Merge from emacs--rel--22, gnus--rel--5.10
[bpt/emacs.git] / man / custom.texi
1 @c This is part of the Emacs manual.
2 @c Copyright (C) 1985, 1986, 1987, 1993, 1994, 1995, 1997, 2000, 2001,
3 @c 2002, 2003, 2004, 2005, 2006, 2007 Free Software Foundation, Inc.
4 @c See file emacs.texi for copying conditions.
5 @node Customization, Quitting, Amusements, Top
6 @chapter Customization
7 @cindex customization
8
9 This chapter talks about various topics relevant to adapting the
10 behavior of Emacs in ways we have anticipated.
11 @iftex
12 See @cite{The Emacs Lisp Reference Manual}
13 @end iftex
14 @ifnottex
15 @xref{Top, Emacs Lisp, Emacs Lisp, elisp, The Emacs Lisp
16 Reference Manual},
17 @end ifnottex
18 for how to make more far-reaching and open-ended changes. @xref{X
19 Resources}, for information on using X resources to customize Emacs.
20
21 Customization that you do within Emacs normally affects only the
22 particular Emacs session that you do it in---it does not persist
23 between sessions unless you save the customization in a file such as
24 your init file (@file{.emacs}) that will affect future sessions.
25 (@xref{Init File}.) When you tell the customization buffer to save
26 customizations for future sessions, this actually works by editing
27 @file{.emacs} for you.
28
29 Another means of customization is the keyboard macro, which is a
30 sequence of keystrokes to be replayed with a single command.
31 @xref{Keyboard Macros}, for full instruction how to record, manage, and
32 replay sequences of keys.
33
34 @menu
35 * Minor Modes:: Each minor mode is one feature you can turn on
36 independently of any others.
37 * Easy Customization:: Convenient way to browse and change settings.
38 * Variables:: Many Emacs commands examine Emacs variables
39 to decide what to do; by setting variables,
40 you can control their functioning.
41 * Key Bindings:: The keymaps say what command each key runs.
42 By changing them, you can "redefine keys".
43 * Syntax:: The syntax table controls how words and
44 expressions are parsed.
45 * Init File:: How to write common customizations in the
46 @file{.emacs} file.
47 @end menu
48
49 @node Minor Modes
50 @section Minor Modes
51 @cindex minor modes
52 @cindex mode, minor
53
54 Minor modes are optional features which you can turn on or off. For
55 example, Auto Fill mode is a minor mode in which @key{SPC} breaks lines
56 between words as you type. All the minor modes are independent of each
57 other and of the selected major mode. Most minor modes say in the mode
58 line when they are enabled; for example, @samp{Fill} in the mode line means
59 that Auto Fill mode is enabled.
60
61 You should append @code{-mode} to the name of a minor mode to
62 produce the name of the command that turns the mode on or off. Thus,
63 the command to enable or disable Auto Fill mode is called
64 @code{auto-fill-mode}. These commands are usually invoked with
65 @kbd{M-x}, but you can bind keys to them if you wish.
66
67 With no argument, the minor mode function turns the mode on if it
68 was off, and off if it was on. This is known as @dfn{toggling}. A
69 positive argument always turns the mode on, and an explicit zero
70 argument or a negative argument always turns it off.
71
72 Some minor modes are global: while enabled, they affect everything
73 you do in the Emacs session, in all buffers. Other minor modes are
74 buffer-local; they apply only to the current buffer, so you can enable
75 the mode in certain buffers and not others.
76
77 For most minor modes, the command name is also the name of a
78 variable. The variable's value is non-@code{nil} if the mode is
79 enabled and @code{nil} if it is disabled. Some minor-mode commands
80 work by just setting the variable. For example, the command
81 @code{abbrev-mode} works by setting the value of @code{abbrev-mode} as
82 a variable; it is this variable that directly turns Abbrev mode on and
83 off. You can directly set the variable's value instead of calling the
84 mode function. For other minor modes, you need to either set the
85 variable through the Customize interface or call the mode function to
86 correctly enable or disable the mode. To check which of these two
87 possibilities applies to a given minor mode, use @kbd{C-h v} to ask
88 for documentation on the variable name.
89
90 For minor mode commands that work by just setting the minor mode
91 variable, that variable provides a good way for Lisp programs to turn
92 minor modes on and off; it is also useful in a file's local variables
93 list (@pxref{File Variables}). But please think twice before setting
94 minor modes with a local variables list, because most minor modes are
95 a matter of user preference---other users editing the same file might
96 not want the same minor modes you prefer.
97
98 The most useful buffer-local minor modes include Abbrev mode, Auto
99 Fill mode, Auto Save mode, Font-Lock mode, Glasses mode, Outline minor
100 mode, Overwrite mode, and Binary Overwrite mode.
101
102 Abbrev mode allows you to define abbreviations that automatically expand
103 as you type them. For example, @samp{amd} might expand to @samp{abbrev
104 mode}. @xref{Abbrevs}, for full information.
105
106 Auto Fill mode allows you to enter filled text without breaking lines
107 explicitly. Emacs inserts newlines as necessary to prevent lines from
108 becoming too long. @xref{Filling}.
109
110 Auto Save mode saves the buffer contents periodically to reduce the
111 amount of work you can lose in case of a crash. @xref{Auto Save}.
112
113 Enriched mode enables editing and saving of formatted text.
114 @xref{Formatted Text}.
115
116 Flyspell mode automatically highlights misspelled words.
117 @xref{Spelling}.
118
119 Font-Lock mode automatically highlights certain textual units found
120 in programs, such as comments, strings, and function names being
121 defined. This requires a display that can show multiple fonts or
122 colors. @xref{Faces}.
123
124 @ignore
125 ISO Accents mode makes the characters @samp{`}, @samp{'}, @samp{"},
126 @samp{^}, @samp{/} and @samp{~} combine with the following letter, to
127 produce an accented letter in the ISO Latin-1 character set. The
128 newer and more general feature of input methods more or less
129 supersedes ISO Accents mode. @xref{Unibyte Mode}.
130 @end ignore
131
132 Outline minor mode provides the same facilities as the major mode
133 called Outline mode; but since it is a minor mode instead, you can
134 combine it with any major mode. @xref{Outline Mode}.
135
136 @cindex Overwrite mode
137 @cindex mode, Overwrite
138 Overwrite mode causes ordinary printing characters to replace existing
139 text instead of shoving it to the right. For example, if point is in
140 front of the @samp{B} in @samp{FOOBAR}, then in Overwrite mode typing a
141 @kbd{G} changes it to @samp{FOOGAR}, instead of producing @samp{FOOGBAR}
142 as usual. In Overwrite mode, the command @kbd{C-q} inserts the next
143 character whatever it may be, even if it is a digit---this gives you a
144 way to insert a character instead of replacing an existing character.
145
146 @findex overwrite-mode
147 @kindex INSERT
148 The command @code{overwrite-mode} is an exception to the rule that
149 commands which toggle minor modes are normally not bound to keys: it is
150 bound to the @key{INSERT} function key. This is because many other
151 programs bind @key{INSERT} to similar functions.
152
153 @findex binary-overwrite-mode
154 Binary Overwrite mode is a variant of Overwrite mode for editing
155 binary files; it treats newlines and tabs like other characters, so that
156 they overwrite other characters and can be overwritten by them.
157 In Binary Overwrite mode, digits after @kbd{C-q} specify an
158 octal character code, as usual.
159
160 Here are some useful minor modes that normally apply to all buffers
161 at once. Since Line Number mode and Transient Mark mode can be
162 enabled or disabled just by setting the value of the minor mode
163 variable, you @emph{can} set them differently for particular buffers,
164 by explicitly making the corresponding variable local in those
165 buffers. @xref{Locals}.
166
167 Icomplete mode displays an indication of available completions when
168 you are in the minibuffer and completion is active. @xref{Completion
169 Options}.
170
171 Line Number mode enables continuous display in the mode line of the
172 line number of point, and Column Number mode enables display of the
173 column number. @xref{Mode Line}.
174
175 Scroll Bar mode gives each window a scroll bar (@pxref{Scroll Bars}).
176 Menu Bar mode gives each frame a menu bar (@pxref{Menu Bars}). Both of
177 these modes are enabled by default when you use the X Window System.
178
179 In Transient Mark mode, every change in the buffer contents
180 ``deactivates'' the mark, so that commands that operate on the region
181 will get an error. This means you must either set the mark, or
182 explicitly ``reactivate'' it, before each command that uses the region.
183 The advantage of Transient Mark mode is that Emacs can display the
184 region highlighted. @xref{Mark}.
185
186 @node Easy Customization
187 @section Easy Customization Interface
188
189 @cindex settings
190 Emacs has many @dfn{settings} which have values that you can specify
191 in order to customize various commands. Many are documented in this
192 manual. Most settings are @dfn{user options}---that is to say, Lisp
193 variables (@pxref{Variables})---so their names appear in the Variable
194 Index (@pxref{Variable Index}). The other settings are faces and
195 their attributes (@pxref{Faces}).
196
197 @findex customize
198 @cindex customization buffer
199 You can browse interactively through settings and change them using
200 @kbd{M-x customize}. This command creates a @dfn{customization
201 buffer}, which offers commands to navigate through a logically
202 organized structure of the Emacs settings; you can also use it to edit
203 and set their values, and to save settings permanently in your
204 @file{~/.emacs} file (@pxref{Init File}).
205
206 The appearance of the example buffers in this section is typically
207 different under a graphical display, since faces are then used to indicate
208 buttons, links and editable fields.
209
210 @menu
211 * Groups: Customization Groups. How settings are classified in a structure.
212 * Browsing: Browsing Custom. Browsing and searching for settings.
213 * Changing a Variable:: How to edit an option's value and set the option.
214 * Saving Customizations:: Specifying the file for saving customizations.
215 * Face Customization:: How to edit the attributes of a face.
216 * Specific Customization:: Making a customization buffer for specific
217 variables, faces, or groups.
218 * Custom Themes:: How to define collections of customized options
219 that can be loaded and unloaded together.
220 @end menu
221
222 @node Customization Groups
223 @subsection Customization Groups
224 @cindex customization groups
225
226 For customization purposes, settings are organized into @dfn{groups}
227 to help you find them. Groups are collected into bigger groups, all
228 the way up to a master group called @code{Emacs}.
229
230 @kbd{M-x customize} creates a customization buffer that shows the
231 top-level @code{Emacs} group and the second-level groups immediately
232 under it. It looks like this, in part:
233
234 @c we want the buffer example to all be on one page, but unfortunately
235 @c that's quite a bit of text, so force all space to the bottom.
236 @page
237 @smallexample
238 @group
239 /- Emacs group: ---------------------------------------------------\
240 [State]: visible group members are all at standard values.
241 Customization of the One True Editor.
242 See also [Manual].
243
244 Editing group: [Go to Group]
245 Basic text editing facilities.
246
247 External group: [Go to Group]
248 Interfacing to external utilities.
249
250 @var{more second-level groups}
251
252 \- Emacs group end ------------------------------------------------/
253 @end group
254 @end smallexample
255
256 @noindent
257 This says that the buffer displays the contents of the @code{Emacs}
258 group. The other groups are listed because they are its contents. But
259 they are listed differently, without indentation and dashes, because
260 @emph{their} contents are not included. Each group has a single-line
261 documentation string; the @code{Emacs} group also has a @samp{[State]}
262 line.
263
264 @cindex editable fields (customization buffer)
265 @cindex buttons (customization buffer)
266 @cindex links (customization buffer)
267 Most of the text in the customization buffer is read-only, but it
268 typically includes some @dfn{editable fields} that you can edit.
269 There are also @dfn{buttons} and @dfn{links}, which do something when
270 you @dfn{invoke} them. To invoke a button or a link, either click on
271 it with @kbd{Mouse-1}, or move point to it and type @key{RET}.
272
273 For example, the phrase @samp{[State]} that appears in
274 a second-level group is a button. It operates on the same
275 customization buffer. The phrase @samp{[Go to Group]} is a kind
276 of hypertext link to another group. Invoking it creates a new
277 customization buffer, which shows that group and its contents.
278
279 The @code{Emacs} group includes a few settings, but mainly it
280 contains other groups, which contain more groups, which contain the
281 settings. By browsing the hierarchy of groups, you will eventually
282 find the feature you are interested in customizing. Then you can use
283 the customization buffer to set that feature's settings. You can also
284 go straight to a particular group by name, using the command @kbd{M-x
285 customize-group}.
286
287 @node Browsing Custom
288 @subsection Browsing and Searching for Options and Faces
289 @findex customize-browse
290
291 @kbd{M-x customize-browse} is another way to browse the available
292 settings. This command creates a special customization buffer which
293 shows only the names of groups and settings, and puts them in a
294 structure.
295
296 In this buffer, you can show the contents of a group by invoking the
297 @samp{[+]} button. When the group contents are visible, this button
298 changes to @samp{[-]}; invoking that hides the group contents again.
299
300 Each group or setting in this buffer has a link which says
301 @samp{[Group]}, @samp{[Option]} or @samp{[Face]}. Invoking this link
302 creates an ordinary customization buffer showing just that group and
303 its contents, just that user option, or just that face. This is the
304 way to change settings that you find with @kbd{M-x customize-browse}.
305
306 If you can guess part of the name of the settings you are interested
307 in, @kbd{M-x customize-apropos} is another way to search for settings.
308 However, unlike @code{customize} and @code{customize-browse},
309 @code{customize-apropos} can only find groups and settings that are
310 loaded in the current Emacs session. @xref{Specific Customization,,
311 Customizing Specific Items}.
312
313 @node Changing a Variable
314 @subsection Changing a Variable
315
316 Here is an example of what a variable (a user option) looks like in
317 the customization buffer:
318
319 @smallexample
320 Kill Ring Max: [Hide Value] 60
321 [State]: STANDARD.
322 Maximum length of kill ring before oldest elements are thrown away.
323 @end smallexample
324
325 The text following @samp{[Hide Value]}, @samp{60} in this case, indicates
326 the current value of the variable. If you see @samp{[Show Value]} instead of
327 @samp{[Hide Value]}, it means that the value is hidden; the customization
328 buffer initially hides values that take up several lines. Invoke
329 @samp{[Show Value]} to show the value.
330
331 The line after the variable name indicates the @dfn{customization
332 state} of the variable: in the example above, it says you have not
333 changed the option yet. The @samp{[State]} button at the beginning of
334 this line gives you a menu of various operations for customizing the
335 variable.
336
337 The line after the @samp{[State]} line displays the beginning of the
338 variable's documentation string. If there are more lines of
339 documentation, this line ends with a @samp{[More]} button; invoke that
340 to show the full documentation string.
341
342 To enter a new value for @samp{Kill Ring Max}, move point to the
343 value and edit it textually. For example, you can type @kbd{M-d},
344 then insert another number. As you begin to alter the text, you will
345 see the @samp{[State]} line change to say that you have edited the
346 value:
347
348 @smallexample
349 [State]: EDITED, shown value does not take effect until you set or @r{@dots{}}
350 save it.
351 @end smallexample
352
353 @cindex user options, how to set
354 @cindex variables, how to set
355 @cindex settings, how to set
356 Editing the value does not actually set the variable. To do that,
357 you must @dfn{set} the variable. To do this, invoke the
358 @samp{[State]} button and choose @samp{Set for Current Session}.
359
360 The state of the variable changes visibly when you set it:
361
362 @smallexample
363 [State]: SET for current session only.
364 @end smallexample
365
366 You don't have to worry about specifying a value that is not valid;
367 the @samp{Set for Current Session} operation checks for validity and
368 will not install an unacceptable value.
369
370 @kindex M-TAB @r{(customization buffer)}
371 @findex widget-complete
372 While editing a field that is a file name, directory name,
373 command name, or anything else for which completion is defined, you
374 can type @kbd{M-@key{TAB}} (@code{widget-complete}) to do completion.
375 (@kbd{@key{ESC} @key{TAB}} and @kbd{C-M-i} do the same thing.)
376
377 Some variables have a small fixed set of possible legitimate values.
378 These variables don't let you edit the value textually. Instead, a
379 @samp{[Value Menu]} button appears before the value; invoke this
380 button to change the value. For a boolean ``on or off'' value, the
381 button says @samp{[Toggle]}, and it changes to the other value.
382 @samp{[Value Menu]} and @samp{[Toggle]} simply edit the buffer; the
383 changes take real effect when you use the @samp{Set for Current
384 Session} operation.
385
386 Some variables have values with complex structure. For example, the
387 value of @code{file-coding-system-alist} is an association list. Here
388 is how it appears in the customization buffer:
389
390 @smallexample
391 File Coding System Alist: [Hide Value]
392 [INS] [DEL] File regexp: \.elc\'
393 Choice: [Value Menu] Encoding/decoding pair:
394 Decoding: emacs-mule
395 Encoding: emacs-mule
396 [INS] [DEL] File regexp: \(\`\|/\)loaddefs.el\'
397 Choice: [Value Menu] Encoding/decoding pair:
398 Decoding: raw-text
399 Encoding: raw-text-unix
400 [INS] [DEL] File regexp: \.tar\'
401 Choice: [Value Menu] Encoding/decoding pair:
402 Decoding: no-conversion
403 Encoding: no-conversion
404 [INS] [DEL] File regexp:
405 Choice: [Value Menu] Encoding/decoding pair:
406 Decoding: undecided
407 Encoding: nil
408 [INS]
409 [State]: STANDARD.
410 Alist to decide a coding system to use for a file I/O @r{@dots{}}
411 operation. [Hide Rest]
412 The format is ((PATTERN . VAL) ...),
413 where PATTERN is a regular expression matching a file name,
414 @r{[@dots{}more lines of documentation@dots{}]}
415 @end smallexample
416
417 @noindent
418 Each association in the list appears on four lines, with several
419 editable fields and/or buttons. You can edit the regexps and coding
420 systems using ordinary editing commands. You can also invoke
421 @samp{[Value Menu]} to switch to a different kind of value---for
422 instance, to specify a function instead of a pair of coding systems.
423
424 To delete an association from the list, invoke the @samp{[DEL]} button
425 for that item. To add an association, invoke @samp{[INS]} at the
426 position where you want to add it. There is an @samp{[INS]} button
427 between each pair of associations, another at the beginning and another
428 at the end, so you can add a new association at any position in the
429 list.
430
431 @kindex TAB @r{(customization buffer)}
432 @kindex S-TAB @r{(customization buffer)}
433 @findex widget-forward
434 @findex widget-backward
435 Two special commands, @key{TAB} and @kbd{S-@key{TAB}}, are useful
436 for moving through the customization buffer. @key{TAB}
437 (@code{widget-forward}) moves forward to the next button or editable
438 field; @kbd{S-@key{TAB}} (@code{widget-backward}) moves backward to
439 the previous button or editable field.
440
441 Typing @key{RET} on an editable field also moves forward, just like
442 @key{TAB}. We set it up this way because people often type @key{RET}
443 when they are finished editing a field. To insert a newline within an
444 editable field, use @kbd{C-o} or @kbd{C-q C-j}.
445
446 @cindex saving a setting
447 @cindex settings, how to save
448 Setting the variable changes its value in the current Emacs session;
449 @dfn{saving} the value changes it for future sessions as well. To
450 save the variable, invoke @samp{[State]} and select the @samp{Save for
451 Future Sessions} operation. This works by writing code so as to set
452 the variable again, each time you start Emacs (@pxref{Saving
453 Customizations}).
454
455 You can also restore the variable to its standard value by invoking
456 @samp{[State]} and selecting the @samp{Erase Customization} operation.
457 There are actually four reset operations:
458
459 @table @samp
460 @item Undo Edits
461 If you have made some modifications and not yet set the variable,
462 this restores the text in the customization buffer to match
463 the actual value.
464
465 @item Reset to Saved
466 This restores the value of the variable to the last saved value,
467 and updates the text accordingly.
468
469 @item Erase Customization
470 This sets the variable to its standard value, and updates the text
471 accordingly. This also eliminates any saved value for the variable,
472 so that you will get the standard value in future Emacs sessions.
473
474 @item Set to Backup Value
475 This sets the variable to a previous value that was set in the
476 customization buffer in this session. If you customize a variable
477 and then reset it, which discards the customized value,
478 you can get the discarded value back again with this operation.
479 @end table
480
481 @cindex comments on customized settings
482 Sometimes it is useful to record a comment about a specific
483 customization. Use the @samp{Add Comment} item from the
484 @samp{[State]} menu to create a field for entering the comment. The
485 comment you enter will be saved, and displayed again if you again view
486 the same variable in a customization buffer, even in another session.
487
488 The state of a group indicates whether anything in that group has been
489 edited, set or saved.
490
491 Near the top of the customization buffer there are two lines of buttons:
492
493 @smallexample
494 [Set for Current Session] [Save for Future Sessions]
495 [Undo Edits] [Reset to Saved] [Erase Customization] [Finish]
496 @end smallexample
497
498 @vindex custom-buffer-done-function
499 @noindent
500 Invoking @samp{[Finish]} either buries or kills this customization
501 buffer according to the setting of the option
502 @code{custom-buffer-done-kill}; the default is to bury the buffer.
503 Each of the other buttons performs an operation---set, save or
504 reset---on each of the settings in the buffer that could meaningfully
505 be set, saved or reset. They do not operate on settings whose values
506 are hidden, nor on subgroups which are hidden or not visible in the buffer.
507
508 @node Saving Customizations
509 @subsection Saving Customizations
510
511 Saving customizations from the customization buffer works by writing
512 code that future sessions will read, code to set up those
513 customizations again.
514
515 @vindex custom-file
516 Normally this saves customizations in your init file,
517 @file{~/.emacs}. If you wish, you can save customizations in another
518 file instead. To make this work, your @file{~/.emacs} should set
519 @code{custom-file} to the name of that file. Then you should load the
520 file by calling @code{load}. For example:
521
522 @example
523 (setq custom-file "~/.emacs-custom.el")
524 (load custom-file)
525 @end example
526
527 You can use @code{custom-file} to specify different customization
528 files for different Emacs versions, like this:
529
530 @example
531 (cond ((< emacs-major-version 21)
532 ;; @r{Emacs 20 customization.}
533 (setq custom-file "~/.custom-20.el"))
534 ((and (= emacs-major-version 21) (< emacs-minor-version 4))
535 ;; @r{Emacs 21 customization, before version 21.4.}
536 (setq custom-file "~/.custom-21.el"))
537 ((< emacs-major-version 22)
538 ;; @r{Emacs version 21.4 or later.}
539 (setq custom-file "~/.custom-21.4.el"))
540 (t
541 ;; @r{Emacs version 22.1 or later.}
542 (setq custom-file "~/.custom-22.el")))
543
544 (load custom-file)
545 @end example
546
547 If Emacs was invoked with the @option{-q} or @option{--no-init-file}
548 options (@pxref{Initial Options}), it will not let you save your
549 customizations in your @file{~/.emacs} init file. This is because
550 saving customizations from such a session would wipe out all the other
551 customizations you might have on your init file.
552
553 @node Face Customization
554 @subsection Customizing Faces
555 @cindex customizing faces
556 @cindex bold font
557 @cindex italic font
558 @cindex fonts and faces
559
560 In addition to variables, some customization groups also include
561 faces. When you show the contents of a group, both the variables and
562 the faces in the group appear in the customization buffer. Here is an
563 example of how a face looks:
564
565 @smallexample
566 Custom Changed Face:(sample) [Hide Face]
567 [State]: STANDARD.
568 Face used when the customize item has been changed.
569 Parent groups: [Custom Magic Faces]
570 Attributes: [ ] Font Family: *
571 [ ] Width: *
572 [ ] Height: *
573 [ ] Weight: *
574 [ ] Slant: *
575 [ ] Underline: *
576 [ ] Overline: *
577 [ ] Strike-through: *
578 [ ] Box around text: *
579 [ ] Inverse-video: *
580 [X] Foreground: white (sample)
581 [X] Background: blue (sample)
582 [ ] Stipple: *
583 [ ] Inherit: *
584 @end smallexample
585
586 Each face attribute has its own line. The @samp{[@var{x}]} button
587 before the attribute name indicates whether the attribute is
588 @dfn{enabled}; @samp{[X]} means that it's enabled, and @samp{[ ]}
589 means that it's disabled. You can enable or disable the attribute by
590 clicking that button. When the attribute is enabled, you can change
591 the attribute value in the usual ways.
592
593 For the colors, you can specify a color name (use @kbd{M-x
594 list-colors-display} for a list of them) or a hexadecimal color
595 specification of the form @samp{#@var{rr}@var{gg}@var{bb}}.
596 (@samp{#000000} is black, @samp{#ff0000} is red, @samp{#00ff00} is
597 green, @samp{#0000ff} is blue, and @samp{#ffffff} is white.) On a
598 black-and-white display, the colors you can use for the background are
599 @samp{black}, @samp{white}, @samp{gray}, @samp{gray1}, and
600 @samp{gray3}. Emacs supports these shades of gray by using background
601 stipple patterns instead of a color.
602
603 Setting, saving and resetting a face work like the same operations for
604 variables (@pxref{Changing a Variable}).
605
606 A face can specify different appearances for different types of
607 display. For example, a face can make text red on a color display, but
608 use a bold font on a monochrome display. To specify multiple
609 appearances for a face, select @samp{For All Kinds of Displays} in the
610 menu you get from invoking @samp{[State]}.
611
612 @findex modify-face
613 Another more basic way to set the attributes of a specific face is
614 with @kbd{M-x modify-face}. This command reads the name of a face, then
615 reads the attributes one by one. For the color and stipple attributes,
616 the attribute's current value is the default---type just @key{RET} if
617 you don't want to change that attribute. Type @samp{none} if you want
618 to clear out the attribute.
619
620 @node Specific Customization
621 @subsection Customizing Specific Items
622
623 Instead of finding the setting you want to change by navigating the
624 structure of groups, here are other ways to specify the settings that
625 you want to customize.
626
627 @table @kbd
628 @item M-x customize-option @key{RET} @var{option} @key{RET}
629 Set up a customization buffer with just one user option variable,
630 @var{option}.
631 @item M-x customize-face @key{RET} @var{face} @key{RET}
632 Set up a customization buffer with just one face, @var{face}.
633 @item M-x customize-group @key{RET} @var{group} @key{RET}
634 Set up a customization buffer with just one group, @var{group}.
635 @item M-x customize-apropos @key{RET} @var{regexp} @key{RET}
636 Set up a customization buffer with all the settings and groups that
637 match @var{regexp}.
638 @item M-x customize-changed @key{RET} @var{version} @key{RET}
639 Set up a customization buffer with all the settings and groups
640 whose meaning has changed since Emacs version @var{version}.
641 @item M-x customize-saved
642 Set up a customization buffer containing all settings that you
643 have saved with customization buffers.
644 @item M-x customize-unsaved
645 Set up a customization buffer containing all settings that you have
646 set but not saved.
647 @end table
648
649 @findex customize-option
650 If you want to alter a particular user option with the customization
651 buffer, and you know its name, you can use the command @kbd{M-x
652 customize-option} and specify the user option (variable) name. This
653 sets up the customization buffer with just one user option---the one
654 that you asked for. Editing, setting and saving the value work as
655 described above, but only for the specified user option. Minibuffer
656 completion is handy if you only know part of the name. However, this
657 command can only see options that have been loaded in the current
658 Emacs session.
659
660 @findex customize-face
661 Likewise, you can modify a specific face, chosen by name, using
662 @kbd{M-x customize-face}. By default it operates on the face used
663 on the character after point.
664
665 @findex customize-group
666 You can also set up the customization buffer with a specific group,
667 using @kbd{M-x customize-group}. The immediate contents of the chosen
668 group, including settings (user options and faces), and other groups,
669 all appear as well (even if not already loaded). However, the
670 subgroups' own contents are not included.
671
672 @findex customize-apropos
673 For a more general way of controlling what to customize, you can use
674 @kbd{M-x customize-apropos}. You specify a regular expression as
675 argument; then all @emph{loaded} settings and groups whose names match
676 this regular expression are set up in the customization buffer. If
677 you specify an empty regular expression, this includes @emph{all}
678 loaded groups and settings---which takes a long time to set up.
679
680 @findex customize-changed
681 When you upgrade to a new Emacs version, you might want to consider
682 customizing new settings, and settings whose meanings or default
683 values have changed. To do this, use @kbd{M-x customize-changed} and
684 specify a previous Emacs version number using the minibuffer. It
685 creates a customization buffer which shows all the settings and groups
686 whose definitions have been changed since the specified version,
687 loading them if necessary.
688
689 @findex customize-saved
690 @findex customize-unsaved
691 If you change settings and then decide the change was a mistake, you
692 can use two special commands to revisit your previous changes. Use
693 @kbd{M-x customize-saved} to look at the settings that you have saved.
694 Use @kbd{M-x customize-unsaved} to look at the settings that you
695 have set but not saved.
696
697 @node Custom Themes
698 @subsection Customization Themes
699 @cindex custom themes
700
701 @dfn{Custom themes} are collections of settings that can be enabled
702 or disabled as a unit. You can use Custom themes to switch quickly
703 and easily between various collections of settings, and to transfer
704 such collections from one computer to another.
705
706 @findex customize-create-theme
707 To define a Custom theme, use @kbd{M-x customize-create-theme},
708 which brings up a buffer named @samp{*New Custom Theme*}. At the top
709 of the buffer is an editable field where you can specify the name of
710 the theme. Click on the button labelled @samp{Insert Variable} to add
711 a variable to the theme, and click on @samp{Insert Face} to add a
712 face. You can edit these values in the @samp{*New Custom Theme*}
713 buffer like in an ordinary Customize buffer. To remove an option from
714 the theme, click on its @samp{State} button and select @samp{Delete}.
715
716 @vindex custom-theme-directory
717 After adding the desired options, click on @samp{Save Theme} to save
718 the Custom theme. This writes the theme definition to a file
719 @file{@var{foo}-theme.el} (where @var{foo} is the theme name you
720 supplied), in the directory @file{~/.emacs.d/}. You can specify the
721 directory by setting @code{custom-theme-directory}.
722
723 You can view and edit the settings of a previously-defined theme by
724 clicking on @samp{Visit Theme} and specifying the theme name. You can
725 also import the variables and faces that you have set using Customize
726 by visiting the ``special'' theme named @samp{user}. This theme, which
727 records all the options that you set in the ordinary customization
728 buffer, is always enabled, and always takes precedence over all other
729 enabled Custom themes. Additionally, the @samp{user} theme is
730 recorded with code in your @file{.emacs} file, rather than a
731 @file{user-theme.el} file.
732
733 @vindex custom-enabled-themes
734 Once you have defined a Custom theme, you can use it by customizing
735 the variable @code{custom-enabled-themes}. This is a list of Custom
736 themes that are @dfn{enabled}, or put into effect. If you set
737 @code{custom-enabled-themes} using the Customize interface, the theme
738 definitions are automatically loaded from the theme files, if they
739 aren't already. If you save the value of @code{custom-enabled-themes}
740 for future Emacs sessions, those Custom themes will be enabled
741 whenever Emacs is started up.
742
743 If two enabled themes specify different values for an option, the
744 theme occurring earlier in @code{custom-enabled-themes} takes effect.
745
746 @findex load-theme
747 @findex enable-theme
748 @findex disable-theme
749 You can temporarily enable a Custom theme with @kbd{M-x
750 enable-theme}. This prompts for a theme name in the minibuffer, loads
751 the theme from the theme file if necessary, and enables the theme.
752 You can @dfn{disable} any enabled theme with the command @kbd{M-x
753 disable-theme}; this returns the options specified in the theme to
754 their original values. To re-enable the theme, type @kbd{M-x
755 enable-theme} again. If a theme file is changed during your Emacs
756 session, you can reload it by typing @kbd{M-x load-theme}. (This also
757 enables the theme.)
758
759 @node Variables
760 @section Variables
761 @cindex variable
762 @cindex option, user
763 @cindex user option
764
765 A @dfn{variable} is a Lisp symbol which has a value. The symbol's
766 name is also called the name of the variable. A variable name can
767 contain any characters that can appear in a file, but conventionally
768 variable names consist of words separated by hyphens. A variable can
769 have a documentation string which describes what kind of value it should
770 have and how the value will be used.
771
772 Emacs Lisp allows any variable (with a few exceptions) to have any
773 kind of value, but most variables that Emacs uses expect a value of a
774 certain type. Often the value should always be a string, or should
775 always be a number. Sometimes we say that a certain feature is turned
776 on if a variable is ``non-@code{nil},'' meaning that if the variable's
777 value is @code{nil}, the feature is off, but the feature is on for
778 @emph{any} other value. The conventional value to use to turn on the
779 feature---since you have to pick one particular value when you set the
780 variable---is @code{t}.
781
782 Emacs uses many Lisp variables for internal record keeping, but the
783 most interesting variables for a non-programmer user are those meant
784 for users to change---these are called @dfn{user options}.
785
786 Each user option that you can set with the customization buffer is
787 in fact a Lisp variable. Emacs does not (usually) change the values
788 of these variables on its own; instead, you set the values in order to
789 control the behavior of certain Emacs commands. Use of the
790 customization buffer is explained above (@pxref{Easy Customization});
791 here we describe other aspects of Emacs variables.
792
793 @menu
794 * Examining:: Examining or setting one variable's value.
795 * Hooks:: Hook variables let you specify programs for parts
796 of Emacs to run on particular occasions.
797 * Locals:: Per-buffer values of variables.
798 * File Variables:: How files can specify variable values.
799 @end menu
800
801 @node Examining
802 @subsection Examining and Setting Variables
803 @cindex setting variables
804
805 @table @kbd
806 @item C-h v @var{var} @key{RET}
807 Display the value and documentation of variable @var{var}
808 (@code{describe-variable}).
809 @item M-x set-variable @key{RET} @var{var} @key{RET} @var{value} @key{RET}
810 Change the value of variable @var{var} to @var{value}.
811 @end table
812
813 To examine the value of a single variable, use @kbd{C-h v}
814 (@code{describe-variable}), which reads a variable name using the
815 minibuffer, with completion. It displays both the value and the
816 documentation of the variable. For example,
817
818 @example
819 C-h v fill-column @key{RET}
820 @end example
821
822 @noindent
823 displays something like this:
824
825 @smallexample
826 fill-column is a variable defined in `C source code'.
827 fill-column's value is 70
828 Local in buffer custom.texi; global value is 70
829 Automatically becomes buffer-local when set in any fashion.
830
831 This variable is safe to use as a file local variable only if its value
832 satisfies the predicate `integerp'.
833
834 Documentation:
835 *Column beyond which automatic line-wrapping should happen.
836 Interactively, you can set the buffer local value using C-x f.
837
838 You can customize this variable.
839 @end smallexample
840
841 @noindent
842 The line that says you can customize the variable indicates that this
843 variable is a user option. (The star also indicates this, but it is
844 an obsolete indicator that may eventually disappear.) @kbd{C-h v} is
845 not restricted to user options; it allows any variable name.
846
847 @findex set-variable
848 The most convenient way to set a specific user option variable is with
849 @kbd{M-x set-variable}. This reads the variable name with the
850 minibuffer (with completion), and then reads a Lisp expression for the
851 new value using the minibuffer a second time (you can insert the old
852 value into the minibuffer for editing via @kbd{M-n}). For example,
853
854 @example
855 M-x set-variable @key{RET} fill-column @key{RET} 75 @key{RET}
856 @end example
857
858 @noindent
859 sets @code{fill-column} to 75.
860
861 @kbd{M-x set-variable} is limited to user option variables, but you can
862 set any variable with a Lisp expression, using the function @code{setq}.
863 Here is a @code{setq} expression to set @code{fill-column}:
864
865 @example
866 (setq fill-column 75)
867 @end example
868
869 To execute an expression like this one, go to the @samp{*scratch*}
870 buffer, type in the expression, and then type @kbd{C-j}. @xref{Lisp
871 Interaction}.
872
873 Setting variables, like all means of customizing Emacs except where
874 otherwise stated, affects only the current Emacs session. The only
875 way to alter the variable in future sessions is to put something in
876 the @file{~/.emacs} file to set it those sessions (@pxref{Init File}).
877
878 @node Hooks
879 @subsection Hooks
880 @cindex hook
881 @cindex running a hook
882
883 @dfn{Hooks} are an important mechanism for customization of Emacs. A
884 hook is a Lisp variable which holds a list of functions, to be called on
885 some well-defined occasion. (This is called @dfn{running the hook}.)
886 The individual functions in the list are called the @dfn{hook functions}
887 of the hook. With rare exceptions, hooks in Emacs are empty when Emacs
888 starts up, so the only hook functions in any given hook are the ones you
889 explicitly put there as customization.
890
891 Most major modes run one or more @dfn{mode hooks} as the last step of
892 initialization. This makes it easy for you to customize the behavior of
893 the mode, by setting up a hook function to override the local variable
894 assignments already made by the mode. But hooks are also used in other
895 contexts. For example, the hook @code{suspend-hook} runs just before
896 Emacs suspends itself (@pxref{Exiting}).
897
898 @cindex normal hook
899 Most Emacs hooks are @dfn{normal hooks}. This means that running the
900 hook operates by calling all the hook functions, unconditionally, with
901 no arguments. We have made an effort to keep most hooks normal so that
902 you can use them in a uniform way. Every variable in Emacs whose name
903 ends in @samp{-hook} is a normal hook.
904
905 @cindex abnormal hook
906 There are also a few @dfn{abnormal hooks}. These variables' names end
907 in @samp{-hooks} or @samp{-functions}, instead of @samp{-hook}. What
908 makes these hooks abnormal is that there is something peculiar about the
909 way its functions are called---perhaps they are given arguments, or
910 perhaps the values they return are used in some way. For example,
911 @code{find-file-not-found-functions} (@pxref{Visiting}) is abnormal because
912 as soon as one hook function returns a non-@code{nil} value, the rest
913 are not called at all. The documentation of each abnormal hook variable
914 explains in detail what is peculiar about it.
915
916 @findex add-hook
917 You can set a hook variable with @code{setq} like any other Lisp
918 variable, but the recommended way to add a hook function to a hook
919 (either normal or abnormal) is by calling @code{add-hook}.
920 @xref{Hooks,,, elisp, The Emacs Lisp Reference Manual}.
921
922 For example, here's how to set up a hook to turn on Auto Fill mode
923 when entering Text mode and other modes based on Text mode:
924
925 @example
926 (add-hook 'text-mode-hook 'turn-on-auto-fill)
927 @end example
928
929 The next example shows how to use a hook to customize the indentation
930 of C code. (People often have strong personal preferences for one
931 format compared to another.) Here the hook function is an anonymous
932 lambda expression.
933
934 @example
935 @group
936 (setq my-c-style
937 '((c-comment-only-line-offset . 4)
938 @end group
939 @group
940 (c-cleanup-list . (scope-operator
941 empty-defun-braces
942 defun-close-semi))
943 @end group
944 @group
945 (c-offsets-alist . ((arglist-close . c-lineup-arglist)
946 (substatement-open . 0)))))
947 @end group
948
949 @group
950 (add-hook 'c-mode-common-hook
951 '(lambda ()
952 (c-add-style "my-style" my-c-style t)))
953 @end group
954 @end example
955
956 It is best to design your hook functions so that the order in which
957 they are executed does not matter. Any dependence on the order is
958 ``asking for trouble.'' However, the order is predictable: the most
959 recently added hook functions are executed first.
960
961 @findex remove-hook
962 If you play with adding various different versions of a hook
963 function by calling @code{add-hook} over and over, remember that all
964 the versions you added will remain in the hook variable together. You
965 can clear out individual functions by calling @code{remove-hook}, or
966 do @code{(setq @var{hook-variable} nil)} to remove everything.
967
968 @node Locals
969 @subsection Local Variables
970
971 @table @kbd
972 @item M-x make-local-variable @key{RET} @var{var} @key{RET}
973 Make variable @var{var} have a local value in the current buffer.
974 @item M-x kill-local-variable @key{RET} @var{var} @key{RET}
975 Make variable @var{var} use its global value in the current buffer.
976 @item M-x make-variable-buffer-local @key{RET} @var{var} @key{RET}
977 Mark variable @var{var} so that setting it will make it local to the
978 buffer that is current at that time.
979 @end table
980
981 @cindex local variables
982 Almost any variable can be made @dfn{local} to a specific Emacs
983 buffer. This means that its value in that buffer is independent of its
984 value in other buffers. A few variables are always local in every
985 buffer. Every other Emacs variable has a @dfn{global} value which is in
986 effect in all buffers that have not made the variable local.
987
988 @findex make-local-variable
989 @kbd{M-x make-local-variable} reads the name of a variable and makes
990 it local to the current buffer. Changing its value subsequently in
991 this buffer will not affect others, and changes in its global value
992 will not affect this buffer.
993
994 @findex make-variable-buffer-local
995 @cindex per-buffer variables
996 @kbd{M-x make-variable-buffer-local} marks a variable so it will
997 become local automatically whenever it is set. More precisely, once a
998 variable has been marked in this way, the usual ways of setting the
999 variable automatically do @code{make-local-variable} first. We call
1000 such variables @dfn{per-buffer} variables. Many variables in Emacs
1001 are normally per-buffer; the variable's document string tells you when
1002 this is so. A per-buffer variable's global value is normally never
1003 effective in any buffer, but it still has a meaning: it is the initial
1004 value of the variable for each new buffer.
1005
1006 Major modes (@pxref{Major Modes}) always make variables local to the
1007 buffer before setting the variables. This is why changing major modes
1008 in one buffer has no effect on other buffers. Minor modes also work
1009 by setting variables---normally, each minor mode has one controlling
1010 variable which is non-@code{nil} when the mode is enabled
1011 (@pxref{Minor Modes}). For many minor modes, the controlling variable
1012 is per buffer, and thus always buffer-local. Otherwise, you can make
1013 it local in a specific buffer like any other variable.
1014
1015 A few variables cannot be local to a buffer because they are always
1016 local to each display instead (@pxref{Multiple Displays}). If you try to
1017 make one of these variables buffer-local, you'll get an error message.
1018
1019 @findex kill-local-variable
1020 @kbd{M-x kill-local-variable} makes a specified variable cease to be
1021 local to the current buffer. The global value of the variable
1022 henceforth is in effect in this buffer. Setting the major mode kills
1023 all the local variables of the buffer except for a few variables
1024 specially marked as @dfn{permanent locals}.
1025
1026 @findex setq-default
1027 To set the global value of a variable, regardless of whether the
1028 variable has a local value in the current buffer, you can use the Lisp
1029 construct @code{setq-default}. This construct is used just like
1030 @code{setq}, but it sets variables' global values instead of their local
1031 values (if any). When the current buffer does have a local value, the
1032 new global value may not be visible until you switch to another buffer.
1033 Here is an example:
1034
1035 @example
1036 (setq-default fill-column 75)
1037 @end example
1038
1039 @noindent
1040 @code{setq-default} is the only way to set the global value of a variable
1041 that has been marked with @code{make-variable-buffer-local}.
1042
1043 @findex default-value
1044 Lisp programs can use @code{default-value} to look at a variable's
1045 default value. This function takes a symbol as argument and returns its
1046 default value. The argument is evaluated; usually you must quote it
1047 explicitly. For example, here's how to obtain the default value of
1048 @code{fill-column}:
1049
1050 @example
1051 (default-value 'fill-column)
1052 @end example
1053
1054 @node File Variables
1055 @subsection Local Variables in Files
1056 @cindex local variables in files
1057 @cindex file local variables
1058
1059 A file can specify local variable values for use when you edit the
1060 file with Emacs. Visiting the file checks for local variable
1061 specifications; it automatically makes these variables local to the
1062 buffer, and sets them to the values specified in the file.
1063
1064 @menu
1065 * Specifying File Variables:: Specifying file local variables.
1066 * Safe File Variables:: Making sure file local variables are safe.
1067 @end menu
1068
1069 @node Specifying File Variables
1070 @subsubsection Specifying File Variables
1071
1072 There are two ways to specify file local variable values: in the first
1073 line, or with a local variables list. Here's how to specify them in the
1074 first line:
1075
1076 @example
1077 -*- mode: @var{modename}; @var{var}: @var{value}; @dots{} -*-
1078 @end example
1079
1080 @noindent
1081 You can specify any number of variables/value pairs in this way, each
1082 pair with a colon and semicolon as shown above. @code{mode:
1083 @var{modename};} specifies the major mode; this should come first in the
1084 line. The @var{value}s are not evaluated; they are used literally.
1085 Here is an example that specifies Lisp mode and sets two variables with
1086 numeric values:
1087
1088 @smallexample
1089 ;; -*- mode: Lisp; fill-column: 75; comment-column: 50; -*-
1090 @end smallexample
1091
1092 You can also specify the coding system for a file in this way: just
1093 specify a value for the ``variable'' named @code{coding}. The ``value''
1094 must be a coding system name that Emacs recognizes. @xref{Coding
1095 Systems}. @w{@samp{unibyte: t}} specifies unibyte loading for a
1096 particular Lisp file. @xref{Enabling Multibyte}.
1097
1098 The @code{eval} pseudo-variable, described below, can be specified in
1099 the first line as well.
1100
1101 @cindex shell scripts, and local file variables
1102 In shell scripts, the first line is used to identify the script
1103 interpreter, so you cannot put any local variables there. To
1104 accommodate this, Emacs looks for local variable specifications in the
1105 @emph{second} line when the first line specifies an interpreter.
1106
1107 A @dfn{local variables list} goes near the end of the file, in the
1108 last page. (It is often best to put it on a page by itself.) The local
1109 variables list starts with a line containing the string @samp{Local
1110 Variables:}, and ends with a line containing the string @samp{End:}. In
1111 between come the variable names and values, one set per line, as
1112 @samp{@var{variable}:@: @var{value}}. The @var{value}s are not
1113 evaluated; they are used literally. If a file has both a local
1114 variables list and a @samp{-*-} line, Emacs processes @emph{everything}
1115 in the @samp{-*-} line first, and @emph{everything} in the local
1116 variables list afterward.
1117
1118 Here is an example of a local variables list:
1119
1120 @example
1121 ;; Local Variables: **
1122 ;; mode:lisp **
1123 ;; comment-column:0 **
1124 ;; comment-start: ";; " **
1125 ;; comment-end:"**" **
1126 ;; End: **
1127 @end example
1128
1129 Each line starts with the prefix @samp{;; } and each line ends with
1130 the suffix @samp{ **}. Emacs recognizes these as the prefix and
1131 suffix based on the first line of the list, by finding them
1132 surrounding the magic string @samp{Local Variables:}; then it
1133 automatically discards them from the other lines of the list.
1134
1135 The usual reason for using a prefix and/or suffix is to embed the
1136 local variables list in a comment, so it won't confuse other programs
1137 that the file is intended as input for. The example above is for a
1138 language where comment lines start with @samp{;; } and end with
1139 @samp{**}; the local values for @code{comment-start} and
1140 @code{comment-end} customize the rest of Emacs for this unusual
1141 syntax. Don't use a prefix (or a suffix) if you don't need one.
1142
1143 If you write a multi-line string value, you should put the prefix
1144 and suffix on each line, even lines that start or end within the
1145 string. They will be stripped off for processing the list. If you
1146 want to split a long string across multiple lines of the file, you can
1147 use backslash-newline, which is ignored in Lisp string constants.
1148 Here's an example of doing this:
1149
1150 @example
1151 # Local Variables:
1152 # compile-command: "cc foo.c -Dfoo=bar -Dhack=whatever \
1153 # -Dmumble=blaah"
1154 # End:
1155 @end example
1156
1157 Some ``variable names'' have special meanings in a local variables
1158 list. Specifying the ``variable'' @code{mode} really sets the major
1159 mode, while any value specified for the ``variable'' @code{eval} is
1160 simply evaluated as an expression (its value is ignored). A value for
1161 @code{coding} specifies the coding system for character code
1162 conversion of this file, and a value of @code{t} for @code{unibyte}
1163 says to visit the file in a unibyte buffer. These four ``variables''
1164 are not really variables; setting them in any other context has no
1165 special meaning.
1166
1167 @emph{If @code{mode} is used to set a major mode, it should be the
1168 first ``variable'' in the list.} Otherwise, the entries that precede
1169 it will usually be ignored, since most modes kill all local variables
1170 as part of their initialization.
1171
1172 You can use the @code{mode} ``variable'' to set minor modes as well
1173 as the major modes; in fact, you can use it more than once, first to
1174 set the major mode and then to set minor modes which are specific to
1175 particular buffers. But most minor modes should not be specified in
1176 the file at all, because they represent user preferences.
1177
1178 For example, you may be tempted to try to turn on Auto Fill mode with
1179 a local variable list. That is a mistake. The choice of Auto Fill mode
1180 or not is a matter of individual taste, not a matter of the contents of
1181 particular files. If you want to use Auto Fill, set up major mode hooks
1182 with your @file{.emacs} file to turn it on (when appropriate) for you
1183 alone (@pxref{Init File}). Don't use a local variable list to impose
1184 your taste on everyone.
1185
1186 The start of the local variables list must be no more than 3000
1187 characters from the end of the file, and must be in the last page if the
1188 file is divided into pages. Otherwise, Emacs will not notice it is
1189 there. The purpose of this rule is so that a stray @samp{Local
1190 Variables:}@: not in the last page does not confuse Emacs, and so that
1191 visiting a long file that is all one page and has no local variables
1192 list need not take the time to search the whole file.
1193
1194 Use the command @code{normal-mode} to reset the local variables and
1195 major mode of a buffer according to the file name and contents,
1196 including the local variables list if any. @xref{Choosing Modes}.
1197
1198 @node Safe File Variables
1199 @subsubsection Safety of File Variables
1200
1201 File-local variables can be dangerous; when you visit someone else's
1202 file, there's no telling what its local variables list could do to
1203 your Emacs. Improper values of the @code{eval} ``variable,'' and
1204 other variables such as @code{load-path}, could execute Lisp code you
1205 didn't intend to run.
1206
1207 Therefore, whenever Emacs encounters file local variable values that
1208 are not known to be safe, it displays the file's entire local
1209 variables list, and asks you for confirmation before setting them.
1210 You can type @kbd{y} or @key{SPC} to put the local variables list into
1211 effect, or @kbd{n} to ignore it. When Emacs is run in batch mode
1212 (@pxref{Initial Options}), it can't really ask you, so it assumes the
1213 answer @kbd{n}.
1214
1215 Emacs normally recognizes certain variables/value pairs as safe.
1216 For instance, it is safe to give @code{comment-column} or
1217 @code{fill-column} any integer value. If a file specifies only
1218 known-safe variable/value pairs, Emacs does not ask for confirmation
1219 before setting them. Otherwise, you can tell Emacs to record all the
1220 variable/value pairs in this file as safe, by typing @kbd{!} at the
1221 confirmation prompt. When Emacs encounters these variable/value pairs
1222 subsequently, in the same file or others, it will assume they are
1223 safe.
1224
1225 @vindex safe-local-variable-values
1226 @cindex risky variable
1227 Some variables, such as @code{load-path}, are considered
1228 particularly @dfn{risky}: there is seldom any reason to specify them
1229 as local variables, and changing them can be dangerous. Even if you
1230 enter @kbd{!} at the confirmation prompt, Emacs will not record any
1231 values as safe for these variables. If you really want to record safe
1232 values for these variables, do it directly by customizing
1233 @samp{safe-local-variable-values} (@pxref{Easy Customization}).
1234
1235 @vindex enable-local-variables
1236 The variable @code{enable-local-variables} allows you to change the
1237 way Emacs processes local variables. Its default value is @code{t},
1238 which specifies the behavior described above. If it is @code{nil},
1239 Emacs simply ignores all file local variables. @code{:safe} means use
1240 only the safe values and ignore the rest. Any other value says to
1241 query you about each file that has local variables, without trying to
1242 determine whether the values are known to be safe.
1243
1244 @vindex enable-local-eval
1245 The variable @code{enable-local-eval} controls whether Emacs
1246 processes @code{eval} variables. The three possibilities for the
1247 variable's value are @code{t}, @code{nil}, and anything else, just as
1248 for @code{enable-local-variables}. The default is @code{maybe}, which
1249 is neither @code{t} nor @code{nil}, so normally Emacs does ask for
1250 confirmation about processing @code{eval} variables.
1251
1252 @vindex safe-local-eval-forms
1253 But there is an exception. The @code{safe-local-eval-forms} is a
1254 customizable list of eval forms which are safe. Emacs does not ask
1255 for confirmation when it finds these forms for the @code{eval}
1256 variable.
1257
1258 @node Key Bindings
1259 @section Customizing Key Bindings
1260 @cindex key bindings
1261
1262 This section describes @dfn{key bindings}, which map keys to commands,
1263 and @dfn{keymaps}, which record key bindings. It also explains how
1264 to customize key bindings.
1265
1266 Recall that a command is a Lisp function whose definition provides for
1267 interactive use. Like every Lisp function, a command has a function
1268 name, which usually consists of lower-case letters and hyphens.
1269
1270 @menu
1271 * Keymaps:: Generalities. The global keymap.
1272 * Prefix Keymaps:: Keymaps for prefix keys.
1273 * Local Keymaps:: Major and minor modes have their own keymaps.
1274 * Minibuffer Maps:: The minibuffer uses its own local keymaps.
1275 * Rebinding:: How to redefine one key's meaning conveniently.
1276 * Init Rebinding:: Rebinding keys with your init file, @file{.emacs}.
1277 * Function Keys:: Rebinding terminal function keys.
1278 * Named ASCII Chars:: Distinguishing @key{TAB} from @kbd{C-i}, and so on.
1279 * Mouse Buttons:: Rebinding mouse buttons in Emacs.
1280 * Disabling:: Disabling a command means confirmation is required
1281 before it can be executed. This is done to protect
1282 beginners from surprises.
1283 @end menu
1284
1285 @node Keymaps
1286 @subsection Keymaps
1287 @cindex keymap
1288
1289 The bindings between key sequences and command functions are recorded
1290 in data structures called @dfn{keymaps}. Emacs has many of these, each
1291 used on particular occasions.
1292
1293 Recall that a @dfn{key sequence} (@dfn{key}, for short) is a sequence
1294 of @dfn{input events} that have a meaning as a unit. Input events
1295 include characters, function keys and mouse buttons---all the inputs
1296 that you can send to the computer with your terminal. A key sequence
1297 gets its meaning from its @dfn{binding}, which says what command it
1298 runs. The function of keymaps is to record these bindings.
1299
1300 @cindex global keymap
1301 The @dfn{global} keymap is the most important keymap because it is
1302 always in effect. The global keymap defines keys for Fundamental mode;
1303 most of these definitions are common to most or all major modes. Each
1304 major or minor mode can have its own keymap which overrides the global
1305 definitions of some keys.
1306
1307 For example, a self-inserting character such as @kbd{g} is
1308 self-inserting because the global keymap binds it to the command
1309 @code{self-insert-command}. The standard Emacs editing characters such
1310 as @kbd{C-a} also get their standard meanings from the global keymap.
1311 Commands to rebind keys, such as @kbd{M-x global-set-key}, actually work
1312 by storing the new binding in the proper place in the global map.
1313 @xref{Rebinding}.
1314
1315 Meta characters work differently; Emacs translates each Meta
1316 character into a pair of characters starting with @key{ESC}. When you
1317 type the character @kbd{M-a} in a key sequence, Emacs replaces it with
1318 @kbd{@key{ESC} a}. A meta key comes in as a single input event, but
1319 becomes two events for purposes of key bindings. The reason for this is
1320 historical, and we might change it someday.
1321
1322 @cindex function key
1323 Most modern keyboards have function keys as well as character keys.
1324 Function keys send input events just as character keys do, and keymaps
1325 can have bindings for them.
1326
1327 On text terminals, typing a function key actually sends the computer a
1328 sequence of characters; the precise details of the sequence depends on
1329 which function key and on the model of terminal you are using. (Often
1330 the sequence starts with @kbd{@key{ESC} [}.) If Emacs understands your
1331 terminal type properly, it recognizes the character sequences forming
1332 function keys wherever they occur in a key sequence (not just at the
1333 beginning). Thus, for most purposes, you can pretend the function keys
1334 reach Emacs directly and ignore their encoding as character sequences.
1335
1336 @cindex mouse
1337 Mouse buttons also produce input events. These events come with other
1338 data---the window and position where you pressed or released the button,
1339 and a time stamp. But only the choice of button matters for key
1340 bindings; the other data matters only if a command looks at it.
1341 (Commands designed for mouse invocation usually do look at the other
1342 data.)
1343
1344 A keymap records definitions for single events. Interpreting a key
1345 sequence of multiple events involves a chain of keymaps. The first
1346 keymap gives a definition for the first event; this definition is
1347 another keymap, which is used to look up the second event in the
1348 sequence, and so on.
1349
1350 Key sequences can mix function keys and characters. For example,
1351 @kbd{C-x @key{SELECT}} is meaningful. If you make @key{SELECT} a prefix
1352 key, then @kbd{@key{SELECT} C-n} makes sense. You can even mix mouse
1353 events with keyboard events, but we recommend against it, because such
1354 key sequences are inconvenient to use.
1355
1356 As a user, you can redefine any key; but it is usually best to stick
1357 to key sequences that consist of @kbd{C-c} followed by a letter (upper
1358 or lower case). These keys are ``reserved for users,'' so they won't
1359 conflict with any properly designed Emacs extension. The function
1360 keys @key{F5} through @key{F9} are also reserved for users. If you
1361 redefine some other key, your definition may be overridden by certain
1362 extensions or major modes which redefine the same key.
1363
1364 @node Prefix Keymaps
1365 @subsection Prefix Keymaps
1366
1367 A prefix key such as @kbd{C-x} or @key{ESC} has its own keymap,
1368 which holds the definition for the event that immediately follows
1369 that prefix.
1370
1371 The definition of a prefix key is usually the keymap to use for
1372 looking up the following event. The definition can also be a Lisp
1373 symbol whose function definition is the following keymap; the effect is
1374 the same, but it provides a command name for the prefix key that can be
1375 used as a description of what the prefix key is for. Thus, the binding
1376 of @kbd{C-x} is the symbol @code{Control-X-prefix}, whose function
1377 definition is the keymap for @kbd{C-x} commands. The definitions of
1378 @kbd{C-c}, @kbd{C-x}, @kbd{C-h} and @key{ESC} as prefix keys appear in
1379 the global map, so these prefix keys are always available.
1380
1381 Aside from ordinary prefix keys, there is a fictitious ``prefix key''
1382 which represents the menu bar; see @ref{Menu Bar,,,elisp, The Emacs Lisp
1383 Reference Manual}, for special information about menu bar key bindings.
1384 Mouse button events that invoke pop-up menus are also prefix keys; see
1385 @ref{Menu Keymaps,,,elisp, The Emacs Lisp Reference Manual}, for more
1386 details.
1387
1388 Some prefix keymaps are stored in variables with names:
1389
1390 @itemize @bullet
1391 @item
1392 @vindex ctl-x-map
1393 @code{ctl-x-map} is the variable name for the map used for characters that
1394 follow @kbd{C-x}.
1395 @item
1396 @vindex help-map
1397 @code{help-map} is for characters that follow @kbd{C-h}.
1398 @item
1399 @vindex esc-map
1400 @code{esc-map} is for characters that follow @key{ESC}. Thus, all Meta
1401 characters are actually defined by this map.
1402 @item
1403 @vindex ctl-x-4-map
1404 @code{ctl-x-4-map} is for characters that follow @kbd{C-x 4}.
1405 @item
1406 @vindex mode-specific-map
1407 @code{mode-specific-map} is for characters that follow @kbd{C-c}.
1408 @end itemize
1409
1410 @node Local Keymaps
1411 @subsection Local Keymaps
1412
1413 @cindex local keymap
1414 So far we have explained the ins and outs of the global map. Major
1415 modes customize Emacs by providing their own key bindings in @dfn{local
1416 keymaps}. For example, C mode overrides @key{TAB} to make it indent the
1417 current line for C code. Portions of text in the buffer can specify
1418 their own keymaps to substitute for the keymap of the buffer's major
1419 mode.
1420
1421 @cindex minor mode keymap
1422 Minor modes can also have local keymaps. Whenever a minor mode is
1423 in effect, the definitions in its keymap override both the major
1424 mode's local keymap and the global keymap.
1425
1426 A local keymap can locally redefine a key as a prefix key by defining
1427 it as a prefix keymap. If the key is also defined globally as a prefix,
1428 then its local and global definitions (both keymaps) effectively
1429 combine: both of them are used to look up the event that follows the
1430 prefix key. Thus, if the mode's local keymap defines @kbd{C-c} as
1431 another keymap, and that keymap defines @kbd{C-z} as a command, this
1432 provides a local meaning for @kbd{C-c C-z}. This does not affect other
1433 sequences that start with @kbd{C-c}; if those sequences don't have their
1434 own local bindings, their global bindings remain in effect.
1435
1436 Another way to think of this is that Emacs handles a multi-event key
1437 sequence by looking in several keymaps, one by one, for a binding of the
1438 whole key sequence. First it checks the minor mode keymaps for minor
1439 modes that are enabled, then it checks the major mode's keymap, and then
1440 it checks the global keymap. This is not precisely how key lookup
1441 works, but it's good enough for understanding the results in ordinary
1442 circumstances.
1443
1444 @cindex rebinding major mode keys
1445 Most major modes construct their keymaps when the mode is used for
1446 the first time in a session. If you wish to change one of these
1447 keymaps, you must use the major mode's @dfn{mode hook}
1448 (@pxref{Hooks}).
1449
1450 @findex define-key
1451 For example, the command @code{texinfo-mode} to select Texinfo mode
1452 runs the hook @code{texinfo-mode-hook}. Here's how you can use the hook
1453 to add local bindings (not very useful, we admit) for @kbd{C-c n} and
1454 @kbd{C-c p} in Texinfo mode:
1455
1456 @example
1457 (add-hook 'texinfo-mode-hook
1458 '(lambda ()
1459 (define-key texinfo-mode-map "\C-cp"
1460 'backward-paragraph)
1461 (define-key texinfo-mode-map "\C-cn"
1462 'forward-paragraph)))
1463 @end example
1464
1465 @node Minibuffer Maps
1466 @subsection Minibuffer Keymaps
1467
1468 @cindex minibuffer keymaps
1469 @vindex minibuffer-local-map
1470 @vindex minibuffer-local-ns-map
1471 @vindex minibuffer-local-completion-map
1472 @vindex minibuffer-local-must-match-map
1473 @vindex minibuffer-local-filename-completion-map
1474 @vindex minibuffer-local-must-match-filename-map
1475 The minibuffer has its own set of local keymaps; they contain various
1476 completion and exit commands.
1477
1478 @itemize @bullet
1479 @item
1480 @code{minibuffer-local-map} is used for ordinary input (no completion).
1481 @item
1482 @code{minibuffer-local-ns-map} is similar, except that @key{SPC} exits
1483 just like @key{RET}. This is used mainly for Mocklisp compatibility.
1484 @item
1485 @code{minibuffer-local-completion-map} is for permissive completion.
1486 @item
1487 @code{minibuffer-local-must-match-map} is for strict completion and
1488 for cautious completion.
1489 @item
1490 Finally, @code{minibuffer-local-filename-completion-map} and
1491 @code{minibuffer-local-must-match-filename-map} are like the two
1492 previous ones, but they are specifically for file name completion.
1493 They do not bind @key{SPC}.
1494 @end itemize
1495
1496 @node Rebinding
1497 @subsection Changing Key Bindings Interactively
1498 @cindex key rebinding, this session
1499 @cindex redefining keys, this session
1500
1501 The way to redefine an Emacs key is to change its entry in a keymap.
1502 You can change the global keymap, in which case the change is effective in
1503 all major modes (except those that have their own overriding local
1504 definitions for the same key). Or you can change the current buffer's
1505 local map, which affects all buffers using the same major mode.
1506
1507 @findex global-set-key
1508 @findex local-set-key
1509 @findex global-unset-key
1510 @findex local-unset-key
1511 @table @kbd
1512 @item M-x global-set-key @key{RET} @var{key} @var{cmd} @key{RET}
1513 Define @var{key} globally to run @var{cmd}.
1514 @item M-x local-set-key @key{RET} @var{key} @var{cmd} @key{RET}
1515 Define @var{key} locally (in the major mode now in effect) to run
1516 @var{cmd}.
1517 @item M-x global-unset-key @key{RET} @var{key}
1518 Make @var{key} undefined in the global map.
1519 @item M-x local-unset-key @key{RET} @var{key}
1520 Make @var{key} undefined locally (in the major mode now in effect).
1521 @end table
1522
1523 For example, suppose you like to execute commands in a subshell within
1524 an Emacs buffer, instead of suspending Emacs and executing commands in
1525 your login shell. Normally, @kbd{C-z} is bound to the function
1526 @code{suspend-emacs} (when not using the X Window System), but you can
1527 change @kbd{C-z} to invoke an interactive subshell within Emacs, by
1528 binding it to @code{shell} as follows:
1529
1530 @example
1531 M-x global-set-key @key{RET} C-z shell @key{RET}
1532 @end example
1533
1534 @noindent
1535 @code{global-set-key} reads the command name after the key. After you
1536 press the key, a message like this appears so that you can confirm that
1537 you are binding the key you want:
1538
1539 @example
1540 Set key C-z to command:
1541 @end example
1542
1543 You can redefine function keys and mouse events in the same way; just
1544 type the function key or click the mouse when it's time to specify the
1545 key to rebind.
1546
1547 You can rebind a key that contains more than one event in the same
1548 way. Emacs keeps reading the key to rebind until it is a complete key
1549 (that is, not a prefix key). Thus, if you type @kbd{C-f} for
1550 @var{key}, that's the end; it enters the minibuffer immediately to
1551 read @var{cmd}. But if you type @kbd{C-x}, since that's a prefix, it
1552 reads another character; if that is @kbd{4}, another prefix character,
1553 it reads one more character, and so on. For example,
1554
1555 @example
1556 M-x global-set-key @key{RET} C-x 4 $ spell-other-window @key{RET}
1557 @end example
1558
1559 @noindent
1560 redefines @kbd{C-x 4 $} to run the (fictitious) command
1561 @code{spell-other-window}.
1562
1563 The two-character keys consisting of @kbd{C-c} followed by a letter
1564 are reserved for user customizations. Lisp programs are not supposed to
1565 define these keys, so the bindings you make for them will be available
1566 in all major modes and will never get in the way of anything.
1567
1568 You can remove the global definition of a key with
1569 @code{global-unset-key}. This makes the key @dfn{undefined}; if you
1570 type it, Emacs will just beep. Similarly, @code{local-unset-key} makes
1571 a key undefined in the current major mode keymap, which makes the global
1572 definition (or lack of one) come back into effect in that major mode.
1573
1574 If you have redefined (or undefined) a key and you subsequently wish
1575 to retract the change, undefining the key will not do the job---you need
1576 to redefine the key with its standard definition. To find the name of
1577 the standard definition of a key, go to a Fundamental mode buffer in a
1578 fresh Emacs and use @kbd{C-h c}. The documentation of keys in this
1579 manual also lists their command names.
1580
1581 If you want to prevent yourself from invoking a command by mistake, it
1582 is better to disable the command than to undefine the key. A disabled
1583 command is less work to invoke when you really want to.
1584 @xref{Disabling}.
1585
1586 @node Init Rebinding
1587 @subsection Rebinding Keys in Your Init File
1588
1589 If you have a set of key bindings that you like to use all the time,
1590 you can specify them in your @file{.emacs} file by using their Lisp
1591 syntax. (@xref{Init File}.)
1592
1593 The simplest method for doing this works for @acronym{ASCII} characters and
1594 Meta-modified @acronym{ASCII} characters only. This method uses a string to
1595 represent the key sequence you want to rebind. For example, here's how
1596 to bind @kbd{C-z} to @code{shell}:
1597
1598 @example
1599 (global-set-key "\C-z" 'shell)
1600 @end example
1601
1602 @noindent
1603 This example uses a string constant containing one character,
1604 @kbd{C-z}. (@samp{\C-} is string syntax for a control character.) The
1605 single-quote before the command name, @code{shell}, marks it as a
1606 constant symbol rather than a variable. If you omit the quote, Emacs
1607 would try to evaluate @code{shell} immediately as a variable. This
1608 probably causes an error; it certainly isn't what you want.
1609
1610 Here is another example that binds the key sequence @kbd{C-x M-l}:
1611
1612 @example
1613 (global-set-key "\C-x\M-l" 'make-symbolic-link)
1614 @end example
1615
1616 To put @key{TAB}, @key{RET}, @key{ESC}, or @key{DEL} in the
1617 string, you can use the Emacs Lisp escape sequences, @samp{\t},
1618 @samp{\r}, @samp{\e}, and @samp{\d}. Here is an example which binds
1619 @kbd{C-x @key{TAB}}:
1620
1621 @example
1622 (global-set-key "\C-x\t" 'indent-rigidly)
1623 @end example
1624
1625 These examples show how to write some other special @acronym{ASCII} characters
1626 in strings for key bindings:
1627
1628 @example
1629 (global-set-key "\r" 'newline) ;; @key{RET}
1630 (global-set-key "\d" 'delete-backward-char) ;; @key{DEL}
1631 (global-set-key "\C-x\e\e" 'repeat-complex-command) ;; @key{ESC}
1632 @end example
1633
1634 When the key sequence includes function keys or mouse button events,
1635 or non-@acronym{ASCII} characters such as @code{C-=} or @code{H-a}, you must use
1636 the more general method of rebinding, which uses a vector to specify the
1637 key sequence.
1638
1639 The way to write a vector in Emacs Lisp is with square brackets around
1640 the vector elements. Use spaces to separate the elements. If an
1641 element is a symbol, simply write the symbol's name---no other
1642 delimiters or punctuation are needed. If a vector element is a
1643 character, write it as a Lisp character constant: @samp{?} followed by
1644 the character as it would appear in a string.
1645
1646 Here are examples of using vectors to rebind @kbd{C-=} (a control
1647 character not in @acronym{ASCII}), @kbd{C-M-=} (not in @acronym{ASCII} because @kbd{C-=}
1648 is not), @kbd{H-a} (a Hyper character; @acronym{ASCII} doesn't have Hyper at
1649 all), @key{F7} (a function key), and @kbd{C-Mouse-1} (a
1650 keyboard-modified mouse button):
1651
1652 @example
1653 (global-set-key [?\C-=] 'make-symbolic-link)
1654 (global-set-key [?\M-\C-=] 'make-symbolic-link)
1655 (global-set-key [?\H-a] 'make-symbolic-link)
1656 (global-set-key [f7] 'make-symbolic-link)
1657 (global-set-key [C-mouse-1] 'make-symbolic-link)
1658 @end example
1659
1660 You can use a vector for the simple cases too. Here's how to
1661 rewrite the first six examples above to use vectors:
1662
1663 @example
1664 (global-set-key [?\C-z] 'shell)
1665 (global-set-key [?\C-x ?l] 'make-symbolic-link)
1666 (global-set-key [?\C-x ?\t] 'indent-rigidly)
1667 (global-set-key [?\r] 'newline)
1668 (global-set-key [?\d] 'delete-backward-char)
1669 (global-set-key [?\C-x ?\e ?\e] 'repeat-complex-command)
1670 @end example
1671
1672 @noindent
1673 As you see, you represent a multi-character key sequence with a vector
1674 by listing all of the characters, in order, within the square brackets
1675 that delimit the vector.
1676
1677 Language and coding systems can cause problems with key bindings
1678 for non-@acronym{ASCII} characters. @xref{Init Non-ASCII}.
1679
1680 @node Function Keys
1681 @subsection Rebinding Function Keys
1682
1683 Key sequences can contain function keys as well as ordinary
1684 characters. Just as Lisp characters (actually integers) represent
1685 keyboard characters, Lisp symbols represent function keys. If the
1686 function key has a word as its label, then that word is also the name of
1687 the corresponding Lisp symbol. Here are the conventional Lisp names for
1688 common function keys:
1689
1690 @table @asis
1691 @item @code{left}, @code{up}, @code{right}, @code{down}
1692 Cursor arrow keys.
1693
1694 @item @code{begin}, @code{end}, @code{home}, @code{next}, @code{prior}
1695 Other cursor repositioning keys.
1696
1697 @item @code{select}, @code{print}, @code{execute}, @code{backtab}
1698 @itemx @code{insert}, @code{undo}, @code{redo}, @code{clearline}
1699 @itemx @code{insertline}, @code{deleteline}, @code{insertchar}, @code{deletechar}
1700 Miscellaneous function keys.
1701
1702 @item @code{f1}, @code{f2}, @dots{} @code{f35}
1703 Numbered function keys (across the top of the keyboard).
1704
1705 @item @code{kp-add}, @code{kp-subtract}, @code{kp-multiply}, @code{kp-divide}
1706 @itemx @code{kp-backtab}, @code{kp-space}, @code{kp-tab}, @code{kp-enter}
1707 @itemx @code{kp-separator}, @code{kp-decimal}, @code{kp-equal}
1708 Keypad keys (to the right of the regular keyboard), with names or punctuation.
1709
1710 @item @code{kp-0}, @code{kp-1}, @dots{} @code{kp-9}
1711 Keypad keys with digits.
1712
1713 @item @code{kp-f1}, @code{kp-f2}, @code{kp-f3}, @code{kp-f4}
1714 Keypad PF keys.
1715 @end table
1716
1717 These names are conventional, but some systems (especially when using
1718 X) may use different names. To make certain what symbol is used for a
1719 given function key on your terminal, type @kbd{C-h c} followed by that
1720 key.
1721
1722 A key sequence which contains function key symbols (or anything but
1723 @acronym{ASCII} characters) must be a vector rather than a string.
1724 Thus, to bind function key @samp{f1} to the command @code{rmail},
1725 write the following:
1726
1727 @example
1728 (global-set-key [f1] 'rmail)
1729 @end example
1730
1731 @noindent
1732 To bind the right-arrow key to the command @code{forward-char}, you can
1733 use this expression:
1734
1735 @example
1736 (global-set-key [right] 'forward-char)
1737 @end example
1738
1739 @noindent
1740 This uses the Lisp syntax for a vector containing the symbol
1741 @code{right}. (This binding is present in Emacs by default.)
1742
1743 @xref{Init Rebinding}, for more information about using vectors for
1744 rebinding.
1745
1746 You can mix function keys and characters in a key sequence. This
1747 example binds @kbd{C-x @key{NEXT}} to the command @code{forward-page}.
1748
1749 @example
1750 (global-set-key [?\C-x next] 'forward-page)
1751 @end example
1752
1753 @noindent
1754 where @code{?\C-x} is the Lisp character constant for the character
1755 @kbd{C-x}. The vector element @code{next} is a symbol and therefore
1756 does not take a question mark.
1757
1758 You can use the modifier keys @key{CTRL}, @key{META}, @key{HYPER},
1759 @key{SUPER}, @key{ALT} and @key{SHIFT} with function keys. To represent
1760 these modifiers, add the strings @samp{C-}, @samp{M-}, @samp{H-},
1761 @samp{s-}, @samp{A-} and @samp{S-} at the front of the symbol name.
1762 Thus, here is how to make @kbd{Hyper-Meta-@key{RIGHT}} move forward a
1763 word:
1764
1765 @example
1766 (global-set-key [H-M-right] 'forward-word)
1767 @end example
1768
1769 @cindex keypad
1770 Many keyboards have a ``numeric keypad'' on the right hand side.
1771 The numeric keys in the keypad double up as cursor motion keys,
1772 toggled by a key labeled @samp{Num Lock}. By default, Emacs
1773 translates these keys to the corresponding keys in the main keyboard.
1774 For example, when @samp{Num Lock} is on, the key labeled @samp{8} on
1775 the numeric keypad produces @code{kp-8}, which is translated to
1776 @kbd{8}; when @samp{Num Lock} is off, the same key produces
1777 @code{kp-up}, which is translated to @key{UP}. If you rebind a key
1778 such as @kbd{8} or @key{UP}, it affects the equivalent keypad key too.
1779 However, if you rebind a @samp{kp-} key directly, that won't affect
1780 its non-keypad equivalent.
1781
1782 Emacs provides a convenient method for binding the numeric keypad
1783 keys, using the variables @code{keypad-setup},
1784 @code{keypad-numlock-setup}, @code{keypad-shifted-setup}, and
1785 @code{keypad-numlock-shifted-setup}. These can be found in the
1786 @samp{keyboard} customization group (@pxref{Easy Customization}). You
1787 can rebind the keys to perform other tasks, such as issuing numeric
1788 prefix arguments.
1789
1790 @node Named ASCII Chars
1791 @subsection Named @acronym{ASCII} Control Characters
1792
1793 @key{TAB}, @key{RET}, @key{BS}, @key{LFD}, @key{ESC} and @key{DEL}
1794 started out as names for certain @acronym{ASCII} control characters,
1795 used so often that they have special keys of their own. For instance,
1796 @key{TAB} was another name for @kbd{C-i}. Later, users found it
1797 convenient to distinguish in Emacs between these keys and the ``same''
1798 control characters typed with the @key{CTRL} key. Therefore, on most
1799 modern terminals, they are no longer the same, and @key{TAB} is
1800 distinguishable from @kbd{C-i}.
1801
1802 Emacs can distinguish these two kinds of input if the keyboard does.
1803 It treats the ``special'' keys as function keys named @code{tab},
1804 @code{return}, @code{backspace}, @code{linefeed}, @code{escape}, and
1805 @code{delete}. These function keys translate automatically into the
1806 corresponding @acronym{ASCII} characters @emph{if} they have no
1807 bindings of their own. As a result, neither users nor Lisp programs
1808 need to pay attention to the distinction unless they care to.
1809
1810 If you do not want to distinguish between (for example) @key{TAB} and
1811 @kbd{C-i}, make just one binding, for the @acronym{ASCII} character @key{TAB}
1812 (octal code 011). If you do want to distinguish, make one binding for
1813 this @acronym{ASCII} character, and another for the ``function key'' @code{tab}.
1814
1815 With an ordinary @acronym{ASCII} terminal, there is no way to distinguish
1816 between @key{TAB} and @kbd{C-i} (and likewise for other such pairs),
1817 because the terminal sends the same character in both cases.
1818
1819 @node Mouse Buttons
1820 @subsection Rebinding Mouse Buttons
1821 @cindex mouse button events
1822 @cindex rebinding mouse buttons
1823 @cindex click events
1824 @cindex drag events
1825 @cindex down events
1826 @cindex button down events
1827
1828 Emacs uses Lisp symbols to designate mouse buttons, too. The ordinary
1829 mouse events in Emacs are @dfn{click} events; these happen when you
1830 press a button and release it without moving the mouse. You can also
1831 get @dfn{drag} events, when you move the mouse while holding the button
1832 down. Drag events happen when you finally let go of the button.
1833
1834 The symbols for basic click events are @code{mouse-1} for the leftmost
1835 button, @code{mouse-2} for the next, and so on. Here is how you can
1836 redefine the second mouse button to split the current window:
1837
1838 @example
1839 (global-set-key [mouse-2] 'split-window-vertically)
1840 @end example
1841
1842 The symbols for drag events are similar, but have the prefix
1843 @samp{drag-} before the word @samp{mouse}. For example, dragging the
1844 first button generates a @code{drag-mouse-1} event.
1845
1846 You can also define bindings for events that occur when a mouse button
1847 is pressed down. These events start with @samp{down-} instead of
1848 @samp{drag-}. Such events are generated only if they have key bindings.
1849 When you get a button-down event, a corresponding click or drag event
1850 will always follow.
1851
1852 @cindex double clicks
1853 @cindex triple clicks
1854 If you wish, you can distinguish single, double, and triple clicks. A
1855 double click means clicking a mouse button twice in approximately the
1856 same place. The first click generates an ordinary click event. The
1857 second click, if it comes soon enough, generates a double-click event
1858 instead. The event type for a double-click event starts with
1859 @samp{double-}: for example, @code{double-mouse-3}.
1860
1861 This means that you can give a special meaning to the second click at
1862 the same place, but it must act on the assumption that the ordinary
1863 single click definition has run when the first click was received.
1864
1865 This constrains what you can do with double clicks, but user interface
1866 designers say that this constraint ought to be followed in any case. A
1867 double click should do something similar to the single click, only
1868 ``more so.'' The command for the double-click event should perform the
1869 extra work for the double click.
1870
1871 If a double-click event has no binding, it changes to the
1872 corresponding single-click event. Thus, if you don't define a
1873 particular double click specially, it executes the single-click command
1874 twice.
1875
1876 Emacs also supports triple-click events whose names start with
1877 @samp{triple-}. Emacs does not distinguish quadruple clicks as event
1878 types; clicks beyond the third generate additional triple-click events.
1879 However, the full number of clicks is recorded in the event list, so
1880 if you know Emacs Lisp you can distinguish if you really want to
1881 (@pxref{Accessing Events,,, elisp, The Emacs Lisp Reference Manual}).
1882 We don't recommend distinct meanings for more than three clicks, but
1883 sometimes it is useful for subsequent clicks to cycle through the same
1884 set of three meanings, so that four clicks are equivalent to one
1885 click, five are equivalent to two, and six are equivalent to three.
1886
1887 Emacs also records multiple presses in drag and button-down events.
1888 For example, when you press a button twice, then move the mouse while
1889 holding the button, Emacs gets a @samp{double-drag-} event. And at the
1890 moment when you press it down for the second time, Emacs gets a
1891 @samp{double-down-} event (which is ignored, like all button-down
1892 events, if it has no binding).
1893
1894 @vindex double-click-time
1895 The variable @code{double-click-time} specifies how much time can
1896 elapse between clicks and still allow them to be grouped as a multiple
1897 click. Its value is in units of milliseconds. If the value is
1898 @code{nil}, double clicks are not detected at all. If the value is
1899 @code{t}, then there is no time limit. The default is 500.
1900
1901 @vindex double-click-fuzz
1902 The variable @code{double-click-fuzz} specifies how much the mouse
1903 can move between clicks and still allow them to be grouped as a multiple
1904 click. Its value is in units of pixels on windowed displays and in
1905 units of 1/8 of a character cell on text-mode terminals; the default is
1906 3.
1907
1908 The symbols for mouse events also indicate the status of the modifier
1909 keys, with the usual prefixes @samp{C-}, @samp{M-}, @samp{H-},
1910 @samp{s-}, @samp{A-} and @samp{S-}. These always precede @samp{double-}
1911 or @samp{triple-}, which always precede @samp{drag-} or @samp{down-}.
1912
1913 A frame includes areas that don't show text from the buffer, such as
1914 the mode line and the scroll bar. You can tell whether a mouse button
1915 comes from a special area of the screen by means of dummy ``prefix
1916 keys.'' For example, if you click the mouse in the mode line, you get
1917 the prefix key @code{mode-line} before the ordinary mouse-button symbol.
1918 Thus, here is how to define the command for clicking the first button in
1919 a mode line to run @code{scroll-up}:
1920
1921 @example
1922 (global-set-key [mode-line mouse-1] 'scroll-up)
1923 @end example
1924
1925 Here is the complete list of these dummy prefix keys and their
1926 meanings:
1927
1928 @table @code
1929 @item mode-line
1930 The mouse was in the mode line of a window.
1931 @item vertical-line
1932 The mouse was in the vertical line separating side-by-side windows. (If
1933 you use scroll bars, they appear in place of these vertical lines.)
1934 @item vertical-scroll-bar
1935 The mouse was in a vertical scroll bar. (This is the only kind of
1936 scroll bar Emacs currently supports.)
1937 @item menu-bar
1938 The mouse was in the menu bar.
1939 @item header-line
1940 The mouse was in a header line.
1941 @ignore
1942 @item horizontal-scroll-bar
1943 The mouse was in a horizontal scroll bar. Horizontal scroll bars do
1944 horizontal scrolling, and people don't use them often.
1945 @end ignore
1946 @end table
1947
1948 You can put more than one mouse button in a key sequence, but it isn't
1949 usual to do so.
1950
1951 @node Disabling
1952 @subsection Disabling Commands
1953 @cindex disabled command
1954
1955 Disabling a command means that invoking it interactively asks for
1956 confirmation from the user. The purpose of disabling a command is to
1957 prevent users from executing it by accident; we do this for commands
1958 that might be confusing to the uninitiated.
1959
1960 Attempting to invoke a disabled command interactively in Emacs
1961 displays a window containing the command's name, its documentation,
1962 and some instructions on what to do immediately; then Emacs asks for
1963 input saying whether to execute the command as requested, enable it
1964 and execute it, or cancel. If you decide to enable the command, you
1965 must then answer another question---whether to do this permanently, or
1966 just for the current session. (Enabling permanently works by
1967 automatically editing your @file{.emacs} file.) You can also type
1968 @kbd{!} to enable @emph{all} commands, for the current session only.
1969
1970 The direct mechanism for disabling a command is to put a
1971 non-@code{nil} @code{disabled} property on the Lisp symbol for the
1972 command. Here is the Lisp program to do this:
1973
1974 @example
1975 (put 'delete-region 'disabled t)
1976 @end example
1977
1978 If the value of the @code{disabled} property is a string, that string
1979 is included in the message displayed when the command is used:
1980
1981 @example
1982 (put 'delete-region 'disabled
1983 "It's better to use `kill-region' instead.\n")
1984 @end example
1985
1986 @findex disable-command
1987 @findex enable-command
1988 You can make a command disabled either by editing the @file{.emacs}
1989 file directly, or with the command @kbd{M-x disable-command}, which edits
1990 the @file{.emacs} file for you. Likewise, @kbd{M-x enable-command}
1991 edits @file{.emacs} to enable a command permanently. @xref{Init File}.
1992
1993 If Emacs was invoked with the @option{-q} or @option{--no-init-file}
1994 options (@pxref{Initial Options}), it will not edit your
1995 @file{~/.emacs} init file. Doing so could lose information
1996 because Emacs has not read your init file.
1997
1998 Whether a command is disabled is independent of what key is used to
1999 invoke it; disabling also applies if the command is invoked using
2000 @kbd{M-x}. However, disabling a command has no effect on calling it
2001 as a function from Lisp programs.
2002
2003 @node Syntax
2004 @section The Syntax Table
2005 @cindex syntax table
2006
2007 All the Emacs commands which parse words or balance parentheses are
2008 controlled by the @dfn{syntax table}. The syntax table says which
2009 characters are opening delimiters, which are parts of words, which are
2010 string quotes, and so on. It does this by assigning each character to
2011 one of fifteen-odd @dfn{syntax classes}. In some cases it specifies
2012 some additional information also.
2013
2014 Each major mode has its own syntax table (though related major modes
2015 sometimes share one syntax table), which it installs in each buffer
2016 that uses the mode. The syntax table installed in the current buffer
2017 is the one that all commands use, so we call it ``the'' syntax table.
2018
2019 @kindex C-h s
2020 @findex describe-syntax
2021 To display a description of the contents of the current syntax
2022 table, type @kbd{C-h s} (@code{describe-syntax}). The description of
2023 each character includes the string you would have to give to
2024 @code{modify-syntax-entry} to set up that character's current syntax,
2025 starting with the character which designates its syntax class, plus
2026 some English text to explain its meaning.
2027
2028 A syntax table is actually a Lisp object, a char-table, whose
2029 elements are cons cells. For full information on the syntax table,
2030 see @ref{Syntax Tables,, Syntax Tables, elisp, The Emacs Lisp
2031 Reference Manual}.
2032
2033 @node Init File
2034 @section The Init File, @file{~/.emacs}
2035 @cindex init file
2036 @cindex Emacs initialization file
2037 @cindex key rebinding, permanent
2038 @cindex rebinding keys, permanently
2039 @cindex startup (init file)
2040
2041 When Emacs is started, it normally loads a Lisp program from the file
2042 @file{.emacs} or @file{.emacs.el} in your home directory (@pxref{Find Init}).
2043 We call this file your @dfn{init file} because it specifies how to
2044 initialize Emacs for you. You can use the command line switch
2045 @samp{-q} to prevent loading your init file, and @samp{-u} (or
2046 @samp{--user}) to specify a different user's init file (@pxref{Initial
2047 Options}).
2048
2049 You can also use @file{~/.emacs.d/init.el} as the init file. Emacs
2050 tries this if it cannot find @file{~/.emacs} or @file{~/.emacs.el}.
2051
2052 @cindex @file{default.el}, the default init file
2053 There can also be a @dfn{default init file}, which is the library
2054 named @file{default.el}, found via the standard search path for
2055 libraries. The Emacs distribution contains no such library; your site
2056 may create one for local customizations. If this library exists, it is
2057 loaded whenever you start Emacs (except when you specify @samp{-q}).
2058 But your init file, if any, is loaded first; if it sets
2059 @code{inhibit-default-init} non-@code{nil}, then @file{default} is not
2060 loaded.
2061
2062 @cindex site init file
2063 @cindex @file{site-start.el}, the site startup file
2064 Your site may also have a @dfn{site startup file}; this is named
2065 @file{site-start.el}, if it exists. Like @file{default.el}, Emacs
2066 finds this file via the standard search path for Lisp libraries.
2067 Emacs loads this library before it loads your init file. To inhibit
2068 loading of this library, use the option @samp{--no-site-file}.
2069 @xref{Initial Options}. We recommend against using
2070 @file{site-start.el} for changes that some users may not like. It is
2071 better to put them in @file{default.el}, so that users can more easily
2072 override them.
2073
2074 You can place @file{default.el} and @file{site-start.el} in any of
2075 the directories which Emacs searches for Lisp libraries. The variable
2076 @code{load-path} (@pxref{Lisp Libraries}) specifies these directories.
2077 Many sites put these files in the @file{site-lisp} subdirectory of the
2078 Emacs installation directory, typically
2079 @file{/usr/local/share/emacs/site-lisp}.
2080
2081 If you have a large amount of code in your @file{.emacs} file, you
2082 should rename it to @file{~/.emacs.el}, and byte-compile it. @xref{Byte
2083 Compilation,, Byte Compilation, elisp, the Emacs Lisp Reference Manual},
2084 for more information about compiling Emacs Lisp programs.
2085
2086 If you are going to write actual Emacs Lisp programs that go beyond
2087 minor customization, you should read the @cite{Emacs Lisp Reference Manual}.
2088 @ifnottex
2089 @xref{Top, Emacs Lisp, Emacs Lisp, elisp, the Emacs Lisp Reference
2090 Manual}.
2091 @end ifnottex
2092
2093 @menu
2094 * Init Syntax:: Syntax of constants in Emacs Lisp.
2095 * Init Examples:: How to do some things with an init file.
2096 * Terminal Init:: Each terminal type can have an init file.
2097 * Find Init:: How Emacs finds the init file.
2098 * Init Non-ASCII:: Using non-@acronym{ASCII} characters in an init file.
2099 @end menu
2100
2101 @node Init Syntax
2102 @subsection Init File Syntax
2103
2104 The @file{.emacs} file contains one or more Lisp function call
2105 expressions. Each of these consists of a function name followed by
2106 arguments, all surrounded by parentheses. For example, @code{(setq
2107 fill-column 60)} calls the function @code{setq} to set the variable
2108 @code{fill-column} (@pxref{Filling}) to 60.
2109
2110 You can set any Lisp variable with @code{setq}, but with certain
2111 variables @code{setq} won't do what you probably want in the
2112 @file{.emacs} file. Some variables automatically become buffer-local
2113 when set with @code{setq}; what you want in @file{.emacs} is to set
2114 the default value, using @code{setq-default}. Some customizable minor
2115 mode variables do special things to enable the mode when you set them
2116 with Customize, but ordinary @code{setq} won't do that; to enable the
2117 mode in your @file{.emacs} file, call the minor mode command. The
2118 following section has examples of both of these methods.
2119
2120 The second argument to @code{setq} is an expression for the new
2121 value of the variable. This can be a constant, a variable, or a
2122 function call expression. In @file{.emacs}, constants are used most
2123 of the time. They can be:
2124
2125 @table @asis
2126 @item Numbers:
2127 Numbers are written in decimal, with an optional initial minus sign.
2128
2129 @item Strings:
2130 @cindex Lisp string syntax
2131 @cindex string syntax
2132 Lisp string syntax is the same as C string syntax with a few extra
2133 features. Use a double-quote character to begin and end a string constant.
2134
2135 In a string, you can include newlines and special characters literally.
2136 But often it is cleaner to use backslash sequences for them: @samp{\n}
2137 for newline, @samp{\b} for backspace, @samp{\r} for carriage return,
2138 @samp{\t} for tab, @samp{\f} for formfeed (control-L), @samp{\e} for
2139 escape, @samp{\\} for a backslash, @samp{\"} for a double-quote, or
2140 @samp{\@var{ooo}} for the character whose octal code is @var{ooo}.
2141 Backslash and double-quote are the only characters for which backslash
2142 sequences are mandatory.
2143
2144 @samp{\C-} can be used as a prefix for a control character, as in
2145 @samp{\C-s} for @acronym{ASCII} control-S, and @samp{\M-} can be used as a prefix for
2146 a Meta character, as in @samp{\M-a} for @kbd{Meta-A} or @samp{\M-\C-a} for
2147 @kbd{Control-Meta-A}.@refill
2148
2149 @xref{Init Non-ASCII}, for information about including
2150 non-@acronym{ASCII} in your init file.
2151
2152 @item Characters:
2153 Lisp character constant syntax consists of a @samp{?} followed by
2154 either a character or an escape sequence starting with @samp{\}.
2155 Examples: @code{?x}, @code{?\n}, @code{?\"}, @code{?\)}. Note that
2156 strings and characters are not interchangeable in Lisp; some contexts
2157 require one and some contexts require the other.
2158
2159 @xref{Init Non-ASCII}, for information about binding commands to
2160 keys which send non-@acronym{ASCII} characters.
2161
2162 @item True:
2163 @code{t} stands for `true'.
2164
2165 @item False:
2166 @code{nil} stands for `false'.
2167
2168 @item Other Lisp objects:
2169 Write a single-quote (@code{'}) followed by the Lisp object you want.
2170 @end table
2171
2172 @node Init Examples
2173 @subsection Init File Examples
2174
2175 Here are some examples of doing certain commonly desired things with
2176 Lisp expressions:
2177
2178 @itemize @bullet
2179 @item
2180 Make @key{TAB} in C mode just insert a tab if point is in the middle of a
2181 line.
2182
2183 @example
2184 (setq c-tab-always-indent nil)
2185 @end example
2186
2187 Here we have a variable whose value is normally @code{t} for `true'
2188 and the alternative is @code{nil} for `false'.
2189
2190 @item
2191 Make searches case sensitive by default (in all buffers that do not
2192 override this).
2193
2194 @example
2195 (setq-default case-fold-search nil)
2196 @end example
2197
2198 This sets the default value, which is effective in all buffers that do
2199 not have local values for the variable. Setting @code{case-fold-search}
2200 with @code{setq} affects only the current buffer's local value, which
2201 is not what you probably want to do in an init file.
2202
2203 @item
2204 @vindex user-mail-address
2205 Specify your own email address, if Emacs can't figure it out correctly.
2206
2207 @example
2208 (setq user-mail-address "rumsfeld@@torture.gov")
2209 @end example
2210
2211 Various Emacs packages that need your own email address use the value of
2212 @code{user-mail-address}.
2213
2214 @item
2215 Make Text mode the default mode for new buffers.
2216
2217 @example
2218 (setq default-major-mode 'text-mode)
2219 @end example
2220
2221 Note that @code{text-mode} is used because it is the command for
2222 entering Text mode. The single-quote before it makes the symbol a
2223 constant; otherwise, @code{text-mode} would be treated as a variable
2224 name.
2225
2226 @need 1500
2227 @item
2228 Set up defaults for the Latin-1 character set
2229 which supports most of the languages of Western Europe.
2230
2231 @example
2232 (set-language-environment "Latin-1")
2233 @end example
2234
2235 @need 1500
2236 @item
2237 Turn off Line Number mode, a global minor mode.
2238
2239 @example
2240 (line-number-mode 0)
2241 @end example
2242
2243 @need 1500
2244 @item
2245 Turn on Auto Fill mode automatically in Text mode and related modes.
2246
2247 @example
2248 (add-hook 'text-mode-hook
2249 '(lambda () (auto-fill-mode 1)))
2250 @end example
2251
2252 This shows how to add a hook function to a normal hook variable
2253 (@pxref{Hooks}). The function we supply is a list starting with
2254 @code{lambda}, with a single-quote in front of it to make it a list
2255 constant rather than an expression.
2256
2257 It's beyond the scope of this manual to explain Lisp functions, but for
2258 this example it is enough to know that the effect is to execute
2259 @code{(auto-fill-mode 1)} when Text mode is entered. You can replace
2260 that with any other expression that you like, or with several
2261 expressions in a row.
2262
2263 Emacs comes with a function named @code{turn-on-auto-fill} whose
2264 definition is @code{(lambda () (auto-fill-mode 1))}. Thus, a simpler
2265 way to write the above example is as follows:
2266
2267 @example
2268 (add-hook 'text-mode-hook 'turn-on-auto-fill)
2269 @end example
2270
2271 @item
2272 Load the installed Lisp library named @file{foo} (actually a file
2273 @file{foo.elc} or @file{foo.el} in a standard Emacs directory).
2274
2275 @example
2276 (load "foo")
2277 @end example
2278
2279 When the argument to @code{load} is a relative file name, not starting
2280 with @samp{/} or @samp{~}, @code{load} searches the directories in
2281 @code{load-path} (@pxref{Lisp Libraries}).
2282
2283 @item
2284 Load the compiled Lisp file @file{foo.elc} from your home directory.
2285
2286 @example
2287 (load "~/foo.elc")
2288 @end example
2289
2290 Here an absolute file name is used, so no searching is done.
2291
2292 @item
2293 @cindex loading Lisp libraries automatically
2294 @cindex autoload Lisp libraries
2295 Tell Emacs to find the definition for the function @code{myfunction}
2296 by loading a Lisp library named @file{mypackage} (i.e.@: a file
2297 @file{mypackage.elc} or @file{mypackage.el}):
2298
2299 @example
2300 (autoload 'myfunction "mypackage" "Do what I say." t)
2301 @end example
2302
2303 @noindent
2304 Here the string @code{"Do what I say."} is the function's
2305 documentation string. You specify it in the @code{autoload}
2306 definition so it will be available for help commands even when the
2307 package is not loaded. The last argument, @code{t}, indicates that
2308 this function is interactive; that is, it can be invoked interactively
2309 by typing @kbd{M-x myfunction @key{RET}} or by binding it to a key.
2310 If the function is not interactive, omit the @code{t} or use
2311 @code{nil}.
2312
2313 @item
2314 Rebind the key @kbd{C-x l} to run the function @code{make-symbolic-link}
2315 (@pxref{Init Rebinding}).
2316
2317 @example
2318 (global-set-key "\C-xl" 'make-symbolic-link)
2319 @end example
2320
2321 or
2322
2323 @example
2324 (define-key global-map "\C-xl" 'make-symbolic-link)
2325 @end example
2326
2327 Note once again the single-quote used to refer to the symbol
2328 @code{make-symbolic-link} instead of its value as a variable.
2329
2330 @item
2331 Do the same thing for Lisp mode only.
2332
2333 @example
2334 (define-key lisp-mode-map "\C-xl" 'make-symbolic-link)
2335 @end example
2336
2337 @item
2338 Redefine all keys which now run @code{next-line} in Fundamental mode
2339 so that they run @code{forward-line} instead.
2340
2341 @findex substitute-key-definition
2342 @example
2343 (substitute-key-definition 'next-line 'forward-line
2344 global-map)
2345 @end example
2346
2347 @item
2348 Make @kbd{C-x C-v} undefined.
2349
2350 @example
2351 (global-unset-key "\C-x\C-v")
2352 @end example
2353
2354 One reason to undefine a key is so that you can make it a prefix.
2355 Simply defining @kbd{C-x C-v @var{anything}} will make @kbd{C-x C-v} a
2356 prefix, but @kbd{C-x C-v} must first be freed of its usual non-prefix
2357 definition.
2358
2359 @item
2360 Make @samp{$} have the syntax of punctuation in Text mode.
2361 Note the use of a character constant for @samp{$}.
2362
2363 @example
2364 (modify-syntax-entry ?\$ "." text-mode-syntax-table)
2365 @end example
2366
2367 @item
2368 Enable the use of the command @code{narrow-to-region} without confirmation.
2369
2370 @example
2371 (put 'narrow-to-region 'disabled nil)
2372 @end example
2373
2374 @item
2375 Adjusting the configuration to various platforms and Emacs versions.
2376
2377 Users typically want Emacs to behave the same on all systems, so the
2378 same init file is right for all platforms. However, sometimes it
2379 happens that a function you use for customizing Emacs is not available
2380 on some platforms or in older Emacs versions. To deal with that
2381 situation, put the customization inside a conditional that tests whether
2382 the function or facility is available, like this:
2383
2384 @example
2385 (if (fboundp 'blink-cursor-mode)
2386 (blink-cursor-mode 0))
2387
2388 (if (boundp 'coding-category-utf-8)
2389 (set-coding-priority '(coding-category-utf-8)))
2390 @end example
2391
2392 @noindent
2393 You can also simply disregard the errors that occur if the
2394 function is not defined.
2395
2396 @example
2397 (condition case ()
2398 (set-face-background 'region "grey75")
2399 (error nil))
2400 @end example
2401
2402 A @code{setq} on a variable which does not exist is generally
2403 harmless, so those do not need a conditional.
2404 @end itemize
2405
2406 @node Terminal Init
2407 @subsection Terminal-specific Initialization
2408
2409 Each terminal type can have a Lisp library to be loaded into Emacs when
2410 it is run on that type of terminal. For a terminal type named
2411 @var{termtype}, the library is called @file{term/@var{termtype}} and it is
2412 found by searching the directories @code{load-path} as usual and trying the
2413 suffixes @samp{.elc} and @samp{.el}. Normally it appears in the
2414 subdirectory @file{term} of the directory where most Emacs libraries are
2415 kept.@refill
2416
2417 The usual purpose of the terminal-specific library is to map the
2418 escape sequences used by the terminal's function keys onto more
2419 meaningful names, using @code{function-key-map}. See the file
2420 @file{term/lk201.el} for an example of how this is done. Many function
2421 keys are mapped automatically according to the information in the
2422 Termcap data base; the terminal-specific library needs to map only the
2423 function keys that Termcap does not specify.
2424
2425 When the terminal type contains a hyphen, only the part of the name
2426 before the first hyphen is significant in choosing the library name.
2427 Thus, terminal types @samp{aaa-48} and @samp{aaa-30-rv} both use
2428 the library @file{term/aaa}. The code in the library can use
2429 @code{(getenv "TERM")} to find the full terminal type name.@refill
2430
2431 @vindex term-file-prefix
2432 The library's name is constructed by concatenating the value of the
2433 variable @code{term-file-prefix} and the terminal type. Your @file{.emacs}
2434 file can prevent the loading of the terminal-specific library by setting
2435 @code{term-file-prefix} to @code{nil}.
2436
2437 @vindex term-setup-hook
2438 Emacs runs the hook @code{term-setup-hook} at the end of
2439 initialization, after both your @file{.emacs} file and any
2440 terminal-specific library have been read in. Add hook functions to this
2441 hook if you wish to override part of any of the terminal-specific
2442 libraries and to define initializations for terminals that do not have a
2443 library. @xref{Hooks}.
2444
2445 @node Find Init
2446 @subsection How Emacs Finds Your Init File
2447
2448 Normally Emacs uses the environment variable @env{HOME}
2449 (@pxref{General Variables, HOME}) to find @file{.emacs}; that's what
2450 @samp{~} means in a file name. If @file{.emacs} is not found inside
2451 @file{~/} (nor @file{.emacs.el}), Emacs looks for
2452 @file{~/.emacs.d/init.el} (which, like @file{~/.emacs.el}, can be
2453 byte-compiled).
2454
2455 However, if you run Emacs from a shell started by @code{su}, Emacs
2456 tries to find your own @file{.emacs}, not that of the user you are
2457 currently pretending to be. The idea is that you should get your own
2458 editor customizations even if you are running as the super user.
2459
2460 More precisely, Emacs first determines which user's init file to use.
2461 It gets your user name from the environment variables @env{LOGNAME} and
2462 @env{USER}; if neither of those exists, it uses effective user-ID.
2463 If that user name matches the real user-ID, then Emacs uses @env{HOME};
2464 otherwise, it looks up the home directory corresponding to that user
2465 name in the system's data base of users.
2466 @c LocalWords: backtab
2467
2468 @node Init Non-ASCII
2469 @subsection Non-@acronym{ASCII} Characters in Init Files
2470 @cindex international characters in @file{.emacs}
2471 @cindex non-@acronym{ASCII} characters in @file{.emacs}
2472 @cindex non-@acronym{ASCII} keys, binding
2473 @cindex rebinding non-@acronym{ASCII} keys
2474
2475 Language and coding systems may cause problems if your init file
2476 contains non-@acronym{ASCII} characters, such as accented letters, in
2477 strings or key bindings.
2478
2479 If you want to use non-@acronym{ASCII} characters in your init file,
2480 you should put a @w{@samp{-*-coding: @var{coding-system}-*-}} tag on
2481 the first line of the init file, and specify a coding system that
2482 supports the character(s) in question. @xref{Recognize Coding}. This
2483 is because the defaults for decoding non-@acronym{ASCII} text might
2484 not yet be set up by the time Emacs reads those parts of your init
2485 file which use such strings, possibly leading Emacs to decode those
2486 strings incorrectly. You should then avoid adding Emacs Lisp code
2487 that modifies the coding system in other ways, such as calls to
2488 @code{set-language-environment}.
2489
2490 To bind non-@acronym{ASCII} keys, you must use a vector (@pxref{Init
2491 Rebinding}). The string syntax cannot be used, since the
2492 non-@acronym{ASCII} characters will be interpreted as meta keys. For
2493 instance:
2494
2495 @example
2496 (global-set-key [?@var{char}] 'some-function)
2497 @end example
2498
2499 @noindent
2500 Type @kbd{C-q}, followed by the key you want to bind, to insert @var{char}.
2501
2502 @strong{Warning:} if you change the keyboard encoding, or change
2503 between multibyte and unibyte mode, or anything that would alter which
2504 code @kbd{C-q} would insert for that character, this keybinding may
2505 stop working. It is therefore advisable to use one and only one
2506 coding system, for your init file as well as the files you edit. For
2507 example, don't mix the @samp{latin-1} and @samp{latin-9} coding
2508 systems.
2509
2510 @ignore
2511 arch-tag: c68abddb-4410-4fb5-925f-63394e971d93
2512 @end ignore