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# Help

Emacs provides extensive help features accessible through 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`. 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. For example, in `query-replace`, it describes the options available. After a prefix key, it displays a list of the alternatives that can follow the prefix key. (A few prefix keys don't support this because they define other meanings for `C-h`.)

Most help buffers use a special major mode, Help mode, which lets you scroll conveniently with `SPC` and `DEL`.

- Key Help: Asking what a key does in Emacs.
- Name Help: Asking about a command, variable or function name.
- Apropos: Asking what pertains to a given topic.
- Library Keywords: Finding Lisp libraries by keywords (topics).
- Misc Help: Other help commands.

Here is a summary of the defined help commands.

`C-h a regexp `RET``
  Display list of commands whose names match regexp (`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`
  Print 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 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 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 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 n`
  Display documentation of Emacs changes, most recent first (`view-emacs-news`).
`C-h p`
  Find packages by topic keyword (`finder-by-keyword`).
`C-h s`
  Display current contents of the syntax table, plus an explanation of what they mean (`describe-syntax`). See section The Syntax Table.
`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``
  Print which keys run the command named command (`where-is`).
`C-h C-f function `RET``
  Enter Info and go to the node documenting the Emacs function function (`Info-goto-emacs-command-node`).
`C-h C-k key`
  Enter Info and go to the node where the key sequence key is documented (`Info-goto-emacs-key-command-node`).
`C-h C-c`
  Display the copying conditions for GNU Emacs.
`C-h C-d`
  Display information about getting new versions of GNU Emacs.
`C-h C-p`
  Display information about the GNU Project.

## 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 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 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.

## 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 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 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 w command `RET`` tells you what keys are bound to command. It prints 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`.

`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.

## 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 does not check user variables by default; specify a numeric argument if you want it to check them.

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. Also note that you can use a regular expression as the argument, for more flexibility (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, 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 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`. 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 regular expression.

The `apropos-value` command is like `apropos` except that it searches symbols' values for matches for the specified 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 you want more information about a function definition, variable or symbol property listed in the Apropos buffer, you can click on it with `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'`
  Support for the bibliography processor `bib`.
``c'`
  C and C++ language support.
``calendar'`
  Calendar and time management support.
``comm'`
  Communications, networking, remote access to files.
``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 using faces (fonts and colors; see section Using Multiple Typefaces).
``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 within 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'`
  Support for using Lisp (including Emacs Lisp).
``local'`
  Libraries local to your site.
``maint'`
  Maintenance aids for the Emacs development group.
``mail'`
  Modes for electronic-mail handling.
``matching'`
  Searching and matching.
``news'`
  Support for netnews reading and posting.
``non-text'`
  Support for editing files that are not ordinary text.
``oop'`
  Support for object-oriented programming.
``outlines'`
  Hierarchical outlining.
``processes'`
  Process, subshell, compilation, and job control support.
``terminals'`
  Support for terminal types.
``tex'`
  Support for the TeX formatter.
``tools'`
  Programming tools.
``unix'`
  Front-ends/assistants for, or emulators of, Unix features.
``vms'`
  Support code for VMS.
``wp'`
  Word processing.

## 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.

There are two special help commands for accessing Emacs documentation through Info. `C-h C-f function `RET`` enters Info and goes straight to the documentation of the Emacs function function. `C-h C-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`.

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 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`) 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 defined by the current minor modes first, then the local bindings defined by the current major mode, and finally 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).

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.)

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 the file ``emacs/etc/DISTRIB'`, which tells you how you can order a copy of the latest version of Emacs. `C-h C-p` (`describe-project`) displays general information about the GNU Project.

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