Commit | Line | Data |
---|---|---|
b8d4c8d0 GM |
1 | @c -*-texinfo-*- |
2 | @c This is part of the GNU Emacs Lisp Reference Manual. | |
acaf905b | 3 | @c Copyright (C) 1990-1995, 1998-1999, 2001-2012 |
d24880de | 4 | @c Free Software Foundation, Inc. |
b8d4c8d0 | 5 | @c See the file elisp.texi for copying conditions. |
6336d8c3 | 6 | @setfilename ../../info/os |
fdc76236 | 7 | @node System Interface, Packaging, Display, Top |
b8d4c8d0 GM |
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 | ||
02a89103 CY |
14 | @xref{Building Emacs}, for related information. @xref{Display}, for |
15 | additional operating system status information pertaining to the | |
16 | terminal and the screen. | |
b8d4c8d0 GM |
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. | |
d24880de | 23 | * Time of Day:: Getting the current time. |
a4180391 | 24 | * Time Conversion:: Converting a time from numeric form to |
3be92e63 | 25 | calendrical data and vice versa. |
b8d4c8d0 GM |
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. | |
d24880de | 30 | * Timers:: Setting a timer to call a function at a certain time. |
b8d4c8d0 GM |
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. | |
8e69dc70 | 36 | * X11 Keysyms:: Operating on key symbols for X Windows. |
b8d4c8d0 GM |
37 | * Batch Mode:: Running Emacs without terminal interaction. |
38 | * Session Management:: Saving and restoring state with X Session Management. | |
00f113eb | 39 | * Dynamic Libraries:: On-demand loading of support libraries. |
b8d4c8d0 GM |
40 | @end menu |
41 | ||
42 | @node Starting Up | |
43 | @section Starting Up Emacs | |
44 | ||
45 | This section describes what Emacs does when it is started, and how you | |
46 | can customize these actions. | |
47 | ||
48 | @menu | |
49 | * Startup Summary:: Sequence of actions Emacs performs at startup. | |
02a89103 | 50 | * Init File:: Details on reading the init file. |
b8d4c8d0 GM |
51 | * Terminal-Specific:: How the terminal-specific Lisp file is read. |
52 | * Command-Line Arguments:: How command-line arguments are processed, | |
53 | and how you can customize them. | |
54 | @end menu | |
55 | ||
56 | @node Startup Summary | |
57 | @subsection Summary: Sequence of Actions at Startup | |
58 | @cindex initialization of Emacs | |
59 | @cindex startup of Emacs | |
60 | @cindex @file{startup.el} | |
61 | ||
02a89103 CY |
62 | When Emacs is started up, it performs the following operations |
63 | (which are defined in @file{startup.el}): | |
b8d4c8d0 GM |
64 | |
65 | @enumerate | |
66 | @item | |
67 | It adds subdirectories to @code{load-path}, by running the file named | |
02a89103 CY |
68 | @file{subdirs.el} in each directory in the list. Normally, this file |
69 | adds the directory's subdirectories to the list, and those are scanned | |
70 | in their turn. The files @file{subdirs.el} are normally generated | |
71 | automatically when Emacs is installed. | |
b8d4c8d0 | 72 | |
f36acfd9 | 73 | @vindex before-init-time |
b8d4c8d0 | 74 | @item |
02a89103 | 75 | It sets the variable @code{before-init-time} to the value of |
f36acfd9 | 76 | @code{current-time} (@pxref{Time of Day}). It also sets |
02a89103 CY |
77 | @code{after-init-time} to @code{nil}, which signals to Lisp programs |
78 | that Emacs is being initialized. | |
b8d4c8d0 | 79 | |
f36acfd9 EZ |
80 | @vindex initial-window-system@r{, and startup} |
81 | @vindex window-system-initialization-alist | |
b8d4c8d0 | 82 | @item |
f36acfd9 | 83 | It loads the initialization library for the window system specified by |
028e2c19 EZ |
84 | the variable @code{initial-window-system} (@pxref{Window Systems, |
85 | initial-window-system}). This library's name is | |
f36acfd9 EZ |
86 | @file{term/@var{windowsystem}-win.el}, where @var{windowsystem} is the |
87 | value of @code{initial-window-system}. From that library, it calls | |
88 | the appropriate initialization function. The initialization function | |
02a89103 CY |
89 | for each supported window system is specified by |
90 | @code{window-system-initialization-alist}. | |
f36acfd9 EZ |
91 | |
92 | @item | |
93 | It sets the language environment and the terminal coding system, | |
94 | if requested by environment variables such as @code{LANG}. | |
b8d4c8d0 GM |
95 | |
96 | @item | |
97 | It processes the initial options. (Some of them are handled | |
98 | even earlier than this.) | |
99 | ||
100 | @item | |
f36acfd9 | 101 | It runs the normal hook @code{before-init-hook}. |
b8d4c8d0 GM |
102 | |
103 | @item | |
f36acfd9 EZ |
104 | It initializes the window frame and faces, if appropriate, and turns |
105 | on the menu bar and tool bar, if the initial frame needs them. | |
106 | ||
107 | @item | |
02a89103 CY |
108 | It loads the library @file{site-start}, if it exists. This is not |
109 | done if the options @samp{-Q} or @samp{--no-site-file} were specified. | |
b8d4c8d0 GM |
110 | @cindex @file{site-start.el} |
111 | ||
112 | @item | |
02a89103 CY |
113 | It loads your init file (@pxref{Init File}). This is not done if the |
114 | options @samp{-q}, @samp{-Q}, or @samp{--batch} were specified. If | |
115 | the @samp{-u} option was specified, Emacs looks for the init file in | |
116 | that user's home directory instead. | |
b8d4c8d0 GM |
117 | |
118 | @item | |
02a89103 CY |
119 | It loads the library @file{default}, if it exists. This is not done |
120 | if @code{inhibit-default-init} is non-@code{nil}, nor if the options | |
121 | @samp{-q}, @samp{-Q}, or @samp{--batch} were specified. | |
b8d4c8d0 GM |
122 | @cindex @file{default.el} |
123 | ||
f36acfd9 EZ |
124 | @item |
125 | It loads your abbrevs from the file specified by | |
02a89103 CY |
126 | @code{abbrev-file-name}, if that file exists and can be read |
127 | (@pxref{Abbrev Files, abbrev-file-name}). This is not done if the | |
128 | option @samp{--batch} was specified. | |
f36acfd9 EZ |
129 | |
130 | @vindex after-init-time | |
131 | @item | |
02a89103 CY |
132 | It sets the variable @code{after-init-time} to the value of |
133 | @code{current-time}. This variable was set to @code{nil} earlier; | |
134 | setting it to the current time signals that the initialization phase | |
135 | is over, and, together with @code{before-init-time}, provides the | |
f36acfd9 EZ |
136 | measurement of how long it took. |
137 | ||
b8d4c8d0 GM |
138 | @item |
139 | It runs the normal hook @code{after-init-hook}. | |
140 | ||
141 | @item | |
02a89103 CY |
142 | If the buffer @samp{*scratch*} exists and is still in Fundamental mode |
143 | (as it should be by default), it sets its major mode according to | |
144 | @code{initial-major-mode}. | |
b8d4c8d0 GM |
145 | |
146 | @item | |
02a89103 CY |
147 | If started on a text-only terminal, it loads the terminal-specific |
148 | Lisp library, which is specified by the variable | |
149 | @code{term-file-prefix} (@pxref{Terminal-Specific}). This is not done | |
150 | in @code{--batch} mode, nor if @code{term-file-prefix} is @code{nil}. | |
b8d4c8d0 GM |
151 | |
152 | @item | |
153 | It displays the initial echo area message, unless you have suppressed | |
154 | that with @code{inhibit-startup-echo-area-message}. | |
155 | ||
156 | @item | |
157 | It processes the action arguments from the command line. | |
158 | ||
02a89103 CY |
159 | @item |
160 | It now exits if the option @code{--batch} was specified. | |
161 | ||
162 | @item | |
163 | If @code{initial-buffer-choice} is a string, it visits the file with | |
164 | that name. Furthermore, if the @samp{*scratch*} buffer exists and is | |
165 | empty, it inserts @code{initial-scratch-message} into that buffer. | |
166 | ||
b8d4c8d0 GM |
167 | @item |
168 | It runs @code{emacs-startup-hook} and then @code{term-setup-hook}. | |
169 | ||
170 | @item | |
171 | It calls @code{frame-notice-user-settings}, which modifies the | |
172 | parameters of the selected frame according to whatever the init files | |
173 | specify. | |
174 | ||
175 | @item | |
176 | It runs @code{window-setup-hook}. @xref{Window Systems}. | |
177 | ||
178 | @item | |
02a89103 CY |
179 | If the option @code{--daemon} was specified, it calls |
180 | @code{server-start} and detaches from the controlling terminal. | |
181 | @xref{Emacs Server,,, emacs, The GNU Emacs Manual}. | |
f36acfd9 EZ |
182 | |
183 | @item | |
02a89103 CY |
184 | It displays the @dfn{startup screen}, which is a special buffer that |
185 | contains information about copyleft and basic Emacs usage. This is | |
186 | not done if @code{initial-buffer-choice} or | |
187 | @code{inhibit-startup-screen} are @code{nil}, nor if the | |
188 | @samp{--no-splash} or @samp{-Q} command-line options were specified. | |
f36acfd9 EZ |
189 | |
190 | @item | |
191 | If started by the X session manager, it calls | |
192 | @code{emacs-session-restore} passing it as argument the ID of the | |
dca019f8 | 193 | previous session. @xref{Session Management}. |
b8d4c8d0 GM |
194 | @end enumerate |
195 | ||
f36acfd9 | 196 | @defopt inhibit-startup-screen |
02a89103 CY |
197 | This variable, if non-@code{nil}, inhibits the startup screen. In |
198 | that case, Emacs typically displays the @samp{*scratch*} buffer; but | |
199 | see @code{initial-buffer-choice}, below. | |
b8d4c8d0 | 200 | |
02a89103 CY |
201 | Do not set this variable in the init file of a new user, or in a way |
202 | that affects more than one user, as that would prevent new users from | |
203 | receiving information about copyleft and basic Emacs usage. | |
f36acfd9 | 204 | |
d3d97050 KR |
205 | @vindex inhibit-startup-message |
206 | @vindex inhibit-splash-screen | |
02a89103 CY |
207 | @code{inhibit-startup-message} and @code{inhibit-splash-screen} are |
208 | aliases for this variable. | |
209 | @end defopt | |
210 | ||
211 | @defopt initial-buffer-choice | |
212 | This variable, if non-@code{nil}, determines a file or buffer for | |
213 | Emacs to display after starting up, instead of the startup screen. If | |
214 | its value is @code{t}, Emacs displays the @samp{*scratch*} buffer. If | |
215 | its value is a string, that specifies the name of a file for Emacs to | |
216 | visit. | |
b8d4c8d0 GM |
217 | @end defopt |
218 | ||
219 | @defopt inhibit-startup-echo-area-message | |
220 | This variable controls the display of the startup echo area message. | |
221 | You can suppress the startup echo area message by adding text with this | |
222 | form to your init file: | |
223 | ||
224 | @example | |
225 | (setq inhibit-startup-echo-area-message | |
226 | "@var{your-login-name}") | |
227 | @end example | |
228 | ||
229 | Emacs explicitly checks for an expression as shown above in your init | |
230 | file; your login name must appear in the expression as a Lisp string | |
231 | constant. Other methods of setting | |
232 | @code{inhibit-startup-echo-area-message} to the same value do not | |
02a89103 CY |
233 | inhibit the startup message. This way, you can easily inhibit the |
234 | message for yourself if you wish, but thoughtless copying of your init | |
235 | file will not inhibit the message for someone else. | |
236 | @end defopt | |
b8d4c8d0 | 237 | |
02a89103 CY |
238 | @defopt initial-scratch-message |
239 | This variable, if non-@code{nil}, should be a string, which is | |
240 | inserted into the @samp{*scratch*} buffer when Emacs starts up. If it | |
241 | is @code{nil}, the @samp{*scratch*} buffer is empty. | |
b8d4c8d0 GM |
242 | @end defopt |
243 | ||
244 | @node Init File | |
245 | @subsection The Init File, @file{.emacs} | |
246 | @cindex init file | |
247 | @cindex @file{.emacs} | |
248 | ||
249 | When you start Emacs, it normally attempts to load your @dfn{init | |
02a89103 CY |
250 | file}. This is either a file named @file{.emacs} or @file{.emacs.el} |
251 | in your home directory, or a file named @file{init.el} in a | |
252 | subdirectory named @file{.emacs.d} in your home directory. Whichever | |
253 | place you use, you can also compile the file (@pxref{Byte | |
254 | Compilation}); then the actual file loaded will be @file{.emacs.elc} | |
255 | or @file{init.elc}. | |
b8d4c8d0 GM |
256 | |
257 | The command-line switches @samp{-q}, @samp{-Q}, and @samp{-u} | |
258 | control whether and where to find the init file; @samp{-q} (and the | |
259 | stronger @samp{-Q}) says not to load an init file, while @samp{-u | |
260 | @var{user}} says to load @var{user}'s init file instead of yours. | |
261 | @xref{Entering Emacs,,, emacs, The GNU Emacs Manual}. If neither | |
262 | option is specified, Emacs uses the @code{LOGNAME} environment | |
263 | variable, or the @code{USER} (most systems) or @code{USERNAME} (MS | |
264 | systems) variable, to find your home directory and thus your init | |
265 | file; this way, even if you have su'd, Emacs still loads your own init | |
266 | file. If those environment variables are absent, though, Emacs uses | |
267 | your user-id to find your home directory. | |
268 | ||
269 | @cindex default init file | |
270 | A site may have a @dfn{default init file}, which is the library | |
271 | named @file{default.el}. Emacs finds the @file{default.el} file | |
272 | through the standard search path for libraries (@pxref{How Programs Do | |
273 | Loading}). The Emacs distribution does not come with this file; sites | |
274 | may provide one for local customizations. If the default init file | |
275 | exists, it is loaded whenever you start Emacs, except in batch mode or | |
276 | if @samp{-q} (or @samp{-Q}) is specified. But your own personal init | |
277 | file, if any, is loaded first; if it sets @code{inhibit-default-init} | |
278 | to a non-@code{nil} value, then Emacs does not subsequently load the | |
279 | @file{default.el} file. | |
280 | ||
281 | Another file for site-customization is @file{site-start.el}. Emacs | |
282 | loads this @emph{before} the user's init file. You can inhibit the | |
283 | loading of this file with the option @samp{--no-site-file}. | |
284 | ||
01f17ae2 | 285 | @defopt site-run-file |
b8d4c8d0 GM |
286 | This variable specifies the site-customization file to load before the |
287 | user's init file. Its normal value is @code{"site-start"}. The only | |
288 | way you can change it with real effect is to do so before dumping | |
289 | Emacs. | |
01f17ae2 | 290 | @end defopt |
b8d4c8d0 GM |
291 | |
292 | @xref{Init Examples,, Init File Examples, emacs, The GNU Emacs Manual}, for | |
293 | examples of how to make various commonly desired customizations in your | |
294 | @file{.emacs} file. | |
295 | ||
296 | @defopt inhibit-default-init | |
297 | This variable prevents Emacs from loading the default initialization | |
298 | library file for your session of Emacs. If its value is non-@code{nil}, | |
299 | then the default library is not loaded. The default value is | |
300 | @code{nil}. | |
301 | @end defopt | |
302 | ||
303 | @defvar before-init-hook | |
304 | This normal hook is run, once, just before loading all the init files | |
305 | (the user's init file, @file{default.el}, and/or @file{site-start.el}). | |
306 | (The only way to change it with real effect is before dumping Emacs.) | |
307 | @end defvar | |
308 | ||
309 | @defvar after-init-hook | |
310 | This normal hook is run, once, just after loading all the init files | |
311 | (the user's init file, @file{default.el}, and/or @file{site-start.el}), | |
312 | before loading the terminal-specific library and processing the | |
313 | command-line action arguments. | |
314 | @end defvar | |
315 | ||
316 | @defvar emacs-startup-hook | |
317 | This normal hook is run, once, just after handling the command line | |
318 | arguments, just before @code{term-setup-hook}. | |
319 | @end defvar | |
320 | ||
321 | @defvar user-init-file | |
322 | This variable holds the absolute file name of the user's init file. If the | |
323 | actual init file loaded is a compiled file, such as @file{.emacs.elc}, | |
324 | the value refers to the corresponding source file. | |
325 | @end defvar | |
326 | ||
327 | @defvar user-emacs-directory | |
328 | This variable holds the name of the @file{.emacs.d} directory. It is | |
329 | ordinarily @file{~/.emacs.d}, but differs on some platforms. | |
330 | @end defvar | |
331 | ||
332 | @node Terminal-Specific | |
333 | @subsection Terminal-Specific Initialization | |
334 | @cindex terminal-specific initialization | |
335 | ||
336 | Each terminal type can have its own Lisp library that Emacs loads when | |
337 | run on that type of terminal. The library's name is constructed by | |
338 | concatenating the value of the variable @code{term-file-prefix} and the | |
339 | terminal type (specified by the environment variable @code{TERM}). | |
340 | Normally, @code{term-file-prefix} has the value | |
341 | @code{"term/"}; changing this is not recommended. Emacs finds the file | |
342 | in the normal manner, by searching the @code{load-path} directories, and | |
343 | trying the @samp{.elc} and @samp{.el} suffixes. | |
344 | ||
345 | @cindex Termcap | |
346 | The usual function of a terminal-specific library is to enable | |
347 | special keys to send sequences that Emacs can recognize. It may also | |
4f4a84ec | 348 | need to set or add to @code{input-decode-map} if the Termcap or |
b8d4c8d0 GM |
349 | Terminfo entry does not specify all the terminal's function keys. |
350 | @xref{Terminal Input}. | |
351 | ||
352 | When the name of the terminal type contains a hyphen, and no library | |
353 | is found whose name is identical to the terminal's name, Emacs strips | |
354 | from the terminal's name the last hyphen and everything that follows | |
355 | it, and tries again. This process is repeated until Emacs finds a | |
356 | matching library or until there are no more hyphens in the name (the | |
357 | latter means the terminal doesn't have any library specific to it). | |
358 | Thus, for example, if there are no @samp{aaa-48} and @samp{aaa-30} | |
359 | libraries, Emacs will try the same library @file{term/aaa.el} for | |
360 | terminal types @samp{aaa-48} and @samp{aaa-30-rv}. If necessary, the | |
361 | library can evaluate @code{(getenv "TERM")} to find the full name of | |
362 | the terminal type.@refill | |
363 | ||
364 | Your init file can prevent the loading of the | |
365 | terminal-specific library by setting the variable | |
366 | @code{term-file-prefix} to @code{nil}. This feature is useful when | |
367 | experimenting with your own peculiar customizations. | |
368 | ||
369 | You can also arrange to override some of the actions of the | |
370 | terminal-specific library by setting the variable | |
371 | @code{term-setup-hook}. This is a normal hook which Emacs runs using | |
372 | @code{run-hooks} at the end of Emacs initialization, after loading both | |
373 | your init file and any terminal-specific libraries. You can | |
374 | use this variable to define initializations for terminals that do not | |
375 | have their own libraries. @xref{Hooks}. | |
376 | ||
377 | @defvar term-file-prefix | |
378 | @cindex @code{TERM} environment variable | |
379 | If the @code{term-file-prefix} variable is non-@code{nil}, Emacs loads | |
380 | a terminal-specific initialization file as follows: | |
381 | ||
382 | @example | |
383 | (load (concat term-file-prefix (getenv "TERM"))) | |
384 | @end example | |
385 | ||
386 | @noindent | |
387 | You may set the @code{term-file-prefix} variable to @code{nil} in your | |
388 | init file if you do not wish to load the | |
389 | terminal-initialization file. To do this, put the following in | |
390 | your init file: @code{(setq term-file-prefix nil)}. | |
391 | ||
392 | On MS-DOS, if the environment variable @code{TERM} is not set, Emacs | |
393 | uses @samp{internal} as the terminal type. | |
394 | @end defvar | |
395 | ||
396 | @defvar term-setup-hook | |
397 | This variable is a normal hook that Emacs runs after loading your | |
398 | init file, the default initialization file (if any) and the | |
399 | terminal-specific Lisp file. | |
400 | ||
401 | You can use @code{term-setup-hook} to override the definitions made by a | |
402 | terminal-specific file. | |
403 | @end defvar | |
404 | ||
405 | See @code{window-setup-hook} in @ref{Window Systems}, for a related | |
406 | feature. | |
407 | ||
408 | @node Command-Line Arguments | |
409 | @subsection Command-Line Arguments | |
410 | @cindex command-line arguments | |
411 | ||
412 | You can use command-line arguments to request various actions when you | |
413 | start Emacs. Since you do not need to start Emacs more than once per | |
414 | day, and will often leave your Emacs session running longer than that, | |
415 | command-line arguments are hardly ever used. As a practical matter, it | |
416 | is best to avoid making the habit of using them, since this habit would | |
417 | encourage you to kill and restart Emacs unnecessarily often. These | |
418 | options exist for two reasons: to be compatible with other editors (for | |
419 | invocation by other programs) and to enable shell scripts to run | |
420 | specific Lisp programs. | |
421 | ||
422 | This section describes how Emacs processes command-line arguments, | |
423 | and how you can customize them. | |
424 | ||
425 | @ignore | |
426 | (Note that some other editors require you to start afresh each time | |
427 | you want to edit a file. With this kind of editor, you will probably | |
428 | specify the file as a command-line argument. The recommended way to | |
429 | use GNU Emacs is to start it only once, just after you log in, and do | |
430 | all your editing in the same Emacs process. Each time you want to edit | |
431 | a different file, you visit it with the existing Emacs, which eventually | |
432 | comes to have many files in it ready for editing. Usually you do not | |
433 | kill the Emacs until you are about to log out.) | |
434 | @end ignore | |
435 | ||
436 | @defun command-line | |
437 | This function parses the command line that Emacs was called with, | |
438 | processes it, loads the user's init file and displays the | |
439 | startup messages. | |
440 | @end defun | |
441 | ||
442 | @defvar command-line-processed | |
443 | The value of this variable is @code{t} once the command line has been | |
444 | processed. | |
445 | ||
446 | If you redump Emacs by calling @code{dump-emacs}, you may wish to set | |
447 | this variable to @code{nil} first in order to cause the new dumped Emacs | |
448 | to process its new command-line arguments. | |
449 | @end defvar | |
450 | ||
451 | @defvar command-switch-alist | |
452 | @cindex switches on command line | |
453 | @cindex options on command line | |
454 | @cindex command-line options | |
455 | The value of this variable is an alist of user-defined command-line | |
456 | options and associated handler functions. This variable exists so you | |
457 | can add elements to it. | |
458 | ||
459 | A @dfn{command-line option} is an argument on the command line, which | |
460 | has the form: | |
461 | ||
462 | @example | |
463 | -@var{option} | |
464 | @end example | |
465 | ||
466 | The elements of the @code{command-switch-alist} look like this: | |
467 | ||
468 | @example | |
469 | (@var{option} . @var{handler-function}) | |
470 | @end example | |
471 | ||
472 | The @sc{car}, @var{option}, is a string, the name of a command-line | |
473 | option (not including the initial hyphen). The @var{handler-function} | |
474 | is called to handle @var{option}, and receives the option name as its | |
475 | sole argument. | |
476 | ||
477 | In some cases, the option is followed in the command line by an | |
478 | argument. In these cases, the @var{handler-function} can find all the | |
479 | remaining command-line arguments in the variable | |
480 | @code{command-line-args-left}. (The entire list of command-line | |
481 | arguments is in @code{command-line-args}.) | |
482 | ||
483 | The command-line arguments are parsed by the @code{command-line-1} | |
484 | function in the @file{startup.el} file. See also @ref{Emacs | |
485 | Invocation, , Command Line Arguments for Emacs Invocation, emacs, The | |
486 | GNU Emacs Manual}. | |
487 | @end defvar | |
488 | ||
489 | @defvar command-line-args | |
490 | The value of this variable is the list of command-line arguments passed | |
491 | to Emacs. | |
492 | @end defvar | |
493 | ||
dca019f8 | 494 | @defvar command-line-args-left |
d3d97050 | 495 | @vindex argv |
dca019f8 CY |
496 | The value of this variable is the list of command-line arguments that |
497 | have not yet been processed. @code{argv} is an alias for this. | |
498 | @end defvar | |
499 | ||
b8d4c8d0 GM |
500 | @defvar command-line-functions |
501 | This variable's value is a list of functions for handling an | |
502 | unrecognized command-line argument. Each time the next argument to be | |
503 | processed has no special meaning, the functions in this list are called, | |
504 | in order of appearance, until one of them returns a non-@code{nil} | |
505 | value. | |
506 | ||
507 | These functions are called with no arguments. They can access the | |
508 | command-line argument under consideration through the variable | |
509 | @code{argi}, which is bound temporarily at this point. The remaining | |
510 | arguments (not including the current one) are in the variable | |
511 | @code{command-line-args-left}. | |
512 | ||
513 | When a function recognizes and processes the argument in @code{argi}, it | |
514 | should return a non-@code{nil} value to say it has dealt with that | |
515 | argument. If it has also dealt with some of the following arguments, it | |
516 | can indicate that by deleting them from @code{command-line-args-left}. | |
517 | ||
518 | If all of these functions return @code{nil}, then the argument is used | |
519 | as a file name to visit. | |
520 | @end defvar | |
521 | ||
522 | @node Getting Out | |
523 | @section Getting Out of Emacs | |
524 | @cindex exiting Emacs | |
525 | ||
526 | There are two ways to get out of Emacs: you can kill the Emacs job, | |
527 | which exits permanently, or you can suspend it, which permits you to | |
528 | reenter the Emacs process later. As a practical matter, you seldom kill | |
529 | Emacs---only when you are about to log out. Suspending is much more | |
530 | common. | |
531 | ||
532 | @menu | |
533 | * Killing Emacs:: Exiting Emacs irreversibly. | |
534 | * Suspending Emacs:: Exiting Emacs reversibly. | |
535 | @end menu | |
536 | ||
537 | @node Killing Emacs | |
538 | @comment node-name, next, previous, up | |
539 | @subsection Killing Emacs | |
540 | @cindex killing Emacs | |
541 | ||
542 | Killing Emacs means ending the execution of the Emacs process. The | |
543 | parent process normally resumes control. The low-level primitive for | |
544 | killing Emacs is @code{kill-emacs}. | |
545 | ||
106e6894 | 546 | @deffn Command kill-emacs &optional exit-data |
ddb54206 CY |
547 | This command calls the hook @code{kill-emacs-hook}, then exits the |
548 | Emacs process and kills it. | |
b8d4c8d0 | 549 | |
ddb54206 CY |
550 | If @var{exit-data} is an integer, that is used as the exit status of |
551 | the Emacs process. (This is useful primarily in batch operation; see | |
b8d4c8d0 GM |
552 | @ref{Batch Mode}.) |
553 | ||
554 | If @var{exit-data} is a string, its contents are stuffed into the | |
555 | terminal input buffer so that the shell (or whatever program next reads | |
556 | input) can read them. | |
106e6894 | 557 | @end deffn |
b8d4c8d0 | 558 | |
ddb54206 CY |
559 | @cindex SIGTERM |
560 | @cindex SIGHUP | |
561 | @cindex SIGINT | |
562 | @cindex operating system signal | |
563 | The @code{kill-emacs} function is normally called via the | |
564 | higher-level command @kbd{C-x C-c} | |
565 | (@code{save-buffers-kill-terminal}). @xref{Exiting,,, emacs, The GNU | |
566 | Emacs Manual}. It is also called automatically if Emacs receives a | |
567 | @code{SIGTERM} or @code{SIGHUP} operating system signal (e.g. when the | |
568 | controlling terminal is disconnected), or if it receives a | |
569 | @code{SIGINT} signal while running in batch mode (@pxref{Batch Mode}). | |
b8d4c8d0 | 570 | |
ddb54206 CY |
571 | @defvar kill-emacs-hook |
572 | This normal hook is run by @code{kill-emacs}, before it kills Emacs. | |
573 | ||
574 | Because @code{kill-emacs} can be called in situations where user | |
575 | interaction is impossible (e.g. when the terminal is disconnected), | |
576 | functions on this hook should not attempt to interact with the user. | |
577 | If you want to interact with the user when Emacs is shutting down, use | |
578 | @code{kill-emacs-query-functions}, described below. | |
b8d4c8d0 GM |
579 | @end defvar |
580 | ||
ddb54206 CY |
581 | When Emacs is killed, all the information in the Emacs process, |
582 | aside from files that have been saved, is lost. Because killing Emacs | |
583 | inadvertently can lose a lot of work, the | |
584 | @code{save-buffers-kill-terminal} command queries for confirmation if | |
585 | you have buffers that need saving or subprocesses that are running. | |
586 | It also runs the abnormal hook @code{kill-emacs-query-functions}: | |
587 | ||
588 | @defvar kill-emacs-query-functions | |
589 | When @code{save-buffers-kill-terminal} is killing Emacs, it calls the | |
590 | functions in this hook, after asking the standard questions and before | |
591 | calling @code{kill-emacs}. The functions are called in order of | |
592 | appearance, with no arguments. Each function can ask for additional | |
593 | confirmation from the user. If any of them returns @code{nil}, | |
594 | @code{save-buffers-kill-emacs} does not kill Emacs, and does not run | |
595 | the remaining functions in this hook. Calling @code{kill-emacs} | |
596 | directly does not run this hook. | |
b8d4c8d0 GM |
597 | @end defvar |
598 | ||
599 | @node Suspending Emacs | |
600 | @subsection Suspending Emacs | |
601 | @cindex suspending Emacs | |
602 | ||
dca019f8 CY |
603 | On text-only terminals, it is possible to @dfn{suspend Emacs}, which |
604 | means stopping Emacs temporarily and returning control to its superior | |
605 | process, which is usually the shell. This allows you to resume | |
606 | editing later in the same Emacs process, with the same buffers, the | |
607 | same kill ring, the same undo history, and so on. To resume Emacs, | |
608 | use the appropriate command in the parent shell---most likely | |
609 | @code{fg}. | |
b8d4c8d0 | 610 | |
62a5303f EZ |
611 | @cindex controlling terminal |
612 | Suspending works only on a terminal device from which the Emacs | |
613 | session was started. We call that device the @dfn{controlling | |
dca019f8 CY |
614 | terminal} of the session. Suspending is not allowed if the |
615 | controlling terminal is a graphical terminal. | |
62a5303f | 616 | |
b8d4c8d0 GM |
617 | Some operating systems do not support suspension of jobs; on these |
618 | systems, ``suspension'' actually creates a new shell temporarily as a | |
619 | subprocess of Emacs. Then you would exit the shell to return to Emacs. | |
620 | ||
106e6894 | 621 | @deffn Command suspend-emacs &optional string |
b8d4c8d0 GM |
622 | This function stops Emacs and returns control to the superior process. |
623 | If and when the superior process resumes Emacs, @code{suspend-emacs} | |
624 | returns @code{nil} to its caller in Lisp. | |
625 | ||
62a5303f EZ |
626 | This function works only on the controlling terminal of the Emacs |
627 | session; to relinquish control of other tty devices, use | |
f71de46c | 628 | @code{suspend-tty} (see below). If the Emacs session uses more than |
dca019f8 CY |
629 | one terminal, you must delete the frames on all the other terminals |
630 | before suspending Emacs, or this function signals an error. | |
631 | @xref{Multiple Terminals}. | |
62a5303f | 632 | |
dca019f8 CY |
633 | If @var{string} is non-@code{nil}, its characters are sent to Emacs's |
634 | superior shell, to be read as terminal input. The characters in | |
b8d4c8d0 GM |
635 | @var{string} are not echoed by the superior shell; only the results |
636 | appear. | |
637 | ||
638 | Before suspending, @code{suspend-emacs} runs the normal hook | |
dca019f8 CY |
639 | @code{suspend-hook}. After the user resumes Emacs, |
640 | @code{suspend-emacs} runs the normal hook @code{suspend-resume-hook}. | |
641 | @xref{Hooks}. | |
b8d4c8d0 GM |
642 | |
643 | The next redisplay after resumption will redraw the entire screen, | |
dca019f8 CY |
644 | unless the variable @code{no-redraw-on-reenter} is non-@code{nil}. |
645 | @xref{Refresh Screen}. | |
b8d4c8d0 GM |
646 | |
647 | In the following example, note that @samp{pwd} is not echoed after | |
648 | Emacs is suspended. But it is read and executed by the shell. | |
649 | ||
650 | @smallexample | |
651 | @group | |
652 | (suspend-emacs) | |
653 | @result{} nil | |
654 | @end group | |
655 | ||
656 | @group | |
657 | (add-hook 'suspend-hook | |
658 | (function (lambda () | |
659 | (or (y-or-n-p | |
660 | "Really suspend? ") | |
661 | (error "Suspend canceled"))))) | |
662 | @result{} (lambda nil | |
663 | (or (y-or-n-p "Really suspend? ") | |
664 | (error "Suspend canceled"))) | |
665 | @end group | |
666 | @group | |
667 | (add-hook 'suspend-resume-hook | |
668 | (function (lambda () (message "Resumed!")))) | |
669 | @result{} (lambda nil (message "Resumed!")) | |
670 | @end group | |
671 | @group | |
672 | (suspend-emacs "pwd") | |
673 | @result{} nil | |
674 | @end group | |
675 | @group | |
676 | ---------- Buffer: Minibuffer ---------- | |
677 | Really suspend? @kbd{y} | |
678 | ---------- Buffer: Minibuffer ---------- | |
679 | @end group | |
680 | ||
681 | @group | |
682 | ---------- Parent Shell ---------- | |
683 | lewis@@slug[23] % /user/lewis/manual | |
684 | lewis@@slug[24] % fg | |
685 | @end group | |
686 | ||
687 | @group | |
688 | ---------- Echo Area ---------- | |
689 | Resumed! | |
690 | @end group | |
691 | @end smallexample | |
106e6894 | 692 | @end deffn |
b8d4c8d0 GM |
693 | |
694 | @defvar suspend-hook | |
695 | This variable is a normal hook that Emacs runs before suspending. | |
696 | @end defvar | |
697 | ||
698 | @defvar suspend-resume-hook | |
699 | This variable is a normal hook that Emacs runs on resuming | |
700 | after a suspension. | |
701 | @end defvar | |
702 | ||
62a5303f EZ |
703 | @defun suspend-tty &optional tty |
704 | If @var{tty} specifies a terminal device used by Emacs, this function | |
705 | relinquishes the device and restores it to its prior state. Frames | |
706 | that used the device continue to exist, but are not updated and Emacs | |
dca019f8 CY |
707 | doesn't read input from them. @var{tty} can be a terminal object, a |
708 | frame (meaning the terminal for that frame), or @code{nil} (meaning | |
709 | the terminal for the selected frame). @xref{Multiple Terminals}. | |
710 | ||
711 | If @var{tty} is already suspended, this function does nothing. | |
712 | ||
d3d97050 | 713 | @vindex suspend-tty-functions |
dca019f8 CY |
714 | This function runs the hook @code{suspend-tty-functions}, passing the |
715 | terminal object as an argument to each function. | |
62a5303f EZ |
716 | @end defun |
717 | ||
718 | @defun resume-tty &optional tty | |
dca019f8 CY |
719 | This function resumes the previously suspended terminal device |
720 | @var{tty}; @var{tty} can be a terminal object, a frame (meaning the | |
721 | terminal for that frame), or @code{nil} (meaning the terminal for the | |
722 | selected frame). | |
62a5303f | 723 | |
d3d97050 | 724 | @vindex resume-tty-functions |
62a5303f EZ |
725 | This function reopens the terminal device, re-initializes it, and |
726 | redraws its with that terminal's selected frame. It then runs the | |
dca019f8 CY |
727 | hook @code{resume-tty-functions}, passing the terminal object as an |
728 | argument to each function. | |
62a5303f EZ |
729 | |
730 | If the same device is already used by another Emacs terminal, this | |
731 | function signals an error. | |
732 | @end defun | |
733 | ||
734 | @defun controlling-tty-p &optional terminal | |
735 | This function returns non-@code{nil} if @var{terminal} is the | |
dca019f8 CY |
736 | controlling terminal of the Emacs session; @code{terminal} can be a |
737 | terminal object, a frame (meaning the terminal for that frame), or | |
738 | @code{nil} (meaning the terminal for the selected frame). | |
62a5303f EZ |
739 | @end defun |
740 | ||
741 | @deffn Command suspend-frame | |
742 | This command @dfn{suspends} a frame. For GUI frames, it calls | |
743 | @code{iconify-frame} (@pxref{Visibility of Frames}); for text-only | |
744 | frames, it calls either @code{suspend-emacs} or @code{suspend-tty}, | |
745 | depending on whether the frame is displayed on the controlling | |
746 | terminal device or not. | |
747 | @end deffn | |
748 | ||
b8d4c8d0 GM |
749 | @node System Environment |
750 | @section Operating System Environment | |
751 | @cindex operating system environment | |
752 | ||
753 | Emacs provides access to variables in the operating system environment | |
754 | through various functions. These variables include the name of the | |
755 | system, the user's @acronym{UID}, and so on. | |
756 | ||
757 | @defvar system-configuration | |
758 | This variable holds the standard GNU configuration name for the | |
759 | hardware/software configuration of your system, as a string. The | |
760 | convenient way to test parts of this string is with | |
761 | @code{string-match}. | |
762 | @end defvar | |
763 | ||
764 | @cindex system type and name | |
765 | @defvar system-type | |
766 | The value of this variable is a symbol indicating the type of operating | |
767 | system Emacs is operating on. Here is a table of the possible values: | |
768 | ||
58e3d8e8 | 769 | @table @code |
1213465a EZ |
770 | @item aix |
771 | IBM's AIX. | |
b8d4c8d0 GM |
772 | |
773 | @item berkeley-unix | |
1213465a | 774 | Berkeley BSD and its variants. |
b8d4c8d0 GM |
775 | |
776 | @item cygwin | |
1213465a EZ |
777 | Cygwin, a Posix layer on top of MS-Windows. |
778 | ||
779 | @item darwin | |
780 | Darwin (Mac OS X). | |
b8d4c8d0 | 781 | |
b8d4c8d0 | 782 | @item gnu |
1213465a | 783 | The GNU system (using the GNU kernel, which consists of the HURD and Mach). |
b8d4c8d0 GM |
784 | |
785 | @item gnu/linux | |
786 | A GNU/Linux system---that is, a variant GNU system, using the Linux | |
787 | kernel. (These systems are the ones people often call ``Linux,'' but | |
788 | actually Linux is just the kernel, not the whole system.) | |
789 | ||
1213465a EZ |
790 | @item gnu/kfreebsd |
791 | A GNU (glibc-based) system with a FreeBSD kernel. | |
792 | ||
b8d4c8d0 GM |
793 | @item hpux |
794 | Hewlett-Packard HPUX operating system. | |
795 | ||
796 | @item irix | |
797 | Silicon Graphics Irix system. | |
798 | ||
799 | @item ms-dos | |
800 | Microsoft MS-DOS ``operating system.'' Emacs compiled with DJGPP for | |
801 | MS-DOS binds @code{system-type} to @code{ms-dos} even when you run it on | |
802 | MS-Windows. | |
803 | ||
b8d4c8d0 | 804 | @item usg-unix-v |
1213465a | 805 | AT&T Unix System V. |
b8d4c8d0 | 806 | |
b8d4c8d0 | 807 | @item windows-nt |
200811d6 EZ |
808 | Microsoft Windows NT and later. The same executable supports Windows |
809 | 9X, but the value of @code{system-type} is @code{windows-nt} in either | |
810 | case. | |
b8d4c8d0 | 811 | |
b8d4c8d0 GM |
812 | @end table |
813 | ||
814 | We do not wish to add new symbols to make finer distinctions unless it | |
815 | is absolutely necessary! In fact, we hope to eliminate some of these | |
816 | alternatives in the future. We recommend using | |
817 | @code{system-configuration} to distinguish between different operating | |
818 | systems. | |
819 | @end defvar | |
820 | ||
821 | @defun system-name | |
822 | This function returns the name of the machine you are running on. | |
823 | @example | |
824 | (system-name) | |
825 | @result{} "www.gnu.org" | |
826 | @end example | |
827 | @end defun | |
828 | ||
829 | The symbol @code{system-name} is a variable as well as a function. In | |
830 | fact, the function returns whatever value the variable | |
831 | @code{system-name} currently holds. Thus, you can set the variable | |
832 | @code{system-name} in case Emacs is confused about the name of your | |
833 | system. The variable is also useful for constructing frame titles | |
834 | (@pxref{Frame Titles}). | |
835 | ||
01f17ae2 | 836 | @defopt mail-host-address |
b8d4c8d0 GM |
837 | If this variable is non-@code{nil}, it is used instead of |
838 | @code{system-name} for purposes of generating email addresses. For | |
839 | example, it is used when constructing the default value of | |
840 | @code{user-mail-address}. @xref{User Identification}. (Since this is | |
841 | done when Emacs starts up, the value actually used is the one saved when | |
842 | Emacs was dumped. @xref{Building Emacs}.) | |
01f17ae2 | 843 | @end defopt |
b8d4c8d0 | 844 | |
106e6894 | 845 | @deffn Command getenv var &optional frame |
b8d4c8d0 GM |
846 | @cindex environment variable access |
847 | This function returns the value of the environment variable @var{var}, | |
848 | as a string. @var{var} should be a string. If @var{var} is undefined | |
849 | in the environment, @code{getenv} returns @code{nil}. If returns | |
850 | @samp{""} if @var{var} is set but null. Within Emacs, the environment | |
851 | variable values are kept in the Lisp variable @code{process-environment}. | |
852 | ||
853 | @example | |
854 | @group | |
855 | (getenv "USER") | |
856 | @result{} "lewis" | |
857 | @end group | |
858 | ||
859 | @group | |
860 | lewis@@slug[10] % printenv | |
861 | PATH=.:/user/lewis/bin:/usr/bin:/usr/local/bin | |
862 | USER=lewis | |
863 | @end group | |
864 | @group | |
865 | TERM=ibmapa16 | |
866 | SHELL=/bin/csh | |
867 | HOME=/user/lewis | |
868 | @end group | |
869 | @end example | |
870 | @end deffn | |
871 | ||
872 | @c Emacs 19 feature | |
873 | @deffn Command setenv variable &optional value | |
874 | This command sets the value of the environment variable named | |
875 | @var{variable} to @var{value}. @var{variable} should be a string. | |
876 | Internally, Emacs Lisp can handle any string. However, normally | |
877 | @var{variable} should be a valid shell identifier, that is, a sequence | |
878 | of letters, digits and underscores, starting with a letter or | |
879 | underscore. Otherwise, errors may occur if subprocesses of Emacs try | |
880 | to access the value of @var{variable}. If @var{value} is omitted or | |
881 | @code{nil}, @code{setenv} removes @var{variable} from the environment. | |
882 | Otherwise, @var{value} should be a string. | |
883 | ||
884 | @code{setenv} works by modifying @code{process-environment}; binding | |
885 | that variable with @code{let} is also reasonable practice. | |
886 | ||
887 | @code{setenv} returns the new value of @var{variable}, or @code{nil} | |
888 | if it removed @var{variable} from the environment. | |
889 | @end deffn | |
890 | ||
891 | @defvar process-environment | |
892 | This variable is a list of strings, each describing one environment | |
893 | variable. The functions @code{getenv} and @code{setenv} work by means | |
894 | of this variable. | |
895 | ||
896 | @smallexample | |
897 | @group | |
898 | process-environment | |
899 | @result{} ("l=/usr/stanford/lib/gnuemacs/lisp" | |
900 | "PATH=.:/user/lewis/bin:/usr/class:/nfsusr/local/bin" | |
901 | "USER=lewis" | |
902 | @end group | |
903 | @group | |
904 | "TERM=ibmapa16" | |
905 | "SHELL=/bin/csh" | |
906 | "HOME=/user/lewis") | |
907 | @end group | |
908 | @end smallexample | |
909 | ||
910 | If @code{process-environment} contains ``duplicate'' elements that | |
911 | specify the same environment variable, the first of these elements | |
912 | specifies the variable, and the other ``duplicates'' are ignored. | |
913 | @end defvar | |
914 | ||
200811d6 EZ |
915 | @defvar initial-environment |
916 | This variable holds the list of environment variables Emacs inherited | |
917 | from its parent process. It is computed during startup, see | |
918 | @ref{Startup Summary}. | |
919 | @end defvar | |
920 | ||
b8d4c8d0 GM |
921 | @defvar path-separator |
922 | This variable holds a string which says which character separates | |
923 | directories in a search path (as found in an environment variable). Its | |
924 | value is @code{":"} for Unix and GNU systems, and @code{";"} for MS-DOS | |
925 | and MS-Windows. | |
926 | @end defvar | |
927 | ||
928 | @defun parse-colon-path path | |
929 | This function takes a search path string such as would be the value of | |
930 | the @code{PATH} environment variable, and splits it at the separators, | |
931 | returning a list of directory names. @code{nil} in this list stands for | |
932 | ``use the current directory.'' Although the function's name says | |
933 | ``colon,'' it actually uses the value of @code{path-separator}. | |
934 | ||
935 | @example | |
936 | (parse-colon-path ":/foo:/bar") | |
937 | @result{} (nil "/foo/" "/bar/") | |
938 | @end example | |
939 | @end defun | |
940 | ||
941 | @defvar invocation-name | |
942 | This variable holds the program name under which Emacs was invoked. The | |
943 | value is a string, and does not include a directory name. | |
944 | @end defvar | |
945 | ||
946 | @defvar invocation-directory | |
947 | This variable holds the directory from which the Emacs executable was | |
948 | invoked, or perhaps @code{nil} if that directory cannot be determined. | |
949 | @end defvar | |
950 | ||
951 | @defvar installation-directory | |
952 | If non-@code{nil}, this is a directory within which to look for the | |
953 | @file{lib-src} and @file{etc} subdirectories. This is non-@code{nil} | |
954 | when Emacs can't find those directories in their standard installed | |
955 | locations, but can find them in a directory related somehow to the one | |
956 | containing the Emacs executable. | |
957 | @end defvar | |
958 | ||
959 | @defun load-average &optional use-float | |
960 | This function returns the current 1-minute, 5-minute, and 15-minute load | |
961 | averages, in a list. | |
962 | ||
963 | By default, the values are integers that are 100 times the system load | |
964 | averages, which indicate the average number of processes trying to run. | |
965 | If @var{use-float} is non-@code{nil}, then they are returned | |
966 | as floating point numbers and without multiplying by 100. | |
967 | ||
968 | If it is impossible to obtain the load average, this function signals | |
969 | an error. On some platforms, access to load averages requires | |
970 | installing Emacs as setuid or setgid so that it can read kernel | |
971 | information, and that usually isn't advisable. | |
972 | ||
973 | If the 1-minute load average is available, but the 5- or 15-minute | |
974 | averages are not, this function returns a shortened list containing | |
975 | the available averages. | |
976 | ||
977 | @example | |
978 | @group | |
979 | (load-average) | |
980 | @result{} (169 48 36) | |
981 | @end group | |
982 | @group | |
983 | (load-average t) | |
984 | @result{} (1.69 0.48 0.36) | |
985 | @end group | |
986 | ||
987 | @group | |
988 | lewis@@rocky[5] % uptime | |
989 | 11:55am up 1 day, 19:37, 3 users, | |
990 | load average: 1.69, 0.48, 0.36 | |
991 | @end group | |
992 | @end example | |
993 | @end defun | |
994 | ||
995 | @defun emacs-pid | |
996 | This function returns the process @acronym{ID} of the Emacs process, | |
997 | as an integer. | |
998 | @end defun | |
999 | ||
1000 | @defvar tty-erase-char | |
1001 | This variable holds the erase character that was selected | |
1002 | in the system's terminal driver, before Emacs was started. | |
1003 | The value is @code{nil} if Emacs is running under a window system. | |
1004 | @end defvar | |
1005 | ||
b8d4c8d0 GM |
1006 | @node User Identification |
1007 | @section User Identification | |
1008 | @cindex user identification | |
1009 | ||
1010 | @defvar init-file-user | |
1011 | This variable says which user's init files should be used by | |
1012 | Emacs---or @code{nil} if none. @code{""} stands for the user who | |
1013 | originally logged in. The value reflects command-line options such as | |
1014 | @samp{-q} or @samp{-u @var{user}}. | |
1015 | ||
1016 | Lisp packages that load files of customizations, or any other sort of | |
1017 | user profile, should obey this variable in deciding where to find it. | |
1018 | They should load the profile of the user name found in this variable. | |
1019 | If @code{init-file-user} is @code{nil}, meaning that the @samp{-q} | |
1020 | option was used, then Lisp packages should not load any customization | |
1021 | files or user profile. | |
1022 | @end defvar | |
1023 | ||
01f17ae2 | 1024 | @defopt user-mail-address |
b8d4c8d0 GM |
1025 | This holds the nominal email address of the user who is using Emacs. |
1026 | Emacs normally sets this variable to a default value after reading your | |
1027 | init files, but not if you have already set it. So you can set the | |
1028 | variable to some other value in your init file if you do not | |
1029 | want to use the default value. | |
01f17ae2 | 1030 | @end defopt |
b8d4c8d0 GM |
1031 | |
1032 | @defun user-login-name &optional uid | |
1033 | If you don't specify @var{uid}, this function returns the name under | |
1034 | which the user is logged in. If the environment variable @code{LOGNAME} | |
1035 | is set, that value is used. Otherwise, if the environment variable | |
1036 | @code{USER} is set, that value is used. Otherwise, the value is based | |
1037 | on the effective @acronym{UID}, not the real @acronym{UID}. | |
1038 | ||
1039 | If you specify @var{uid}, the value is the user name that corresponds | |
1040 | to @var{uid} (which should be an integer), or @code{nil} if there is | |
1041 | no such user. | |
1042 | ||
1043 | @example | |
1044 | @group | |
1045 | (user-login-name) | |
1046 | @result{} "lewis" | |
1047 | @end group | |
1048 | @end example | |
1049 | @end defun | |
1050 | ||
1051 | @defun user-real-login-name | |
1052 | This function returns the user name corresponding to Emacs's real | |
1053 | @acronym{UID}. This ignores the effective @acronym{UID} and ignores the | |
1054 | environment variables @code{LOGNAME} and @code{USER}. | |
1055 | @end defun | |
1056 | ||
1057 | @defun user-full-name &optional uid | |
1058 | This function returns the full name of the logged-in user---or the value | |
1059 | of the environment variable @code{NAME}, if that is set. | |
1060 | ||
1061 | @c "Bil" is the correct spelling. | |
1062 | @example | |
1063 | @group | |
1064 | (user-full-name) | |
1065 | @result{} "Bil Lewis" | |
1066 | @end group | |
1067 | @end example | |
1068 | ||
1069 | If the Emacs job's user-id does not correspond to any known user (and | |
1070 | provided @code{NAME} is not set), the value is @code{"unknown"}. | |
1071 | ||
1072 | If @var{uid} is non-@code{nil}, then it should be a number (a user-id) | |
1073 | or a string (a login name). Then @code{user-full-name} returns the full | |
1074 | name corresponding to that user-id or login name. If you specify a | |
1075 | user-id or login name that isn't defined, it returns @code{nil}. | |
1076 | @end defun | |
1077 | ||
1078 | @vindex user-full-name | |
1079 | @vindex user-real-login-name | |
1080 | @vindex user-login-name | |
1081 | The symbols @code{user-login-name}, @code{user-real-login-name} and | |
1082 | @code{user-full-name} are variables as well as functions. The functions | |
1083 | return the same values that the variables hold. These variables allow | |
1084 | you to ``fake out'' Emacs by telling the functions what to return. The | |
1085 | variables are also useful for constructing frame titles (@pxref{Frame | |
1086 | Titles}). | |
1087 | ||
1088 | @defun user-real-uid | |
1089 | This function returns the real @acronym{UID} of the user. | |
1090 | The value may be a floating point number. | |
1091 | ||
1092 | @example | |
1093 | @group | |
1094 | (user-real-uid) | |
1095 | @result{} 19 | |
1096 | @end group | |
1097 | @end example | |
1098 | @end defun | |
1099 | ||
1100 | @defun user-uid | |
1101 | This function returns the effective @acronym{UID} of the user. | |
1102 | The value may be a floating point number. | |
1103 | @end defun | |
1104 | ||
1105 | @node Time of Day | |
1106 | @section Time of Day | |
1107 | ||
1108 | This section explains how to determine the current time and the time | |
1109 | zone. | |
1110 | ||
1111 | @defun current-time-string &optional time-value | |
1112 | This function returns the current time and date as a human-readable | |
1113 | string. The format of the string is unvarying; the number of characters | |
1114 | used for each part is always the same, so you can reliably use | |
1115 | @code{substring} to extract pieces of it. It is wise to count the | |
1116 | characters from the beginning of the string rather than from the end, as | |
1117 | additional information may some day be added at the end. | |
1118 | ||
b8d4c8d0 | 1119 | The argument @var{time-value}, if given, specifies a time to format |
edd6a733 CY |
1120 | instead of the current time. This argument should have the same form |
1121 | as the times obtained from @code{current-time} (see below) and from | |
1122 | @code{file-attributes} (@pxref{Definition of file-attributes}). It | |
1123 | should be a list whose first two elements are integers; a third | |
1124 | (microsecond) element, if present, is ignored. @var{time-value} can | |
1125 | also be a cons of two integers, but this usage is obsolete. | |
b8d4c8d0 GM |
1126 | |
1127 | @example | |
1128 | @group | |
1129 | (current-time-string) | |
1130 | @result{} "Wed Oct 14 22:21:05 1987" | |
1131 | @end group | |
1132 | @end example | |
1133 | @end defun | |
1134 | ||
b8d4c8d0 GM |
1135 | @defun current-time |
1136 | This function returns the system's time value as a list of three | |
1137 | integers: @code{(@var{high} @var{low} @var{microsec})}. The integers | |
1138 | @var{high} and @var{low} combine to give the number of seconds since | |
1139 | 0:00 January 1, 1970 UTC (Coordinated Universal Time), which is | |
1140 | @ifnottex | |
1141 | @var{high} * 2**16 + @var{low}. | |
1142 | @end ifnottex | |
1143 | @tex | |
1144 | $high*2^{16}+low$. | |
1145 | @end tex | |
1146 | ||
1147 | The third element, @var{microsec}, gives the microseconds since the | |
1148 | start of the current second (or 0 for systems that return time with | |
1149 | the resolution of only one second). | |
1150 | ||
1151 | The first two elements can be compared with file time values such as you | |
1152 | get with the function @code{file-attributes}. | |
1153 | @xref{Definition of file-attributes}. | |
1154 | @end defun | |
1155 | ||
51a714e1 CY |
1156 | @defun float-time &optional time-value |
1157 | This function returns the current time as a floating-point number of | |
1158 | seconds since the epoch. The argument @var{time-value}, if given, | |
1159 | specifies a time to convert instead of the current time. The argument | |
1160 | should have the same form as for @code{current-time-string} (see | |
1161 | above). Thus, it accepts the output of @code{current-time} and | |
1162 | @code{file-attributes} (@pxref{Definition of file-attributes}). | |
1163 | ||
1164 | @emph{Warning}: Since the result is floating point, it may not be | |
1165 | exact. Do not use this function if precise time stamps are required. | |
1166 | @end defun | |
1167 | ||
b8d4c8d0 GM |
1168 | @defun current-time-zone &optional time-value |
1169 | This function returns a list describing the time zone that the user is | |
1170 | in. | |
1171 | ||
1172 | The value has the form @code{(@var{offset} @var{name})}. Here | |
1173 | @var{offset} is an integer giving the number of seconds ahead of UTC | |
1174 | (east of Greenwich). A negative value means west of Greenwich. The | |
1175 | second element, @var{name}, is a string giving the name of the time | |
1176 | zone. Both elements change when daylight saving time begins or ends; | |
1177 | if the user has specified a time zone that does not use a seasonal time | |
1178 | adjustment, then the value is constant through time. | |
1179 | ||
1180 | If the operating system doesn't supply all the information necessary to | |
1181 | compute the value, the unknown elements of the list are @code{nil}. | |
1182 | ||
1183 | The argument @var{time-value}, if given, specifies a time to analyze | |
1184 | instead of the current time. The argument should have the same form | |
1185 | as for @code{current-time-string} (see above). Thus, you can use | |
1186 | times obtained from @code{current-time} (see above) and from | |
1187 | @code{file-attributes}. @xref{Definition of file-attributes}. | |
1188 | @end defun | |
1189 | ||
51a714e1 CY |
1190 | The current time zone is determined by the @samp{TZ} environment |
1191 | variable. @xref{System Environment}. For example, you can tell Emacs | |
1192 | to use universal time with @code{(setenv "TZ" "UTC0")}. If @samp{TZ} | |
1193 | is not in the environment, Emacs uses a platform-dependent default | |
1194 | time zone. | |
b8d4c8d0 GM |
1195 | |
1196 | @node Time Conversion | |
1197 | @section Time Conversion | |
1198 | ||
1199 | These functions convert time values (lists of two or three integers) | |
1200 | to calendrical information and vice versa. You can get time values | |
1201 | from the functions @code{current-time} (@pxref{Time of Day}) and | |
1202 | @code{file-attributes} (@pxref{Definition of file-attributes}). | |
1203 | ||
be14b9ab | 1204 | Many 32-bit operating systems are limited to time values that contain 32 bits |
b8d4c8d0 | 1205 | of information; these systems typically handle only the times from |
be14b9ab PE |
1206 | 1901-12-13 20:45:52 UTC through 2038-01-19 03:14:07 UTC. However, 64-bit |
1207 | and some 32-bit operating systems have larger time values, and can | |
1208 | represent times far in the past or future. | |
b8d4c8d0 GM |
1209 | |
1210 | Time conversion functions always use the Gregorian calendar, even | |
1211 | for dates before the Gregorian calendar was introduced. Year numbers | |
1212 | count the number of years since the year 1 B.C., and do not skip zero | |
1213 | as traditional Gregorian years do; for example, the year number | |
1214 | @minus{}37 represents the Gregorian year 38 B.C@. | |
1215 | ||
1216 | @defun decode-time &optional time | |
1217 | This function converts a time value into calendrical information. If | |
1218 | you don't specify @var{time}, it decodes the current time. The return | |
1219 | value is a list of nine elements, as follows: | |
1220 | ||
1221 | @example | |
1222 | (@var{seconds} @var{minutes} @var{hour} @var{day} @var{month} @var{year} @var{dow} @var{dst} @var{zone}) | |
1223 | @end example | |
1224 | ||
1225 | Here is what the elements mean: | |
1226 | ||
1227 | @table @var | |
1228 | @item seconds | |
1229 | The number of seconds past the minute, as an integer between 0 and 59. | |
1230 | On some operating systems, this is 60 for leap seconds. | |
1231 | @item minutes | |
1232 | The number of minutes past the hour, as an integer between 0 and 59. | |
1233 | @item hour | |
1234 | The hour of the day, as an integer between 0 and 23. | |
1235 | @item day | |
1236 | The day of the month, as an integer between 1 and 31. | |
1237 | @item month | |
1238 | The month of the year, as an integer between 1 and 12. | |
1239 | @item year | |
1240 | The year, an integer typically greater than 1900. | |
1241 | @item dow | |
1242 | The day of week, as an integer between 0 and 6, where 0 stands for | |
1243 | Sunday. | |
1244 | @item dst | |
1245 | @code{t} if daylight saving time is effect, otherwise @code{nil}. | |
1246 | @item zone | |
1247 | An integer indicating the time zone, as the number of seconds east of | |
1248 | Greenwich. | |
1249 | @end table | |
1250 | ||
1251 | @strong{Common Lisp Note:} Common Lisp has different meanings for | |
1252 | @var{dow} and @var{zone}. | |
1253 | @end defun | |
1254 | ||
1255 | @defun encode-time seconds minutes hour day month year &optional zone | |
1256 | This function is the inverse of @code{decode-time}. It converts seven | |
1257 | items of calendrical data into a time value. For the meanings of the | |
1258 | arguments, see the table above under @code{decode-time}. | |
1259 | ||
1260 | Year numbers less than 100 are not treated specially. If you want them | |
1261 | to stand for years above 1900, or years above 2000, you must alter them | |
1262 | yourself before you call @code{encode-time}. | |
1263 | ||
1264 | The optional argument @var{zone} defaults to the current time zone and | |
1265 | its daylight saving time rules. If specified, it can be either a list | |
1266 | (as you would get from @code{current-time-zone}), a string as in the | |
1267 | @code{TZ} environment variable, @code{t} for Universal Time, or an | |
1268 | integer (as you would get from @code{decode-time}). The specified | |
1269 | zone is used without any further alteration for daylight saving time. | |
1270 | ||
1271 | If you pass more than seven arguments to @code{encode-time}, the first | |
1272 | six are used as @var{seconds} through @var{year}, the last argument is | |
1273 | used as @var{zone}, and the arguments in between are ignored. This | |
1274 | feature makes it possible to use the elements of a list returned by | |
1275 | @code{decode-time} as the arguments to @code{encode-time}, like this: | |
1276 | ||
1277 | @example | |
1278 | (apply 'encode-time (decode-time @dots{})) | |
1279 | @end example | |
1280 | ||
1281 | You can perform simple date arithmetic by using out-of-range values for | |
1282 | the @var{seconds}, @var{minutes}, @var{hour}, @var{day}, and @var{month} | |
1283 | arguments; for example, day 0 means the day preceding the given month. | |
1284 | ||
1285 | The operating system puts limits on the range of possible time values; | |
1286 | if you try to encode a time that is out of range, an error results. | |
1287 | For instance, years before 1970 do not work on some systems; | |
1288 | on others, years as early as 1901 do work. | |
1289 | @end defun | |
1290 | ||
1291 | @node Time Parsing | |
1292 | @section Parsing and Formatting Times | |
1293 | ||
1294 | These functions convert time values (lists of two or three integers) | |
1295 | to text in a string, and vice versa. | |
1296 | ||
1297 | @defun date-to-time string | |
1298 | This function parses the time-string @var{string} and returns the | |
1299 | corresponding time value. | |
1300 | @end defun | |
1301 | ||
1302 | @defun format-time-string format-string &optional time universal | |
1303 | This function converts @var{time} (or the current time, if @var{time} is | |
1304 | omitted) to a string according to @var{format-string}. The argument | |
1305 | @var{format-string} may contain @samp{%}-sequences which say to | |
1306 | substitute parts of the time. Here is a table of what the | |
1307 | @samp{%}-sequences mean: | |
1308 | ||
1309 | @table @samp | |
1310 | @item %a | |
1311 | This stands for the abbreviated name of the day of week. | |
1312 | @item %A | |
1313 | This stands for the full name of the day of week. | |
1314 | @item %b | |
1315 | This stands for the abbreviated name of the month. | |
1316 | @item %B | |
1317 | This stands for the full name of the month. | |
1318 | @item %c | |
1319 | This is a synonym for @samp{%x %X}. | |
1320 | @item %C | |
1321 | This has a locale-specific meaning. In the default locale (named C), it | |
1322 | is equivalent to @samp{%A, %B %e, %Y}. | |
1323 | @item %d | |
1324 | This stands for the day of month, zero-padded. | |
1325 | @item %D | |
1326 | This is a synonym for @samp{%m/%d/%y}. | |
1327 | @item %e | |
1328 | This stands for the day of month, blank-padded. | |
1329 | @item %h | |
1330 | This is a synonym for @samp{%b}. | |
1331 | @item %H | |
1332 | This stands for the hour (00-23). | |
1333 | @item %I | |
1334 | This stands for the hour (01-12). | |
1335 | @item %j | |
1336 | This stands for the day of the year (001-366). | |
1337 | @item %k | |
1338 | This stands for the hour (0-23), blank padded. | |
1339 | @item %l | |
1340 | This stands for the hour (1-12), blank padded. | |
1341 | @item %m | |
1342 | This stands for the month (01-12). | |
1343 | @item %M | |
1344 | This stands for the minute (00-59). | |
1345 | @item %n | |
1346 | This stands for a newline. | |
a4180391 PE |
1347 | @item %N |
1348 | This stands for the nanoseconds (000000000-999999999). To ask for | |
1349 | fewer digits, use @samp{%3N} for milliseconds, @samp{%6N} for | |
1350 | microseconds, etc. Any excess digits are discarded, without rounding. | |
1351 | Currently Emacs time stamps are at best microsecond resolution so the | |
1352 | last three digits generated by plain @samp{%N} are always zero. | |
b8d4c8d0 GM |
1353 | @item %p |
1354 | This stands for @samp{AM} or @samp{PM}, as appropriate. | |
1355 | @item %r | |
1356 | This is a synonym for @samp{%I:%M:%S %p}. | |
1357 | @item %R | |
1358 | This is a synonym for @samp{%H:%M}. | |
1359 | @item %S | |
1360 | This stands for the seconds (00-59). | |
1361 | @item %t | |
1362 | This stands for a tab character. | |
1363 | @item %T | |
1364 | This is a synonym for @samp{%H:%M:%S}. | |
1365 | @item %U | |
1366 | This stands for the week of the year (01-52), assuming that weeks | |
1367 | start on Sunday. | |
1368 | @item %w | |
1369 | This stands for the numeric day of week (0-6). Sunday is day 0. | |
1370 | @item %W | |
1371 | This stands for the week of the year (01-52), assuming that weeks | |
1372 | start on Monday. | |
1373 | @item %x | |
1374 | This has a locale-specific meaning. In the default locale (named | |
1375 | @samp{C}), it is equivalent to @samp{%D}. | |
1376 | @item %X | |
1377 | This has a locale-specific meaning. In the default locale (named | |
1378 | @samp{C}), it is equivalent to @samp{%T}. | |
1379 | @item %y | |
1380 | This stands for the year without century (00-99). | |
1381 | @item %Y | |
1382 | This stands for the year with century. | |
1383 | @item %Z | |
1384 | This stands for the time zone abbreviation (e.g., @samp{EST}). | |
1385 | @item %z | |
1386 | This stands for the time zone numerical offset (e.g., @samp{-0500}). | |
1387 | @end table | |
1388 | ||
1389 | You can also specify the field width and type of padding for any of | |
1390 | these @samp{%}-sequences. This works as in @code{printf}: you write | |
1391 | the field width as digits in the middle of a @samp{%}-sequences. If you | |
1392 | start the field width with @samp{0}, it means to pad with zeros. If you | |
1393 | start the field width with @samp{_}, it means to pad with spaces. | |
1394 | ||
1395 | For example, @samp{%S} specifies the number of seconds since the minute; | |
1396 | @samp{%03S} means to pad this with zeros to 3 positions, @samp{%_3S} to | |
1397 | pad with spaces to 3 positions. Plain @samp{%3S} pads with zeros, | |
1398 | because that is how @samp{%S} normally pads to two positions. | |
1399 | ||
1400 | The characters @samp{E} and @samp{O} act as modifiers when used between | |
1401 | @samp{%} and one of the letters in the table above. @samp{E} specifies | |
1402 | using the current locale's ``alternative'' version of the date and time. | |
1403 | In a Japanese locale, for example, @code{%Ex} might yield a date format | |
1404 | based on the Japanese Emperors' reigns. @samp{E} is allowed in | |
1405 | @samp{%Ec}, @samp{%EC}, @samp{%Ex}, @samp{%EX}, @samp{%Ey}, and | |
1406 | @samp{%EY}. | |
1407 | ||
1408 | @samp{O} means to use the current locale's ``alternative'' | |
1409 | representation of numbers, instead of the ordinary decimal digits. This | |
1410 | is allowed with most letters, all the ones that output numbers. | |
1411 | ||
1412 | If @var{universal} is non-@code{nil}, that means to describe the time as | |
1413 | Universal Time; @code{nil} means describe it using what Emacs believes | |
1414 | is the local time zone (see @code{current-time-zone}). | |
1415 | ||
1416 | This function uses the C library function @code{strftime} | |
1417 | (@pxref{Formatting Calendar Time,,, libc, The GNU C Library Reference | |
1418 | Manual}) to do most of the work. In order to communicate with that | |
1419 | function, it first encodes its argument using the coding system | |
1420 | specified by @code{locale-coding-system} (@pxref{Locales}); after | |
1421 | @code{strftime} returns the resulting string, | |
1422 | @code{format-time-string} decodes the string using that same coding | |
1423 | system. | |
1424 | @end defun | |
1425 | ||
1426 | @defun seconds-to-time seconds | |
1427 | This function converts @var{seconds}, a floating point number of | |
1428 | seconds since the epoch, to a time value and returns that. To perform | |
1429 | the inverse conversion, use @code{float-time}. | |
1430 | @end defun | |
1431 | ||
53728487 EZ |
1432 | @defun format-seconds format-string seconds |
1433 | This function converts its argument @var{seconds} into a string of | |
1434 | years, days, hours, etc., according to @var{format-string}. The | |
1435 | argument @var{format-string} may contain @samp{%}-sequences which | |
1436 | control the conversion. Here is a table of what the | |
1437 | @samp{%}-sequences mean: | |
1438 | ||
1439 | @table @samp | |
1440 | @item %y | |
1441 | @itemx %Y | |
3051e4bf | 1442 | The integer number of 365-day years. |
53728487 EZ |
1443 | @item %d |
1444 | @itemx %D | |
3051e4bf | 1445 | The integer number of days. |
53728487 EZ |
1446 | @item %h |
1447 | @itemx %H | |
3051e4bf | 1448 | The integer number of hours. |
53728487 EZ |
1449 | @item %m |
1450 | @itemx %M | |
3051e4bf | 1451 | The integer number of minutes. |
53728487 EZ |
1452 | @item %s |
1453 | @itemx %S | |
3051e4bf | 1454 | The integer number of seconds. |
53728487 EZ |
1455 | @item %z |
1456 | Non-printing control flag. When it is used, other specifiers must be | |
1457 | given in the order of decreasing size, i.e.@: years before days, hours | |
1458 | before minutes, etc. Nothing will be produced in the result string to | |
1459 | the left of @samp{%z} until the first non-zero conversion is | |
1460 | encountered. For example, the default format used by | |
1461 | @code{emacs-uptime} (@pxref{Processor Run Time, emacs-uptime}) | |
1462 | @w{@code{"%Y, %D, %H, %M, %z%S"}} means that the number of seconds | |
1463 | will always be produced, but years, days, hours, and minutes will only | |
1464 | be shown if they are non-zero. | |
1465 | @item %% | |
1466 | Produces a literal @samp{%}. | |
1467 | @end table | |
1468 | ||
1469 | Upper-case format sequences produce the units in addition to the | |
1470 | numbers, lower-case formats produce only the numbers. | |
1471 | ||
1472 | You can also specify the field width by following the @samp{%} with a | |
1473 | number; shorter numbers will be padded with blanks. An optional | |
1474 | period before the width requests zero-padding instead. For example, | |
1475 | @code{"%.3Y"} might produce @code{"004 years"}. | |
1476 | ||
1477 | @emph{Warning:} This function works only with values of @var{seconds} | |
1478 | that don't exceed @code{most-positive-fixnum} (@pxref{Integer Basics, | |
1479 | most-positive-fixnum}). | |
1480 | @end defun | |
1481 | ||
b8d4c8d0 GM |
1482 | @node Processor Run Time |
1483 | @section Processor Run time | |
1484 | @cindex processor run time | |
53728487 EZ |
1485 | @cindex Emacs process run time |
1486 | ||
1487 | Emacs provides several functions and primitives that return time, | |
1488 | both elapsed and processor time, used by the Emacs process. | |
1489 | ||
106e6894 | 1490 | @deffn Command emacs-uptime &optional format |
53728487 EZ |
1491 | This function returns a string representing the Emacs |
1492 | @dfn{uptime}---the elapsed wall-clock time this instance of Emacs is | |
3051e4bf EZ |
1493 | running. The string is formatted by @code{format-seconds} according |
1494 | to the optional argument @var{format}. For the available format | |
1495 | descriptors, see @ref{Time Parsing, format-seconds}. If @var{format} | |
e2b7cebb CY |
1496 | is @code{nil} or omitted, it defaults to @code{"%Y, %D, %H, %M, |
1497 | %z%S"}. | |
106e6894 CY |
1498 | |
1499 | When called interactively, it prints the uptime in the echo area. | |
1500 | @end deffn | |
b8d4c8d0 GM |
1501 | |
1502 | @defun get-internal-run-time | |
1503 | This function returns the processor run time used by Emacs as a list | |
1504 | of three integers: @code{(@var{high} @var{low} @var{microsec})}. The | |
1505 | integers @var{high} and @var{low} combine to give the number of | |
1506 | seconds, which is | |
1507 | @ifnottex | |
1508 | @var{high} * 2**16 + @var{low}. | |
1509 | @end ifnottex | |
1510 | @tex | |
1511 | $high*2^{16}+low$. | |
1512 | @end tex | |
1513 | ||
1514 | The third element, @var{microsec}, gives the microseconds (or 0 for | |
1515 | systems that return time with the resolution of only one second). | |
1516 | ||
53728487 EZ |
1517 | Note that the time returned by this function excludes the time Emacs |
1518 | was not using the processor, and if the Emacs process has several | |
1519 | threads, the returned value is the sum of the processor times used up | |
1520 | by all Emacs threads. | |
1521 | ||
b8d4c8d0 | 1522 | If the system doesn't provide a way to determine the processor run |
53728487 EZ |
1523 | time, @code{get-internal-run-time} returns the same time as |
1524 | @code{current-time}. | |
1525 | @end defun | |
1526 | ||
106e6894 | 1527 | @deffn Command emacs-init-time |
53728487 | 1528 | This function returns the duration of the Emacs initialization |
106e6894 CY |
1529 | (@pxref{Startup Summary}) in seconds, as a string. When called |
1530 | interactively, it prints the duration in the echo area. | |
1531 | @end deffn | |
b8d4c8d0 GM |
1532 | |
1533 | @node Time Calculations | |
1534 | @section Time Calculations | |
1535 | ||
1536 | These functions perform calendrical computations using time values | |
1537 | (the kind of list that @code{current-time} returns). | |
1538 | ||
1539 | @defun time-less-p t1 t2 | |
1540 | This returns @code{t} if time value @var{t1} is less than time value | |
1541 | @var{t2}. | |
1542 | @end defun | |
1543 | ||
1544 | @defun time-subtract t1 t2 | |
1545 | This returns the time difference @var{t1} @minus{} @var{t2} between | |
1546 | two time values, in the same format as a time value. | |
1547 | @end defun | |
1548 | ||
1549 | @defun time-add t1 t2 | |
1550 | This returns the sum of two time values, one of which ought to | |
1551 | represent a time difference rather than a point in time. | |
1552 | Here is how to add a number of seconds to a time value: | |
1553 | ||
1554 | @example | |
1555 | (time-add @var{time} (seconds-to-time @var{seconds})) | |
1556 | @end example | |
1557 | @end defun | |
1558 | ||
1559 | @defun time-to-days time | |
1560 | This function returns the number of days between the beginning of year | |
1561 | 1 and @var{time}. | |
1562 | @end defun | |
1563 | ||
1564 | @defun time-to-day-in-year time | |
1565 | This returns the day number within the year corresponding to @var{time}. | |
1566 | @end defun | |
1567 | ||
1568 | @defun date-leap-year-p year | |
1569 | This function returns @code{t} if @var{year} is a leap year. | |
1570 | @end defun | |
1571 | ||
1572 | @node Timers | |
1573 | @section Timers for Delayed Execution | |
1574 | @cindex timer | |
1575 | ||
1576 | You can set up a @dfn{timer} to call a function at a specified | |
1577 | future time or after a certain length of idleness. | |
1578 | ||
1579 | Emacs cannot run timers at any arbitrary point in a Lisp program; it | |
1580 | can run them only when Emacs could accept output from a subprocess: | |
1581 | namely, while waiting or inside certain primitive functions such as | |
1582 | @code{sit-for} or @code{read-event} which @emph{can} wait. Therefore, a | |
1583 | timer's execution may be delayed if Emacs is busy. However, the time of | |
1584 | execution is very precise if Emacs is idle. | |
1585 | ||
1586 | Emacs binds @code{inhibit-quit} to @code{t} before calling the timer | |
1587 | function, because quitting out of many timer functions can leave | |
1588 | things in an inconsistent state. This is normally unproblematical | |
1589 | because most timer functions don't do a lot of work. Indeed, for a | |
1590 | timer to call a function that takes substantial time to run is likely | |
1591 | to be annoying. If a timer function needs to allow quitting, it | |
1592 | should use @code{with-local-quit} (@pxref{Quitting}). For example, if | |
1593 | a timer function calls @code{accept-process-output} to receive output | |
1594 | from an external process, that call should be wrapped inside | |
1595 | @code{with-local-quit}, to ensure that @kbd{C-g} works if the external | |
1596 | process hangs. | |
1597 | ||
1598 | It is usually a bad idea for timer functions to alter buffer | |
1599 | contents. When they do, they usually should call @code{undo-boundary} | |
1600 | both before and after changing the buffer, to separate the timer's | |
1601 | changes from user commands' changes and prevent a single undo entry | |
1602 | from growing to be quite large. | |
1603 | ||
1604 | Timer functions should also avoid calling functions that cause Emacs | |
1605 | to wait, such as @code{sit-for} (@pxref{Waiting}). This can lead to | |
1606 | unpredictable effects, since other timers (or even the same timer) can | |
1607 | run while waiting. If a timer function needs to perform an action | |
1608 | after a certain time has elapsed, it can do this by scheduling a new | |
1609 | timer. | |
1610 | ||
1611 | If a timer function calls functions that can change the match data, | |
1612 | it should save and restore the match data. @xref{Saving Match Data}. | |
1613 | ||
1614 | @deffn Command run-at-time time repeat function &rest args | |
1615 | This sets up a timer that calls the function @var{function} with | |
1616 | arguments @var{args} at time @var{time}. If @var{repeat} is a number | |
1617 | (integer or floating point), the timer is scheduled to run again every | |
1618 | @var{repeat} seconds after @var{time}. If @var{repeat} is @code{nil}, | |
1619 | the timer runs only once. | |
1620 | ||
1621 | @var{time} may specify an absolute or a relative time. | |
1622 | ||
1623 | Absolute times may be specified using a string with a limited variety | |
1624 | of formats, and are taken to be times @emph{today}, even if already in | |
1625 | the past. The recognized forms are @samp{@var{xxxx}}, | |
1626 | @samp{@var{x}:@var{xx}}, or @samp{@var{xx}:@var{xx}} (military time), | |
1627 | and @samp{@var{xx}am}, @samp{@var{xx}AM}, @samp{@var{xx}pm}, | |
1628 | @samp{@var{xx}PM}, @samp{@var{xx}:@var{xx}am}, | |
1629 | @samp{@var{xx}:@var{xx}AM}, @samp{@var{xx}:@var{xx}pm}, or | |
1630 | @samp{@var{xx}:@var{xx}PM}. A period can be used instead of a colon | |
1631 | to separate the hour and minute parts. | |
1632 | ||
1633 | To specify a relative time as a string, use numbers followed by units. | |
1634 | For example: | |
1635 | ||
1636 | @table @samp | |
1637 | @item 1 min | |
1638 | denotes 1 minute from now. | |
1639 | @item 1 min 5 sec | |
1640 | denotes 65 seconds from now. | |
1641 | @item 1 min 2 sec 3 hour 4 day 5 week 6 fortnight 7 month 8 year | |
1642 | denotes exactly 103 months, 123 days, and 10862 seconds from now. | |
1643 | @end table | |
1644 | ||
1645 | For relative time values, Emacs considers a month to be exactly thirty | |
1646 | days, and a year to be exactly 365.25 days. | |
1647 | ||
1648 | Not all convenient formats are strings. If @var{time} is a number | |
1649 | (integer or floating point), that specifies a relative time measured in | |
1650 | seconds. The result of @code{encode-time} can also be used to specify | |
1651 | an absolute value for @var{time}. | |
1652 | ||
1653 | In most cases, @var{repeat} has no effect on when @emph{first} call | |
1654 | takes place---@var{time} alone specifies that. There is one exception: | |
1655 | if @var{time} is @code{t}, then the timer runs whenever the time is a | |
1656 | multiple of @var{repeat} seconds after the epoch. This is useful for | |
1657 | functions like @code{display-time}. | |
1658 | ||
1659 | The function @code{run-at-time} returns a timer value that identifies | |
1660 | the particular scheduled future action. You can use this value to call | |
1661 | @code{cancel-timer} (see below). | |
1662 | @end deffn | |
1663 | ||
1664 | A repeating timer nominally ought to run every @var{repeat} seconds, | |
1665 | but remember that any invocation of a timer can be late. Lateness of | |
1666 | one repetition has no effect on the scheduled time of the next | |
1667 | repetition. For instance, if Emacs is busy computing for long enough | |
1668 | to cover three scheduled repetitions of the timer, and then starts to | |
1669 | wait, it will immediately call the timer function three times in | |
1670 | immediate succession (presuming no other timers trigger before or | |
1671 | between them). If you want a timer to run again no less than @var{n} | |
1672 | seconds after the last invocation, don't use the @var{repeat} argument. | |
1673 | Instead, the timer function should explicitly reschedule the timer. | |
1674 | ||
1675 | @defvar timer-max-repeats | |
1676 | This variable's value specifies the maximum number of times to repeat | |
1677 | calling a timer function in a row, when many previously scheduled | |
1678 | calls were unavoidably delayed. | |
1679 | @end defvar | |
1680 | ||
1681 | @defmac with-timeout (seconds timeout-forms@dots{}) body@dots{} | |
1682 | Execute @var{body}, but give up after @var{seconds} seconds. If | |
1683 | @var{body} finishes before the time is up, @code{with-timeout} returns | |
1684 | the value of the last form in @var{body}. If, however, the execution of | |
1685 | @var{body} is cut short by the timeout, then @code{with-timeout} | |
1686 | executes all the @var{timeout-forms} and returns the value of the last | |
1687 | of them. | |
1688 | ||
1689 | This macro works by setting a timer to run after @var{seconds} seconds. If | |
1690 | @var{body} finishes before that time, it cancels the timer. If the | |
1691 | timer actually runs, it terminates execution of @var{body}, then | |
1692 | executes @var{timeout-forms}. | |
1693 | ||
1694 | Since timers can run within a Lisp program only when the program calls a | |
1695 | primitive that can wait, @code{with-timeout} cannot stop executing | |
1696 | @var{body} while it is in the midst of a computation---only when it | |
1697 | calls one of those primitives. So use @code{with-timeout} only with a | |
1698 | @var{body} that waits for input, not one that does a long computation. | |
1699 | @end defmac | |
1700 | ||
1701 | The function @code{y-or-n-p-with-timeout} provides a simple way to use | |
1702 | a timer to avoid waiting too long for an answer. @xref{Yes-or-No | |
1703 | Queries}. | |
1704 | ||
1705 | @defun cancel-timer timer | |
1706 | This cancels the requested action for @var{timer}, which should be a | |
1707 | timer---usually, one previously returned by @code{run-at-time} or | |
1708 | @code{run-with-idle-timer}. This cancels the effect of that call to | |
1709 | one of these functions; the arrival of the specified time will not | |
1710 | cause anything special to happen. | |
1711 | @end defun | |
1712 | ||
1713 | @node Idle Timers | |
1714 | @section Idle Timers | |
1715 | ||
1716 | Here is how to set up a timer that runs when Emacs is idle for a | |
1717 | certain length of time. Aside from how to set them up, idle timers | |
1718 | work just like ordinary timers. | |
1719 | ||
1720 | @deffn Command run-with-idle-timer secs repeat function &rest args | |
1721 | Set up a timer which runs when Emacs has been idle for @var{secs} | |
1722 | seconds. The value of @var{secs} may be an integer or a floating point | |
1723 | number; a value of the type returned by @code{current-idle-time} | |
1724 | is also allowed. | |
1725 | ||
1726 | If @var{repeat} is @code{nil}, the timer runs just once, the first time | |
1727 | Emacs remains idle for a long enough time. More often @var{repeat} is | |
1728 | non-@code{nil}, which means to run the timer @emph{each time} Emacs | |
1729 | remains idle for @var{secs} seconds. | |
1730 | ||
1731 | The function @code{run-with-idle-timer} returns a timer value which you | |
1732 | can use in calling @code{cancel-timer} (@pxref{Timers}). | |
1733 | @end deffn | |
1734 | ||
1735 | @cindex idleness | |
1736 | Emacs becomes ``idle'' when it starts waiting for user input, and it | |
1737 | remains idle until the user provides some input. If a timer is set for | |
1738 | five seconds of idleness, it runs approximately five seconds after Emacs | |
1739 | first becomes idle. Even if @var{repeat} is non-@code{nil}, this timer | |
1740 | will not run again as long as Emacs remains idle, because the duration | |
1741 | of idleness will continue to increase and will not go down to five | |
1742 | seconds again. | |
1743 | ||
1744 | Emacs can do various things while idle: garbage collect, autosave or | |
1745 | handle data from a subprocess. But these interludes during idleness do | |
1746 | not interfere with idle timers, because they do not reset the clock of | |
1747 | idleness to zero. An idle timer set for 600 seconds will run when ten | |
1748 | minutes have elapsed since the last user command was finished, even if | |
1749 | subprocess output has been accepted thousands of times within those ten | |
1750 | minutes, and even if there have been garbage collections and autosaves. | |
1751 | ||
1752 | When the user supplies input, Emacs becomes non-idle while executing the | |
1753 | input. Then it becomes idle again, and all the idle timers that are | |
1754 | set up to repeat will subsequently run another time, one by one. | |
1755 | ||
1756 | @c Emacs 19 feature | |
1757 | @defun current-idle-time | |
17bec671 RS |
1758 | If Emacs is idle, this function returns the length of time Emacs has |
1759 | been idle, as a list of three integers: @code{(@var{high} @var{low} | |
1760 | @var{microsec})}. The integers @var{high} and @var{low} combine to | |
1761 | give the number of seconds of idleness, which is | |
b8d4c8d0 GM |
1762 | @ifnottex |
1763 | @var{high} * 2**16 + @var{low}. | |
1764 | @end ifnottex | |
1765 | @tex | |
1766 | $high*2^{16}+low$. | |
1767 | @end tex | |
1768 | ||
1769 | The third element, @var{microsec}, gives the microseconds since the | |
1770 | start of the current second (or 0 for systems that return time with | |
1771 | the resolution of only one second). | |
1772 | ||
17bec671 RS |
1773 | When Emacs is not idle, @code{current-idle-time} returns @code{nil}. |
1774 | This is a convenient way to test whether Emacs is idle. | |
1775 | ||
b8d4c8d0 GM |
1776 | The main use of this function is when an idle timer function wants to |
1777 | ``take a break'' for a while. It can set up another idle timer to | |
1778 | call the same function again, after a few seconds more idleness. | |
1779 | Here's an example: | |
1780 | ||
1781 | @smallexample | |
1782 | (defvar resume-timer nil | |
1783 | "Timer that `timer-function' used to reschedule itself, or nil.") | |
1784 | ||
1785 | (defun timer-function () | |
1786 | ;; @r{If the user types a command while @code{resume-timer}} | |
1787 | ;; @r{is active, the next time this function is called from} | |
1788 | ;; @r{its main idle timer, deactivate @code{resume-timer}.} | |
1789 | (when resume-timer | |
1790 | (cancel-timer resume-timer)) | |
1791 | ...@var{do the work for a while}... | |
1792 | (when @var{taking-a-break} | |
1793 | (setq resume-timer | |
1794 | (run-with-idle-timer | |
1795 | ;; Compute an idle time @var{break-length} | |
1796 | ;; more than the current value. | |
1797 | (time-add (current-idle-time) | |
1798 | (seconds-to-time @var{break-length})) | |
1799 | nil | |
1800 | 'timer-function)))) | |
1801 | @end smallexample | |
1802 | @end defun | |
1803 | ||
1804 | Some idle timer functions in user Lisp packages have a loop that | |
1805 | does a certain amount of processing each time around, and exits when | |
1806 | @code{(input-pending-p)} is non-@code{nil}. That approach seems very | |
1807 | natural but has two problems: | |
1808 | ||
1809 | @itemize | |
1810 | @item | |
1811 | It blocks out all process output (since Emacs accepts process output | |
1812 | only while waiting). | |
1813 | ||
1814 | @item | |
1815 | It blocks out any idle timers that ought to run during that time. | |
1816 | @end itemize | |
1817 | ||
1818 | @noindent | |
1819 | To avoid these problems, don't use that technique. Instead, write | |
1820 | such idle timers to reschedule themselves after a brief pause, using | |
1821 | the method in the @code{timer-function} example above. | |
1822 | ||
1823 | @node Terminal Input | |
1824 | @section Terminal Input | |
1825 | @cindex terminal input | |
1826 | ||
1827 | This section describes functions and variables for recording or | |
1828 | manipulating terminal input. See @ref{Display}, for related | |
1829 | functions. | |
1830 | ||
1831 | @menu | |
d24880de GM |
1832 | * Input Modes:: Options for how input is processed. |
1833 | * Recording Input:: Saving histories of recent or all input events. | |
b8d4c8d0 GM |
1834 | @end menu |
1835 | ||
1836 | @node Input Modes | |
1837 | @subsection Input Modes | |
1838 | @cindex input modes | |
1839 | @cindex terminal input modes | |
1840 | ||
1841 | @defun set-input-mode interrupt flow meta &optional quit-char | |
1842 | This function sets the mode for reading keyboard input. If | |
1843 | @var{interrupt} is non-null, then Emacs uses input interrupts. If it is | |
1844 | @code{nil}, then it uses @sc{cbreak} mode. The default setting is | |
1845 | system-dependent. Some systems always use @sc{cbreak} mode regardless | |
1846 | of what is specified. | |
1847 | ||
1848 | When Emacs communicates directly with X, it ignores this argument and | |
1849 | uses interrupts if that is the way it knows how to communicate. | |
1850 | ||
1851 | If @var{flow} is non-@code{nil}, then Emacs uses @sc{xon/xoff} | |
1852 | (@kbd{C-q}, @kbd{C-s}) flow control for output to the terminal. This | |
1853 | has no effect except in @sc{cbreak} mode. | |
1854 | ||
1855 | @c Emacs 19 feature | |
1856 | The argument @var{meta} controls support for input character codes | |
1857 | above 127. If @var{meta} is @code{t}, Emacs converts characters with | |
1858 | the 8th bit set into Meta characters. If @var{meta} is @code{nil}, | |
1859 | Emacs disregards the 8th bit; this is necessary when the terminal uses | |
1860 | it as a parity bit. If @var{meta} is neither @code{t} nor @code{nil}, | |
1861 | Emacs uses all 8 bits of input unchanged. This is good for terminals | |
1862 | that use 8-bit character sets. | |
1863 | ||
1864 | @c Emacs 19 feature | |
1865 | If @var{quit-char} is non-@code{nil}, it specifies the character to | |
1866 | use for quitting. Normally this character is @kbd{C-g}. | |
1867 | @xref{Quitting}. | |
1868 | @end defun | |
1869 | ||
1870 | The @code{current-input-mode} function returns the input mode settings | |
1871 | Emacs is currently using. | |
1872 | ||
1873 | @c Emacs 19 feature | |
1874 | @defun current-input-mode | |
1875 | This function returns the current mode for reading keyboard input. It | |
1876 | returns a list, corresponding to the arguments of @code{set-input-mode}, | |
1877 | of the form @code{(@var{interrupt} @var{flow} @var{meta} @var{quit})} in | |
1878 | which: | |
1879 | @table @var | |
1880 | @item interrupt | |
1881 | is non-@code{nil} when Emacs is using interrupt-driven input. If | |
1882 | @code{nil}, Emacs is using @sc{cbreak} mode. | |
1883 | @item flow | |
1884 | is non-@code{nil} if Emacs uses @sc{xon/xoff} (@kbd{C-q}, @kbd{C-s}) | |
1885 | flow control for output to the terminal. This value is meaningful only | |
1886 | when @var{interrupt} is @code{nil}. | |
1887 | @item meta | |
1888 | is @code{t} if Emacs treats the eighth bit of input characters as | |
1889 | the meta bit; @code{nil} means Emacs clears the eighth bit of every | |
1890 | input character; any other value means Emacs uses all eight bits as the | |
1891 | basic character code. | |
1892 | @item quit | |
1893 | is the character Emacs currently uses for quitting, usually @kbd{C-g}. | |
1894 | @end table | |
1895 | @end defun | |
1896 | ||
1897 | @node Recording Input | |
1898 | @subsection Recording Input | |
1899 | @cindex recording input | |
1900 | ||
1901 | @defun recent-keys | |
1902 | This function returns a vector containing the last 300 input events from | |
1903 | the keyboard or mouse. All input events are included, whether or not | |
1904 | they were used as parts of key sequences. Thus, you always get the last | |
1905 | 100 input events, not counting events generated by keyboard macros. | |
1906 | (These are excluded because they are less interesting for debugging; it | |
1907 | should be enough to see the events that invoked the macros.) | |
1908 | ||
1909 | A call to @code{clear-this-command-keys} (@pxref{Command Loop Info}) | |
1910 | causes this function to return an empty vector immediately afterward. | |
1911 | @end defun | |
1912 | ||
1913 | @deffn Command open-dribble-file filename | |
1914 | @cindex dribble file | |
1915 | This function opens a @dfn{dribble file} named @var{filename}. When a | |
1916 | dribble file is open, each input event from the keyboard or mouse (but | |
1917 | not those from keyboard macros) is written in that file. A | |
1918 | non-character event is expressed using its printed representation | |
1919 | surrounded by @samp{<@dots{}>}. | |
1920 | ||
1921 | You close the dribble file by calling this function with an argument | |
1922 | of @code{nil}. | |
1923 | ||
1924 | This function is normally used to record the input necessary to | |
1925 | trigger an Emacs bug, for the sake of a bug report. | |
1926 | ||
1927 | @example | |
1928 | @group | |
1929 | (open-dribble-file "~/dribble") | |
1930 | @result{} nil | |
1931 | @end group | |
1932 | @end example | |
1933 | @end deffn | |
1934 | ||
1935 | See also the @code{open-termscript} function (@pxref{Terminal Output}). | |
1936 | ||
1937 | @node Terminal Output | |
1938 | @section Terminal Output | |
1939 | @cindex terminal output | |
1940 | ||
1941 | The terminal output functions send output to a text terminal, or keep | |
1942 | track of output sent to the terminal. The variable @code{baud-rate} | |
1943 | tells you what Emacs thinks is the output speed of the terminal. | |
1944 | ||
01f17ae2 | 1945 | @defopt baud-rate |
b8d4c8d0 GM |
1946 | This variable's value is the output speed of the terminal, as far as |
1947 | Emacs knows. Setting this variable does not change the speed of actual | |
1948 | data transmission, but the value is used for calculations such as | |
1949 | padding. | |
1950 | ||
1951 | It also affects decisions about whether to scroll part of the | |
1952 | screen or repaint on text terminals. @xref{Forcing Redisplay}, | |
1953 | for the corresponding functionality on graphical terminals. | |
1954 | ||
1955 | The value is measured in baud. | |
01f17ae2 | 1956 | @end defopt |
b8d4c8d0 GM |
1957 | |
1958 | If you are running across a network, and different parts of the | |
1959 | network work at different baud rates, the value returned by Emacs may be | |
1960 | different from the value used by your local terminal. Some network | |
1961 | protocols communicate the local terminal speed to the remote machine, so | |
1962 | that Emacs and other programs can get the proper value, but others do | |
1963 | not. If Emacs has the wrong value, it makes decisions that are less | |
1964 | than optimal. To fix the problem, set @code{baud-rate}. | |
1965 | ||
106e6894 CY |
1966 | @defun send-string-to-terminal string &optional terminal |
1967 | This function sends @var{string} to @var{terminal} without alteration. | |
b8d4c8d0 | 1968 | Control characters in @var{string} have terminal-dependent effects. |
106e6894 CY |
1969 | This function operates only on text terminals. @var{terminal} may be |
1970 | a terminal object, a frame, or @code{nil} for the selected frame's | |
f804f446 | 1971 | terminal. In batch mode, @var{string} is sent to @code{stdout} when |
f58a7c7e | 1972 | @var{terminal} is @code{nil}. |
b8d4c8d0 GM |
1973 | |
1974 | One use of this function is to define function keys on terminals that | |
1975 | have downloadable function key definitions. For example, this is how (on | |
1976 | certain terminals) to define function key 4 to move forward four | |
1977 | characters (by transmitting the characters @kbd{C-u C-f} to the | |
1978 | computer): | |
1979 | ||
1980 | @example | |
1981 | @group | |
1982 | (send-string-to-terminal "\eF4\^U\^F") | |
1983 | @result{} nil | |
1984 | @end group | |
1985 | @end example | |
1986 | @end defun | |
1987 | ||
1988 | @deffn Command open-termscript filename | |
1989 | @cindex termscript file | |
1990 | This function is used to open a @dfn{termscript file} that will record | |
1991 | all the characters sent by Emacs to the terminal. It returns | |
1992 | @code{nil}. Termscript files are useful for investigating problems | |
1993 | where Emacs garbles the screen, problems that are due to incorrect | |
1994 | Termcap entries or to undesirable settings of terminal options more | |
1995 | often than to actual Emacs bugs. Once you are certain which characters | |
1996 | were actually output, you can determine reliably whether they correspond | |
1997 | to the Termcap specifications in use. | |
1998 | ||
1999 | You close the termscript file by calling this function with an | |
2000 | argument of @code{nil}. | |
2001 | ||
2002 | See also @code{open-dribble-file} in @ref{Recording Input}. | |
2003 | ||
2004 | @example | |
2005 | @group | |
2006 | (open-termscript "../junk/termscript") | |
2007 | @result{} nil | |
2008 | @end group | |
2009 | @end example | |
2010 | @end deffn | |
2011 | ||
2012 | @node Sound Output | |
2013 | @section Sound Output | |
2014 | @cindex sound | |
2015 | ||
2016 | To play sound using Emacs, use the function @code{play-sound}. Only | |
2017 | certain systems are supported; if you call @code{play-sound} on a system | |
2018 | which cannot really do the job, it gives an error. Emacs version 20 and | |
2019 | earlier did not support sound at all. | |
2020 | ||
2021 | The sound must be stored as a file in RIFF-WAVE format (@samp{.wav}) | |
2022 | or Sun Audio format (@samp{.au}). | |
2023 | ||
2024 | @defun play-sound sound | |
2025 | This function plays a specified sound. The argument, @var{sound}, has | |
2026 | the form @code{(sound @var{properties}...)}, where the @var{properties} | |
2027 | consist of alternating keywords (particular symbols recognized | |
2028 | specially) and values corresponding to them. | |
2029 | ||
2030 | Here is a table of the keywords that are currently meaningful in | |
2031 | @var{sound}, and their meanings: | |
2032 | ||
2033 | @table @code | |
2034 | @item :file @var{file} | |
2035 | This specifies the file containing the sound to play. | |
2036 | If the file name is not absolute, it is expanded against | |
2037 | the directory @code{data-directory}. | |
2038 | ||
2039 | @item :data @var{data} | |
2040 | This specifies the sound to play without need to refer to a file. The | |
2041 | value, @var{data}, should be a string containing the same bytes as a | |
2042 | sound file. We recommend using a unibyte string. | |
2043 | ||
2044 | @item :volume @var{volume} | |
2045 | This specifies how loud to play the sound. It should be a number in the | |
2046 | range of 0 to 1. The default is to use whatever volume has been | |
2047 | specified before. | |
2048 | ||
2049 | @item :device @var{device} | |
2050 | This specifies the system device on which to play the sound, as a | |
2051 | string. The default device is system-dependent. | |
2052 | @end table | |
2053 | ||
2054 | Before actually playing the sound, @code{play-sound} | |
2055 | calls the functions in the list @code{play-sound-functions}. | |
2056 | Each function is called with one argument, @var{sound}. | |
2057 | @end defun | |
2058 | ||
2059 | @defun play-sound-file file &optional volume device | |
2060 | This function is an alternative interface to playing a sound @var{file} | |
2061 | specifying an optional @var{volume} and @var{device}. | |
2062 | @end defun | |
2063 | ||
2064 | @defvar play-sound-functions | |
2065 | A list of functions to be called before playing a sound. Each function | |
2066 | is called with one argument, a property list that describes the sound. | |
2067 | @end defvar | |
2068 | ||
2069 | @node X11 Keysyms | |
2070 | @section Operating on X11 Keysyms | |
2071 | @cindex X11 keysyms | |
2072 | ||
2073 | To define system-specific X11 keysyms, set the variable | |
2074 | @code{system-key-alist}. | |
2075 | ||
2076 | @defvar system-key-alist | |
2077 | This variable's value should be an alist with one element for each | |
2078 | system-specific keysym. Each element has the form @code{(@var{code} | |
2079 | . @var{symbol})}, where @var{code} is the numeric keysym code (not | |
2080 | including the ``vendor specific'' bit, | |
2081 | @ifnottex | |
2082 | -2**28), | |
2083 | @end ifnottex | |
2084 | @tex | |
2085 | $-2^{28}$), | |
2086 | @end tex | |
2087 | and @var{symbol} is the name for the function key. | |
2088 | ||
2089 | For example @code{(168 . mute-acute)} defines a system-specific key (used | |
2090 | by HP X servers) whose numeric code is | |
2091 | @ifnottex | |
2092 | -2**28 | |
2093 | @end ifnottex | |
2094 | @tex | |
2095 | $-2^{28}$ | |
2096 | @end tex | |
2097 | + 168. | |
2098 | ||
2099 | It is not crucial to exclude from the alist the keysyms of other X | |
2100 | servers; those do no harm, as long as they don't conflict with the ones | |
2101 | used by the X server actually in use. | |
2102 | ||
2103 | The variable is always local to the current terminal, and cannot be | |
3ec61d4e | 2104 | buffer-local. @xref{Multiple Terminals}. |
b8d4c8d0 GM |
2105 | @end defvar |
2106 | ||
2107 | You can specify which keysyms Emacs should use for the Meta, Alt, Hyper, and Super modifiers by setting these variables: | |
2108 | ||
2109 | @defvar x-alt-keysym | |
2110 | @defvarx x-meta-keysym | |
2111 | @defvarx x-hyper-keysym | |
2112 | @defvarx x-super-keysym | |
2113 | The name of the keysym that should stand for the Alt modifier | |
2114 | (respectively, for Meta, Hyper, and Super). For example, here is | |
2115 | how to swap the Meta and Alt modifiers within Emacs: | |
2116 | @lisp | |
2117 | (setq x-alt-keysym 'meta) | |
2118 | (setq x-meta-keysym 'alt) | |
2119 | @end lisp | |
2120 | @end defvar | |
2121 | ||
2122 | @node Batch Mode | |
2123 | @section Batch Mode | |
2124 | @cindex batch mode | |
2125 | ||
2126 | The command-line option @samp{-batch} causes Emacs to run | |
2127 | noninteractively. In this mode, Emacs does not read commands from the | |
2128 | terminal, it does not alter the terminal modes, and it does not expect | |
2129 | to be outputting to an erasable screen. The idea is that you specify | |
2130 | Lisp programs to run; when they are finished, Emacs should exit. The | |
2131 | way to specify the programs to run is with @samp{-l @var{file}}, which | |
2132 | loads the library named @var{file}, or @samp{-f @var{function}}, which | |
2133 | calls @var{function} with no arguments, or @samp{--eval @var{form}}. | |
2134 | ||
2135 | Any Lisp program output that would normally go to the echo area, | |
2136 | either using @code{message}, or using @code{prin1}, etc., with @code{t} | |
2137 | as the stream, goes instead to Emacs's standard error descriptor when | |
2138 | in batch mode. Similarly, input that would normally come from the | |
2139 | minibuffer is read from the standard input descriptor. | |
2140 | Thus, Emacs behaves much like a noninteractive | |
2141 | application program. (The echo area output that Emacs itself normally | |
2142 | generates, such as command echoing, is suppressed entirely.) | |
2143 | ||
2144 | @defvar noninteractive | |
2145 | This variable is non-@code{nil} when Emacs is running in batch mode. | |
2146 | @end defvar | |
2147 | ||
2148 | @node Session Management | |
2149 | @section Session Management | |
2150 | @cindex session manager | |
2151 | ||
dca019f8 CY |
2152 | Emacs supports the X Session Management Protocol, which is used to |
2153 | suspend and restart applications. In the X Window System, a program | |
2154 | called the @dfn{session manager} is responsible for keeping track of | |
2155 | the applications that are running. When the X server shuts down, the | |
2156 | session manager asks applications to save their state, and delays the | |
2157 | actual shutdown until they respond. An application can also cancel | |
2158 | the shutdown. | |
b8d4c8d0 GM |
2159 | |
2160 | When the session manager restarts a suspended session, it directs | |
2161 | these applications to individually reload their saved state. It does | |
2162 | this by specifying a special command-line argument that says what | |
2163 | saved session to restore. For Emacs, this argument is @samp{--smid | |
2164 | @var{session}}. | |
2165 | ||
2166 | @defvar emacs-save-session-functions | |
dca019f8 CY |
2167 | Emacs supports saving state via a hook called |
2168 | @code{emacs-save-session-functions}. Emacs runs this hook when the | |
2169 | session manager tells it that the window system is shutting down. The | |
2170 | functions are called with no arguments, and with the current buffer | |
2171 | set to a temporary buffer. Each function can use @code{insert} to add | |
2172 | Lisp code to this buffer. At the end, Emacs saves the buffer in a | |
2173 | file, called the @dfn{session file}. | |
2174 | ||
2175 | @findex emacs-session-restore | |
2176 | Subsequently, when the session manager restarts Emacs, it loads the | |
2177 | session file automatically (@pxref{Loading}). This is performed by a | |
2178 | function named @code{emacs-session-restore}, which is called during | |
2179 | startup. @xref{Startup Summary}. | |
b8d4c8d0 GM |
2180 | |
2181 | If a function in @code{emacs-save-session-functions} returns | |
2182 | non-@code{nil}, Emacs tells the session manager to cancel the | |
2183 | shutdown. | |
2184 | @end defvar | |
2185 | ||
2186 | Here is an example that just inserts some text into @samp{*scratch*} when | |
2187 | Emacs is restarted by the session manager. | |
2188 | ||
2189 | @example | |
2190 | @group | |
2191 | (add-hook 'emacs-save-session-functions 'save-yourself-test) | |
2192 | @end group | |
2193 | ||
2194 | @group | |
2195 | (defun save-yourself-test () | |
c57008f6 | 2196 | (insert "(save-current-buffer |
b8d4c8d0 GM |
2197 | (switch-to-buffer \"*scratch*\") |
2198 | (insert \"I am restored\"))") | |
2199 | nil) | |
2200 | @end group | |
2201 | @end example | |
2202 | ||
00f113eb JB |
2203 | @node Dynamic Libraries |
2204 | @section Dynamically Loaded Libraries | |
2205 | @cindex dynamic libraries | |
2206 | ||
2207 | A @dfn{dynamically loaded library} is a library that is loaded on | |
2208 | demand, when its facilities are first needed. Emacs supports such | |
2209 | on-demand loading of support libraries for some of its features. | |
2210 | ||
2211 | @defvar dynamic-library-alist | |
2212 | This is an alist of dynamic libraries and external library files | |
2213 | implementing them. | |
2214 | ||
2215 | Each element is a list of the form | |
2216 | @w{@code{(@var{library} @var{files}@dots{})}}, where the @code{car} is | |
2217 | a symbol representing a supported external library, and the rest are | |
2218 | strings giving alternate filenames for that library. | |
2219 | ||
2220 | Emacs tries to load the library from the files in the order they | |
2221 | appear in the list; if none is found, the running session of Emacs | |
2222 | won't have access to that library, and the features that depend on the | |
2223 | library will be unavailable. | |
2224 | ||
2225 | Image support on some platforms uses this facility. Here's an example | |
2226 | of setting this variable for supporting images on MS-Windows: | |
2227 | ||
2228 | @lisp | |
2229 | (setq dynamic-library-alist | |
2230 | '((xpm "libxpm.dll" "xpm4.dll" "libXpm-nox4.dll") | |
2231 | (png "libpng12d.dll" "libpng12.dll" "libpng.dll" | |
2232 | "libpng13d.dll" "libpng13.dll") | |
2233 | (jpeg "jpeg62.dll" "libjpeg.dll" "jpeg-62.dll" "jpeg.dll") | |
2234 | (tiff "libtiff3.dll" "libtiff.dll") | |
2235 | (gif "giflib4.dll" "libungif4.dll" "libungif.dll") | |
2236 | (svg "librsvg-2-2.dll") | |
2237 | (gdk-pixbuf "libgdk_pixbuf-2.0-0.dll") | |
2238 | (glib "libglib-2.0-0.dll") | |
2239 | (gobject "libgobject-2.0-0.dll"))) | |
2240 | @end lisp | |
2241 | ||
2242 | Note that image types @code{pbm} and @code{xbm} do not need entries in | |
2243 | this variable because they do not depend on external libraries and are | |
2244 | always available in Emacs. | |
2245 | ||
2246 | Also note that this variable is not meant to be a generic facility for | |
2247 | accessing external libraries; only those already known by Emacs can | |
2248 | be loaded through it. | |
2249 | ||
2250 | This variable is ignored if the given @var{library} is statically | |
2251 | linked into Emacs. | |
2252 | @end defvar |