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8. Help

XEmacs 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, and then asks you to type the desired option. It prompts with the string:

 
A B C F I K L M N P S T V W C-c C-d C-f C-i C-k C-n C-w;  ? 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.

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

8.1 Help Summary  Brief list of all Help commands.
8.2 Documentation for a Key  Asking what a key does in XEmacs.
8.3 Help by Command or Variable Name  Asking about a command, variable or function name.
8.4 Apropos  Asking what pertains to a given topic.
8.5 Keyword Search for Lisp Libraries  Finding Lisp libraries by keywords (topics).
8.6 Help Mode Commands  Special features of Help mode and Help buffers.
8.7 Other Help Commands  Other help commands.


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8.1 Help Summary

Here is a summary of the defined help commands.

C-h a regexp RET
Display a list of functions and variables whose names match regexp (hyper-apropos).
C-h A regexp
Show all commands whose names contain matches for regexp (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). Here c stands for `character'. For more extensive information on key, use C-h k.
C-h d function RET
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 XEmacs manual is available online 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 n
C-h C-n
Display documentation of XEmacs changes, most recent first (view-emacs-news).
C-h p
Find packages by topic keyword (finder-by-keyword).
C-h C-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). See section 27.6 The Syntax Table.
C-h t
Enter the XEmacs 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 B RET
Display info on how to deal with Beta versions of XEmacs (describe-beta).
C-h C group RET
Select customization buffer for group (customize).
C-h F RET
View the local copy of the XEmacs FAQ (xemacs-local-faq).
C-h C-i file RET
Read Info file file with Info browser (Info-query).
C-h C-c command RET
Look up an Emacs command command in the Emacs manual in the Info system (Info-goto-emacs-command-node).
C-h C-f function RET
Look up an Emacs Lisp function function in the Elisp manual in the Info system (Info-elisp-ref).


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8.2 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 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.

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


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8.3 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 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 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.

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 (where-is) 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 section 27.3 Variables.


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8.4 Apropos

C-h A
Show only symbols that are names of commands (command-apropos).

M-x apropos regexp
Show all symbols whose names contain matches for regexp.

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 command-apropos. 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 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, 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, for more flexibility (see section 12.5 Syntax of Regular Expressions).

Here is a set of arguments to give to C-h a that covers many classes of XEmacs commands, since there are strong conventions for naming the standard XEmacs 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 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 the variable apropos-do-all is non-nil, the commands above all behave as if they had been given a prefix argument.

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.


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8.5 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             C, C++, and Objective-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
dumped        files preloaded into Emacs
emulations    emulations of other editors
extensions    Emacs Lisp language extensions
faces         support for multiple fonts
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
mule          multi-language extensions
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           code related to the TeX formatter
tools         programming tools
unix          front-ends/assistants for, or emulators of, UNIX features
vms           support code for vms
wp            word processing


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8.6 Help Mode Commands

Help buffers provide the commands of View mode (see section 14.10 Miscellaneous File Operations), plus a few special commands of their own.

SPC
Scroll forward.
DEL
BS
Scroll backward.

When a command name (see section Running Commands by Name) or variable name (see section 27.3 Variables) appears in the documentation, it normally appears inside paired single-quotes.


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8.7 Other Help Commands

C-h i (info) runs the Info program, which is used for browsing through structured documentation files. The entire XEmacs 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 you specify a numeric 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 XEmacs documentation through Info. C-h C-f function RET enters Info and goes straight to the documentation of the XEmacs 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-elisp-ref and Info-goto-emacs-key-command-node. (GNU Emacs binds C-h C-f to Info-goto-emacs-command-node, but this is less helpful to programmers.)

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.

XEmacs 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 XEmacs mode that is not covered by C-h m. C-h b displays a list of all the key bindings currently in effect, with the local bindings of the current major mode first, followed by the global bindings (see section 27.5 Customizing Key Bindings). C-h s displays the contents of the syntax table with explanations of each character's syntax (see section 27.6 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 (describe-no-warranty) displays the full details on the complete absence of warranty for XEmacs. C-h n (view-emacs-news) displays the file `xemacs/etc/NEWS', which contains documentation on XEmacs changes arranged chronologically. C-h F (xemacs-local-faq) displays the local version of the XEmacs FAQ (Frequently Answered Questions list). C-h t (help-with-tutorial) displays the learn-by-doing XEmacs tutorial. C-h C-c (describe-copying) displays the file `xemacs/etc/COPYING', which tells you the conditions you must obey in distributing copies of XEmacs. C-h C-d (describe-distribution displays the section of the FAQ that tells you how you can get the latest version of XEmacs.


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