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1 | @c -*-texinfo-*- |
2 | @c This is part of the GNU Emacs Lisp Reference Manual. | |
3 | @c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2001, | |
4 | @c 2002, 2003, 2004, 2005, 2006, 2007 Free Software Foundation, Inc. | |
5 | @c See the file elisp.texi for copying conditions. | |
6336d8c3 | 6 | @setfilename ../../info/os |
b8d4c8d0 GM |
7 | @node System Interface, Antinews, Display, Top |
8 | @chapter Operating System Interface | |
9 | ||
10 | This chapter is about starting and getting out of Emacs, access to | |
11 | values in the operating system environment, and terminal input, output, | |
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 | |
19 | * Starting Up:: Customizing Emacs startup processing. | |
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. | |
24 | * Time Conversion:: Converting a time from numeric form | |
25 | to calendrical data, and vice versa). | |
26 | * Time Parsing:: Converting a time from numeric form to text | |
27 | and vice versa. | |
28 | * Processor Run Time:: Getting the run time used by Emacs. | |
29 | * Time Calculations:: Adding, subtracting, comparing times, etc. | |
30 | * Timers:: Setting a timer to call a function at a certain time. | |
31 | * Idle Timers:: Setting a timer to call a function when Emacs has | |
32 | been idle for a certain length of time. | |
33 | * Terminal Input:: Accessing and recording terminal input. | |
34 | * Terminal Output:: Controlling and recording terminal output. | |
35 | * Sound Output:: Playing sounds on the computer's speaker. | |
36 | * X11 Keysyms:: Operating on key symbols for X Windows | |
37 | * Batch Mode:: Running Emacs without terminal interaction. | |
38 | * Session Management:: Saving and restoring state with X Session Management. | |
39 | @end menu | |
40 | ||
41 | @node Starting Up | |
42 | @section Starting Up Emacs | |
43 | ||
44 | This section describes what Emacs does when it is started, and how you | |
45 | can customize these actions. | |
46 | ||
47 | @menu | |
48 | * Startup Summary:: Sequence of actions Emacs performs at startup. | |
49 | * Init File:: Details on reading the init file (@file{.emacs}). | |
50 | * Terminal-Specific:: How the terminal-specific Lisp file is read. | |
51 | * Command-Line Arguments:: How command-line arguments are processed, | |
52 | and how you can customize them. | |
53 | @end menu | |
54 | ||
55 | @node Startup Summary | |
56 | @subsection Summary: Sequence of Actions at Startup | |
57 | @cindex initialization of Emacs | |
58 | @cindex startup of Emacs | |
59 | @cindex @file{startup.el} | |
60 | ||
61 | The order of operations performed (in @file{startup.el}) by Emacs when | |
62 | it is started up is as follows: | |
63 | ||
64 | @enumerate | |
65 | @item | |
66 | It adds subdirectories to @code{load-path}, by running the file named | |
67 | @file{subdirs.el} in each directory in the list. Normally this file | |
68 | adds the directory's subdirectories to the list, and these will be | |
69 | scanned in their turn. The files @file{subdirs.el} are normally | |
70 | generated automatically by Emacs installation. | |
71 | ||
72 | @item | |
73 | It sets the language environment and the terminal coding system, | |
74 | if requested by environment variables such as @code{LANG}. | |
75 | ||
76 | @item | |
77 | It loads the initialization library for the window system, if you are | |
78 | using a window system. This library's name is | |
79 | @file{term/@var{windowsystem}-win.el}. | |
80 | ||
81 | @item | |
82 | It processes the initial options. (Some of them are handled | |
83 | even earlier than this.) | |
84 | ||
85 | @item | |
86 | It initializes the window frame and faces, if appropriate. | |
87 | ||
88 | @item | |
89 | It runs the normal hook @code{before-init-hook}. | |
90 | ||
91 | @item | |
92 | It loads the library @file{site-start} (if any), unless the option | |
93 | @samp{-Q} (or @samp{--no-site-file}) was specified. The library's file | |
94 | name is usually @file{site-start.el}. | |
95 | @cindex @file{site-start.el} | |
96 | ||
97 | @item | |
98 | It loads your init file (usually @file{~/.emacs}), unless the option | |
99 | @samp{-q} (or @samp{--no-init-file}), @samp{-Q}, or @samp{--batch} was | |
100 | specified on the command line. The @samp{-u} option can specify | |
101 | another user whose home directory should be used instead of @file{~}. | |
102 | ||
103 | @item | |
104 | It loads the library @file{default} (if any), unless | |
105 | @code{inhibit-default-init} is non-@code{nil}. (This is not done in | |
106 | @samp{-batch} mode, or if @samp{-Q} or @samp{-q} was specified on the | |
107 | command line.) The library's file name is usually @file{default.el}. | |
108 | @cindex @file{default.el} | |
109 | ||
110 | @item | |
111 | It runs the normal hook @code{after-init-hook}. | |
112 | ||
113 | @item | |
114 | It sets the major mode according to @code{initial-major-mode}, provided | |
115 | the buffer @samp{*scratch*} is still current and still in Fundamental | |
116 | mode. | |
117 | ||
118 | @item | |
119 | It loads the terminal-specific Lisp file, if any, except when in batch | |
120 | mode or using a window system. | |
121 | ||
122 | @item | |
123 | It displays the initial echo area message, unless you have suppressed | |
124 | that with @code{inhibit-startup-echo-area-message}. | |
125 | ||
126 | @item | |
127 | It processes the action arguments from the command line. | |
128 | ||
129 | @item | |
130 | It runs @code{emacs-startup-hook} and then @code{term-setup-hook}. | |
131 | ||
132 | @item | |
133 | It calls @code{frame-notice-user-settings}, which modifies the | |
134 | parameters of the selected frame according to whatever the init files | |
135 | specify. | |
136 | ||
137 | @item | |
138 | It runs @code{window-setup-hook}. @xref{Window Systems}. | |
139 | ||
140 | @item | |
141 | It displays copyleft, nonwarranty, and basic use information, provided | |
142 | the value of @code{inhibit-startup-message} is @code{nil}, you didn't | |
143 | specify @samp{--no-splash} or @samp{-Q}. | |
144 | @end enumerate | |
145 | ||
146 | @defopt inhibit-startup-message | |
147 | This variable inhibits the initial startup messages (the nonwarranty, | |
148 | etc.). If it is non-@code{nil}, then the messages are not printed. | |
149 | ||
150 | This variable exists so you can set it in your personal init file, once | |
151 | you are familiar with the contents of the startup message. Do not set | |
152 | this variable in the init file of a new user, or in a way that affects | |
153 | more than one user, because that would prevent new users from receiving | |
154 | the information they are supposed to see. | |
155 | @end defopt | |
156 | ||
157 | @defopt inhibit-startup-echo-area-message | |
158 | This variable controls the display of the startup echo area message. | |
159 | You can suppress the startup echo area message by adding text with this | |
160 | form to your init file: | |
161 | ||
162 | @example | |
163 | (setq inhibit-startup-echo-area-message | |
164 | "@var{your-login-name}") | |
165 | @end example | |
166 | ||
167 | Emacs explicitly checks for an expression as shown above in your init | |
168 | file; your login name must appear in the expression as a Lisp string | |
169 | constant. Other methods of setting | |
170 | @code{inhibit-startup-echo-area-message} to the same value do not | |
171 | inhibit the startup message. | |
172 | ||
173 | This way, you can easily inhibit the message for yourself if you wish, | |
174 | but thoughtless copying of your init file will not inhibit the message | |
175 | for someone else. | |
176 | @end defopt | |
177 | ||
178 | @node Init File | |
179 | @subsection The Init File, @file{.emacs} | |
180 | @cindex init file | |
181 | @cindex @file{.emacs} | |
182 | ||
183 | When you start Emacs, it normally attempts to load your @dfn{init | |
184 | file}, a file in your home directory. Its normal name is | |
185 | @file{.emacs}, but you can also call it @file{.emacs.el}. | |
186 | Alternatively, you can use a file named @file{init.el} in a | |
187 | subdirectory @file{.emacs.d}. Whichever place you use, you can also | |
188 | compile the file (@pxref{Byte Compilation}); then the actual file | |
189 | loaded will be @file{.emacs.elc} or @file{init.elc}. | |
190 | ||
191 | The command-line switches @samp{-q}, @samp{-Q}, and @samp{-u} | |
192 | control whether and where to find the init file; @samp{-q} (and the | |
193 | stronger @samp{-Q}) says not to load an init file, while @samp{-u | |
194 | @var{user}} says to load @var{user}'s init file instead of yours. | |
195 | @xref{Entering Emacs,,, emacs, The GNU Emacs Manual}. If neither | |
196 | option is specified, Emacs uses the @code{LOGNAME} environment | |
197 | variable, or the @code{USER} (most systems) or @code{USERNAME} (MS | |
198 | systems) variable, to find your home directory and thus your init | |
199 | file; this way, even if you have su'd, Emacs still loads your own init | |
200 | file. If those environment variables are absent, though, Emacs uses | |
201 | your user-id to find your home directory. | |
202 | ||
203 | @cindex default init file | |
204 | A site may have a @dfn{default init file}, which is the library | |
205 | named @file{default.el}. Emacs finds the @file{default.el} file | |
206 | through the standard search path for libraries (@pxref{How Programs Do | |
207 | Loading}). The Emacs distribution does not come with this file; sites | |
208 | may provide one for local customizations. If the default init file | |
209 | exists, it is loaded whenever you start Emacs, except in batch mode or | |
210 | if @samp{-q} (or @samp{-Q}) is specified. But your own personal init | |
211 | file, if any, is loaded first; if it sets @code{inhibit-default-init} | |
212 | to a non-@code{nil} value, then Emacs does not subsequently load the | |
213 | @file{default.el} file. | |
214 | ||
215 | Another file for site-customization is @file{site-start.el}. Emacs | |
216 | loads this @emph{before} the user's init file. You can inhibit the | |
217 | loading of this file with the option @samp{--no-site-file}. | |
218 | ||
219 | @defvar site-run-file | |
220 | This variable specifies the site-customization file to load before the | |
221 | user's init file. Its normal value is @code{"site-start"}. The only | |
222 | way you can change it with real effect is to do so before dumping | |
223 | Emacs. | |
224 | @end defvar | |
225 | ||
226 | @xref{Init Examples,, Init File Examples, emacs, The GNU Emacs Manual}, for | |
227 | examples of how to make various commonly desired customizations in your | |
228 | @file{.emacs} file. | |
229 | ||
230 | @defopt inhibit-default-init | |
231 | This variable prevents Emacs from loading the default initialization | |
232 | library file for your session of Emacs. If its value is non-@code{nil}, | |
233 | then the default library is not loaded. The default value is | |
234 | @code{nil}. | |
235 | @end defopt | |
236 | ||
237 | @defvar before-init-hook | |
238 | This normal hook is run, once, just before loading all the init files | |
239 | (the user's init file, @file{default.el}, and/or @file{site-start.el}). | |
240 | (The only way to change it with real effect is before dumping Emacs.) | |
241 | @end defvar | |
242 | ||
243 | @defvar after-init-hook | |
244 | This normal hook is run, once, just after loading all the init files | |
245 | (the user's init file, @file{default.el}, and/or @file{site-start.el}), | |
246 | before loading the terminal-specific library and processing the | |
247 | command-line action arguments. | |
248 | @end defvar | |
249 | ||
250 | @defvar emacs-startup-hook | |
251 | This normal hook is run, once, just after handling the command line | |
252 | arguments, just before @code{term-setup-hook}. | |
253 | @end defvar | |
254 | ||
255 | @defvar user-init-file | |
256 | This variable holds the absolute file name of the user's init file. If the | |
257 | actual init file loaded is a compiled file, such as @file{.emacs.elc}, | |
258 | the value refers to the corresponding source file. | |
259 | @end defvar | |
260 | ||
261 | @defvar user-emacs-directory | |
262 | This variable holds the name of the @file{.emacs.d} directory. It is | |
263 | ordinarily @file{~/.emacs.d}, but differs on some platforms. | |
264 | @end defvar | |
265 | ||
266 | @node Terminal-Specific | |
267 | @subsection Terminal-Specific Initialization | |
268 | @cindex terminal-specific initialization | |
269 | ||
270 | Each terminal type can have its own Lisp library that Emacs loads when | |
271 | run on that type of terminal. The library's name is constructed by | |
272 | concatenating the value of the variable @code{term-file-prefix} and the | |
273 | terminal type (specified by the environment variable @code{TERM}). | |
274 | Normally, @code{term-file-prefix} has the value | |
275 | @code{"term/"}; changing this is not recommended. Emacs finds the file | |
276 | in the normal manner, by searching the @code{load-path} directories, and | |
277 | trying the @samp{.elc} and @samp{.el} suffixes. | |
278 | ||
279 | @cindex Termcap | |
280 | The usual function of a terminal-specific library is to enable | |
281 | special keys to send sequences that Emacs can recognize. It may also | |
4f4a84ec | 282 | need to set or add to @code{input-decode-map} if the Termcap or |
b8d4c8d0 GM |
283 | Terminfo entry does not specify all the terminal's function keys. |
284 | @xref{Terminal Input}. | |
285 | ||
286 | When the name of the terminal type contains a hyphen, and no library | |
287 | is found whose name is identical to the terminal's name, Emacs strips | |
288 | from the terminal's name the last hyphen and everything that follows | |
289 | it, and tries again. This process is repeated until Emacs finds a | |
290 | matching library or until there are no more hyphens in the name (the | |
291 | latter means the terminal doesn't have any library specific to it). | |
292 | Thus, for example, if there are no @samp{aaa-48} and @samp{aaa-30} | |
293 | libraries, Emacs will try the same library @file{term/aaa.el} for | |
294 | terminal types @samp{aaa-48} and @samp{aaa-30-rv}. If necessary, the | |
295 | library can evaluate @code{(getenv "TERM")} to find the full name of | |
296 | the terminal type.@refill | |
297 | ||
298 | Your init file can prevent the loading of the | |
299 | terminal-specific library by setting the variable | |
300 | @code{term-file-prefix} to @code{nil}. This feature is useful when | |
301 | experimenting with your own peculiar customizations. | |
302 | ||
303 | You can also arrange to override some of the actions of the | |
304 | terminal-specific library by setting the variable | |
305 | @code{term-setup-hook}. This is a normal hook which Emacs runs using | |
306 | @code{run-hooks} at the end of Emacs initialization, after loading both | |
307 | your init file and any terminal-specific libraries. You can | |
308 | use this variable to define initializations for terminals that do not | |
309 | have their own libraries. @xref{Hooks}. | |
310 | ||
311 | @defvar term-file-prefix | |
312 | @cindex @code{TERM} environment variable | |
313 | If the @code{term-file-prefix} variable is non-@code{nil}, Emacs loads | |
314 | a terminal-specific initialization file as follows: | |
315 | ||
316 | @example | |
317 | (load (concat term-file-prefix (getenv "TERM"))) | |
318 | @end example | |
319 | ||
320 | @noindent | |
321 | You may set the @code{term-file-prefix} variable to @code{nil} in your | |
322 | init file if you do not wish to load the | |
323 | terminal-initialization file. To do this, put the following in | |
324 | your init file: @code{(setq term-file-prefix nil)}. | |
325 | ||
326 | On MS-DOS, if the environment variable @code{TERM} is not set, Emacs | |
327 | uses @samp{internal} as the terminal type. | |
328 | @end defvar | |
329 | ||
330 | @defvar term-setup-hook | |
331 | This variable is a normal hook that Emacs runs after loading your | |
332 | init file, the default initialization file (if any) and the | |
333 | terminal-specific Lisp file. | |
334 | ||
335 | You can use @code{term-setup-hook} to override the definitions made by a | |
336 | terminal-specific file. | |
337 | @end defvar | |
338 | ||
339 | See @code{window-setup-hook} in @ref{Window Systems}, for a related | |
340 | feature. | |
341 | ||
342 | @node Command-Line Arguments | |
343 | @subsection Command-Line Arguments | |
344 | @cindex command-line arguments | |
345 | ||
346 | You can use command-line arguments to request various actions when you | |
347 | start Emacs. Since you do not need to start Emacs more than once per | |
348 | day, and will often leave your Emacs session running longer than that, | |
349 | command-line arguments are hardly ever used. As a practical matter, it | |
350 | is best to avoid making the habit of using them, since this habit would | |
351 | encourage you to kill and restart Emacs unnecessarily often. These | |
352 | options exist for two reasons: to be compatible with other editors (for | |
353 | invocation by other programs) and to enable shell scripts to run | |
354 | specific Lisp programs. | |
355 | ||
356 | This section describes how Emacs processes command-line arguments, | |
357 | and how you can customize them. | |
358 | ||
359 | @ignore | |
360 | (Note that some other editors require you to start afresh each time | |
361 | you want to edit a file. With this kind of editor, you will probably | |
362 | specify the file as a command-line argument. The recommended way to | |
363 | use GNU Emacs is to start it only once, just after you log in, and do | |
364 | all your editing in the same Emacs process. Each time you want to edit | |
365 | a different file, you visit it with the existing Emacs, which eventually | |
366 | comes to have many files in it ready for editing. Usually you do not | |
367 | kill the Emacs until you are about to log out.) | |
368 | @end ignore | |
369 | ||
370 | @defun command-line | |
371 | This function parses the command line that Emacs was called with, | |
372 | processes it, loads the user's init file and displays the | |
373 | startup messages. | |
374 | @end defun | |
375 | ||
376 | @defvar command-line-processed | |
377 | The value of this variable is @code{t} once the command line has been | |
378 | processed. | |
379 | ||
380 | If you redump Emacs by calling @code{dump-emacs}, you may wish to set | |
381 | this variable to @code{nil} first in order to cause the new dumped Emacs | |
382 | to process its new command-line arguments. | |
383 | @end defvar | |
384 | ||
385 | @defvar command-switch-alist | |
386 | @cindex switches on command line | |
387 | @cindex options on command line | |
388 | @cindex command-line options | |
389 | The value of this variable is an alist of user-defined command-line | |
390 | options and associated handler functions. This variable exists so you | |
391 | can add elements to it. | |
392 | ||
393 | A @dfn{command-line option} is an argument on the command line, which | |
394 | has the form: | |
395 | ||
396 | @example | |
397 | -@var{option} | |
398 | @end example | |
399 | ||
400 | The elements of the @code{command-switch-alist} look like this: | |
401 | ||
402 | @example | |
403 | (@var{option} . @var{handler-function}) | |
404 | @end example | |
405 | ||
406 | The @sc{car}, @var{option}, is a string, the name of a command-line | |
407 | option (not including the initial hyphen). The @var{handler-function} | |
408 | is called to handle @var{option}, and receives the option name as its | |
409 | sole argument. | |
410 | ||
411 | In some cases, the option is followed in the command line by an | |
412 | argument. In these cases, the @var{handler-function} can find all the | |
413 | remaining command-line arguments in the variable | |
414 | @code{command-line-args-left}. (The entire list of command-line | |
415 | arguments is in @code{command-line-args}.) | |
416 | ||
417 | The command-line arguments are parsed by the @code{command-line-1} | |
418 | function in the @file{startup.el} file. See also @ref{Emacs | |
419 | Invocation, , Command Line Arguments for Emacs Invocation, emacs, The | |
420 | GNU Emacs Manual}. | |
421 | @end defvar | |
422 | ||
423 | @defvar command-line-args | |
424 | The value of this variable is the list of command-line arguments passed | |
425 | to Emacs. | |
426 | @end defvar | |
427 | ||
428 | @defvar command-line-functions | |
429 | This variable's value is a list of functions for handling an | |
430 | unrecognized command-line argument. Each time the next argument to be | |
431 | processed has no special meaning, the functions in this list are called, | |
432 | in order of appearance, until one of them returns a non-@code{nil} | |
433 | value. | |
434 | ||
435 | These functions are called with no arguments. They can access the | |
436 | command-line argument under consideration through the variable | |
437 | @code{argi}, which is bound temporarily at this point. The remaining | |
438 | arguments (not including the current one) are in the variable | |
439 | @code{command-line-args-left}. | |
440 | ||
441 | When a function recognizes and processes the argument in @code{argi}, it | |
442 | should return a non-@code{nil} value to say it has dealt with that | |
443 | argument. If it has also dealt with some of the following arguments, it | |
444 | can indicate that by deleting them from @code{command-line-args-left}. | |
445 | ||
446 | If all of these functions return @code{nil}, then the argument is used | |
447 | as a file name to visit. | |
448 | @end defvar | |
449 | ||
450 | @node Getting Out | |
451 | @section Getting Out of Emacs | |
452 | @cindex exiting Emacs | |
453 | ||
454 | There are two ways to get out of Emacs: you can kill the Emacs job, | |
455 | which exits permanently, or you can suspend it, which permits you to | |
456 | reenter the Emacs process later. As a practical matter, you seldom kill | |
457 | Emacs---only when you are about to log out. Suspending is much more | |
458 | common. | |
459 | ||
460 | @menu | |
461 | * Killing Emacs:: Exiting Emacs irreversibly. | |
462 | * Suspending Emacs:: Exiting Emacs reversibly. | |
463 | @end menu | |
464 | ||
465 | @node Killing Emacs | |
466 | @comment node-name, next, previous, up | |
467 | @subsection Killing Emacs | |
468 | @cindex killing Emacs | |
469 | ||
470 | Killing Emacs means ending the execution of the Emacs process. The | |
471 | parent process normally resumes control. The low-level primitive for | |
472 | killing Emacs is @code{kill-emacs}. | |
473 | ||
474 | @defun kill-emacs &optional exit-data | |
475 | This function exits the Emacs process and kills it. | |
476 | ||
477 | If @var{exit-data} is an integer, then it is used as the exit status | |
478 | of the Emacs process. (This is useful primarily in batch operation; see | |
479 | @ref{Batch Mode}.) | |
480 | ||
481 | If @var{exit-data} is a string, its contents are stuffed into the | |
482 | terminal input buffer so that the shell (or whatever program next reads | |
483 | input) can read them. | |
484 | @end defun | |
485 | ||
486 | All the information in the Emacs process, aside from files that have | |
487 | been saved, is lost when the Emacs process is killed. Because killing | |
488 | Emacs inadvertently can lose a lot of work, Emacs queries for | |
489 | confirmation before actually terminating if you have buffers that need | |
490 | saving or subprocesses that are running. This is done in the function | |
491 | @code{save-buffers-kill-emacs}, the higher level function from which | |
492 | @code{kill-emacs} is usually called. | |
493 | ||
494 | @defvar kill-emacs-query-functions | |
495 | After asking the standard questions, @code{save-buffers-kill-emacs} | |
496 | calls the functions in the list @code{kill-emacs-query-functions}, in | |
497 | order of appearance, with no arguments. These functions can ask for | |
498 | additional confirmation from the user. If any of them returns | |
499 | @code{nil}, @code{save-buffers-kill-emacs} does not kill Emacs, and | |
500 | does not run the remaining functions in this hook. Calling | |
501 | @code{kill-emacs} directly does not run this hook. | |
502 | @end defvar | |
503 | ||
504 | @defvar kill-emacs-hook | |
505 | This variable is a normal hook; once @code{save-buffers-kill-emacs} is | |
506 | finished with all file saving and confirmation, it calls | |
507 | @code{kill-emacs} which runs the functions in this hook. | |
508 | @code{kill-emacs} does not run this hook in batch mode. | |
509 | ||
510 | @code{kill-emacs} may be invoked directly (that is not via | |
511 | @code{save-buffers-kill-emacs}) if the terminal is disconnected, or in | |
512 | similar situations where interaction with the user is not possible. | |
513 | Thus, if your hook needs to interact with the user, put it on | |
514 | @code{kill-emacs-query-functions}; if it needs to run regardless of | |
515 | how Emacs is killed, put it on @code{kill-emacs-hook}. | |
516 | @end defvar | |
517 | ||
518 | @node Suspending Emacs | |
519 | @subsection Suspending Emacs | |
520 | @cindex suspending Emacs | |
521 | ||
522 | @dfn{Suspending Emacs} means stopping Emacs temporarily and returning | |
523 | control to its superior process, which is usually the shell. This | |
524 | allows you to resume editing later in the same Emacs process, with the | |
525 | same buffers, the same kill ring, the same undo history, and so on. To | |
526 | resume Emacs, use the appropriate command in the parent shell---most | |
527 | likely @code{fg}. | |
528 | ||
529 | Some operating systems do not support suspension of jobs; on these | |
530 | systems, ``suspension'' actually creates a new shell temporarily as a | |
531 | subprocess of Emacs. Then you would exit the shell to return to Emacs. | |
532 | ||
533 | Suspension is not useful with window systems, because the Emacs job | |
534 | may not have a parent that can resume it again, and in any case you can | |
535 | give input to some other job such as a shell merely by moving to a | |
536 | different window. Therefore, suspending is not allowed when Emacs is using | |
537 | a window system (X, MS Windows, or Mac). | |
538 | ||
539 | @defun suspend-emacs &optional string | |
540 | This function stops Emacs and returns control to the superior process. | |
541 | If and when the superior process resumes Emacs, @code{suspend-emacs} | |
542 | returns @code{nil} to its caller in Lisp. | |
543 | ||
544 | If @var{string} is non-@code{nil}, its characters are sent to be read | |
545 | as terminal input by Emacs's superior shell. The characters in | |
546 | @var{string} are not echoed by the superior shell; only the results | |
547 | appear. | |
548 | ||
549 | Before suspending, @code{suspend-emacs} runs the normal hook | |
550 | @code{suspend-hook}. | |
551 | ||
552 | After the user resumes Emacs, @code{suspend-emacs} runs the normal hook | |
553 | @code{suspend-resume-hook}. @xref{Hooks}. | |
554 | ||
555 | The next redisplay after resumption will redraw the entire screen, | |
556 | unless the variable @code{no-redraw-on-reenter} is non-@code{nil} | |
557 | (@pxref{Refresh Screen}). | |
558 | ||
559 | In the following example, note that @samp{pwd} is not echoed after | |
560 | Emacs is suspended. But it is read and executed by the shell. | |
561 | ||
562 | @smallexample | |
563 | @group | |
564 | (suspend-emacs) | |
565 | @result{} nil | |
566 | @end group | |
567 | ||
568 | @group | |
569 | (add-hook 'suspend-hook | |
570 | (function (lambda () | |
571 | (or (y-or-n-p | |
572 | "Really suspend? ") | |
573 | (error "Suspend canceled"))))) | |
574 | @result{} (lambda nil | |
575 | (or (y-or-n-p "Really suspend? ") | |
576 | (error "Suspend canceled"))) | |
577 | @end group | |
578 | @group | |
579 | (add-hook 'suspend-resume-hook | |
580 | (function (lambda () (message "Resumed!")))) | |
581 | @result{} (lambda nil (message "Resumed!")) | |
582 | @end group | |
583 | @group | |
584 | (suspend-emacs "pwd") | |
585 | @result{} nil | |
586 | @end group | |
587 | @group | |
588 | ---------- Buffer: Minibuffer ---------- | |
589 | Really suspend? @kbd{y} | |
590 | ---------- Buffer: Minibuffer ---------- | |
591 | @end group | |
592 | ||
593 | @group | |
594 | ---------- Parent Shell ---------- | |
595 | lewis@@slug[23] % /user/lewis/manual | |
596 | lewis@@slug[24] % fg | |
597 | @end group | |
598 | ||
599 | @group | |
600 | ---------- Echo Area ---------- | |
601 | Resumed! | |
602 | @end group | |
603 | @end smallexample | |
604 | @end defun | |
605 | ||
606 | @defvar suspend-hook | |
607 | This variable is a normal hook that Emacs runs before suspending. | |
608 | @end defvar | |
609 | ||
610 | @defvar suspend-resume-hook | |
611 | This variable is a normal hook that Emacs runs on resuming | |
612 | after a suspension. | |
613 | @end defvar | |
614 | ||
615 | @node System Environment | |
616 | @section Operating System Environment | |
617 | @cindex operating system environment | |
618 | ||
619 | Emacs provides access to variables in the operating system environment | |
620 | through various functions. These variables include the name of the | |
621 | system, the user's @acronym{UID}, and so on. | |
622 | ||
623 | @defvar system-configuration | |
624 | This variable holds the standard GNU configuration name for the | |
625 | hardware/software configuration of your system, as a string. The | |
626 | convenient way to test parts of this string is with | |
627 | @code{string-match}. | |
628 | @end defvar | |
629 | ||
630 | @cindex system type and name | |
631 | @defvar system-type | |
632 | The value of this variable is a symbol indicating the type of operating | |
633 | system Emacs is operating on. Here is a table of the possible values: | |
634 | ||
635 | @table @code | |
636 | @item alpha-vms | |
637 | VMS on the Alpha. | |
638 | ||
639 | @item aix-v3 | |
640 | AIX. | |
641 | ||
642 | @item berkeley-unix | |
643 | Berkeley BSD. | |
644 | ||
645 | @item cygwin | |
646 | Cygwin. | |
647 | ||
648 | @item dgux | |
649 | Data General DGUX operating system. | |
650 | ||
651 | @item gnu | |
652 | the GNU system (using the GNU kernel, which consists of the HURD and Mach). | |
653 | ||
654 | @item gnu/linux | |
655 | A GNU/Linux system---that is, a variant GNU system, using the Linux | |
656 | kernel. (These systems are the ones people often call ``Linux,'' but | |
657 | actually Linux is just the kernel, not the whole system.) | |
658 | ||
659 | @item hpux | |
660 | Hewlett-Packard HPUX operating system. | |
661 | ||
662 | @item irix | |
663 | Silicon Graphics Irix system. | |
664 | ||
665 | @item ms-dos | |
666 | Microsoft MS-DOS ``operating system.'' Emacs compiled with DJGPP for | |
667 | MS-DOS binds @code{system-type} to @code{ms-dos} even when you run it on | |
668 | MS-Windows. | |
669 | ||
670 | @item next-mach | |
671 | NeXT Mach-based system. | |
672 | ||
673 | @item rtu | |
674 | Masscomp RTU, UCB universe. | |
675 | ||
676 | @item unisoft-unix | |
677 | UniSoft UniPlus. | |
678 | ||
679 | @item usg-unix-v | |
680 | AT&T System V. | |
681 | ||
682 | @item vax-vms | |
683 | VAX VMS. | |
684 | ||
685 | @item windows-nt | |
686 | Microsoft windows NT. The same executable supports Windows 9X, but the | |
687 | value of @code{system-type} is @code{windows-nt} in either case. | |
688 | ||
689 | @item xenix | |
690 | SCO Xenix 386. | |
691 | @end table | |
692 | ||
693 | We do not wish to add new symbols to make finer distinctions unless it | |
694 | is absolutely necessary! In fact, we hope to eliminate some of these | |
695 | alternatives in the future. We recommend using | |
696 | @code{system-configuration} to distinguish between different operating | |
697 | systems. | |
698 | @end defvar | |
699 | ||
700 | @defun system-name | |
701 | This function returns the name of the machine you are running on. | |
702 | @example | |
703 | (system-name) | |
704 | @result{} "www.gnu.org" | |
705 | @end example | |
706 | @end defun | |
707 | ||
708 | The symbol @code{system-name} is a variable as well as a function. In | |
709 | fact, the function returns whatever value the variable | |
710 | @code{system-name} currently holds. Thus, you can set the variable | |
711 | @code{system-name} in case Emacs is confused about the name of your | |
712 | system. The variable is also useful for constructing frame titles | |
713 | (@pxref{Frame Titles}). | |
714 | ||
715 | @defvar mail-host-address | |
716 | If this variable is non-@code{nil}, it is used instead of | |
717 | @code{system-name} for purposes of generating email addresses. For | |
718 | example, it is used when constructing the default value of | |
719 | @code{user-mail-address}. @xref{User Identification}. (Since this is | |
720 | done when Emacs starts up, the value actually used is the one saved when | |
721 | Emacs was dumped. @xref{Building Emacs}.) | |
722 | @end defvar | |
723 | ||
724 | @deffn Command getenv var | |
725 | @cindex environment variable access | |
726 | This function returns the value of the environment variable @var{var}, | |
727 | as a string. @var{var} should be a string. If @var{var} is undefined | |
728 | in the environment, @code{getenv} returns @code{nil}. If returns | |
729 | @samp{""} if @var{var} is set but null. Within Emacs, the environment | |
730 | variable values are kept in the Lisp variable @code{process-environment}. | |
731 | ||
732 | @example | |
733 | @group | |
734 | (getenv "USER") | |
735 | @result{} "lewis" | |
736 | @end group | |
737 | ||
738 | @group | |
739 | lewis@@slug[10] % printenv | |
740 | PATH=.:/user/lewis/bin:/usr/bin:/usr/local/bin | |
741 | USER=lewis | |
742 | @end group | |
743 | @group | |
744 | TERM=ibmapa16 | |
745 | SHELL=/bin/csh | |
746 | HOME=/user/lewis | |
747 | @end group | |
748 | @end example | |
749 | @end deffn | |
750 | ||
751 | @c Emacs 19 feature | |
752 | @deffn Command setenv variable &optional value | |
753 | This command sets the value of the environment variable named | |
754 | @var{variable} to @var{value}. @var{variable} should be a string. | |
755 | Internally, Emacs Lisp can handle any string. However, normally | |
756 | @var{variable} should be a valid shell identifier, that is, a sequence | |
757 | of letters, digits and underscores, starting with a letter or | |
758 | underscore. Otherwise, errors may occur if subprocesses of Emacs try | |
759 | to access the value of @var{variable}. If @var{value} is omitted or | |
760 | @code{nil}, @code{setenv} removes @var{variable} from the environment. | |
761 | Otherwise, @var{value} should be a string. | |
762 | ||
763 | @code{setenv} works by modifying @code{process-environment}; binding | |
764 | that variable with @code{let} is also reasonable practice. | |
765 | ||
766 | @code{setenv} returns the new value of @var{variable}, or @code{nil} | |
767 | if it removed @var{variable} from the environment. | |
768 | @end deffn | |
769 | ||
770 | @defvar process-environment | |
771 | This variable is a list of strings, each describing one environment | |
772 | variable. The functions @code{getenv} and @code{setenv} work by means | |
773 | of this variable. | |
774 | ||
775 | @smallexample | |
776 | @group | |
777 | process-environment | |
778 | @result{} ("l=/usr/stanford/lib/gnuemacs/lisp" | |
779 | "PATH=.:/user/lewis/bin:/usr/class:/nfsusr/local/bin" | |
780 | "USER=lewis" | |
781 | @end group | |
782 | @group | |
783 | "TERM=ibmapa16" | |
784 | "SHELL=/bin/csh" | |
785 | "HOME=/user/lewis") | |
786 | @end group | |
787 | @end smallexample | |
788 | ||
789 | If @code{process-environment} contains ``duplicate'' elements that | |
790 | specify the same environment variable, the first of these elements | |
791 | specifies the variable, and the other ``duplicates'' are ignored. | |
792 | @end defvar | |
793 | ||
794 | @defvar path-separator | |
795 | This variable holds a string which says which character separates | |
796 | directories in a search path (as found in an environment variable). Its | |
797 | value is @code{":"} for Unix and GNU systems, and @code{";"} for MS-DOS | |
798 | and MS-Windows. | |
799 | @end defvar | |
800 | ||
801 | @defun parse-colon-path path | |
802 | This function takes a search path string such as would be the value of | |
803 | the @code{PATH} environment variable, and splits it at the separators, | |
804 | returning a list of directory names. @code{nil} in this list stands for | |
805 | ``use the current directory.'' Although the function's name says | |
806 | ``colon,'' it actually uses the value of @code{path-separator}. | |
807 | ||
808 | @example | |
809 | (parse-colon-path ":/foo:/bar") | |
810 | @result{} (nil "/foo/" "/bar/") | |
811 | @end example | |
812 | @end defun | |
813 | ||
814 | @defvar invocation-name | |
815 | This variable holds the program name under which Emacs was invoked. The | |
816 | value is a string, and does not include a directory name. | |
817 | @end defvar | |
818 | ||
819 | @defvar invocation-directory | |
820 | This variable holds the directory from which the Emacs executable was | |
821 | invoked, or perhaps @code{nil} if that directory cannot be determined. | |
822 | @end defvar | |
823 | ||
824 | @defvar installation-directory | |
825 | If non-@code{nil}, this is a directory within which to look for the | |
826 | @file{lib-src} and @file{etc} subdirectories. This is non-@code{nil} | |
827 | when Emacs can't find those directories in their standard installed | |
828 | locations, but can find them in a directory related somehow to the one | |
829 | containing the Emacs executable. | |
830 | @end defvar | |
831 | ||
832 | @defun load-average &optional use-float | |
833 | This function returns the current 1-minute, 5-minute, and 15-minute load | |
834 | averages, in a list. | |
835 | ||
836 | By default, the values are integers that are 100 times the system load | |
837 | averages, which indicate the average number of processes trying to run. | |
838 | If @var{use-float} is non-@code{nil}, then they are returned | |
839 | as floating point numbers and without multiplying by 100. | |
840 | ||
841 | If it is impossible to obtain the load average, this function signals | |
842 | an error. On some platforms, access to load averages requires | |
843 | installing Emacs as setuid or setgid so that it can read kernel | |
844 | information, and that usually isn't advisable. | |
845 | ||
846 | If the 1-minute load average is available, but the 5- or 15-minute | |
847 | averages are not, this function returns a shortened list containing | |
848 | the available averages. | |
849 | ||
850 | @example | |
851 | @group | |
852 | (load-average) | |
853 | @result{} (169 48 36) | |
854 | @end group | |
855 | @group | |
856 | (load-average t) | |
857 | @result{} (1.69 0.48 0.36) | |
858 | @end group | |
859 | ||
860 | @group | |
861 | lewis@@rocky[5] % uptime | |
862 | 11:55am up 1 day, 19:37, 3 users, | |
863 | load average: 1.69, 0.48, 0.36 | |
864 | @end group | |
865 | @end example | |
866 | @end defun | |
867 | ||
868 | @defun emacs-pid | |
869 | This function returns the process @acronym{ID} of the Emacs process, | |
870 | as an integer. | |
871 | @end defun | |
872 | ||
873 | @defvar tty-erase-char | |
874 | This variable holds the erase character that was selected | |
875 | in the system's terminal driver, before Emacs was started. | |
876 | The value is @code{nil} if Emacs is running under a window system. | |
877 | @end defvar | |
878 | ||
879 | @defun setprv privilege-name &optional setp getprv | |
880 | This function sets or resets a VMS privilege. (It does not exist on | |
881 | other systems.) The first argument is the privilege name, as a string. | |
882 | The second argument, @var{setp}, is @code{t} or @code{nil}, indicating | |
883 | whether the privilege is to be turned on or off. Its default is | |
884 | @code{nil}. The function returns @code{t} if successful, @code{nil} | |
885 | otherwise. | |
886 | ||
887 | If the third argument, @var{getprv}, is non-@code{nil}, @code{setprv} | |
888 | does not change the privilege, but returns @code{t} or @code{nil} | |
889 | indicating whether the privilege is currently enabled. | |
890 | @end defun | |
891 | ||
892 | @node User Identification | |
893 | @section User Identification | |
894 | @cindex user identification | |
895 | ||
896 | @defvar init-file-user | |
897 | This variable says which user's init files should be used by | |
898 | Emacs---or @code{nil} if none. @code{""} stands for the user who | |
899 | originally logged in. The value reflects command-line options such as | |
900 | @samp{-q} or @samp{-u @var{user}}. | |
901 | ||
902 | Lisp packages that load files of customizations, or any other sort of | |
903 | user profile, should obey this variable in deciding where to find it. | |
904 | They should load the profile of the user name found in this variable. | |
905 | If @code{init-file-user} is @code{nil}, meaning that the @samp{-q} | |
906 | option was used, then Lisp packages should not load any customization | |
907 | files or user profile. | |
908 | @end defvar | |
909 | ||
910 | @defvar user-mail-address | |
911 | This holds the nominal email address of the user who is using Emacs. | |
912 | Emacs normally sets this variable to a default value after reading your | |
913 | init files, but not if you have already set it. So you can set the | |
914 | variable to some other value in your init file if you do not | |
915 | want to use the default value. | |
916 | @end defvar | |
917 | ||
918 | @defun user-login-name &optional uid | |
919 | If you don't specify @var{uid}, this function returns the name under | |
920 | which the user is logged in. If the environment variable @code{LOGNAME} | |
921 | is set, that value is used. Otherwise, if the environment variable | |
922 | @code{USER} is set, that value is used. Otherwise, the value is based | |
923 | on the effective @acronym{UID}, not the real @acronym{UID}. | |
924 | ||
925 | If you specify @var{uid}, the value is the user name that corresponds | |
926 | to @var{uid} (which should be an integer), or @code{nil} if there is | |
927 | no such user. | |
928 | ||
929 | @example | |
930 | @group | |
931 | (user-login-name) | |
932 | @result{} "lewis" | |
933 | @end group | |
934 | @end example | |
935 | @end defun | |
936 | ||
937 | @defun user-real-login-name | |
938 | This function returns the user name corresponding to Emacs's real | |
939 | @acronym{UID}. This ignores the effective @acronym{UID} and ignores the | |
940 | environment variables @code{LOGNAME} and @code{USER}. | |
941 | @end defun | |
942 | ||
943 | @defun user-full-name &optional uid | |
944 | This function returns the full name of the logged-in user---or the value | |
945 | of the environment variable @code{NAME}, if that is set. | |
946 | ||
947 | @c "Bil" is the correct spelling. | |
948 | @example | |
949 | @group | |
950 | (user-full-name) | |
951 | @result{} "Bil Lewis" | |
952 | @end group | |
953 | @end example | |
954 | ||
955 | If the Emacs job's user-id does not correspond to any known user (and | |
956 | provided @code{NAME} is not set), the value is @code{"unknown"}. | |
957 | ||
958 | If @var{uid} is non-@code{nil}, then it should be a number (a user-id) | |
959 | or a string (a login name). Then @code{user-full-name} returns the full | |
960 | name corresponding to that user-id or login name. If you specify a | |
961 | user-id or login name that isn't defined, it returns @code{nil}. | |
962 | @end defun | |
963 | ||
964 | @vindex user-full-name | |
965 | @vindex user-real-login-name | |
966 | @vindex user-login-name | |
967 | The symbols @code{user-login-name}, @code{user-real-login-name} and | |
968 | @code{user-full-name} are variables as well as functions. The functions | |
969 | return the same values that the variables hold. These variables allow | |
970 | you to ``fake out'' Emacs by telling the functions what to return. The | |
971 | variables are also useful for constructing frame titles (@pxref{Frame | |
972 | Titles}). | |
973 | ||
974 | @defun user-real-uid | |
975 | This function returns the real @acronym{UID} of the user. | |
976 | The value may be a floating point number. | |
977 | ||
978 | @example | |
979 | @group | |
980 | (user-real-uid) | |
981 | @result{} 19 | |
982 | @end group | |
983 | @end example | |
984 | @end defun | |
985 | ||
986 | @defun user-uid | |
987 | This function returns the effective @acronym{UID} of the user. | |
988 | The value may be a floating point number. | |
989 | @end defun | |
990 | ||
991 | @node Time of Day | |
992 | @section Time of Day | |
993 | ||
994 | This section explains how to determine the current time and the time | |
995 | zone. | |
996 | ||
997 | @defun current-time-string &optional time-value | |
998 | This function returns the current time and date as a human-readable | |
999 | string. The format of the string is unvarying; the number of characters | |
1000 | used for each part is always the same, so you can reliably use | |
1001 | @code{substring} to extract pieces of it. It is wise to count the | |
1002 | characters from the beginning of the string rather than from the end, as | |
1003 | additional information may some day be added at the end. | |
1004 | ||
1005 | @c Emacs 19 feature | |
1006 | The argument @var{time-value}, if given, specifies a time to format | |
1007 | instead of the current time. The argument should be a list whose first | |
1008 | two elements are integers. Thus, you can use times obtained from | |
1009 | @code{current-time} (see below) and from @code{file-attributes} | |
1010 | (@pxref{Definition of file-attributes}). @var{time-value} can also be | |
1011 | a cons of two integers, but this is considered obsolete. | |
1012 | ||
1013 | @example | |
1014 | @group | |
1015 | (current-time-string) | |
1016 | @result{} "Wed Oct 14 22:21:05 1987" | |
1017 | @end group | |
1018 | @end example | |
1019 | @end defun | |
1020 | ||
1021 | @c Emacs 19 feature | |
1022 | @defun current-time | |
1023 | This function returns the system's time value as a list of three | |
1024 | integers: @code{(@var{high} @var{low} @var{microsec})}. The integers | |
1025 | @var{high} and @var{low} combine to give the number of seconds since | |
1026 | 0:00 January 1, 1970 UTC (Coordinated Universal Time), which is | |
1027 | @ifnottex | |
1028 | @var{high} * 2**16 + @var{low}. | |
1029 | @end ifnottex | |
1030 | @tex | |
1031 | $high*2^{16}+low$. | |
1032 | @end tex | |
1033 | ||
1034 | The third element, @var{microsec}, gives the microseconds since the | |
1035 | start of the current second (or 0 for systems that return time with | |
1036 | the resolution of only one second). | |
1037 | ||
1038 | The first two elements can be compared with file time values such as you | |
1039 | get with the function @code{file-attributes}. | |
1040 | @xref{Definition of file-attributes}. | |
1041 | @end defun | |
1042 | ||
1043 | @c Emacs 19 feature | |
1044 | @defun current-time-zone &optional time-value | |
1045 | This function returns a list describing the time zone that the user is | |
1046 | in. | |
1047 | ||
1048 | The value has the form @code{(@var{offset} @var{name})}. Here | |
1049 | @var{offset} is an integer giving the number of seconds ahead of UTC | |
1050 | (east of Greenwich). A negative value means west of Greenwich. The | |
1051 | second element, @var{name}, is a string giving the name of the time | |
1052 | zone. Both elements change when daylight saving time begins or ends; | |
1053 | if the user has specified a time zone that does not use a seasonal time | |
1054 | adjustment, then the value is constant through time. | |
1055 | ||
1056 | If the operating system doesn't supply all the information necessary to | |
1057 | compute the value, the unknown elements of the list are @code{nil}. | |
1058 | ||
1059 | The argument @var{time-value}, if given, specifies a time to analyze | |
1060 | instead of the current time. The argument should have the same form | |
1061 | as for @code{current-time-string} (see above). Thus, you can use | |
1062 | times obtained from @code{current-time} (see above) and from | |
1063 | @code{file-attributes}. @xref{Definition of file-attributes}. | |
1064 | @end defun | |
1065 | ||
1066 | @defun set-time-zone-rule tz | |
1067 | This function specifies the local time zone according to @var{tz}. If | |
1068 | @var{tz} is @code{nil}, that means to use an implementation-defined | |
1069 | default time zone. If @var{tz} is @code{t}, that means to use | |
1070 | Universal Time. Otherwise, @var{tz} should be a string specifying a | |
1071 | time zone rule. | |
1072 | @end defun | |
1073 | ||
1074 | @defun float-time &optional time-value | |
1075 | This function returns the current time as a floating-point number of | |
1076 | seconds since the epoch. The argument @var{time-value}, if given, | |
1077 | specifies a time to convert instead of the current time. The argument | |
1078 | should have the same form as for @code{current-time-string} (see | |
1079 | above). Thus, it accepts the output of @code{current-time} and | |
1080 | @code{file-attributes}. | |
1081 | ||
1082 | @emph{Warning}: Since the result is floating point, it may not be | |
1083 | exact. Do not use this function if precise time stamps are required. | |
1084 | @end defun | |
1085 | ||
1086 | @node Time Conversion | |
1087 | @section Time Conversion | |
1088 | ||
1089 | These functions convert time values (lists of two or three integers) | |
1090 | to calendrical information and vice versa. You can get time values | |
1091 | from the functions @code{current-time} (@pxref{Time of Day}) and | |
1092 | @code{file-attributes} (@pxref{Definition of file-attributes}). | |
1093 | ||
1094 | Many operating systems are limited to time values that contain 32 bits | |
1095 | of information; these systems typically handle only the times from | |
1096 | 1901-12-13 20:45:52 UTC through 2038-01-19 03:14:07 UTC. However, some | |
1097 | operating systems have larger time values, and can represent times far | |
1098 | in the past or future. | |
1099 | ||
1100 | Time conversion functions always use the Gregorian calendar, even | |
1101 | for dates before the Gregorian calendar was introduced. Year numbers | |
1102 | count the number of years since the year 1 B.C., and do not skip zero | |
1103 | as traditional Gregorian years do; for example, the year number | |
1104 | @minus{}37 represents the Gregorian year 38 B.C@. | |
1105 | ||
1106 | @defun decode-time &optional time | |
1107 | This function converts a time value into calendrical information. If | |
1108 | you don't specify @var{time}, it decodes the current time. The return | |
1109 | value is a list of nine elements, as follows: | |
1110 | ||
1111 | @example | |
1112 | (@var{seconds} @var{minutes} @var{hour} @var{day} @var{month} @var{year} @var{dow} @var{dst} @var{zone}) | |
1113 | @end example | |
1114 | ||
1115 | Here is what the elements mean: | |
1116 | ||
1117 | @table @var | |
1118 | @item seconds | |
1119 | The number of seconds past the minute, as an integer between 0 and 59. | |
1120 | On some operating systems, this is 60 for leap seconds. | |
1121 | @item minutes | |
1122 | The number of minutes past the hour, as an integer between 0 and 59. | |
1123 | @item hour | |
1124 | The hour of the day, as an integer between 0 and 23. | |
1125 | @item day | |
1126 | The day of the month, as an integer between 1 and 31. | |
1127 | @item month | |
1128 | The month of the year, as an integer between 1 and 12. | |
1129 | @item year | |
1130 | The year, an integer typically greater than 1900. | |
1131 | @item dow | |
1132 | The day of week, as an integer between 0 and 6, where 0 stands for | |
1133 | Sunday. | |
1134 | @item dst | |
1135 | @code{t} if daylight saving time is effect, otherwise @code{nil}. | |
1136 | @item zone | |
1137 | An integer indicating the time zone, as the number of seconds east of | |
1138 | Greenwich. | |
1139 | @end table | |
1140 | ||
1141 | @strong{Common Lisp Note:} Common Lisp has different meanings for | |
1142 | @var{dow} and @var{zone}. | |
1143 | @end defun | |
1144 | ||
1145 | @defun encode-time seconds minutes hour day month year &optional zone | |
1146 | This function is the inverse of @code{decode-time}. It converts seven | |
1147 | items of calendrical data into a time value. For the meanings of the | |
1148 | arguments, see the table above under @code{decode-time}. | |
1149 | ||
1150 | Year numbers less than 100 are not treated specially. If you want them | |
1151 | to stand for years above 1900, or years above 2000, you must alter them | |
1152 | yourself before you call @code{encode-time}. | |
1153 | ||
1154 | The optional argument @var{zone} defaults to the current time zone and | |
1155 | its daylight saving time rules. If specified, it can be either a list | |
1156 | (as you would get from @code{current-time-zone}), a string as in the | |
1157 | @code{TZ} environment variable, @code{t} for Universal Time, or an | |
1158 | integer (as you would get from @code{decode-time}). The specified | |
1159 | zone is used without any further alteration for daylight saving time. | |
1160 | ||
1161 | If you pass more than seven arguments to @code{encode-time}, the first | |
1162 | six are used as @var{seconds} through @var{year}, the last argument is | |
1163 | used as @var{zone}, and the arguments in between are ignored. This | |
1164 | feature makes it possible to use the elements of a list returned by | |
1165 | @code{decode-time} as the arguments to @code{encode-time}, like this: | |
1166 | ||
1167 | @example | |
1168 | (apply 'encode-time (decode-time @dots{})) | |
1169 | @end example | |
1170 | ||
1171 | You can perform simple date arithmetic by using out-of-range values for | |
1172 | the @var{seconds}, @var{minutes}, @var{hour}, @var{day}, and @var{month} | |
1173 | arguments; for example, day 0 means the day preceding the given month. | |
1174 | ||
1175 | The operating system puts limits on the range of possible time values; | |
1176 | if you try to encode a time that is out of range, an error results. | |
1177 | For instance, years before 1970 do not work on some systems; | |
1178 | on others, years as early as 1901 do work. | |
1179 | @end defun | |
1180 | ||
1181 | @node Time Parsing | |
1182 | @section Parsing and Formatting Times | |
1183 | ||
1184 | These functions convert time values (lists of two or three integers) | |
1185 | to text in a string, and vice versa. | |
1186 | ||
1187 | @defun date-to-time string | |
1188 | This function parses the time-string @var{string} and returns the | |
1189 | corresponding time value. | |
1190 | @end defun | |
1191 | ||
1192 | @defun format-time-string format-string &optional time universal | |
1193 | This function converts @var{time} (or the current time, if @var{time} is | |
1194 | omitted) to a string according to @var{format-string}. The argument | |
1195 | @var{format-string} may contain @samp{%}-sequences which say to | |
1196 | substitute parts of the time. Here is a table of what the | |
1197 | @samp{%}-sequences mean: | |
1198 | ||
1199 | @table @samp | |
1200 | @item %a | |
1201 | This stands for the abbreviated name of the day of week. | |
1202 | @item %A | |
1203 | This stands for the full name of the day of week. | |
1204 | @item %b | |
1205 | This stands for the abbreviated name of the month. | |
1206 | @item %B | |
1207 | This stands for the full name of the month. | |
1208 | @item %c | |
1209 | This is a synonym for @samp{%x %X}. | |
1210 | @item %C | |
1211 | This has a locale-specific meaning. In the default locale (named C), it | |
1212 | is equivalent to @samp{%A, %B %e, %Y}. | |
1213 | @item %d | |
1214 | This stands for the day of month, zero-padded. | |
1215 | @item %D | |
1216 | This is a synonym for @samp{%m/%d/%y}. | |
1217 | @item %e | |
1218 | This stands for the day of month, blank-padded. | |
1219 | @item %h | |
1220 | This is a synonym for @samp{%b}. | |
1221 | @item %H | |
1222 | This stands for the hour (00-23). | |
1223 | @item %I | |
1224 | This stands for the hour (01-12). | |
1225 | @item %j | |
1226 | This stands for the day of the year (001-366). | |
1227 | @item %k | |
1228 | This stands for the hour (0-23), blank padded. | |
1229 | @item %l | |
1230 | This stands for the hour (1-12), blank padded. | |
1231 | @item %m | |
1232 | This stands for the month (01-12). | |
1233 | @item %M | |
1234 | This stands for the minute (00-59). | |
1235 | @item %n | |
1236 | This stands for a newline. | |
1237 | @item %p | |
1238 | This stands for @samp{AM} or @samp{PM}, as appropriate. | |
1239 | @item %r | |
1240 | This is a synonym for @samp{%I:%M:%S %p}. | |
1241 | @item %R | |
1242 | This is a synonym for @samp{%H:%M}. | |
1243 | @item %S | |
1244 | This stands for the seconds (00-59). | |
1245 | @item %t | |
1246 | This stands for a tab character. | |
1247 | @item %T | |
1248 | This is a synonym for @samp{%H:%M:%S}. | |
1249 | @item %U | |
1250 | This stands for the week of the year (01-52), assuming that weeks | |
1251 | start on Sunday. | |
1252 | @item %w | |
1253 | This stands for the numeric day of week (0-6). Sunday is day 0. | |
1254 | @item %W | |
1255 | This stands for the week of the year (01-52), assuming that weeks | |
1256 | start on Monday. | |
1257 | @item %x | |
1258 | This has a locale-specific meaning. In the default locale (named | |
1259 | @samp{C}), it is equivalent to @samp{%D}. | |
1260 | @item %X | |
1261 | This has a locale-specific meaning. In the default locale (named | |
1262 | @samp{C}), it is equivalent to @samp{%T}. | |
1263 | @item %y | |
1264 | This stands for the year without century (00-99). | |
1265 | @item %Y | |
1266 | This stands for the year with century. | |
1267 | @item %Z | |
1268 | This stands for the time zone abbreviation (e.g., @samp{EST}). | |
1269 | @item %z | |
1270 | This stands for the time zone numerical offset (e.g., @samp{-0500}). | |
1271 | @end table | |
1272 | ||
1273 | You can also specify the field width and type of padding for any of | |
1274 | these @samp{%}-sequences. This works as in @code{printf}: you write | |
1275 | the field width as digits in the middle of a @samp{%}-sequences. If you | |
1276 | start the field width with @samp{0}, it means to pad with zeros. If you | |
1277 | start the field width with @samp{_}, it means to pad with spaces. | |
1278 | ||
1279 | For example, @samp{%S} specifies the number of seconds since the minute; | |
1280 | @samp{%03S} means to pad this with zeros to 3 positions, @samp{%_3S} to | |
1281 | pad with spaces to 3 positions. Plain @samp{%3S} pads with zeros, | |
1282 | because that is how @samp{%S} normally pads to two positions. | |
1283 | ||
1284 | The characters @samp{E} and @samp{O} act as modifiers when used between | |
1285 | @samp{%} and one of the letters in the table above. @samp{E} specifies | |
1286 | using the current locale's ``alternative'' version of the date and time. | |
1287 | In a Japanese locale, for example, @code{%Ex} might yield a date format | |
1288 | based on the Japanese Emperors' reigns. @samp{E} is allowed in | |
1289 | @samp{%Ec}, @samp{%EC}, @samp{%Ex}, @samp{%EX}, @samp{%Ey}, and | |
1290 | @samp{%EY}. | |
1291 | ||
1292 | @samp{O} means to use the current locale's ``alternative'' | |
1293 | representation of numbers, instead of the ordinary decimal digits. This | |
1294 | is allowed with most letters, all the ones that output numbers. | |
1295 | ||
1296 | If @var{universal} is non-@code{nil}, that means to describe the time as | |
1297 | Universal Time; @code{nil} means describe it using what Emacs believes | |
1298 | is the local time zone (see @code{current-time-zone}). | |
1299 | ||
1300 | This function uses the C library function @code{strftime} | |
1301 | (@pxref{Formatting Calendar Time,,, libc, The GNU C Library Reference | |
1302 | Manual}) to do most of the work. In order to communicate with that | |
1303 | function, it first encodes its argument using the coding system | |
1304 | specified by @code{locale-coding-system} (@pxref{Locales}); after | |
1305 | @code{strftime} returns the resulting string, | |
1306 | @code{format-time-string} decodes the string using that same coding | |
1307 | system. | |
1308 | @end defun | |
1309 | ||
1310 | @defun seconds-to-time seconds | |
1311 | This function converts @var{seconds}, a floating point number of | |
1312 | seconds since the epoch, to a time value and returns that. To perform | |
1313 | the inverse conversion, use @code{float-time}. | |
1314 | @end defun | |
1315 | ||
1316 | @node Processor Run Time | |
1317 | @section Processor Run time | |
1318 | @cindex processor run time | |
1319 | ||
1320 | @defun get-internal-run-time | |
1321 | This function returns the processor run time used by Emacs as a list | |
1322 | of three integers: @code{(@var{high} @var{low} @var{microsec})}. The | |
1323 | integers @var{high} and @var{low} combine to give the number of | |
1324 | seconds, which is | |
1325 | @ifnottex | |
1326 | @var{high} * 2**16 + @var{low}. | |
1327 | @end ifnottex | |
1328 | @tex | |
1329 | $high*2^{16}+low$. | |
1330 | @end tex | |
1331 | ||
1332 | The third element, @var{microsec}, gives the microseconds (or 0 for | |
1333 | systems that return time with the resolution of only one second). | |
1334 | ||
1335 | If the system doesn't provide a way to determine the processor run | |
1336 | time, get-internal-run-time returns the same time as current-time. | |
1337 | @end defun | |
1338 | ||
1339 | @node Time Calculations | |
1340 | @section Time Calculations | |
1341 | ||
1342 | These functions perform calendrical computations using time values | |
1343 | (the kind of list that @code{current-time} returns). | |
1344 | ||
1345 | @defun time-less-p t1 t2 | |
1346 | This returns @code{t} if time value @var{t1} is less than time value | |
1347 | @var{t2}. | |
1348 | @end defun | |
1349 | ||
1350 | @defun time-subtract t1 t2 | |
1351 | This returns the time difference @var{t1} @minus{} @var{t2} between | |
1352 | two time values, in the same format as a time value. | |
1353 | @end defun | |
1354 | ||
1355 | @defun time-add t1 t2 | |
1356 | This returns the sum of two time values, one of which ought to | |
1357 | represent a time difference rather than a point in time. | |
1358 | Here is how to add a number of seconds to a time value: | |
1359 | ||
1360 | @example | |
1361 | (time-add @var{time} (seconds-to-time @var{seconds})) | |
1362 | @end example | |
1363 | @end defun | |
1364 | ||
1365 | @defun time-to-days time | |
1366 | This function returns the number of days between the beginning of year | |
1367 | 1 and @var{time}. | |
1368 | @end defun | |
1369 | ||
1370 | @defun time-to-day-in-year time | |
1371 | This returns the day number within the year corresponding to @var{time}. | |
1372 | @end defun | |
1373 | ||
1374 | @defun date-leap-year-p year | |
1375 | This function returns @code{t} if @var{year} is a leap year. | |
1376 | @end defun | |
1377 | ||
1378 | @node Timers | |
1379 | @section Timers for Delayed Execution | |
1380 | @cindex timer | |
1381 | ||
1382 | You can set up a @dfn{timer} to call a function at a specified | |
1383 | future time or after a certain length of idleness. | |
1384 | ||
1385 | Emacs cannot run timers at any arbitrary point in a Lisp program; it | |
1386 | can run them only when Emacs could accept output from a subprocess: | |
1387 | namely, while waiting or inside certain primitive functions such as | |
1388 | @code{sit-for} or @code{read-event} which @emph{can} wait. Therefore, a | |
1389 | timer's execution may be delayed if Emacs is busy. However, the time of | |
1390 | execution is very precise if Emacs is idle. | |
1391 | ||
1392 | Emacs binds @code{inhibit-quit} to @code{t} before calling the timer | |
1393 | function, because quitting out of many timer functions can leave | |
1394 | things in an inconsistent state. This is normally unproblematical | |
1395 | because most timer functions don't do a lot of work. Indeed, for a | |
1396 | timer to call a function that takes substantial time to run is likely | |
1397 | to be annoying. If a timer function needs to allow quitting, it | |
1398 | should use @code{with-local-quit} (@pxref{Quitting}). For example, if | |
1399 | a timer function calls @code{accept-process-output} to receive output | |
1400 | from an external process, that call should be wrapped inside | |
1401 | @code{with-local-quit}, to ensure that @kbd{C-g} works if the external | |
1402 | process hangs. | |
1403 | ||
1404 | It is usually a bad idea for timer functions to alter buffer | |
1405 | contents. When they do, they usually should call @code{undo-boundary} | |
1406 | both before and after changing the buffer, to separate the timer's | |
1407 | changes from user commands' changes and prevent a single undo entry | |
1408 | from growing to be quite large. | |
1409 | ||
1410 | Timer functions should also avoid calling functions that cause Emacs | |
1411 | to wait, such as @code{sit-for} (@pxref{Waiting}). This can lead to | |
1412 | unpredictable effects, since other timers (or even the same timer) can | |
1413 | run while waiting. If a timer function needs to perform an action | |
1414 | after a certain time has elapsed, it can do this by scheduling a new | |
1415 | timer. | |
1416 | ||
1417 | If a timer function calls functions that can change the match data, | |
1418 | it should save and restore the match data. @xref{Saving Match Data}. | |
1419 | ||
1420 | @deffn Command run-at-time time repeat function &rest args | |
1421 | This sets up a timer that calls the function @var{function} with | |
1422 | arguments @var{args} at time @var{time}. If @var{repeat} is a number | |
1423 | (integer or floating point), the timer is scheduled to run again every | |
1424 | @var{repeat} seconds after @var{time}. If @var{repeat} is @code{nil}, | |
1425 | the timer runs only once. | |
1426 | ||
1427 | @var{time} may specify an absolute or a relative time. | |
1428 | ||
1429 | Absolute times may be specified using a string with a limited variety | |
1430 | of formats, and are taken to be times @emph{today}, even if already in | |
1431 | the past. The recognized forms are @samp{@var{xxxx}}, | |
1432 | @samp{@var{x}:@var{xx}}, or @samp{@var{xx}:@var{xx}} (military time), | |
1433 | and @samp{@var{xx}am}, @samp{@var{xx}AM}, @samp{@var{xx}pm}, | |
1434 | @samp{@var{xx}PM}, @samp{@var{xx}:@var{xx}am}, | |
1435 | @samp{@var{xx}:@var{xx}AM}, @samp{@var{xx}:@var{xx}pm}, or | |
1436 | @samp{@var{xx}:@var{xx}PM}. A period can be used instead of a colon | |
1437 | to separate the hour and minute parts. | |
1438 | ||
1439 | To specify a relative time as a string, use numbers followed by units. | |
1440 | For example: | |
1441 | ||
1442 | @table @samp | |
1443 | @item 1 min | |
1444 | denotes 1 minute from now. | |
1445 | @item 1 min 5 sec | |
1446 | denotes 65 seconds from now. | |
1447 | @item 1 min 2 sec 3 hour 4 day 5 week 6 fortnight 7 month 8 year | |
1448 | denotes exactly 103 months, 123 days, and 10862 seconds from now. | |
1449 | @end table | |
1450 | ||
1451 | For relative time values, Emacs considers a month to be exactly thirty | |
1452 | days, and a year to be exactly 365.25 days. | |
1453 | ||
1454 | Not all convenient formats are strings. If @var{time} is a number | |
1455 | (integer or floating point), that specifies a relative time measured in | |
1456 | seconds. The result of @code{encode-time} can also be used to specify | |
1457 | an absolute value for @var{time}. | |
1458 | ||
1459 | In most cases, @var{repeat} has no effect on when @emph{first} call | |
1460 | takes place---@var{time} alone specifies that. There is one exception: | |
1461 | if @var{time} is @code{t}, then the timer runs whenever the time is a | |
1462 | multiple of @var{repeat} seconds after the epoch. This is useful for | |
1463 | functions like @code{display-time}. | |
1464 | ||
1465 | The function @code{run-at-time} returns a timer value that identifies | |
1466 | the particular scheduled future action. You can use this value to call | |
1467 | @code{cancel-timer} (see below). | |
1468 | @end deffn | |
1469 | ||
1470 | A repeating timer nominally ought to run every @var{repeat} seconds, | |
1471 | but remember that any invocation of a timer can be late. Lateness of | |
1472 | one repetition has no effect on the scheduled time of the next | |
1473 | repetition. For instance, if Emacs is busy computing for long enough | |
1474 | to cover three scheduled repetitions of the timer, and then starts to | |
1475 | wait, it will immediately call the timer function three times in | |
1476 | immediate succession (presuming no other timers trigger before or | |
1477 | between them). If you want a timer to run again no less than @var{n} | |
1478 | seconds after the last invocation, don't use the @var{repeat} argument. | |
1479 | Instead, the timer function should explicitly reschedule the timer. | |
1480 | ||
1481 | @defvar timer-max-repeats | |
1482 | This variable's value specifies the maximum number of times to repeat | |
1483 | calling a timer function in a row, when many previously scheduled | |
1484 | calls were unavoidably delayed. | |
1485 | @end defvar | |
1486 | ||
1487 | @defmac with-timeout (seconds timeout-forms@dots{}) body@dots{} | |
1488 | Execute @var{body}, but give up after @var{seconds} seconds. If | |
1489 | @var{body} finishes before the time is up, @code{with-timeout} returns | |
1490 | the value of the last form in @var{body}. If, however, the execution of | |
1491 | @var{body} is cut short by the timeout, then @code{with-timeout} | |
1492 | executes all the @var{timeout-forms} and returns the value of the last | |
1493 | of them. | |
1494 | ||
1495 | This macro works by setting a timer to run after @var{seconds} seconds. If | |
1496 | @var{body} finishes before that time, it cancels the timer. If the | |
1497 | timer actually runs, it terminates execution of @var{body}, then | |
1498 | executes @var{timeout-forms}. | |
1499 | ||
1500 | Since timers can run within a Lisp program only when the program calls a | |
1501 | primitive that can wait, @code{with-timeout} cannot stop executing | |
1502 | @var{body} while it is in the midst of a computation---only when it | |
1503 | calls one of those primitives. So use @code{with-timeout} only with a | |
1504 | @var{body} that waits for input, not one that does a long computation. | |
1505 | @end defmac | |
1506 | ||
1507 | The function @code{y-or-n-p-with-timeout} provides a simple way to use | |
1508 | a timer to avoid waiting too long for an answer. @xref{Yes-or-No | |
1509 | Queries}. | |
1510 | ||
1511 | @defun cancel-timer timer | |
1512 | This cancels the requested action for @var{timer}, which should be a | |
1513 | timer---usually, one previously returned by @code{run-at-time} or | |
1514 | @code{run-with-idle-timer}. This cancels the effect of that call to | |
1515 | one of these functions; the arrival of the specified time will not | |
1516 | cause anything special to happen. | |
1517 | @end defun | |
1518 | ||
1519 | @node Idle Timers | |
1520 | @section Idle Timers | |
1521 | ||
1522 | Here is how to set up a timer that runs when Emacs is idle for a | |
1523 | certain length of time. Aside from how to set them up, idle timers | |
1524 | work just like ordinary timers. | |
1525 | ||
1526 | @deffn Command run-with-idle-timer secs repeat function &rest args | |
1527 | Set up a timer which runs when Emacs has been idle for @var{secs} | |
1528 | seconds. The value of @var{secs} may be an integer or a floating point | |
1529 | number; a value of the type returned by @code{current-idle-time} | |
1530 | is also allowed. | |
1531 | ||
1532 | If @var{repeat} is @code{nil}, the timer runs just once, the first time | |
1533 | Emacs remains idle for a long enough time. More often @var{repeat} is | |
1534 | non-@code{nil}, which means to run the timer @emph{each time} Emacs | |
1535 | remains idle for @var{secs} seconds. | |
1536 | ||
1537 | The function @code{run-with-idle-timer} returns a timer value which you | |
1538 | can use in calling @code{cancel-timer} (@pxref{Timers}). | |
1539 | @end deffn | |
1540 | ||
1541 | @cindex idleness | |
1542 | Emacs becomes ``idle'' when it starts waiting for user input, and it | |
1543 | remains idle until the user provides some input. If a timer is set for | |
1544 | five seconds of idleness, it runs approximately five seconds after Emacs | |
1545 | first becomes idle. Even if @var{repeat} is non-@code{nil}, this timer | |
1546 | will not run again as long as Emacs remains idle, because the duration | |
1547 | of idleness will continue to increase and will not go down to five | |
1548 | seconds again. | |
1549 | ||
1550 | Emacs can do various things while idle: garbage collect, autosave or | |
1551 | handle data from a subprocess. But these interludes during idleness do | |
1552 | not interfere with idle timers, because they do not reset the clock of | |
1553 | idleness to zero. An idle timer set for 600 seconds will run when ten | |
1554 | minutes have elapsed since the last user command was finished, even if | |
1555 | subprocess output has been accepted thousands of times within those ten | |
1556 | minutes, and even if there have been garbage collections and autosaves. | |
1557 | ||
1558 | When the user supplies input, Emacs becomes non-idle while executing the | |
1559 | input. Then it becomes idle again, and all the idle timers that are | |
1560 | set up to repeat will subsequently run another time, one by one. | |
1561 | ||
1562 | @c Emacs 19 feature | |
1563 | @defun current-idle-time | |
1564 | This function returns the length of time Emacs has been idle, as a | |
1565 | list of three integers: @code{(@var{high} @var{low} @var{microsec})}. | |
1566 | The integers @var{high} and @var{low} combine to give the number of | |
1567 | seconds of idleness, which is | |
1568 | @ifnottex | |
1569 | @var{high} * 2**16 + @var{low}. | |
1570 | @end ifnottex | |
1571 | @tex | |
1572 | $high*2^{16}+low$. | |
1573 | @end tex | |
1574 | ||
1575 | The third element, @var{microsec}, gives the microseconds since the | |
1576 | start of the current second (or 0 for systems that return time with | |
1577 | the resolution of only one second). | |
1578 | ||
1579 | The main use of this function is when an idle timer function wants to | |
1580 | ``take a break'' for a while. It can set up another idle timer to | |
1581 | call the same function again, after a few seconds more idleness. | |
1582 | Here's an example: | |
1583 | ||
1584 | @smallexample | |
1585 | (defvar resume-timer nil | |
1586 | "Timer that `timer-function' used to reschedule itself, or nil.") | |
1587 | ||
1588 | (defun timer-function () | |
1589 | ;; @r{If the user types a command while @code{resume-timer}} | |
1590 | ;; @r{is active, the next time this function is called from} | |
1591 | ;; @r{its main idle timer, deactivate @code{resume-timer}.} | |
1592 | (when resume-timer | |
1593 | (cancel-timer resume-timer)) | |
1594 | ...@var{do the work for a while}... | |
1595 | (when @var{taking-a-break} | |
1596 | (setq resume-timer | |
1597 | (run-with-idle-timer | |
1598 | ;; Compute an idle time @var{break-length} | |
1599 | ;; more than the current value. | |
1600 | (time-add (current-idle-time) | |
1601 | (seconds-to-time @var{break-length})) | |
1602 | nil | |
1603 | 'timer-function)))) | |
1604 | @end smallexample | |
1605 | @end defun | |
1606 | ||
1607 | Some idle timer functions in user Lisp packages have a loop that | |
1608 | does a certain amount of processing each time around, and exits when | |
1609 | @code{(input-pending-p)} is non-@code{nil}. That approach seems very | |
1610 | natural but has two problems: | |
1611 | ||
1612 | @itemize | |
1613 | @item | |
1614 | It blocks out all process output (since Emacs accepts process output | |
1615 | only while waiting). | |
1616 | ||
1617 | @item | |
1618 | It blocks out any idle timers that ought to run during that time. | |
1619 | @end itemize | |
1620 | ||
1621 | @noindent | |
1622 | To avoid these problems, don't use that technique. Instead, write | |
1623 | such idle timers to reschedule themselves after a brief pause, using | |
1624 | the method in the @code{timer-function} example above. | |
1625 | ||
1626 | @node Terminal Input | |
1627 | @section Terminal Input | |
1628 | @cindex terminal input | |
1629 | ||
1630 | This section describes functions and variables for recording or | |
1631 | manipulating terminal input. See @ref{Display}, for related | |
1632 | functions. | |
1633 | ||
1634 | @menu | |
1635 | * Input Modes:: Options for how input is processed. | |
1636 | * Recording Input:: Saving histories of recent or all input events. | |
1637 | @end menu | |
1638 | ||
1639 | @node Input Modes | |
1640 | @subsection Input Modes | |
1641 | @cindex input modes | |
1642 | @cindex terminal input modes | |
1643 | ||
1644 | @defun set-input-mode interrupt flow meta &optional quit-char | |
1645 | This function sets the mode for reading keyboard input. If | |
1646 | @var{interrupt} is non-null, then Emacs uses input interrupts. If it is | |
1647 | @code{nil}, then it uses @sc{cbreak} mode. The default setting is | |
1648 | system-dependent. Some systems always use @sc{cbreak} mode regardless | |
1649 | of what is specified. | |
1650 | ||
1651 | When Emacs communicates directly with X, it ignores this argument and | |
1652 | uses interrupts if that is the way it knows how to communicate. | |
1653 | ||
1654 | If @var{flow} is non-@code{nil}, then Emacs uses @sc{xon/xoff} | |
1655 | (@kbd{C-q}, @kbd{C-s}) flow control for output to the terminal. This | |
1656 | has no effect except in @sc{cbreak} mode. | |
1657 | ||
1658 | @c Emacs 19 feature | |
1659 | The argument @var{meta} controls support for input character codes | |
1660 | above 127. If @var{meta} is @code{t}, Emacs converts characters with | |
1661 | the 8th bit set into Meta characters. If @var{meta} is @code{nil}, | |
1662 | Emacs disregards the 8th bit; this is necessary when the terminal uses | |
1663 | it as a parity bit. If @var{meta} is neither @code{t} nor @code{nil}, | |
1664 | Emacs uses all 8 bits of input unchanged. This is good for terminals | |
1665 | that use 8-bit character sets. | |
1666 | ||
1667 | @c Emacs 19 feature | |
1668 | If @var{quit-char} is non-@code{nil}, it specifies the character to | |
1669 | use for quitting. Normally this character is @kbd{C-g}. | |
1670 | @xref{Quitting}. | |
1671 | @end defun | |
1672 | ||
1673 | The @code{current-input-mode} function returns the input mode settings | |
1674 | Emacs is currently using. | |
1675 | ||
1676 | @c Emacs 19 feature | |
1677 | @defun current-input-mode | |
1678 | This function returns the current mode for reading keyboard input. It | |
1679 | returns a list, corresponding to the arguments of @code{set-input-mode}, | |
1680 | of the form @code{(@var{interrupt} @var{flow} @var{meta} @var{quit})} in | |
1681 | which: | |
1682 | @table @var | |
1683 | @item interrupt | |
1684 | is non-@code{nil} when Emacs is using interrupt-driven input. If | |
1685 | @code{nil}, Emacs is using @sc{cbreak} mode. | |
1686 | @item flow | |
1687 | is non-@code{nil} if Emacs uses @sc{xon/xoff} (@kbd{C-q}, @kbd{C-s}) | |
1688 | flow control for output to the terminal. This value is meaningful only | |
1689 | when @var{interrupt} is @code{nil}. | |
1690 | @item meta | |
1691 | is @code{t} if Emacs treats the eighth bit of input characters as | |
1692 | the meta bit; @code{nil} means Emacs clears the eighth bit of every | |
1693 | input character; any other value means Emacs uses all eight bits as the | |
1694 | basic character code. | |
1695 | @item quit | |
1696 | is the character Emacs currently uses for quitting, usually @kbd{C-g}. | |
1697 | @end table | |
1698 | @end defun | |
1699 | ||
1700 | @node Recording Input | |
1701 | @subsection Recording Input | |
1702 | @cindex recording input | |
1703 | ||
1704 | @defun recent-keys | |
1705 | This function returns a vector containing the last 300 input events from | |
1706 | the keyboard or mouse. All input events are included, whether or not | |
1707 | they were used as parts of key sequences. Thus, you always get the last | |
1708 | 100 input events, not counting events generated by keyboard macros. | |
1709 | (These are excluded because they are less interesting for debugging; it | |
1710 | should be enough to see the events that invoked the macros.) | |
1711 | ||
1712 | A call to @code{clear-this-command-keys} (@pxref{Command Loop Info}) | |
1713 | causes this function to return an empty vector immediately afterward. | |
1714 | @end defun | |
1715 | ||
1716 | @deffn Command open-dribble-file filename | |
1717 | @cindex dribble file | |
1718 | This function opens a @dfn{dribble file} named @var{filename}. When a | |
1719 | dribble file is open, each input event from the keyboard or mouse (but | |
1720 | not those from keyboard macros) is written in that file. A | |
1721 | non-character event is expressed using its printed representation | |
1722 | surrounded by @samp{<@dots{}>}. | |
1723 | ||
1724 | You close the dribble file by calling this function with an argument | |
1725 | of @code{nil}. | |
1726 | ||
1727 | This function is normally used to record the input necessary to | |
1728 | trigger an Emacs bug, for the sake of a bug report. | |
1729 | ||
1730 | @example | |
1731 | @group | |
1732 | (open-dribble-file "~/dribble") | |
1733 | @result{} nil | |
1734 | @end group | |
1735 | @end example | |
1736 | @end deffn | |
1737 | ||
1738 | See also the @code{open-termscript} function (@pxref{Terminal Output}). | |
1739 | ||
1740 | @node Terminal Output | |
1741 | @section Terminal Output | |
1742 | @cindex terminal output | |
1743 | ||
1744 | The terminal output functions send output to a text terminal, or keep | |
1745 | track of output sent to the terminal. The variable @code{baud-rate} | |
1746 | tells you what Emacs thinks is the output speed of the terminal. | |
1747 | ||
1748 | @defvar baud-rate | |
1749 | This variable's value is the output speed of the terminal, as far as | |
1750 | Emacs knows. Setting this variable does not change the speed of actual | |
1751 | data transmission, but the value is used for calculations such as | |
1752 | padding. | |
1753 | ||
1754 | It also affects decisions about whether to scroll part of the | |
1755 | screen or repaint on text terminals. @xref{Forcing Redisplay}, | |
1756 | for the corresponding functionality on graphical terminals. | |
1757 | ||
1758 | The value is measured in baud. | |
1759 | @end defvar | |
1760 | ||
1761 | If you are running across a network, and different parts of the | |
1762 | network work at different baud rates, the value returned by Emacs may be | |
1763 | different from the value used by your local terminal. Some network | |
1764 | protocols communicate the local terminal speed to the remote machine, so | |
1765 | that Emacs and other programs can get the proper value, but others do | |
1766 | not. If Emacs has the wrong value, it makes decisions that are less | |
1767 | than optimal. To fix the problem, set @code{baud-rate}. | |
1768 | ||
1769 | @defun baud-rate | |
1770 | This obsolete function returns the value of the variable | |
1771 | @code{baud-rate}. | |
1772 | @end defun | |
1773 | ||
1774 | @defun send-string-to-terminal string | |
1775 | This function sends @var{string} to the terminal without alteration. | |
1776 | Control characters in @var{string} have terminal-dependent effects. | |
1777 | This function operates only on text terminals. | |
1778 | ||
1779 | One use of this function is to define function keys on terminals that | |
1780 | have downloadable function key definitions. For example, this is how (on | |
1781 | certain terminals) to define function key 4 to move forward four | |
1782 | characters (by transmitting the characters @kbd{C-u C-f} to the | |
1783 | computer): | |
1784 | ||
1785 | @example | |
1786 | @group | |
1787 | (send-string-to-terminal "\eF4\^U\^F") | |
1788 | @result{} nil | |
1789 | @end group | |
1790 | @end example | |
1791 | @end defun | |
1792 | ||
1793 | @deffn Command open-termscript filename | |
1794 | @cindex termscript file | |
1795 | This function is used to open a @dfn{termscript file} that will record | |
1796 | all the characters sent by Emacs to the terminal. It returns | |
1797 | @code{nil}. Termscript files are useful for investigating problems | |
1798 | where Emacs garbles the screen, problems that are due to incorrect | |
1799 | Termcap entries or to undesirable settings of terminal options more | |
1800 | often than to actual Emacs bugs. Once you are certain which characters | |
1801 | were actually output, you can determine reliably whether they correspond | |
1802 | to the Termcap specifications in use. | |
1803 | ||
1804 | You close the termscript file by calling this function with an | |
1805 | argument of @code{nil}. | |
1806 | ||
1807 | See also @code{open-dribble-file} in @ref{Recording Input}. | |
1808 | ||
1809 | @example | |
1810 | @group | |
1811 | (open-termscript "../junk/termscript") | |
1812 | @result{} nil | |
1813 | @end group | |
1814 | @end example | |
1815 | @end deffn | |
1816 | ||
1817 | @node Sound Output | |
1818 | @section Sound Output | |
1819 | @cindex sound | |
1820 | ||
1821 | To play sound using Emacs, use the function @code{play-sound}. Only | |
1822 | certain systems are supported; if you call @code{play-sound} on a system | |
1823 | which cannot really do the job, it gives an error. Emacs version 20 and | |
1824 | earlier did not support sound at all. | |
1825 | ||
1826 | The sound must be stored as a file in RIFF-WAVE format (@samp{.wav}) | |
1827 | or Sun Audio format (@samp{.au}). | |
1828 | ||
1829 | @defun play-sound sound | |
1830 | This function plays a specified sound. The argument, @var{sound}, has | |
1831 | the form @code{(sound @var{properties}...)}, where the @var{properties} | |
1832 | consist of alternating keywords (particular symbols recognized | |
1833 | specially) and values corresponding to them. | |
1834 | ||
1835 | Here is a table of the keywords that are currently meaningful in | |
1836 | @var{sound}, and their meanings: | |
1837 | ||
1838 | @table @code | |
1839 | @item :file @var{file} | |
1840 | This specifies the file containing the sound to play. | |
1841 | If the file name is not absolute, it is expanded against | |
1842 | the directory @code{data-directory}. | |
1843 | ||
1844 | @item :data @var{data} | |
1845 | This specifies the sound to play without need to refer to a file. The | |
1846 | value, @var{data}, should be a string containing the same bytes as a | |
1847 | sound file. We recommend using a unibyte string. | |
1848 | ||
1849 | @item :volume @var{volume} | |
1850 | This specifies how loud to play the sound. It should be a number in the | |
1851 | range of 0 to 1. The default is to use whatever volume has been | |
1852 | specified before. | |
1853 | ||
1854 | @item :device @var{device} | |
1855 | This specifies the system device on which to play the sound, as a | |
1856 | string. The default device is system-dependent. | |
1857 | @end table | |
1858 | ||
1859 | Before actually playing the sound, @code{play-sound} | |
1860 | calls the functions in the list @code{play-sound-functions}. | |
1861 | Each function is called with one argument, @var{sound}. | |
1862 | @end defun | |
1863 | ||
1864 | @defun play-sound-file file &optional volume device | |
1865 | This function is an alternative interface to playing a sound @var{file} | |
1866 | specifying an optional @var{volume} and @var{device}. | |
1867 | @end defun | |
1868 | ||
1869 | @defvar play-sound-functions | |
1870 | A list of functions to be called before playing a sound. Each function | |
1871 | is called with one argument, a property list that describes the sound. | |
1872 | @end defvar | |
1873 | ||
1874 | @node X11 Keysyms | |
1875 | @section Operating on X11 Keysyms | |
1876 | @cindex X11 keysyms | |
1877 | ||
1878 | To define system-specific X11 keysyms, set the variable | |
1879 | @code{system-key-alist}. | |
1880 | ||
1881 | @defvar system-key-alist | |
1882 | This variable's value should be an alist with one element for each | |
1883 | system-specific keysym. Each element has the form @code{(@var{code} | |
1884 | . @var{symbol})}, where @var{code} is the numeric keysym code (not | |
1885 | including the ``vendor specific'' bit, | |
1886 | @ifnottex | |
1887 | -2**28), | |
1888 | @end ifnottex | |
1889 | @tex | |
1890 | $-2^{28}$), | |
1891 | @end tex | |
1892 | and @var{symbol} is the name for the function key. | |
1893 | ||
1894 | For example @code{(168 . mute-acute)} defines a system-specific key (used | |
1895 | by HP X servers) whose numeric code is | |
1896 | @ifnottex | |
1897 | -2**28 | |
1898 | @end ifnottex | |
1899 | @tex | |
1900 | $-2^{28}$ | |
1901 | @end tex | |
1902 | + 168. | |
1903 | ||
1904 | It is not crucial to exclude from the alist the keysyms of other X | |
1905 | servers; those do no harm, as long as they don't conflict with the ones | |
1906 | used by the X server actually in use. | |
1907 | ||
1908 | The variable is always local to the current terminal, and cannot be | |
1909 | buffer-local. @xref{Multiple Displays}. | |
1910 | @end defvar | |
1911 | ||
1912 | You can specify which keysyms Emacs should use for the Meta, Alt, Hyper, and Super modifiers by setting these variables: | |
1913 | ||
1914 | @defvar x-alt-keysym | |
1915 | @defvarx x-meta-keysym | |
1916 | @defvarx x-hyper-keysym | |
1917 | @defvarx x-super-keysym | |
1918 | The name of the keysym that should stand for the Alt modifier | |
1919 | (respectively, for Meta, Hyper, and Super). For example, here is | |
1920 | how to swap the Meta and Alt modifiers within Emacs: | |
1921 | @lisp | |
1922 | (setq x-alt-keysym 'meta) | |
1923 | (setq x-meta-keysym 'alt) | |
1924 | @end lisp | |
1925 | @end defvar | |
1926 | ||
1927 | @node Batch Mode | |
1928 | @section Batch Mode | |
1929 | @cindex batch mode | |
1930 | ||
1931 | The command-line option @samp{-batch} causes Emacs to run | |
1932 | noninteractively. In this mode, Emacs does not read commands from the | |
1933 | terminal, it does not alter the terminal modes, and it does not expect | |
1934 | to be outputting to an erasable screen. The idea is that you specify | |
1935 | Lisp programs to run; when they are finished, Emacs should exit. The | |
1936 | way to specify the programs to run is with @samp{-l @var{file}}, which | |
1937 | loads the library named @var{file}, or @samp{-f @var{function}}, which | |
1938 | calls @var{function} with no arguments, or @samp{--eval @var{form}}. | |
1939 | ||
1940 | Any Lisp program output that would normally go to the echo area, | |
1941 | either using @code{message}, or using @code{prin1}, etc., with @code{t} | |
1942 | as the stream, goes instead to Emacs's standard error descriptor when | |
1943 | in batch mode. Similarly, input that would normally come from the | |
1944 | minibuffer is read from the standard input descriptor. | |
1945 | Thus, Emacs behaves much like a noninteractive | |
1946 | application program. (The echo area output that Emacs itself normally | |
1947 | generates, such as command echoing, is suppressed entirely.) | |
1948 | ||
1949 | @defvar noninteractive | |
1950 | This variable is non-@code{nil} when Emacs is running in batch mode. | |
1951 | @end defvar | |
1952 | ||
1953 | @node Session Management | |
1954 | @section Session Management | |
1955 | @cindex session manager | |
1956 | ||
1957 | Emacs supports the X Session Management Protocol for suspension and | |
1958 | restart of applications. In the X Window System, a program called the | |
1959 | @dfn{session manager} has the responsibility to keep track of the | |
1960 | applications that are running. During shutdown, the session manager | |
1961 | asks applications to save their state, and delays the actual shutdown | |
1962 | until they respond. An application can also cancel the shutdown. | |
1963 | ||
1964 | When the session manager restarts a suspended session, it directs | |
1965 | these applications to individually reload their saved state. It does | |
1966 | this by specifying a special command-line argument that says what | |
1967 | saved session to restore. For Emacs, this argument is @samp{--smid | |
1968 | @var{session}}. | |
1969 | ||
1970 | @defvar emacs-save-session-functions | |
1971 | Emacs supports saving state by using a hook called | |
1972 | @code{emacs-save-session-functions}. Each function in this hook is | |
1973 | called when the session manager tells Emacs that the window system is | |
1974 | shutting down. The functions are called with no arguments and with the | |
1975 | current buffer set to a temporary buffer. Each function can use | |
1976 | @code{insert} to add Lisp code to this buffer. At the end, Emacs | |
1977 | saves the buffer in a file that a subsequent Emacs invocation will | |
1978 | load in order to restart the saved session. | |
1979 | ||
1980 | If a function in @code{emacs-save-session-functions} returns | |
1981 | non-@code{nil}, Emacs tells the session manager to cancel the | |
1982 | shutdown. | |
1983 | @end defvar | |
1984 | ||
1985 | Here is an example that just inserts some text into @samp{*scratch*} when | |
1986 | Emacs is restarted by the session manager. | |
1987 | ||
1988 | @example | |
1989 | @group | |
1990 | (add-hook 'emacs-save-session-functions 'save-yourself-test) | |
1991 | @end group | |
1992 | ||
1993 | @group | |
1994 | (defun save-yourself-test () | |
1995 | (insert "(save-excursion | |
1996 | (switch-to-buffer \"*scratch*\") | |
1997 | (insert \"I am restored\"))") | |
1998 | nil) | |
1999 | @end group | |
2000 | @end example | |
2001 | ||
2002 | @ignore | |
2003 | arch-tag: 8378814a-30d7-467c-9615-74a80b9988a7 | |
2004 | @end ignore |