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1 | @c -*-texinfo-*- |
2 | @c This is part of the GNU Emacs Lisp Reference Manual. | |
fd897522 | 3 | @c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999 |
c60ee5e7 | 4 | @c Free Software Foundation, Inc. |
73804d4b RS |
5 | @c See the file elisp.texi for copying conditions. |
6 | @setfilename ../info/os | |
513331d3 | 7 | @node System Interface, Antinews, Calendar, Top |
73804d4b RS |
8 | @chapter Operating System Interface |
9 | ||
10 | This chapter is about starting and getting out of Emacs, access to | |
78608595 | 11 | values in the operating system environment, and terminal input, output, |
73804d4b RS |
12 | and flow control. |
13 | ||
14 | @xref{Building Emacs}, for related information. See also | |
15 | @ref{Display}, for additional operating system status information | |
16 | pertaining to the terminal and the screen. | |
17 | ||
18 | @menu | |
8241495d | 19 | * Starting Up:: Customizing Emacs startup processing. |
73804d4b RS |
20 | * Getting Out:: How exiting works (permanent or temporary). |
21 | * System Environment:: Distinguish the name and kind of system. | |
22 | * User Identification:: Finding the name and user id of the user. | |
23 | * Time of Day:: Getting the current time. | |
22697dac KH |
24 | * Time Conversion:: Converting a time from numeric form to a string, or |
25 | to calendrical data (or vice versa). | |
baee1397 | 26 | * Time Calculations:: Adding, subtracting, comparing times, etc. |
73804d4b RS |
27 | * Timers:: Setting a timer to call a function at a certain time. |
28 | * Terminal Input:: Recording terminal input for debugging. | |
29 | * Terminal Output:: Recording terminal output for debugging. | |
8241495d | 30 | * Sound Output:: Playing sounds on the computer's speaker. |
1ce58cc0 | 31 | * X11 Keysyms:: Operating on key symbols for X Windows |
73804d4b RS |
32 | * Flow Control:: How to turn output flow control on or off. |
33 | * Batch Mode:: Running Emacs without terminal interaction. | |
750c3b02 | 34 | * Session Management:: Saving and restoring state with X Session Management. |
73804d4b RS |
35 | @end menu |
36 | ||
37 | @node Starting Up | |
38 | @section Starting Up Emacs | |
39 | ||
40 | This section describes what Emacs does when it is started, and how you | |
41 | can customize these actions. | |
42 | ||
43 | @menu | |
8241495d | 44 | * Startup Summary:: Sequence of actions Emacs performs at startup. |
73804d4b RS |
45 | * Init File:: Details on reading the init file (@file{.emacs}). |
46 | * Terminal-Specific:: How the terminal-specific Lisp file is read. | |
8241495d | 47 | * Command-Line Arguments:: How command-line arguments are processed, |
73804d4b RS |
48 | and how you can customize them. |
49 | @end menu | |
50 | ||
8241495d RS |
51 | @node Startup Summary |
52 | @subsection Summary: Sequence of Actions at Startup | |
73804d4b | 53 | @cindex initialization |
8241495d | 54 | @cindex startup of Emacs |
73804d4b RS |
55 | @cindex @file{startup.el} |
56 | ||
57 | The order of operations performed (in @file{startup.el}) by Emacs when | |
58 | it is started up is as follows: | |
59 | ||
60 | @enumerate | |
a9f0a989 | 61 | @item |
5858d11f RS |
62 | It adds subdirectories to @code{load-path}, by running the file named |
63 | @file{subdirs.el} in each directory in the list. Normally this file | |
64 | adds the directory's subdirectories to the list, and these will be | |
65 | scanned in their turn. The files @file{subdirs.el} are normally | |
66 | generated automatically by Emacs installation. | |
a9f0a989 RS |
67 | |
68 | @item | |
69 | It sets the language environment and the terminal coding system, | |
70 | if requested by environment variables such as @code{LANG}. | |
71 | ||
73804d4b RS |
72 | @item |
73 | It loads the initialization library for the window system, if you are | |
74 | using a window system. This library's name is | |
75 | @file{term/@var{windowsystem}-win.el}. | |
76 | ||
bfe721d1 KH |
77 | @item |
78 | It processes the initial options. (Some of them are handled | |
79 | even earlier than this.) | |
80 | ||
73804d4b | 81 | @item |
969fe9b5 | 82 | It initializes the window frame and faces, if appropriate. |
73804d4b RS |
83 | |
84 | @item | |
85 | It runs the normal hook @code{before-init-hook}. | |
86 | ||
87 | @item | |
88 | It loads the library @file{site-start}, unless the option | |
89 | @samp{-no-site-file} was specified. The library's file name is usually | |
90 | @file{site-start.el}. | |
91 | @cindex @file{site-start.el} | |
92 | ||
c60ee5e7 | 93 | @item |
3f705836 GM |
94 | It loads your init file (usually @file{~/.emacs}), unless @samp{-q}, |
95 | @samp{-no-init-file}, or @samp{-batch} was specified on the command line. | |
96 | The @samp{-u} option can specify another user whose home directory | |
97 | should be used instead of @file{~}. | |
73804d4b | 98 | |
c60ee5e7 | 99 | @item |
969fe9b5 | 100 | It loads the library @file{default}, unless @code{inhibit-default-init} |
73804d4b | 101 | is non-@code{nil}. (This is not done in @samp{-batch} mode or if |
78608595 RS |
102 | @samp{-q} was specified on the command line.) The library's file name |
103 | is usually @file{default.el}. | |
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104 | @cindex @file{default.el} |
105 | ||
106 | @item | |
107 | It runs the normal hook @code{after-init-hook}. | |
108 | ||
109 | @item | |
110 | It sets the major mode according to @code{initial-major-mode}, provided | |
111 | the buffer @samp{*scratch*} is still current and still in Fundamental | |
112 | mode. | |
113 | ||
c60ee5e7 | 114 | @item |
73804d4b RS |
115 | It loads the terminal-specific Lisp file, if any, except when in batch |
116 | mode or using a window system. | |
117 | ||
118 | @item | |
119 | It displays the initial echo area message, unless you have suppressed | |
120 | that with @code{inhibit-startup-echo-area-message}. | |
121 | ||
c60ee5e7 | 122 | @item |
bfe721d1 | 123 | It processes the action arguments from the command line. |
73804d4b | 124 | |
c60ee5e7 | 125 | @item |
7ba6d818 | 126 | It runs @code{emacs-startup-hook} and then @code{term-setup-hook}. |
73804d4b RS |
127 | |
128 | @item | |
129 | It calls @code{frame-notice-user-settings}, which modifies the | |
130 | parameters of the selected frame according to whatever the init files | |
131 | specify. | |
132 | ||
c60ee5e7 | 133 | @item |
73804d4b RS |
134 | It runs @code{window-setup-hook}. @xref{Window Systems}. |
135 | ||
c60ee5e7 | 136 | @item |
78608595 | 137 | It displays copyleft, nonwarranty, and basic use information, provided |
8241495d | 138 | there were no remaining command-line arguments (a few steps above), |
f9f59935 RS |
139 | the value of @code{inhibit-startup-message} is @code{nil}, and the |
140 | buffer is still empty. | |
73804d4b RS |
141 | @end enumerate |
142 | ||
143 | @defopt inhibit-startup-message | |
144 | This variable inhibits the initial startup messages (the nonwarranty, | |
145 | etc.). If it is non-@code{nil}, then the messages are not printed. | |
146 | ||
147 | This variable exists so you can set it in your personal init file, once | |
148 | you are familiar with the contents of the startup message. Do not set | |
149 | this variable in the init file of a new user, or in a way that affects | |
150 | more than one user, because that would prevent new users from receiving | |
151 | the information they are supposed to see. | |
152 | @end defopt | |
153 | ||
154 | @defopt inhibit-startup-echo-area-message | |
155 | This variable controls the display of the startup echo area message. | |
156 | You can suppress the startup echo area message by adding text with this | |
a40d4712 | 157 | form to your init file: |
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158 | |
159 | @example | |
160 | (setq inhibit-startup-echo-area-message | |
161 | "@var{your-login-name}") | |
162 | @end example | |
163 | ||
a40d4712 PR |
164 | Emacs explicitly checks for an expression as shown above in your init |
165 | file; your login name must appear in the expression as a Lisp string | |
166 | constant. Other methods of setting | |
a9f0a989 RS |
167 | @code{inhibit-startup-echo-area-message} to the same value do not |
168 | inhibit the startup message. | |
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169 | |
170 | This way, you can easily inhibit the message for yourself if you wish, | |
a40d4712 PR |
171 | but thoughtless copying of your init file will not inhibit the message |
172 | for someone else. | |
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173 | @end defopt |
174 | ||
175 | @node Init File | |
a40d4712 | 176 | @subsection The Init File, @file{.emacs} |
73804d4b RS |
177 | @cindex init file |
178 | @cindex @file{.emacs} | |
179 | ||
a40d4712 PR |
180 | When you start Emacs, it normally attempts to load your @dfn{init |
181 | file}, a file in your home directory. Its normal name is @file{.emacs}, | |
182 | but you can alternatively call it @file{.emacs.el}, which enables you to | |
183 | byte-compile it (@pxref{Byte Compilation}); then the actual file loaded | |
184 | will be @file{.emacs.elc}. | |
185 | ||
186 | The command-line switches @samp{-q} and @samp{-u} control whether and | |
187 | where to find the init file; @samp{-q} says not to load an init file, | |
188 | and @samp{-u @var{user}} says to load @var{user}'s init file instead of | |
189 | yours. @xref{Entering Emacs,,, emacs, The GNU Emacs Manual}. If | |
190 | neither option is specified, Emacs uses the @code{LOGNAME} environment | |
191 | variable, or the @code{USER} (most systems) or @code{USERNAME} (MS | |
192 | systems) variable, to find your home directory and thus your init file; | |
193 | this way, even if you have su'd, Emacs still loads your own init file. | |
194 | If those environment variables are absent, though, Emacs uses your | |
195 | user-id to find your home directory. | |
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196 | |
197 | @cindex default init file | |
198 | A site may have a @dfn{default init file}, which is the library named | |
199 | @file{default.el}. Emacs finds the @file{default.el} file through the | |
200 | standard search path for libraries (@pxref{How Programs Do Loading}). | |
201 | The Emacs distribution does not come with this file; sites may provide | |
202 | one for local customizations. If the default init file exists, it is | |
203 | loaded whenever you start Emacs, except in batch mode or if @samp{-q} is | |
204 | specified. But your own personal init file, if any, is loaded first; if | |
205 | it sets @code{inhibit-default-init} to a non-@code{nil} value, then | |
206 | Emacs does not subsequently load the @file{default.el} file. | |
207 | ||
208 | Another file for site-customization is @file{site-start.el}. Emacs | |
209 | loads this @emph{before} the user's init file. You can inhibit the | |
210 | loading of this file with the option @samp{-no-site-file}. | |
211 | ||
bfe721d1 | 212 | @defvar site-run-file |
ebc6903b RS |
213 | This variable specifies the site-customization file to load before the |
214 | user's init file. Its normal value is @code{"site-start"}. The only | |
215 | way you can change it with real effect is to do so before dumping | |
216 | Emacs. | |
bfe721d1 KH |
217 | @end defvar |
218 | ||
333c5fc5 | 219 | @xref{Init Examples,, Init File Examples, emacs, The GNU Emacs Manual}, for |
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220 | examples of how to make various commonly desired customizations in your |
221 | @file{.emacs} file. | |
222 | ||
223 | @defopt inhibit-default-init | |
224 | This variable prevents Emacs from loading the default initialization | |
225 | library file for your session of Emacs. If its value is non-@code{nil}, | |
226 | then the default library is not loaded. The default value is | |
227 | @code{nil}. | |
228 | @end defopt | |
229 | ||
230 | @defvar before-init-hook | |
1911e6e5 | 231 | This normal hook is run, once, just before loading all the init files |
a9f0a989 | 232 | (the user's init file, @file{default.el}, and/or @file{site-start.el}). |
1911e6e5 | 233 | (The only way to change it with real effect is before dumping Emacs.) |
a9f0a989 RS |
234 | @end defvar |
235 | ||
236 | @defvar after-init-hook | |
1911e6e5 | 237 | This normal hook is run, once, just after loading all the init files |
a9f0a989 | 238 | (the user's init file, @file{default.el}, and/or @file{site-start.el}), |
7ba6d818 RS |
239 | before loading the terminal-specific library and processing the |
240 | command-line arguments. | |
241 | @end defvar | |
242 | ||
243 | @defvar emacs-startup-hook | |
244 | @tindex emacs-startup-hook | |
245 | This normal hook is run, once, just after handling the command line | |
246 | arguments, just before @code{term-setup-hook}. | |
247 | @end defvar | |
248 | ||
249 | @defvar user-init-file | |
250 | @tindex user-init-file | |
251 | This variable holds the file name of the user's init file. If the | |
252 | actual init file loaded is a compiled file, such as @file{.emacs.elc}, | |
253 | the value refers to the corresponding source file. | |
73804d4b RS |
254 | @end defvar |
255 | ||
256 | @node Terminal-Specific | |
257 | @subsection Terminal-Specific Initialization | |
258 | @cindex terminal-specific initialization | |
259 | ||
260 | Each terminal type can have its own Lisp library that Emacs loads when | |
a9f0a989 RS |
261 | run on that type of terminal. The library's name is constructed by |
262 | concatenating the value of the variable @code{term-file-prefix} and the | |
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263 | terminal type (specified by the environment variable @code{TERM}). |
264 | Normally, @code{term-file-prefix} has the value | |
a9f0a989 RS |
265 | @code{"term/"}; changing this is not recommended. Emacs finds the file |
266 | in the normal manner, by searching the @code{load-path} directories, and | |
267 | trying the @samp{.elc} and @samp{.el} suffixes. | |
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268 | |
269 | The usual function of a terminal-specific library is to enable special | |
270 | keys to send sequences that Emacs can recognize. It may also need to | |
271 | set or add to @code{function-key-map} if the Termcap entry does not | |
272 | specify all the terminal's function keys. @xref{Terminal Input}. | |
273 | ||
274 | @cindex Termcap | |
275 | When the name of the terminal type contains a hyphen, only the part of | |
276 | the name before the first hyphen is significant in choosing the library | |
277 | name. Thus, terminal types @samp{aaa-48} and @samp{aaa-30-rv} both use | |
278 | the @file{term/aaa} library. If necessary, the library can evaluate | |
279 | @code{(getenv "TERM")} to find the full name of the terminal | |
280 | type.@refill | |
281 | ||
a40d4712 | 282 | Your init file can prevent the loading of the |
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283 | terminal-specific library by setting the variable |
284 | @code{term-file-prefix} to @code{nil}. This feature is useful when | |
285 | experimenting with your own peculiar customizations. | |
286 | ||
287 | You can also arrange to override some of the actions of the | |
288 | terminal-specific library by setting the variable | |
289 | @code{term-setup-hook}. This is a normal hook which Emacs runs using | |
290 | @code{run-hooks} at the end of Emacs initialization, after loading both | |
a40d4712 | 291 | your init file and any terminal-specific libraries. You can |
73804d4b RS |
292 | use this variable to define initializations for terminals that do not |
293 | have their own libraries. @xref{Hooks}. | |
294 | ||
295 | @defvar term-file-prefix | |
296 | @cindex @code{TERM} environment variable | |
297 | If the @code{term-file-prefix} variable is non-@code{nil}, Emacs loads | |
298 | a terminal-specific initialization file as follows: | |
299 | ||
300 | @example | |
301 | (load (concat term-file-prefix (getenv "TERM"))) | |
302 | @end example | |
303 | ||
304 | @noindent | |
305 | You may set the @code{term-file-prefix} variable to @code{nil} in your | |
a40d4712 | 306 | init file if you do not wish to load the |
73804d4b | 307 | terminal-initialization file. To do this, put the following in |
a40d4712 | 308 | your init file: @code{(setq term-file-prefix nil)}. |
8241495d RS |
309 | |
310 | On MS-DOS, if the environment variable @code{TERM} is not set, Emacs | |
311 | uses @samp{internal} as the terminal type. | |
73804d4b RS |
312 | @end defvar |
313 | ||
c60ee5e7 | 314 | @defvar term-setup-hook |
78608595 | 315 | This variable is a normal hook that Emacs runs after loading your |
a40d4712 | 316 | init file, the default initialization file (if any) and the |
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317 | terminal-specific Lisp file. |
318 | ||
319 | You can use @code{term-setup-hook} to override the definitions made by a | |
320 | terminal-specific file. | |
321 | @end defvar | |
322 | ||
323 | See @code{window-setup-hook} in @ref{Window Systems}, for a related | |
324 | feature. | |
325 | ||
8241495d RS |
326 | @node Command-Line Arguments |
327 | @subsection Command-Line Arguments | |
328 | @cindex command-line arguments | |
73804d4b | 329 | |
8241495d | 330 | You can use command-line arguments to request various actions when you |
73804d4b RS |
331 | start Emacs. Since you do not need to start Emacs more than once per |
332 | day, and will often leave your Emacs session running longer than that, | |
8241495d | 333 | command-line arguments are hardly ever used. As a practical matter, it |
73804d4b RS |
334 | is best to avoid making the habit of using them, since this habit would |
335 | encourage you to kill and restart Emacs unnecessarily often. These | |
336 | options exist for two reasons: to be compatible with other editors (for | |
337 | invocation by other programs) and to enable shell scripts to run | |
338 | specific Lisp programs. | |
339 | ||
8241495d | 340 | This section describes how Emacs processes command-line arguments, |
73804d4b RS |
341 | and how you can customize them. |
342 | ||
343 | @ignore | |
344 | (Note that some other editors require you to start afresh each time | |
345 | you want to edit a file. With this kind of editor, you will probably | |
8241495d | 346 | specify the file as a command-line argument. The recommended way to |
73804d4b RS |
347 | use GNU Emacs is to start it only once, just after you log in, and do |
348 | all your editing in the same Emacs process. Each time you want to edit | |
349 | a different file, you visit it with the existing Emacs, which eventually | |
350 | comes to have many files in it ready for editing. Usually you do not | |
351 | kill the Emacs until you are about to log out.) | |
352 | @end ignore | |
353 | ||
354 | @defun command-line | |
78608595 | 355 | This function parses the command line that Emacs was called with, |
a40d4712 | 356 | processes it, loads the user's init file and displays the |
78608595 | 357 | startup messages. |
73804d4b RS |
358 | @end defun |
359 | ||
360 | @defvar command-line-processed | |
361 | The value of this variable is @code{t} once the command line has been | |
362 | processed. | |
363 | ||
364 | If you redump Emacs by calling @code{dump-emacs}, you may wish to set | |
365 | this variable to @code{nil} first in order to cause the new dumped Emacs | |
8241495d | 366 | to process its new command-line arguments. |
73804d4b RS |
367 | @end defvar |
368 | ||
369 | @defvar command-switch-alist | |
370 | @cindex switches on command line | |
371 | @cindex options on command line | |
8241495d | 372 | @cindex command-line options |
73804d4b RS |
373 | The value of this variable is an alist of user-defined command-line |
374 | options and associated handler functions. This variable exists so you | |
375 | can add elements to it. | |
376 | ||
8241495d RS |
377 | A @dfn{command-line option} is an argument on the command line, which |
378 | has the form: | |
73804d4b RS |
379 | |
380 | @example | |
381 | -@var{option} | |
382 | @end example | |
383 | ||
c60ee5e7 | 384 | The elements of the @code{command-switch-alist} look like this: |
73804d4b RS |
385 | |
386 | @example | |
387 | (@var{option} . @var{handler-function}) | |
388 | @end example | |
389 | ||
8241495d RS |
390 | The @sc{car}, @var{option}, is a string, the name of a command-line |
391 | option (not including the initial hyphen). The @var{handler-function} | |
392 | is called to handle @var{option}, and receives the option name as its | |
393 | sole argument. | |
73804d4b RS |
394 | |
395 | In some cases, the option is followed in the command line by an | |
396 | argument. In these cases, the @var{handler-function} can find all the | |
397 | remaining command-line arguments in the variable | |
398 | @code{command-line-args-left}. (The entire list of command-line | |
399 | arguments is in @code{command-line-args}.) | |
400 | ||
8241495d | 401 | The command-line arguments are parsed by the @code{command-line-1} |
73804d4b | 402 | function in the @file{startup.el} file. See also @ref{Command |
333c5fc5 | 403 | Arguments, , Command Line Arguments, emacs, The GNU Emacs Manual}. |
73804d4b RS |
404 | @end defvar |
405 | ||
406 | @defvar command-line-args | |
8241495d | 407 | The value of this variable is the list of command-line arguments passed |
73804d4b RS |
408 | to Emacs. |
409 | @end defvar | |
410 | ||
411 | @defvar command-line-functions | |
412 | This variable's value is a list of functions for handling an | |
413 | unrecognized command-line argument. Each time the next argument to be | |
414 | processed has no special meaning, the functions in this list are called, | |
78608595 | 415 | in order of appearance, until one of them returns a non-@code{nil} |
73804d4b RS |
416 | value. |
417 | ||
418 | These functions are called with no arguments. They can access the | |
419 | command-line argument under consideration through the variable | |
f9f59935 RS |
420 | @code{argi}, which is bound temporarily at this point. The remaining |
421 | arguments (not including the current one) are in the variable | |
422 | @code{command-line-args-left}. | |
73804d4b RS |
423 | |
424 | When a function recognizes and processes the argument in @code{argi}, it | |
425 | should return a non-@code{nil} value to say it has dealt with that | |
426 | argument. If it has also dealt with some of the following arguments, it | |
427 | can indicate that by deleting them from @code{command-line-args-left}. | |
428 | ||
429 | If all of these functions return @code{nil}, then the argument is used | |
430 | as a file name to visit. | |
431 | @end defvar | |
432 | ||
433 | @node Getting Out | |
434 | @section Getting Out of Emacs | |
435 | @cindex exiting Emacs | |
436 | ||
437 | There are two ways to get out of Emacs: you can kill the Emacs job, | |
438 | which exits permanently, or you can suspend it, which permits you to | |
439 | reenter the Emacs process later. As a practical matter, you seldom kill | |
440 | Emacs---only when you are about to log out. Suspending is much more | |
441 | common. | |
442 | ||
443 | @menu | |
444 | * Killing Emacs:: Exiting Emacs irreversibly. | |
445 | * Suspending Emacs:: Exiting Emacs reversibly. | |
446 | @end menu | |
447 | ||
448 | @node Killing Emacs | |
449 | @comment node-name, next, previous, up | |
450 | @subsection Killing Emacs | |
451 | @cindex killing Emacs | |
452 | ||
453 | Killing Emacs means ending the execution of the Emacs process. The | |
454 | parent process normally resumes control. The low-level primitive for | |
455 | killing Emacs is @code{kill-emacs}. | |
456 | ||
457 | @defun kill-emacs &optional exit-data | |
458 | This function exits the Emacs process and kills it. | |
459 | ||
460 | If @var{exit-data} is an integer, then it is used as the exit status | |
461 | of the Emacs process. (This is useful primarily in batch operation; see | |
462 | @ref{Batch Mode}.) | |
463 | ||
464 | If @var{exit-data} is a string, its contents are stuffed into the | |
465 | terminal input buffer so that the shell (or whatever program next reads | |
466 | input) can read them. | |
467 | @end defun | |
468 | ||
469 | All the information in the Emacs process, aside from files that have | |
8241495d RS |
470 | been saved, is lost when the Emacs process is killed. Because killing |
471 | Emacs inadvertently can lose a lot of work, Emacs queries for | |
472 | confirmation before actually terminating if you have buffers that need | |
473 | saving or subprocesses that are running. This is done in the function | |
73804d4b RS |
474 | @code{save-buffers-kill-emacs}. |
475 | ||
476 | @defvar kill-emacs-query-functions | |
477 | After asking the standard questions, @code{save-buffers-kill-emacs} | |
f9f59935 | 478 | calls the functions in the list @code{kill-emacs-query-functions}, in |
73804d4b RS |
479 | order of appearance, with no arguments. These functions can ask for |
480 | additional confirmation from the user. If any of them returns | |
48bad490 | 481 | @code{nil}, Emacs is not killed. |
73804d4b RS |
482 | @end defvar |
483 | ||
484 | @defvar kill-emacs-hook | |
485 | This variable is a normal hook; once @code{save-buffers-kill-emacs} is | |
486 | finished with all file saving and confirmation, it runs the functions in | |
50befdcd | 487 | this hook. This hook is not run in batch mode. |
73804d4b RS |
488 | @end defvar |
489 | ||
490 | @node Suspending Emacs | |
491 | @subsection Suspending Emacs | |
492 | @cindex suspending Emacs | |
493 | ||
494 | @dfn{Suspending Emacs} means stopping Emacs temporarily and returning | |
495 | control to its superior process, which is usually the shell. This | |
496 | allows you to resume editing later in the same Emacs process, with the | |
497 | same buffers, the same kill ring, the same undo history, and so on. To | |
498 | resume Emacs, use the appropriate command in the parent shell---most | |
499 | likely @code{fg}. | |
500 | ||
501 | Some operating systems do not support suspension of jobs; on these | |
502 | systems, ``suspension'' actually creates a new shell temporarily as a | |
503 | subprocess of Emacs. Then you would exit the shell to return to Emacs. | |
504 | ||
969fe9b5 RS |
505 | Suspension is not useful with window systems, because the Emacs job |
506 | may not have a parent that can resume it again, and in any case you can | |
507 | give input to some other job such as a shell merely by moving to a | |
508 | different window. Therefore, suspending is not allowed when Emacs is using | |
e294b7f1 | 509 | a window system (X or MS Windows). |
73804d4b RS |
510 | |
511 | @defun suspend-emacs string | |
512 | This function stops Emacs and returns control to the superior process. | |
513 | If and when the superior process resumes Emacs, @code{suspend-emacs} | |
514 | returns @code{nil} to its caller in Lisp. | |
515 | ||
516 | If @var{string} is non-@code{nil}, its characters are sent to be read | |
517 | as terminal input by Emacs's superior shell. The characters in | |
518 | @var{string} are not echoed by the superior shell; only the results | |
519 | appear. | |
520 | ||
521 | Before suspending, @code{suspend-emacs} runs the normal hook | |
969fe9b5 | 522 | @code{suspend-hook}. |
73804d4b | 523 | |
78608595 | 524 | After the user resumes Emacs, @code{suspend-emacs} runs the normal hook |
73804d4b RS |
525 | @code{suspend-resume-hook}. @xref{Hooks}. |
526 | ||
527 | The next redisplay after resumption will redraw the entire screen, | |
528 | unless the variable @code{no-redraw-on-reenter} is non-@code{nil} | |
529 | (@pxref{Refresh Screen}). | |
530 | ||
531 | In the following example, note that @samp{pwd} is not echoed after | |
532 | Emacs is suspended. But it is read and executed by the shell. | |
533 | ||
534 | @smallexample | |
535 | @group | |
536 | (suspend-emacs) | |
537 | @result{} nil | |
538 | @end group | |
539 | ||
540 | @group | |
541 | (add-hook 'suspend-hook | |
542 | (function (lambda () | |
543 | (or (y-or-n-p | |
544 | "Really suspend? ") | |
545 | (error "Suspend cancelled"))))) | |
546 | @result{} (lambda nil | |
547 | (or (y-or-n-p "Really suspend? ") | |
548 | (error "Suspend cancelled"))) | |
549 | @end group | |
550 | @group | |
551 | (add-hook 'suspend-resume-hook | |
552 | (function (lambda () (message "Resumed!")))) | |
553 | @result{} (lambda nil (message "Resumed!")) | |
554 | @end group | |
555 | @group | |
556 | (suspend-emacs "pwd") | |
557 | @result{} nil | |
558 | @end group | |
559 | @group | |
560 | ---------- Buffer: Minibuffer ---------- | |
561 | Really suspend? @kbd{y} | |
562 | ---------- Buffer: Minibuffer ---------- | |
563 | @end group | |
564 | ||
565 | @group | |
566 | ---------- Parent Shell ---------- | |
567 | lewis@@slug[23] % /user/lewis/manual | |
568 | lewis@@slug[24] % fg | |
569 | @end group | |
570 | ||
571 | @group | |
572 | ---------- Echo Area ---------- | |
573 | Resumed! | |
574 | @end group | |
575 | @end smallexample | |
576 | @end defun | |
577 | ||
578 | @defvar suspend-hook | |
8241495d | 579 | This variable is a normal hook that Emacs runs before suspending. |
73804d4b RS |
580 | @end defvar |
581 | ||
582 | @defvar suspend-resume-hook | |
8241495d RS |
583 | This variable is a normal hook that Emacs runs on resuming |
584 | after a suspension. | |
73804d4b RS |
585 | @end defvar |
586 | ||
587 | @node System Environment | |
588 | @section Operating System Environment | |
589 | @cindex operating system environment | |
590 | ||
591 | Emacs provides access to variables in the operating system environment | |
592 | through various functions. These variables include the name of the | |
593 | system, the user's @sc{uid}, and so on. | |
594 | ||
969fe9b5 RS |
595 | @defvar system-configuration |
596 | This variable holds the GNU configuration name for the hardware/software | |
597 | configuration of your system, as a string. The convenient way to test | |
598 | parts of this string is with @code{string-match}. | |
599 | @end defvar | |
600 | ||
73804d4b | 601 | @defvar system-type |
bfe721d1 KH |
602 | The value of this variable is a symbol indicating the type of operating |
603 | system Emacs is operating on. Here is a table of the possible values: | |
73804d4b RS |
604 | |
605 | @table @code | |
1911e6e5 RS |
606 | @item alpha-vms |
607 | VMS on the Alpha. | |
608 | ||
73804d4b RS |
609 | @item aix-v3 |
610 | AIX. | |
611 | ||
612 | @item berkeley-unix | |
613 | Berkeley BSD. | |
614 | ||
c60ee5e7 JB |
615 | @item cygwin |
616 | Cygwin. | |
617 | ||
bfe721d1 KH |
618 | @item dgux |
619 | Data General DGUX operating system. | |
620 | ||
621 | @item gnu | |
969fe9b5 | 622 | the GNU system (using the GNU kernel, which consists of the HURD and Mach). |
0c124126 RS |
623 | |
624 | @item gnu/linux | |
969fe9b5 RS |
625 | A GNU/Linux system---that is, a variant GNU system, using the Linux |
626 | kernel. (These systems are the ones people often call ``Linux,'' but | |
627 | actually Linux is just the kernel, not the whole system.) | |
bfe721d1 | 628 | |
73804d4b | 629 | @item hpux |
bfe721d1 | 630 | Hewlett-Packard HPUX operating system. |
73804d4b RS |
631 | |
632 | @item irix | |
633 | Silicon Graphics Irix system. | |
634 | ||
bfe721d1 | 635 | @item ms-dos |
8241495d RS |
636 | Microsoft MS-DOS ``operating system.'' Emacs compiled with DJGPP for |
637 | MS-DOS binds @code{system-type} to @code{ms-dos} even when you run it on | |
638 | MS-Windows. | |
bfe721d1 KH |
639 | |
640 | @item next-mach | |
641 | NeXT Mach-based system. | |
6705a2a6 | 642 | |
73804d4b RS |
643 | @item rtu |
644 | Masscomp RTU, UCB universe. | |
645 | ||
646 | @item unisoft-unix | |
647 | UniSoft UniPlus. | |
648 | ||
649 | @item usg-unix-v | |
650 | AT&T System V. | |
651 | ||
652 | @item vax-vms | |
653 | VAX VMS. | |
654 | ||
bfe721d1 | 655 | @item windows-nt |
8241495d RS |
656 | Microsoft windows NT. The same executable supports Windows 9X, but the |
657 | value of @code{system-type} is @code{windows-nt} in either case. | |
bfe721d1 | 658 | |
73804d4b RS |
659 | @item xenix |
660 | SCO Xenix 386. | |
661 | @end table | |
662 | ||
663 | We do not wish to add new symbols to make finer distinctions unless it | |
664 | is absolutely necessary! In fact, we hope to eliminate some of these | |
665 | alternatives in the future. We recommend using | |
666 | @code{system-configuration} to distinguish between different operating | |
667 | systems. | |
668 | @end defvar | |
669 | ||
73804d4b RS |
670 | @defun system-name |
671 | This function returns the name of the machine you are running on. | |
672 | @example | |
673 | (system-name) | |
a9f0a989 | 674 | @result{} "www.gnu.org" |
73804d4b RS |
675 | @end example |
676 | @end defun | |
677 | ||
22697dac KH |
678 | The symbol @code{system-name} is a variable as well as a function. In |
679 | fact, the function returns whatever value the variable | |
680 | @code{system-name} currently holds. Thus, you can set the variable | |
681 | @code{system-name} in case Emacs is confused about the name of your | |
682 | system. The variable is also useful for constructing frame titles | |
683 | (@pxref{Frame Titles}). | |
684 | ||
685 | @defvar mail-host-address | |
686 | If this variable is non-@code{nil}, it is used instead of | |
687 | @code{system-name} for purposes of generating email addresses. For | |
688 | example, it is used when constructing the default value of | |
689 | @code{user-mail-address}. @xref{User Identification}. (Since this is | |
690 | done when Emacs starts up, the value actually used is the one saved when | |
691 | Emacs was dumped. @xref{Building Emacs}.) | |
692 | @end defvar | |
693 | ||
5633ded3 | 694 | @deffn Command getenv var |
73804d4b RS |
695 | @cindex environment variable access |
696 | This function returns the value of the environment variable @var{var}, | |
697 | as a string. Within Emacs, the environment variable values are kept in | |
698 | the Lisp variable @code{process-environment}. | |
699 | ||
700 | @example | |
701 | @group | |
702 | (getenv "USER") | |
703 | @result{} "lewis" | |
704 | @end group | |
705 | ||
706 | @group | |
707 | lewis@@slug[10] % printenv | |
708 | PATH=.:/user/lewis/bin:/usr/bin:/usr/local/bin | |
709 | USER=lewis | |
710 | @end group | |
711 | @group | |
712 | TERM=ibmapa16 | |
713 | SHELL=/bin/csh | |
714 | HOME=/user/lewis | |
715 | @end group | |
716 | @end example | |
a0b972de | 717 | @end deffn |
73804d4b RS |
718 | |
719 | @c Emacs 19 feature | |
720 | @deffn Command setenv variable value | |
721 | This command sets the value of the environment variable named | |
722 | @var{variable} to @var{value}. Both arguments should be strings. This | |
723 | function works by modifying @code{process-environment}; binding that | |
724 | variable with @code{let} is also reasonable practice. | |
725 | @end deffn | |
726 | ||
727 | @defvar process-environment | |
728 | This variable is a list of strings, each describing one environment | |
729 | variable. The functions @code{getenv} and @code{setenv} work by means | |
730 | of this variable. | |
731 | ||
732 | @smallexample | |
733 | @group | |
734 | process-environment | |
735 | @result{} ("l=/usr/stanford/lib/gnuemacs/lisp" | |
736 | "PATH=.:/user/lewis/bin:/usr/class:/nfsusr/local/bin" | |
c60ee5e7 | 737 | "USER=lewis" |
73804d4b RS |
738 | @end group |
739 | @group | |
c60ee5e7 | 740 | "TERM=ibmapa16" |
73804d4b RS |
741 | "SHELL=/bin/csh" |
742 | "HOME=/user/lewis") | |
743 | @end group | |
744 | @end smallexample | |
9cee54f8 RS |
745 | |
746 | If @code{process-environment} contains ``duplicate'' elements that | |
747 | specify the same environment variable, the first of these elements | |
748 | specifies the variable, and the other ``duplicates'' are ignored. | |
73804d4b RS |
749 | @end defvar |
750 | ||
bfe721d1 KH |
751 | @defvar path-separator |
752 | This variable holds a string which says which character separates | |
753 | directories in a search path (as found in an environment variable). Its | |
754 | value is @code{":"} for Unix and GNU systems, and @code{";"} for MS-DOS | |
8241495d | 755 | and MS-Windows. |
bfe721d1 KH |
756 | @end defvar |
757 | ||
5557b83b RS |
758 | @defun parse-colon-path path |
759 | @tindex parse-colon-path | |
760 | This function takes a search path string such as would be the value of | |
761 | the @code{PATH} environment variable, and splits it at the separators, | |
762 | returning a list of directory names. @code{nil} in this list stands for | |
763 | ``use the current directory.'' Although the function's name says | |
764 | ``colon,'' it actually uses the value of @code{path-separator}. | |
765 | ||
766 | @example | |
767 | (parse-colon-path ":/foo:/bar") | |
768 | @result{} (nil "/foo/" "/bar/") | |
769 | @end example | |
770 | @end defun | |
771 | ||
a890e1b0 RS |
772 | @defvar invocation-name |
773 | This variable holds the program name under which Emacs was invoked. The | |
774 | value is a string, and does not include a directory name. | |
775 | @end defvar | |
776 | ||
777 | @defvar invocation-directory | |
778 | This variable holds the directory from which the Emacs executable was | |
779 | invoked, or perhaps @code{nil} if that directory cannot be determined. | |
780 | @end defvar | |
781 | ||
782 | @defvar installation-directory | |
783 | If non-@code{nil}, this is a directory within which to look for the | |
784 | @file{lib-src} and @file{etc} subdirectories. This is non-@code{nil} | |
785 | when Emacs can't find those directories in their standard installed | |
78608595 RS |
786 | locations, but can find them in a directory related somehow to the one |
787 | containing the Emacs executable. | |
a890e1b0 RS |
788 | @end defvar |
789 | ||
a9f0a989 | 790 | @defun load-average &optional use-float |
1911e6e5 RS |
791 | This function returns the current 1-minute, 5-minute, and 15-minute load |
792 | averages, in a list. | |
a9f0a989 RS |
793 | |
794 | By default, the values are integers that are 100 times the system load | |
795 | averages, which indicate the average number of processes trying to run. | |
796 | If @var{use-float} is non-@code{nil}, then they are returned | |
1911e6e5 | 797 | as floating point numbers and without multiplying by 100. |
73804d4b RS |
798 | |
799 | @example | |
800 | @group | |
801 | (load-average) | |
802 | @result{} (169 48 36) | |
803 | @end group | |
a9f0a989 RS |
804 | @group |
805 | (load-average t) | |
806 | @result{} (1.69 0.48 0.36) | |
807 | @end group | |
73804d4b RS |
808 | |
809 | @group | |
810 | lewis@@rocky[5] % uptime | |
811 | 11:55am up 1 day, 19:37, 3 users, | |
812 | load average: 1.69, 0.48, 0.36 | |
813 | @end group | |
814 | @end example | |
815 | @end defun | |
816 | ||
817 | @defun emacs-pid | |
818 | This function returns the process @sc{id} of the Emacs process. | |
819 | @end defun | |
820 | ||
f9f59935 RS |
821 | @defvar tty-erase-char |
822 | This variable holds the erase character that was selected | |
823 | in the system's terminal driver, before Emacs was started. | |
824 | @end defvar | |
825 | ||
73804d4b RS |
826 | @defun setprv privilege-name &optional setp getprv |
827 | This function sets or resets a VMS privilege. (It does not exist on | |
8241495d RS |
828 | other systems.) The first argument is the privilege name, as a string. |
829 | The second argument, @var{setp}, is @code{t} or @code{nil}, indicating | |
830 | whether the privilege is to be turned on or off. Its default is | |
831 | @code{nil}. The function returns @code{t} if successful, @code{nil} | |
832 | otherwise. | |
73804d4b RS |
833 | |
834 | If the third argument, @var{getprv}, is non-@code{nil}, @code{setprv} | |
835 | does not change the privilege, but returns @code{t} or @code{nil} | |
836 | indicating whether the privilege is currently enabled. | |
837 | @end defun | |
838 | ||
839 | @node User Identification | |
840 | @section User Identification | |
841 | ||
f9f59935 RS |
842 | @defvar init-file-user |
843 | This variable says which user's init files should be used by Emacs---or | |
8241495d | 844 | @code{nil} if none. The value reflects command-line options such as |
f9f59935 RS |
845 | @samp{-q} or @samp{-u @var{user}}. |
846 | ||
847 | Lisp packages that load files of customizations, or any other sort of | |
848 | user profile, should obey this variable in deciding where to find it. | |
849 | They should load the profile of the user name found in this variable. | |
850 | If @code{init-file-user} is @code{nil}, meaning that the @samp{-q} | |
851 | option was used, then Lisp packages should not load any customization | |
852 | files or user profile. | |
853 | @end defvar | |
854 | ||
22697dac KH |
855 | @defvar user-mail-address |
856 | This holds the nominal email address of the user who is using Emacs. | |
485dbcf2 RS |
857 | Emacs normally sets this variable to a default value after reading your |
858 | init files, but not if you have already set it. So you can set the | |
a40d4712 | 859 | variable to some other value in your init file if you do not |
485dbcf2 | 860 | want to use the default value. |
22697dac KH |
861 | @end defvar |
862 | ||
863 | @defun user-login-name &optional uid | |
864 | If you don't specify @var{uid}, this function returns the name under | |
865 | which the user is logged in. If the environment variable @code{LOGNAME} | |
866 | is set, that value is used. Otherwise, if the environment variable | |
867 | @code{USER} is set, that value is used. Otherwise, the value is based | |
868 | on the effective @sc{uid}, not the real @sc{uid}. | |
869 | ||
870 | If you specify @var{uid}, the value is the user name that corresponds | |
871 | to @var{uid} (which should be an integer). | |
73804d4b RS |
872 | |
873 | @example | |
874 | @group | |
875 | (user-login-name) | |
876 | @result{} "lewis" | |
877 | @end group | |
878 | @end example | |
879 | @end defun | |
880 | ||
881 | @defun user-real-login-name | |
882 | This function returns the user name corresponding to Emacs's real | |
883 | @sc{uid}. This ignores the effective @sc{uid} and ignores the | |
884 | environment variables @code{LOGNAME} and @code{USER}. | |
885 | @end defun | |
886 | ||
f9f59935 RS |
887 | @defun user-full-name &optional uid |
888 | This function returns the full name of the logged-in user---or the value | |
8241495d | 889 | of the environment variable @code{NAME}, if that is set. |
73804d4b | 890 | |
8241495d | 891 | @c "Bil" is the correct spelling. |
73804d4b RS |
892 | @example |
893 | @group | |
894 | (user-full-name) | |
895 | @result{} "Bil Lewis" | |
896 | @end group | |
897 | @end example | |
f9f59935 | 898 | |
52f51621 KH |
899 | If the Emacs job's user-id does not correspond to any known user (and |
900 | provided @code{NAME} is not set), the value is @code{"unknown"}. | |
901 | ||
902 | If @var{uid} is non-@code{nil}, then it should be an integer (a user-id) | |
903 | or a string (a login name). Then @code{user-full-name} returns the full | |
904 | name corresponding to that user-id or login name. If you specify a | |
905 | user-id or login name that isn't defined, it returns @code{nil}. | |
73804d4b RS |
906 | @end defun |
907 | ||
22697dac KH |
908 | @vindex user-full-name |
909 | @vindex user-real-login-name | |
910 | @vindex user-login-name | |
911 | The symbols @code{user-login-name}, @code{user-real-login-name} and | |
912 | @code{user-full-name} are variables as well as functions. The functions | |
913 | return the same values that the variables hold. These variables allow | |
914 | you to ``fake out'' Emacs by telling the functions what to return. The | |
915 | variables are also useful for constructing frame titles (@pxref{Frame | |
916 | Titles}). | |
917 | ||
73804d4b RS |
918 | @defun user-real-uid |
919 | This function returns the real @sc{uid} of the user. | |
dd726314 | 920 | The value may be a floating point number. |
73804d4b RS |
921 | |
922 | @example | |
923 | @group | |
924 | (user-real-uid) | |
925 | @result{} 19 | |
926 | @end group | |
927 | @end example | |
928 | @end defun | |
929 | ||
930 | @defun user-uid | |
c60ee5e7 | 931 | This function returns the effective @sc{uid} of the user. |
dd726314 | 932 | The value may be a floating point number. |
73804d4b RS |
933 | @end defun |
934 | ||
935 | @node Time of Day | |
936 | @section Time of Day | |
937 | ||
938 | This section explains how to determine the current time and the time | |
939 | zone. | |
940 | ||
941 | @defun current-time-string &optional time-value | |
a9f0a989 | 942 | This function returns the current time and date as a human-readable |
73804d4b RS |
943 | string. The format of the string is unvarying; the number of characters |
944 | used for each part is always the same, so you can reliably use | |
bfe721d1 KH |
945 | @code{substring} to extract pieces of it. It is wise to count the |
946 | characters from the beginning of the string rather than from the end, as | |
f9f59935 | 947 | additional information may some day be added at the end. |
73804d4b RS |
948 | |
949 | @c Emacs 19 feature | |
950 | The argument @var{time-value}, if given, specifies a time to format | |
bfe721d1 KH |
951 | instead of the current time. The argument should be a list whose first |
952 | two elements are integers. Thus, you can use times obtained from | |
953 | @code{current-time} (see below) and from @code{file-attributes} | |
954 | (@pxref{File Attributes}). | |
73804d4b RS |
955 | |
956 | @example | |
957 | @group | |
958 | (current-time-string) | |
959 | @result{} "Wed Oct 14 22:21:05 1987" | |
960 | @end group | |
961 | @end example | |
962 | @end defun | |
963 | ||
964 | @c Emacs 19 feature | |
965 | @defun current-time | |
966 | This function returns the system's time value as a list of three | |
967 | integers: @code{(@var{high} @var{low} @var{microsec})}. The integers | |
968 | @var{high} and @var{low} combine to give the number of seconds since | |
8241495d | 969 | 0:00 January 1, 1970 (local time), which is |
37680279 | 970 | @ifnottex |
73804d4b | 971 | @var{high} * 2**16 + @var{low}. |
37680279 | 972 | @end ifnottex |
73804d4b | 973 | @tex |
78608595 | 974 | $high*2^{16}+low$. |
73804d4b RS |
975 | @end tex |
976 | ||
977 | The third element, @var{microsec}, gives the microseconds since the | |
8241495d RS |
978 | start of the current second (or 0 for systems that return time with |
979 | the resolution of only one second). | |
73804d4b RS |
980 | |
981 | The first two elements can be compared with file time values such as you | |
982 | get with the function @code{file-attributes}. @xref{File Attributes}. | |
983 | @end defun | |
984 | ||
985 | @c Emacs 19 feature | |
986 | @defun current-time-zone &optional time-value | |
987 | This function returns a list describing the time zone that the user is | |
988 | in. | |
989 | ||
990 | The value has the form @code{(@var{offset} @var{name})}. Here | |
991 | @var{offset} is an integer giving the number of seconds ahead of UTC | |
992 | (east of Greenwich). A negative value means west of Greenwich. The | |
8241495d | 993 | second element, @var{name}, is a string giving the name of the time |
73804d4b RS |
994 | zone. Both elements change when daylight savings time begins or ends; |
995 | if the user has specified a time zone that does not use a seasonal time | |
996 | adjustment, then the value is constant through time. | |
997 | ||
998 | If the operating system doesn't supply all the information necessary to | |
999 | compute the value, both elements of the list are @code{nil}. | |
1000 | ||
1001 | The argument @var{time-value}, if given, specifies a time to analyze | |
1002 | instead of the current time. The argument should be a cons cell | |
1003 | containing two integers, or a list whose first two elements are | |
1004 | integers. Thus, you can use times obtained from @code{current-time} | |
22697dac KH |
1005 | (see above) and from @code{file-attributes} (@pxref{File Attributes}). |
1006 | @end defun | |
1007 | ||
de0df8e2 EZ |
1008 | @defun float-time &optional time-value |
1009 | This function returns the current time as a floating-point number of | |
1010 | seconds since the epoch. The argument @var{time-value}, if given, | |
1011 | specifies a time to convert instead of the current time. The argument | |
1012 | should have the same form as for @code{current-time-string} (see | |
1013 | above), and it also accepts the output of @code{current-time} and | |
1014 | @code{file-attributes}. | |
1015 | ||
1016 | @emph{Warning}: Since the result is floating point, it may not be | |
1017 | exact. Do not use this function if precise time stamps are required. | |
1018 | @end defun | |
1019 | ||
22697dac KH |
1020 | @node Time Conversion |
1021 | @section Time Conversion | |
1022 | ||
1023 | These functions convert time values (lists of two or three integers) | |
1024 | to strings or to calendrical information. There is also a function to | |
1025 | convert calendrical information to a time value. You can get time | |
1026 | values from the functions @code{current-time} (@pxref{Time of Day}) and | |
1027 | @code{file-attributes} (@pxref{File Attributes}). | |
1028 | ||
cfbaa90c RS |
1029 | Many operating systems are limited to time values that contain 32 bits |
1030 | of information; these systems typically handle only the times from | |
1031 | 1901-12-13 20:45:52 UTC through 2038-01-19 03:14:07 UTC. However, some | |
1032 | operating systems have larger time values, and can represent times far | |
1033 | in the past or future. | |
1034 | ||
1035 | Time conversion functions always use the Gregorian calendar, even for | |
1036 | dates before the Gregorian calendar was introduced. Year numbers count | |
1037 | the number of years since the year 1 B.C., and do not skip zero as | |
969fe9b5 | 1038 | traditional Gregorian years do; for example, the year number @minus{}37 |
cfbaa90c RS |
1039 | represents the Gregorian year 38 B.C@. |
1040 | ||
baee1397 RS |
1041 | @defun date-to-time string |
1042 | This function parses the time-string @var{string} and returns the | |
1043 | corresponding time value. | |
1044 | @end defun | |
1045 | ||
3f705836 GM |
1046 | @defun format-time-string format-string &optional time universal |
1047 | This function converts @var{time} (or the current time, if @var{time} is | |
1048 | omitted) to a string according to @var{format-string}. The argument | |
1049 | @var{format-string} may contain @samp{%}-sequences which say to | |
1050 | substitute parts of the time. Here is a table of what the | |
1051 | @samp{%}-sequences mean: | |
22697dac KH |
1052 | |
1053 | @table @samp | |
1054 | @item %a | |
1055 | This stands for the abbreviated name of the day of week. | |
1056 | @item %A | |
1057 | This stands for the full name of the day of week. | |
1058 | @item %b | |
1059 | This stands for the abbreviated name of the month. | |
1060 | @item %B | |
1061 | This stands for the full name of the month. | |
1062 | @item %c | |
1063 | This is a synonym for @samp{%x %X}. | |
1064 | @item %C | |
bfe721d1 KH |
1065 | This has a locale-specific meaning. In the default locale (named C), it |
1066 | is equivalent to @samp{%A, %B %e, %Y}. | |
22697dac KH |
1067 | @item %d |
1068 | This stands for the day of month, zero-padded. | |
1069 | @item %D | |
1070 | This is a synonym for @samp{%m/%d/%y}. | |
1071 | @item %e | |
1072 | This stands for the day of month, blank-padded. | |
1073 | @item %h | |
1074 | This is a synonym for @samp{%b}. | |
1075 | @item %H | |
1076 | This stands for the hour (00-23). | |
1077 | @item %I | |
8241495d | 1078 | This stands for the hour (01-12). |
22697dac KH |
1079 | @item %j |
1080 | This stands for the day of the year (001-366). | |
1081 | @item %k | |
1082 | This stands for the hour (0-23), blank padded. | |
1083 | @item %l | |
1084 | This stands for the hour (1-12), blank padded. | |
1085 | @item %m | |
1086 | This stands for the month (01-12). | |
1087 | @item %M | |
1088 | This stands for the minute (00-59). | |
1089 | @item %n | |
1090 | This stands for a newline. | |
1091 | @item %p | |
1092 | This stands for @samp{AM} or @samp{PM}, as appropriate. | |
1093 | @item %r | |
1094 | This is a synonym for @samp{%I:%M:%S %p}. | |
1095 | @item %R | |
1096 | This is a synonym for @samp{%H:%M}. | |
1097 | @item %S | |
8241495d | 1098 | This stands for the seconds (00-59). |
22697dac KH |
1099 | @item %t |
1100 | This stands for a tab character. | |
1101 | @item %T | |
1102 | This is a synonym for @samp{%H:%M:%S}. | |
1103 | @item %U | |
1104 | This stands for the week of the year (01-52), assuming that weeks | |
1105 | start on Sunday. | |
1106 | @item %w | |
1107 | This stands for the numeric day of week (0-6). Sunday is day 0. | |
1108 | @item %W | |
1109 | This stands for the week of the year (01-52), assuming that weeks | |
1110 | start on Monday. | |
1111 | @item %x | |
969fe9b5 RS |
1112 | This has a locale-specific meaning. In the default locale (named |
1113 | @samp{C}), it is equivalent to @samp{%D}. | |
22697dac | 1114 | @item %X |
969fe9b5 RS |
1115 | This has a locale-specific meaning. In the default locale (named |
1116 | @samp{C}), it is equivalent to @samp{%T}. | |
22697dac KH |
1117 | @item %y |
1118 | This stands for the year without century (00-99). | |
1119 | @item %Y | |
1120 | This stands for the year with century. | |
1121 | @item %Z | |
1122 | This stands for the time zone abbreviation. | |
1123 | @end table | |
f9f59935 RS |
1124 | |
1125 | You can also specify the field width and type of padding for any of | |
969fe9b5 RS |
1126 | these @samp{%}-sequences. This works as in @code{printf}: you write |
1127 | the field width as digits in the middle of a @samp{%}-sequences. If you | |
a9f0a989 RS |
1128 | start the field width with @samp{0}, it means to pad with zeros. If you |
1129 | start the field width with @samp{_}, it means to pad with spaces. | |
f9f59935 RS |
1130 | |
1131 | For example, @samp{%S} specifies the number of seconds since the minute; | |
1132 | @samp{%03S} means to pad this with zeros to 3 positions, @samp{%_3S} to | |
1133 | pad with spaces to 3 positions. Plain @samp{%3S} pads with zeros, | |
1134 | because that is how @samp{%S} normally pads to two positions. | |
3f705836 GM |
1135 | |
1136 | The characters @samp{E} and @samp{O} act as modifiers when used between | |
1137 | @samp{%} and one of the letters in the table above. @samp{E} specifies | |
79ddc9c9 GM |
1138 | using the current locale's ``alternative'' version of the date and time. |
1139 | In a Japanese locale, for example, @code{%Ex} might yield a date format | |
1140 | based on the Japanese Emperors' reigns. @samp{E} is allowed in | |
1141 | @samp{%Ec}, @samp{%EC}, @samp{%Ex}, @samp{%EX}, @samp{%Ey}, and | |
1142 | @samp{%EY}. | |
1143 | ||
1144 | @samp{O} means to use the current locale's ``alternative'' | |
1145 | representation of numbers, instead of the ordinary decimal digits. This | |
1146 | is allowed with most letters, all the ones that output numbers. | |
3f705836 GM |
1147 | |
1148 | If @var{universal} is non-@code{nil}, that means to describe the time as | |
1149 | Universal Time; @code{nil} means describe it using what Emacs believes | |
1150 | is the local time zone (see @code{current-time-zone}). | |
2468d0c0 DL |
1151 | |
1152 | This function uses the C library function @code{strftime} to do most of | |
1153 | the work. In order to communicate with that function, it first encodes | |
1154 | its argument using the coding system specified by | |
1155 | @code{locale-coding-system} (@pxref{Locales}); after @code{strftime} | |
1156 | returns the resulting string, @code{format-time-string} decodes the | |
1157 | string using that same coding system. | |
22697dac KH |
1158 | @end defun |
1159 | ||
baee1397 RS |
1160 | @defun seconds-to-time seconds |
1161 | This function converts @var{seconds}, a floating point number of | |
1162 | seconds since the epoch, to a time value and returns that. To perform | |
1163 | the inverse conversion, use @code{float-time}. | |
1164 | @end defun | |
1165 | ||
75442b3f RS |
1166 | @defun decode-time &optional time |
1167 | This function converts a time value into calendrical information. If | |
1168 | you don't specify @var{time}, it decodes the current time. The return | |
1169 | value is a list of nine elements, as follows: | |
22697dac KH |
1170 | |
1171 | @example | |
1172 | (@var{seconds} @var{minutes} @var{hour} @var{day} @var{month} @var{year} @var{dow} @var{dst} @var{zone}) | |
1173 | @end example | |
1174 | ||
1175 | Here is what the elements mean: | |
1176 | ||
1177 | @table @var | |
8241495d | 1178 | @item seconds |
22697dac | 1179 | The number of seconds past the minute, as an integer between 0 and 59. |
8241495d | 1180 | @item minutes |
22697dac KH |
1181 | The number of minutes past the hour, as an integer between 0 and 59. |
1182 | @item hour | |
1183 | The hour of the day, as an integer between 0 and 23. | |
1184 | @item day | |
1185 | The day of the month, as an integer between 1 and 31. | |
1186 | @item month | |
1187 | The month of the year, as an integer between 1 and 12. | |
1188 | @item year | |
1189 | The year, an integer typically greater than 1900. | |
1190 | @item dow | |
1191 | The day of week, as an integer between 0 and 6, where 0 stands for | |
1192 | Sunday. | |
1193 | @item dst | |
1194 | @code{t} if daylight savings time is effect, otherwise @code{nil}. | |
1195 | @item zone | |
bfe721d1 KH |
1196 | An integer indicating the time zone, as the number of seconds east of |
1197 | Greenwich. | |
22697dac KH |
1198 | @end table |
1199 | ||
969fe9b5 RS |
1200 | @strong{Common Lisp Note:} Common Lisp has different meanings for |
1201 | @var{dow} and @var{zone}. | |
22697dac KH |
1202 | @end defun |
1203 | ||
d59b6ae6 | 1204 | @defun encode-time seconds minutes hour day month year &optional zone |
22697dac | 1205 | This function is the inverse of @code{decode-time}. It converts seven |
bfe721d1 KH |
1206 | items of calendrical data into a time value. For the meanings of the |
1207 | arguments, see the table above under @code{decode-time}. | |
22697dac | 1208 | |
8241495d | 1209 | Year numbers less than 100 are not treated specially. If you want them |
4f939ab8 RS |
1210 | to stand for years above 1900, or years above 2000, you must alter them |
1211 | yourself before you call @code{encode-time}. | |
22697dac KH |
1212 | |
1213 | The optional argument @var{zone} defaults to the current time zone and | |
1214 | its daylight savings time rules. If specified, it can be either a list | |
f9f59935 RS |
1215 | (as you would get from @code{current-time-zone}), a string as in the |
1216 | @code{TZ} environment variable, or an integer (as you would get from | |
1217 | @code{decode-time}). The specified zone is used without any further | |
1218 | alteration for daylight savings time. | |
0c124126 RS |
1219 | |
1220 | If you pass more than seven arguments to @code{encode-time}, the first | |
1221 | six are used as @var{seconds} through @var{year}, the last argument is | |
1222 | used as @var{zone}, and the arguments in between are ignored. This | |
1223 | feature makes it possible to use the elements of a list returned by | |
1224 | @code{decode-time} as the arguments to @code{encode-time}, like this: | |
1225 | ||
1226 | @example | |
1227 | (apply 'encode-time (decode-time @dots{})) | |
1228 | @end example | |
f9f59935 RS |
1229 | |
1230 | You can perform simple date arithmetic by using out-of-range values for | |
8241495d | 1231 | the @var{seconds}, @var{minutes}, @var{hour}, @var{day}, and @var{month} |
f9f59935 | 1232 | arguments; for example, day 0 means the day preceding the given month. |
a9f0a989 RS |
1233 | |
1234 | The operating system puts limits on the range of possible time values; | |
1235 | if you try to encode a time that is out of range, an error results. | |
67c1c88f RS |
1236 | For instance, years before 1970 do not work on some systems; |
1237 | on others, years as early as 1901 do work. | |
73804d4b RS |
1238 | @end defun |
1239 | ||
baee1397 RS |
1240 | @node Time Calculations |
1241 | @section Time Calculations | |
1242 | ||
1243 | These functions perform calendrical computations using time values | |
1244 | (the kind of list that @code{current-time} returns). | |
1245 | ||
1246 | @defun time-less-p t1 t2 | |
1247 | This returns @code{t} if time value @var{t1} is less than time value | |
1248 | @var{t2}. | |
1249 | @end defun | |
1250 | ||
1251 | @defun time-subtract t1 t2 | |
1252 | This returns the time difference @var{t1} @minus{} @var{t2} between | |
1253 | two time values, in the same format as a time value. | |
1254 | @end defun | |
1255 | ||
1256 | @defun time-add t1 t2 | |
1257 | This returns the sum of two time values, one of which ought to | |
1258 | represent a time difference rather than a point in time. | |
1259 | Here is how to add a number of seconds to a time value: | |
1260 | ||
1261 | @example | |
1262 | (time-add @var{time} (seconds-to-time @var{seconds})) | |
1263 | @end example | |
1264 | @end defun | |
1265 | ||
1266 | @defun time-to-days time | |
1267 | This function returns the number of days between the beginning of year | |
1268 | 1 and @var{time}. | |
1269 | @end defun | |
1270 | ||
1271 | @defun time-to-day-in-year time | |
1272 | This returns the day number within the year corresponding to @var{time}. | |
1273 | @end defun | |
1274 | ||
1275 | @defun date-leap-year-p year | |
1276 | This function returns @code{t} if @var{year} is a leap year. | |
1277 | @end defun | |
1278 | ||
73804d4b | 1279 | @node Timers |
bfe721d1 | 1280 | @section Timers for Delayed Execution |
0c124126 | 1281 | @cindex timer |
73804d4b | 1282 | |
d64f1a9d RS |
1283 | You can set up a @dfn{timer} to call a function at a specified |
1284 | future time or after a certain length of idleness. | |
0c124126 | 1285 | |
969fe9b5 | 1286 | Emacs cannot run timers at any arbitrary point in a Lisp program; it |
0c124126 RS |
1287 | can run them only when Emacs could accept output from a subprocess: |
1288 | namely, while waiting or inside certain primitive functions such as | |
1911e6e5 | 1289 | @code{sit-for} or @code{read-event} which @emph{can} wait. Therefore, a |
0c124126 RS |
1290 | timer's execution may be delayed if Emacs is busy. However, the time of |
1291 | execution is very precise if Emacs is idle. | |
73804d4b | 1292 | |
d64f1a9d RS |
1293 | Emacs binds @code{inhibit-quit} to @code{t} before calling the timer |
1294 | function, because quitting out of many timer functions can leave | |
1295 | things in an inconsistent state. This is normally unproblematical | |
1296 | because most timer functions don't do a lot of work. Indeed, for a | |
1297 | timer to calls a function that takes substantial time to run is likely | |
1298 | to be annoying. | |
1299 | ||
73804d4b RS |
1300 | @defun run-at-time time repeat function &rest args |
1301 | This function arranges to call @var{function} with arguments @var{args} | |
1302 | at time @var{time}. The argument @var{function} is a function to call | |
1303 | later, and @var{args} are the arguments to give it when it is called. | |
1304 | The time @var{time} is specified as a string. | |
1305 | ||
1911e6e5 RS |
1306 | Absolute times may be specified in a wide variety of formats; this |
1307 | function tries to accept all the commonly used date formats. Valid | |
1308 | formats include these two, | |
a9f0a989 RS |
1309 | |
1310 | @example | |
1311 | @var{year}-@var{month}-@var{day} @var{hour}:@var{min}:@var{sec} @var{timezone} | |
1312 | ||
1313 | @var{hour}:@var{min}:@var{sec} @var{timezone} @var{month}/@var{day}/@var{year} | |
1314 | @end example | |
1315 | ||
1316 | @noindent | |
1317 | where in both examples all fields are numbers; the format that | |
1318 | @code{current-time-string} returns is also allowed, and many others | |
1319 | as well. | |
73804d4b RS |
1320 | |
1321 | To specify a relative time, use numbers followed by units. | |
1322 | For example: | |
1323 | ||
1324 | @table @samp | |
1325 | @item 1 min | |
1326 | denotes 1 minute from now. | |
1327 | @item 1 min 5 sec | |
1328 | denotes 65 seconds from now. | |
1329 | @item 1 min 2 sec 3 hour 4 day 5 week 6 fortnight 7 month 8 year | |
1330 | denotes exactly 103 months, 123 days, and 10862 seconds from now. | |
1331 | @end table | |
1332 | ||
8241495d RS |
1333 | For relative time values, Emacs considers a month to be exactly thirty |
1334 | days, and a year to be exactly 365.25 days. | |
1335 | ||
0c124126 RS |
1336 | If @var{time} is a number (integer or floating point), that specifies a |
1337 | relative time measured in seconds. | |
73804d4b RS |
1338 | |
1339 | The argument @var{repeat} specifies how often to repeat the call. If | |
1340 | @var{repeat} is @code{nil}, there are no repetitions; @var{function} is | |
0c124126 | 1341 | called just once, at @var{time}. If @var{repeat} is a number, it |
f9f59935 RS |
1342 | specifies a repetition period measured in seconds. |
1343 | ||
1344 | In most cases, @var{repeat} has no effect on when @emph{first} call | |
1345 | takes place---@var{time} alone specifies that. There is one exception: | |
1346 | if @var{time} is @code{t}, then the timer runs whenever the time is a | |
1347 | multiple of @var{repeat} seconds after the epoch. This is useful for | |
1348 | functions like @code{display-time}. | |
78608595 RS |
1349 | |
1350 | The function @code{run-at-time} returns a timer value that identifies | |
1351 | the particular scheduled future action. You can use this value to call | |
0c124126 RS |
1352 | @code{cancel-timer} (see below). |
1353 | @end defun | |
1354 | ||
1355 | @defmac with-timeout (seconds timeout-forms@dots{}) body@dots{} | |
1356 | Execute @var{body}, but give up after @var{seconds} seconds. If | |
1357 | @var{body} finishes before the time is up, @code{with-timeout} returns | |
1358 | the value of the last form in @var{body}. If, however, the execution of | |
1359 | @var{body} is cut short by the timeout, then @code{with-timeout} | |
1360 | executes all the @var{timeout-forms} and returns the value of the last | |
1361 | of them. | |
1362 | ||
a9f0a989 | 1363 | This macro works by setting a timer to run after @var{seconds} seconds. If |
0c124126 RS |
1364 | @var{body} finishes before that time, it cancels the timer. If the |
1365 | timer actually runs, it terminates execution of @var{body}, then | |
1366 | executes @var{timeout-forms}. | |
1367 | ||
1368 | Since timers can run within a Lisp program only when the program calls a | |
1369 | primitive that can wait, @code{with-timeout} cannot stop executing | |
1370 | @var{body} while it is in the midst of a computation---only when it | |
1371 | calls one of those primitives. So use @code{with-timeout} only with a | |
1372 | @var{body} that waits for input, not one that does a long computation. | |
1373 | @end defmac | |
1374 | ||
1375 | The function @code{y-or-n-p-with-timeout} provides a simple way to use | |
1376 | a timer to avoid waiting too long for an answer. @xref{Yes-or-No | |
1377 | Queries}. | |
1378 | ||
1379 | @defun run-with-idle-timer secs repeat function &rest args | |
1380 | Set up a timer which runs when Emacs has been idle for @var{secs} | |
1381 | seconds. The value of @var{secs} may be an integer or a floating point | |
1382 | number. | |
1383 | ||
1384 | If @var{repeat} is @code{nil}, the timer runs just once, the first time | |
1385 | Emacs remains idle for a long enough time. More often @var{repeat} is | |
1386 | non-@code{nil}, which means to run the timer @emph{each time} Emacs | |
1387 | remains idle for @var{secs} seconds. | |
1388 | ||
1389 | The function @code{run-with-idle-timer} returns a timer value which you | |
1390 | can use in calling @code{cancel-timer} (see below). | |
73804d4b RS |
1391 | @end defun |
1392 | ||
0c124126 RS |
1393 | @cindex idleness |
1394 | Emacs becomes ``idle'' when it starts waiting for user input, and it | |
1395 | remains idle until the user provides some input. If a timer is set for | |
1396 | five seconds of idleness, it runs approximately five seconds after Emacs | |
8241495d RS |
1397 | first becomes idle. Even if @var{repeat} is non-@code{nil}, this timer |
1398 | will not run again as long as Emacs remains idle, because the duration | |
1399 | of idleness will continue to increase and will not go down to five | |
1400 | seconds again. | |
0c124126 RS |
1401 | |
1402 | Emacs can do various things while idle: garbage collect, autosave or | |
969fe9b5 RS |
1403 | handle data from a subprocess. But these interludes during idleness do |
1404 | not interfere with idle timers, because they do not reset the clock of | |
1405 | idleness to zero. An idle timer set for 600 seconds will run when ten | |
1406 | minutes have elapsed since the last user command was finished, even if | |
1407 | subprocess output has been accepted thousands of times within those ten | |
8241495d | 1408 | minutes, and even if there have been garbage collections and autosaves. |
0c124126 RS |
1409 | |
1410 | When the user supplies input, Emacs becomes non-idle while executing the | |
1411 | input. Then it becomes idle again, and all the idle timers that are | |
1412 | set up to repeat will subsequently run another time, one by one. | |
1413 | ||
73804d4b RS |
1414 | @defun cancel-timer timer |
1415 | Cancel the requested action for @var{timer}, which should be a value | |
0c124126 RS |
1416 | previously returned by @code{run-at-time} or @code{run-with-idle-timer}. |
1417 | This cancels the effect of that call to @code{run-at-time}; the arrival | |
1418 | of the specified time will not cause anything special to happen. | |
73804d4b RS |
1419 | @end defun |
1420 | ||
1421 | @node Terminal Input | |
1422 | @section Terminal Input | |
1423 | @cindex terminal input | |
1424 | ||
1425 | This section describes functions and variables for recording or | |
1426 | manipulating terminal input. See @ref{Display}, for related | |
1427 | functions. | |
1428 | ||
1429 | @menu | |
1430 | * Input Modes:: Options for how input is processed. | |
1431 | * Translating Input:: Low level conversion of some characters or events | |
1432 | into others. | |
1433 | * Recording Input:: Saving histories of recent or all input events. | |
1434 | @end menu | |
1435 | ||
1436 | @node Input Modes | |
1437 | @subsection Input Modes | |
1438 | @cindex input modes | |
1439 | @cindex terminal input modes | |
1440 | ||
1441 | @defun set-input-mode interrupt flow meta quit-char | |
1442 | This function sets the mode for reading keyboard input. If | |
1443 | @var{interrupt} is non-null, then Emacs uses input interrupts. If it is | |
969fe9b5 | 1444 | @code{nil}, then it uses @sc{cbreak} mode. The default setting is |
8241495d | 1445 | system-dependent. Some systems always use @sc{cbreak} mode regardless |
969fe9b5 | 1446 | of what is specified. |
73804d4b | 1447 | |
969fe9b5 RS |
1448 | When Emacs communicates directly with X, it ignores this argument and |
1449 | uses interrupts if that is the way it knows how to communicate. | |
73804d4b | 1450 | |
969fe9b5 RS |
1451 | If @var{flow} is non-@code{nil}, then Emacs uses @sc{xon/xoff} |
1452 | (@kbd{C-q}, @kbd{C-s}) flow control for output to the terminal. This | |
1453 | has no effect except in @sc{cbreak} mode. @xref{Flow Control}. | |
73804d4b RS |
1454 | |
1455 | @c Emacs 19 feature | |
1456 | The argument @var{meta} controls support for input character codes | |
1457 | above 127. If @var{meta} is @code{t}, Emacs converts characters with | |
1458 | the 8th bit set into Meta characters. If @var{meta} is @code{nil}, | |
1459 | Emacs disregards the 8th bit; this is necessary when the terminal uses | |
1460 | it as a parity bit. If @var{meta} is neither @code{t} nor @code{nil}, | |
1461 | Emacs uses all 8 bits of input unchanged. This is good for terminals | |
969fe9b5 | 1462 | that use 8-bit character sets. |
73804d4b RS |
1463 | |
1464 | @c Emacs 19 feature | |
1465 | If @var{quit-char} is non-@code{nil}, it specifies the character to | |
1466 | use for quitting. Normally this character is @kbd{C-g}. | |
1467 | @xref{Quitting}. | |
1468 | @end defun | |
1469 | ||
1470 | The @code{current-input-mode} function returns the input mode settings | |
1471 | Emacs is currently using. | |
1472 | ||
1473 | @c Emacs 19 feature | |
1474 | @defun current-input-mode | |
8241495d | 1475 | This function returns the current mode for reading keyboard input. It |
73804d4b RS |
1476 | returns a list, corresponding to the arguments of @code{set-input-mode}, |
1477 | of the form @code{(@var{interrupt} @var{flow} @var{meta} @var{quit})} in | |
1478 | which: | |
1479 | @table @var | |
1480 | @item interrupt | |
1481 | is non-@code{nil} when Emacs is using interrupt-driven input. If | |
1482 | @code{nil}, Emacs is using @sc{cbreak} mode. | |
1483 | @item flow | |
1484 | is non-@code{nil} if Emacs uses @sc{xon/xoff} (@kbd{C-q}, @kbd{C-s}) | |
a9f0a989 RS |
1485 | flow control for output to the terminal. This value is meaningful only |
1486 | when @var{interrupt} is @code{nil}. | |
73804d4b | 1487 | @item meta |
bfe721d1 | 1488 | is @code{t} if Emacs treats the eighth bit of input characters as |
73804d4b RS |
1489 | the meta bit; @code{nil} means Emacs clears the eighth bit of every |
1490 | input character; any other value means Emacs uses all eight bits as the | |
1491 | basic character code. | |
1492 | @item quit | |
1493 | is the character Emacs currently uses for quitting, usually @kbd{C-g}. | |
1494 | @end table | |
1495 | @end defun | |
1496 | ||
73804d4b RS |
1497 | @node Translating Input |
1498 | @subsection Translating Input Events | |
1499 | @cindex translating input events | |
1500 | ||
0c124126 RS |
1501 | This section describes features for translating input events into |
1502 | other input events before they become part of key sequences. These | |
1503 | features apply to each event in the order they are described here: each | |
1504 | event is first modified according to @code{extra-keyboard-modifiers}, | |
969fe9b5 RS |
1505 | then translated through @code{keyboard-translate-table} (if applicable), |
1506 | and finally decoded with the specified keyboard coding system. If it is | |
1507 | being read as part of a key sequence, it is then added to the sequence | |
1508 | being read; then subsequences containing it are checked first with | |
1509 | @code{function-key-map} and then with @code{key-translation-map}. | |
73804d4b RS |
1510 | |
1511 | @c Emacs 19 feature | |
1512 | @defvar extra-keyboard-modifiers | |
1513 | This variable lets Lisp programs ``press'' the modifier keys on the | |
1514 | keyboard. The value is a bit mask: | |
1515 | ||
1516 | @table @asis | |
1517 | @item 1 | |
1518 | The @key{SHIFT} key. | |
1519 | @item 2 | |
1520 | The @key{LOCK} key. | |
1521 | @item 4 | |
1522 | The @key{CTL} key. | |
1523 | @item 8 | |
1524 | The @key{META} key. | |
1525 | @end table | |
1526 | ||
1527 | Each time the user types a keyboard key, it is altered as if the | |
1528 | modifier keys specified in the bit mask were held down. | |
1529 | ||
969fe9b5 RS |
1530 | When using a window system, the program can ``press'' any of the |
1531 | modifier keys in this way. Otherwise, only the @key{CTL} and @key{META} | |
1532 | keys can be virtually pressed. | |
73804d4b RS |
1533 | @end defvar |
1534 | ||
1535 | @defvar keyboard-translate-table | |
1536 | This variable is the translate table for keyboard characters. It lets | |
1537 | you reshuffle the keys on the keyboard without changing any command | |
f9f59935 | 1538 | bindings. Its value is normally a char-table, or else @code{nil}. |
73804d4b | 1539 | |
8241495d RS |
1540 | If @code{keyboard-translate-table} is a char-table |
1541 | (@pxref{Char-Tables}), then each character read from the keyboard is | |
1542 | looked up in this char-table. If the value found there is | |
1543 | non-@code{nil}, then it is used instead of the actual input character. | |
73804d4b RS |
1544 | |
1545 | In the example below, we set @code{keyboard-translate-table} to a | |
f9f59935 RS |
1546 | char-table. Then we fill it in to swap the characters @kbd{C-s} and |
1547 | @kbd{C-\} and the characters @kbd{C-q} and @kbd{C-^}. Subsequently, | |
1548 | typing @kbd{C-\} has all the usual effects of typing @kbd{C-s}, and vice | |
476a78b9 | 1549 | versa. (@xref{Flow Control}, for more information on this subject.) |
73804d4b RS |
1550 | |
1551 | @cindex flow control example | |
1552 | @example | |
1553 | @group | |
1554 | (defun evade-flow-control () | |
1555 | "Replace C-s with C-\ and C-q with C-^." | |
1556 | (interactive) | |
1557 | @end group | |
1558 | @group | |
f9f59935 | 1559 | (setq keyboard-translate-table |
a9f0a989 | 1560 | (make-char-table 'keyboard-translate-table nil)) |
f9f59935 RS |
1561 | @end group |
1562 | @group | |
1563 | ;; @r{Swap @kbd{C-s} and @kbd{C-\}.} | |
1564 | (aset keyboard-translate-table ?\034 ?\^s) | |
1565 | (aset keyboard-translate-table ?\^s ?\034) | |
73804d4b | 1566 | @end group |
73804d4b | 1567 | @group |
f9f59935 RS |
1568 | ;; @r{Swap @kbd{C-q} and @kbd{C-^}.} |
1569 | (aset keyboard-translate-table ?\036 ?\^q) | |
1570 | (aset keyboard-translate-table ?\^q ?\036)) | |
73804d4b RS |
1571 | @end group |
1572 | @end example | |
1573 | ||
1574 | Note that this translation is the first thing that happens to a | |
1575 | character after it is read from the terminal. Record-keeping features | |
1576 | such as @code{recent-keys} and dribble files record the characters after | |
1577 | translation. | |
1578 | @end defvar | |
1579 | ||
1580 | @defun keyboard-translate from to | |
1581 | This function modifies @code{keyboard-translate-table} to translate | |
1582 | character code @var{from} into character code @var{to}. It creates | |
f9f59935 | 1583 | the keyboard translate table if necessary. |
73804d4b RS |
1584 | @end defun |
1585 | ||
0c124126 RS |
1586 | The remaining translation features translate subsequences of key |
1587 | sequences being read. They are implemented in @code{read-key-sequence} | |
969fe9b5 | 1588 | and have no effect on input read with @code{read-event}. |
0c124126 | 1589 | |
73804d4b | 1590 | @defvar function-key-map |
f9f59935 RS |
1591 | This variable holds a keymap that describes the character sequences sent |
1592 | by function keys on an ordinary character terminal. This keymap has the | |
1593 | same structure as other keymaps, but is used differently: it specifies | |
1594 | translations to make while reading key sequences, rather than bindings | |
1595 | for key sequences. | |
73804d4b RS |
1596 | |
1597 | If @code{function-key-map} ``binds'' a key sequence @var{k} to a vector | |
1598 | @var{v}, then when @var{k} appears as a subsequence @emph{anywhere} in a | |
1599 | key sequence, it is replaced with the events in @var{v}. | |
1600 | ||
1601 | For example, VT100 terminals send @kbd{@key{ESC} O P} when the | |
969fe9b5 | 1602 | keypad @key{PF1} key is pressed. Therefore, we want Emacs to translate |
73804d4b RS |
1603 | that sequence of events into the single event @code{pf1}. We accomplish |
1604 | this by ``binding'' @kbd{@key{ESC} O P} to @code{[pf1]} in | |
1605 | @code{function-key-map}, when using a VT100. | |
1606 | ||
1607 | Thus, typing @kbd{C-c @key{PF1}} sends the character sequence @kbd{C-c | |
1608 | @key{ESC} O P}; later the function @code{read-key-sequence} translates | |
1609 | this back into @kbd{C-c @key{PF1}}, which it returns as the vector | |
1610 | @code{[?\C-c pf1]}. | |
1611 | ||
1612 | Entries in @code{function-key-map} are ignored if they conflict with | |
1613 | bindings made in the minor mode, local, or global keymaps. The intent | |
1614 | is that the character sequences that function keys send should not have | |
969fe9b5 RS |
1615 | command bindings in their own right---but if they do, the ordinary |
1616 | bindings take priority. | |
73804d4b RS |
1617 | |
1618 | The value of @code{function-key-map} is usually set up automatically | |
1619 | according to the terminal's Terminfo or Termcap entry, but sometimes | |
1620 | those need help from terminal-specific Lisp files. Emacs comes with | |
1621 | terminal-specific files for many common terminals; their main purpose is | |
1622 | to make entries in @code{function-key-map} beyond those that can be | |
1623 | deduced from Termcap and Terminfo. @xref{Terminal-Specific}. | |
73804d4b RS |
1624 | @end defvar |
1625 | ||
1626 | @defvar key-translation-map | |
1627 | This variable is another keymap used just like @code{function-key-map} | |
1628 | to translate input events into other events. It differs from | |
1629 | @code{function-key-map} in two ways: | |
1630 | ||
1631 | @itemize @bullet | |
1632 | @item | |
1633 | @code{key-translation-map} goes to work after @code{function-key-map} is | |
1634 | finished; it receives the results of translation by | |
1635 | @code{function-key-map}. | |
1636 | ||
1637 | @item | |
0c124126 RS |
1638 | @code{key-translation-map} overrides actual key bindings. For example, |
1639 | if @kbd{C-x f} has a binding in @code{key-translation-map}, that | |
1640 | translation takes effect even though @kbd{C-x f} also has a key binding | |
1641 | in the global map. | |
73804d4b RS |
1642 | @end itemize |
1643 | ||
1644 | The intent of @code{key-translation-map} is for users to map one | |
1645 | character set to another, including ordinary characters normally bound | |
1646 | to @code{self-insert-command}. | |
1647 | @end defvar | |
1648 | ||
1649 | @cindex key translation function | |
1650 | You can use @code{function-key-map} or @code{key-translation-map} for | |
1651 | more than simple aliases, by using a function, instead of a key | |
1652 | sequence, as the ``translation'' of a key. Then this function is called | |
1653 | to compute the translation of that key. | |
1654 | ||
1655 | The key translation function receives one argument, which is the prompt | |
1656 | that was specified in @code{read-key-sequence}---or @code{nil} if the | |
1657 | key sequence is being read by the editor command loop. In most cases | |
1658 | you can ignore the prompt value. | |
1659 | ||
1660 | If the function reads input itself, it can have the effect of altering | |
1661 | the event that follows. For example, here's how to define @kbd{C-c h} | |
1662 | to turn the character that follows into a Hyper character: | |
1663 | ||
1664 | @example | |
bda144f4 | 1665 | @group |
73804d4b RS |
1666 | (defun hyperify (prompt) |
1667 | (let ((e (read-event))) | |
1668 | (vector (if (numberp e) | |
f9f59935 | 1669 | (logior (lsh 1 24) e) |
73804d4b RS |
1670 | (if (memq 'hyper (event-modifiers e)) |
1671 | e | |
1672 | (add-event-modifier "H-" e)))))) | |
1673 | ||
1674 | (defun add-event-modifier (string e) | |
1675 | (let ((symbol (if (symbolp e) e (car e)))) | |
1676 | (setq symbol (intern (concat string | |
1677 | (symbol-name symbol)))) | |
bda144f4 MW |
1678 | @end group |
1679 | @group | |
73804d4b RS |
1680 | (if (symbolp e) |
1681 | symbol | |
1682 | (cons symbol (cdr e))))) | |
1683 | ||
1684 | (define-key function-key-map "\C-ch" 'hyperify) | |
bda144f4 | 1685 | @end group |
73804d4b RS |
1686 | @end example |
1687 | ||
969fe9b5 RS |
1688 | Finally, if you have enabled keyboard character set decoding using |
1689 | @code{set-keyboard-coding-system}, decoding is done after the | |
1690 | translations listed above. @xref{Specifying Coding Systems}. In future | |
1691 | Emacs versions, character set decoding may be done before the other | |
1692 | translations. | |
73804d4b RS |
1693 | |
1694 | @node Recording Input | |
1695 | @subsection Recording Input | |
1696 | ||
1697 | @defun recent-keys | |
969fe9b5 RS |
1698 | This function returns a vector containing the last 100 input events from |
1699 | the keyboard or mouse. All input events are included, whether or not | |
1700 | they were used as parts of key sequences. Thus, you always get the last | |
1701 | 100 input events, not counting events generated by keyboard macros. | |
1702 | (These are excluded because they are less interesting for debugging; it | |
78608595 | 1703 | should be enough to see the events that invoked the macros.) |
de0df8e2 EZ |
1704 | |
1705 | A call to @code{clear-this-command-keys} (@pxref{Command Loop Info}) | |
caae20c7 | 1706 | causes this function to return an empty vector immediately afterward. |
73804d4b RS |
1707 | @end defun |
1708 | ||
3f705836 | 1709 | @deffn Command open-dribble-file filename |
73804d4b RS |
1710 | @cindex dribble file |
1711 | This function opens a @dfn{dribble file} named @var{filename}. When a | |
1712 | dribble file is open, each input event from the keyboard or mouse (but | |
1713 | not those from keyboard macros) is written in that file. A | |
1714 | non-character event is expressed using its printed representation | |
1715 | surrounded by @samp{<@dots{}>}. | |
1716 | ||
1717 | You close the dribble file by calling this function with an argument | |
1718 | of @code{nil}. | |
1719 | ||
1720 | This function is normally used to record the input necessary to | |
1721 | trigger an Emacs bug, for the sake of a bug report. | |
1722 | ||
1723 | @example | |
1724 | @group | |
1725 | (open-dribble-file "~/dribble") | |
1726 | @result{} nil | |
1727 | @end group | |
1728 | @end example | |
1729 | @end deffn | |
1730 | ||
1731 | See also the @code{open-termscript} function (@pxref{Terminal Output}). | |
1732 | ||
1733 | @node Terminal Output | |
1734 | @section Terminal Output | |
1735 | @cindex terminal output | |
1736 | ||
8241495d | 1737 | The terminal output functions send output to the terminal, or keep |
73804d4b RS |
1738 | track of output sent to the terminal. The variable @code{baud-rate} |
1739 | tells you what Emacs thinks is the output speed of the terminal. | |
1740 | ||
1741 | @defvar baud-rate | |
1742 | This variable's value is the output speed of the terminal, as far as | |
1743 | Emacs knows. Setting this variable does not change the speed of actual | |
1744 | data transmission, but the value is used for calculations such as | |
1745 | padding. It also affects decisions about whether to scroll part of the | |
78608595 | 1746 | screen or repaint---even when using a window system. (We designed it |
73804d4b RS |
1747 | this way despite the fact that a window system has no true ``output |
1748 | speed'', to give you a way to tune these decisions.) | |
1749 | ||
1750 | The value is measured in baud. | |
1751 | @end defvar | |
1752 | ||
1753 | If you are running across a network, and different parts of the | |
1754 | network work at different baud rates, the value returned by Emacs may be | |
1755 | different from the value used by your local terminal. Some network | |
1756 | protocols communicate the local terminal speed to the remote machine, so | |
1757 | that Emacs and other programs can get the proper value, but others do | |
1758 | not. If Emacs has the wrong value, it makes decisions that are less | |
1759 | than optimal. To fix the problem, set @code{baud-rate}. | |
1760 | ||
1761 | @defun baud-rate | |
969fe9b5 RS |
1762 | This obsolete function returns the value of the variable |
1763 | @code{baud-rate}. | |
73804d4b RS |
1764 | @end defun |
1765 | ||
1766 | @defun send-string-to-terminal string | |
1767 | This function sends @var{string} to the terminal without alteration. | |
1768 | Control characters in @var{string} have terminal-dependent effects. | |
1769 | ||
1770 | One use of this function is to define function keys on terminals that | |
8241495d RS |
1771 | have downloadable function key definitions. For example, this is how (on |
1772 | certain terminals) to define function key 4 to move forward four | |
73804d4b RS |
1773 | characters (by transmitting the characters @kbd{C-u C-f} to the |
1774 | computer): | |
1775 | ||
1776 | @example | |
1777 | @group | |
1778 | (send-string-to-terminal "\eF4\^U\^F") | |
1779 | @result{} nil | |
1780 | @end group | |
1781 | @end example | |
1782 | @end defun | |
1783 | ||
1784 | @deffn Command open-termscript filename | |
1785 | @cindex termscript file | |
1786 | This function is used to open a @dfn{termscript file} that will record | |
1787 | all the characters sent by Emacs to the terminal. It returns | |
1788 | @code{nil}. Termscript files are useful for investigating problems | |
1789 | where Emacs garbles the screen, problems that are due to incorrect | |
1790 | Termcap entries or to undesirable settings of terminal options more | |
1791 | often than to actual Emacs bugs. Once you are certain which characters | |
1792 | were actually output, you can determine reliably whether they correspond | |
1793 | to the Termcap specifications in use. | |
1794 | ||
1795 | See also @code{open-dribble-file} in @ref{Terminal Input}. | |
1796 | ||
1797 | @example | |
1798 | @group | |
1799 | (open-termscript "../junk/termscript") | |
1800 | @result{} nil | |
1801 | @end group | |
1802 | @end example | |
1803 | @end deffn | |
1804 | ||
8241495d RS |
1805 | @node Sound Output |
1806 | @section Sound Output | |
1807 | @cindex sound | |
1808 | ||
1809 | To play sound using Emacs, use the function @code{play-sound}. Only | |
1810 | certain systems are supported; if you call @code{play-sound} on a system | |
1811 | which cannot really do the job, it gives an error. Emacs version 20 and | |
1812 | earlier did not support sound at all. | |
1813 | ||
1814 | The sound must be stored as a file in RIFF-WAVE format (@samp{.wav}) | |
1815 | or Sun Audio format (@samp{.au}). | |
1816 | ||
1817 | @tindex play-sound | |
1818 | @defun play-sound sound | |
1819 | This function plays a specified sound. The argument, @var{sound}, has | |
1820 | the form @code{(sound @var{properties}...)}, where the @var{properties} | |
1821 | consist of alternating keywords (particular symbols recognized | |
1822 | specially) and values corresponding to them. | |
1823 | ||
1824 | Here is a table of the keywords that are currently meaningful in | |
1825 | @var{sound}, and their meanings: | |
1826 | ||
1827 | @table @code | |
1828 | @item :file @var{file} | |
1829 | This specifies the file containing the sound to play. | |
1830 | If the file name is not absolute, it is expanded against | |
1831 | the directory @code{data-directory}. | |
1832 | ||
8f3efb4e RS |
1833 | @item :data @var{data} |
1834 | This specifies the sound to play without need to refer to a file. The | |
1835 | value, @var{data}, should be a string containing the same bytes as a | |
1836 | sound file. We recommend using a unibyte string. | |
1837 | ||
8241495d RS |
1838 | @item :volume @var{volume} |
1839 | This specifies how loud to play the sound. It should be a number in the | |
1840 | range of 0 to 1. The default is to use whatever volume has been | |
1841 | specified before. | |
a6b8df2f DL |
1842 | |
1843 | @item :device @var{device} | |
1844 | This specifies the system device on which to play the sound, as a | |
1845 | string. The default device is system-dependent. | |
8241495d RS |
1846 | @end table |
1847 | ||
1848 | Before actually playing the sound, @code{play-sound} | |
1849 | calls the functions in the list @code{play-sound-functions}. | |
1850 | Each function is called with one argument, @var{sound}. | |
1851 | @end defun | |
1852 | ||
a6b8df2f DL |
1853 | @defun play-sound-file file &optional volume device |
1854 | @tindex play-sound-file | |
1855 | This function is an alternative interface to playing a sound @var{file} | |
1856 | specifying an optional @var{volume} and @var{device}. | |
1857 | @end defun | |
1858 | ||
8241495d RS |
1859 | @tindex play-sound-functions |
1860 | @defvar play-sound-functions | |
1861 | A list of functions to be called before playing a sound. Each function | |
1862 | is called with one argument, a property list that describes the sound. | |
1863 | @end defvar | |
1864 | ||
1ce58cc0 RS |
1865 | @node X11 Keysyms |
1866 | @section Operating on X11 Keysyms | |
73804d4b RS |
1867 | |
1868 | To define system-specific X11 keysyms, set the variable | |
1869 | @code{system-key-alist}. | |
1870 | ||
1871 | @defvar system-key-alist | |
1872 | This variable's value should be an alist with one element for each | |
8241495d | 1873 | system-specific keysym. Each element has the form @code{(@var{code} |
73804d4b | 1874 | . @var{symbol})}, where @var{code} is the numeric keysym code (not |
c60ee5e7 | 1875 | including the ``vendor specific'' bit, |
37680279 | 1876 | @ifnottex |
86494bd5 | 1877 | -2**28), |
37680279 | 1878 | @end ifnottex |
c60ee5e7 | 1879 | @tex |
86494bd5 | 1880 | $-2^{28}$), |
969fe9b5 RS |
1881 | @end tex |
1882 | and @var{symbol} is the name for the function key. | |
73804d4b | 1883 | |
8241495d RS |
1884 | For example @code{(168 . mute-acute)} defines a system-specific key (used |
1885 | by HP X servers) whose numeric code is | |
37680279 | 1886 | @ifnottex |
969fe9b5 | 1887 | -2**28 |
37680279 | 1888 | @end ifnottex |
c60ee5e7 | 1889 | @tex |
969fe9b5 RS |
1890 | $-2^{28}$ |
1891 | @end tex | |
1892 | + 168. | |
73804d4b | 1893 | |
969fe9b5 RS |
1894 | It is not crucial to exclude from the alist the keysyms of other X |
1895 | servers; those do no harm, as long as they don't conflict with the ones | |
1896 | used by the X server actually in use. | |
22697dac | 1897 | |
1911e6e5 | 1898 | The variable is always local to the current terminal, and cannot be |
22697dac | 1899 | buffer-local. @xref{Multiple Displays}. |
73804d4b RS |
1900 | @end defvar |
1901 | ||
1ce58cc0 RS |
1902 | You can specify which keysyms Emacs should use for the Meta, Alt, Hyper, and Super modifiers by setting these variables: |
1903 | ||
1904 | @defvar x-alt-keysym | |
1905 | @defvarx x-meta-keysym | |
1906 | @defvarx x-hyper-keysym | |
1907 | @defvarx x-super-keysym | |
1908 | The name of the keysym that should stand for the Alt modifier | |
1909 | (respectively, for Meta, Hyper, and Super). For example, here is | |
1910 | how to swap the Meta and Alt modifiers within Emacs: | |
1911 | @lisp | |
1912 | (setq x-alt-keysym 'meta) | |
1913 | (setq x-meta-keysym 'alt) | |
1914 | @end lisp | |
1915 | @end defvar | |
1916 | ||
73804d4b RS |
1917 | @node Flow Control |
1918 | @section Flow Control | |
1919 | @cindex flow control characters | |
1920 | ||
969fe9b5 RS |
1921 | This section attempts to answer the question ``Why does Emacs use |
1922 | flow-control characters in its command character set?'' For a second | |
1923 | view on this issue, read the comments on flow control in the | |
73804d4b RS |
1924 | @file{emacs/INSTALL} file from the distribution; for help with Termcap |
1925 | entries and DEC terminal concentrators, see @file{emacs/etc/TERMS}. | |
1926 | ||
1927 | @cindex @kbd{C-s} | |
1928 | @cindex @kbd{C-q} | |
1929 | At one time, most terminals did not need flow control, and none used | |
1930 | @code{C-s} and @kbd{C-q} for flow control. Therefore, the choice of | |
969fe9b5 RS |
1931 | @kbd{C-s} and @kbd{C-q} as command characters for searching and quoting |
1932 | was natural and uncontroversial. With so many commands needing key | |
8241495d | 1933 | assignments, of course we assigned meanings to nearly all @sc{ascii} |
969fe9b5 | 1934 | control characters. |
73804d4b RS |
1935 | |
1936 | Later, some terminals were introduced which required these characters | |
1937 | for flow control. They were not very good terminals for full-screen | |
969fe9b5 RS |
1938 | editing, so Emacs maintainers ignored them. In later years, flow |
1939 | control with @kbd{C-s} and @kbd{C-q} became widespread among terminals, | |
1940 | but by this time it was usually an option. And the majority of Emacs | |
1941 | users, who can turn flow control off, did not want to switch to less | |
1942 | mnemonic key bindings for the sake of flow control. | |
73804d4b | 1943 | |
969fe9b5 | 1944 | So which usage is ``right''---Emacs's or that of some terminal and |
73804d4b RS |
1945 | concentrator manufacturers? This question has no simple answer. |
1946 | ||
1947 | One reason why we are reluctant to cater to the problems caused by | |
1948 | @kbd{C-s} and @kbd{C-q} is that they are gratuitous. There are other | |
1949 | techniques (albeit less common in practice) for flow control that | |
1950 | preserve transparency of the character stream. Note also that their use | |
1951 | for flow control is not an official standard. Interestingly, on the | |
969fe9b5 RS |
1952 | model 33 teletype with a paper tape punch (around 1970), @kbd{C-s} and |
1953 | @kbd{C-q} were sent by the computer to turn the punch on and off! | |
73804d4b | 1954 | |
969fe9b5 RS |
1955 | As window systems and PC terminal emulators replace character-only |
1956 | terminals, the flow control problem is gradually disappearing. For the | |
1957 | mean time, Emacs provides a convenient way of enabling flow control if | |
1958 | you want it: call the function @code{enable-flow-control}. | |
73804d4b | 1959 | |
f9f59935 | 1960 | @deffn Command enable-flow-control |
73804d4b RS |
1961 | This function enables use of @kbd{C-s} and @kbd{C-q} for output flow |
1962 | control, and provides the characters @kbd{C-\} and @kbd{C-^} as aliases | |
1963 | for them using @code{keyboard-translate-table} (@pxref{Translating Input}). | |
f9f59935 | 1964 | @end deffn |
73804d4b RS |
1965 | |
1966 | You can use the function @code{enable-flow-control-on} in your | |
a40d4712 | 1967 | init file to enable flow control automatically on certain |
73804d4b RS |
1968 | terminal types. |
1969 | ||
1970 | @defun enable-flow-control-on &rest termtypes | |
1971 | This function enables flow control, and the aliases @kbd{C-\} and @kbd{C-^}, | |
1972 | if the terminal type is one of @var{termtypes}. For example: | |
1973 | ||
1974 | @smallexample | |
1975 | (enable-flow-control-on "vt200" "vt300" "vt101" "vt131") | |
1976 | @end smallexample | |
1977 | @end defun | |
1978 | ||
1979 | Here is how @code{enable-flow-control} does its job: | |
1980 | ||
1981 | @enumerate | |
1982 | @item | |
1983 | @cindex @sc{cbreak} | |
1984 | It sets @sc{cbreak} mode for terminal input, and tells the operating | |
1985 | system to handle flow control, with @code{(set-input-mode nil t)}. | |
1986 | ||
1987 | @item | |
1988 | It sets up @code{keyboard-translate-table} to translate @kbd{C-\} and | |
78608595 | 1989 | @kbd{C-^} into @kbd{C-s} and @kbd{C-q}. Except at its very |
73804d4b RS |
1990 | lowest level, Emacs never knows that the characters typed were anything |
1991 | but @kbd{C-s} and @kbd{C-q}, so you can in effect type them as @kbd{C-\} | |
1992 | and @kbd{C-^} even when they are input for other commands. | |
1993 | @xref{Translating Input}. | |
a890e1b0 | 1994 | @end enumerate |
73804d4b RS |
1995 | |
1996 | If the terminal is the source of the flow control characters, then once | |
1997 | you enable kernel flow control handling, you probably can make do with | |
1998 | less padding than normal for that terminal. You can reduce the amount | |
1999 | of padding by customizing the Termcap entry. You can also reduce it by | |
2000 | setting @code{baud-rate} to a smaller value so that Emacs uses a smaller | |
2001 | speed when calculating the padding needed. @xref{Terminal Output}. | |
2002 | ||
2003 | @node Batch Mode | |
2004 | @section Batch Mode | |
2005 | @cindex batch mode | |
2006 | @cindex noninteractive use | |
2007 | ||
8241495d | 2008 | The command-line option @samp{-batch} causes Emacs to run |
73804d4b RS |
2009 | noninteractively. In this mode, Emacs does not read commands from the |
2010 | terminal, it does not alter the terminal modes, and it does not expect | |
2011 | to be outputting to an erasable screen. The idea is that you specify | |
2012 | Lisp programs to run; when they are finished, Emacs should exit. The | |
2013 | way to specify the programs to run is with @samp{-l @var{file}}, which | |
2014 | loads the library named @var{file}, and @samp{-f @var{function}}, which | |
2015 | calls @var{function} with no arguments. | |
2016 | ||
2017 | Any Lisp program output that would normally go to the echo area, | |
8241495d | 2018 | either using @code{message}, or using @code{prin1}, etc., with @code{t} |
bfe721d1 | 2019 | as the stream, goes instead to Emacs's standard error descriptor when |
d70ba855 DL |
2020 | in batch mode. Similarly, input that would normally come from the |
2021 | minibuffer is read from the standard input descriptor. | |
2022 | Thus, Emacs behaves much like a noninteractive | |
73804d4b RS |
2023 | application program. (The echo area output that Emacs itself normally |
2024 | generates, such as command echoing, is suppressed entirely.) | |
2025 | ||
2026 | @defvar noninteractive | |
2027 | This variable is non-@code{nil} when Emacs is running in batch mode. | |
2028 | @end defvar | |
750c3b02 JD |
2029 | |
2030 | @node Session Management | |
2031 | @section Session Management | |
f8e7eebe | 2032 | @cindex session manager |
750c3b02 | 2033 | |
f8e7eebe RS |
2034 | Emacs supports the X Session Management Protocol for suspension and |
2035 | restart of applications. In the X Window System, a program called the | |
2036 | @dfn{session manager} has the responsibility to keep track of the | |
2037 | applications that are running. During shutdown, the session manager | |
2038 | asks applications to save their state, and delays the actual shutdown | |
2039 | until they respond. An application can also cancel the shutdown. | |
750c3b02 | 2040 | |
f8e7eebe RS |
2041 | When the session manager restarts a suspended session, it directs |
2042 | these applications to individually reload their saved state. It does | |
2043 | this by specifying a special command-line argument that says what | |
2044 | saved session to restore. For Emacs, this argument is @samp{--smid | |
2045 | @var{session}}. | |
750c3b02 JD |
2046 | |
2047 | @defvar emacs-save-session-functions | |
2048 | @tindex emacs-save-session-functions | |
2049 | Emacs supports saving state by using a hook called | |
2050 | @code{emacs-save-session-functions}. Each function in this hook is | |
2051 | called when the session manager tells Emacs that the window system is | |
f8e7eebe RS |
2052 | shutting down. The functions are called with the current buffer set |
2053 | to a temporary buffer. Each functions can use @code{insert} to add | |
2054 | Lisp code to this buffer. At the end, Emacs saves the buffer in a | |
2055 | file that Emacs will load in order to restart the saved session. | |
2056 | ||
2057 | If a function in @code{emacs-save-session-functions} returns | |
2058 | non-@code{nil}, Emacs tells the session manager to cancel the | |
2059 | shutdown. | |
750c3b02 JD |
2060 | @end defvar |
2061 | ||
f8e7eebe RS |
2062 | Here is an example that just inserts some text into *scratch* when |
2063 | Emacs is restarted by the session manager. | |
750c3b02 JD |
2064 | |
2065 | @example | |
2066 | @group | |
2067 | (add-hook 'emacs-save-session-functions 'save-yourself-test) | |
2068 | @end group | |
2069 | ||
2070 | @group | |
2071 | (defun save-yourself-test () | |
f8e7eebe RS |
2072 | (insert "(save-excursion |
2073 | (switch-to-buffer \"*scratch*\") | |
2074 | (insert \"I am restored\"))") | |
2075 | nil) | |
750c3b02 JD |
2076 | @end group |
2077 | @end example | |
ab5796a9 MB |
2078 | |
2079 | @ignore | |
2080 | arch-tag: 8378814a-30d7-467c-9615-74a80b9988a7 | |
2081 | @end ignore |