h C-CHAR; that is, C-h followed by a control character.

The other C-h options display various files containing useful information.

C-h C-c
     Displays the Emacs copying conditions (describe-copying). These are the rules under which you can copy and redistribute Emacs.

C-h C-d
     Displays information on how to download or order the latest version of Emacs and other GNU software (describe-distribution).

C-h C-e
     Displays the list of known Emacs problems, sometimes with suggested workarounds (view-emacs-problems).

C-h C-f
     Displays the Emacs frequently-answered-questions list (view-emacs-FAQ).

C-h C-n
     Displays the Emacs ``news'' file, which lists new Emacs features, most recent first (view-emacs-news).

C-h C-p
     Displays general information about the GNU Project (describe-project).

C-h C-t
     Displays the Emacs to-do list (view-todo).

C-h C-w
     Displays the full details on the complete absence of warranty for GNU Emacs (describe-no-warranty).

Help on Active Text and Tooltips
================================

When a region of text is ``active,'' so that you can select it with the mouse or a key like RET, it often has associated help text. Areas of the mode line are examples.  On most window systems, the help text is displayed as a ``tooltip'' (sometimes known as ``balloon help''), when you move the mouse over the active text.  See Tooltips. On some systems, it is shown in the echo area.  On text-only terminals, Emacs may not be able to follow the mouse and hence will not show the help text on mouse-over.

You can also access text region help info using the keyboard.  The command C-h . (display-local-help) displays any help text associated with the text at point, using the echo area.  If you want help text to be displayed automatically whenever it is available at point, set the variable help-at-pt-display-when-idle to t.