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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 | |
b59af549 | 11 | values in the operating system environment, and terminal input, output. |
b8d4c8d0 | 12 | |
02a89103 CY |
13 | @xref{Building Emacs}, for related information. @xref{Display}, for |
14 | additional operating system status information pertaining to the | |
15 | terminal and the screen. | |
b8d4c8d0 GM |
16 | |
17 | @menu | |
18 | * Starting Up:: Customizing Emacs startup processing. | |
19 | * Getting Out:: How exiting works (permanent or temporary). | |
20 | * System Environment:: Distinguish the name and kind of system. | |
21 | * User Identification:: Finding the name and user id of the user. | |
d24880de | 22 | * Time of Day:: Getting the current time. |
a4180391 | 23 | * Time Conversion:: Converting a time from numeric form to |
3be92e63 | 24 | calendrical data and vice versa. |
b8d4c8d0 GM |
25 | * Time Parsing:: Converting a time from numeric form to text |
26 | and vice versa. | |
27 | * Processor Run Time:: Getting the run time used by Emacs. | |
28 | * Time Calculations:: Adding, subtracting, comparing times, etc. | |
d24880de | 29 | * Timers:: Setting a timer to call a function at a certain time. |
b8d4c8d0 GM |
30 | * Idle Timers:: Setting a timer to call a function when Emacs has |
31 | been idle for a certain length of time. | |
32 | * Terminal Input:: Accessing and recording terminal input. | |
33 | * Terminal Output:: Controlling and recording terminal output. | |
34 | * Sound Output:: Playing sounds on the computer's speaker. | |
8e69dc70 | 35 | * X11 Keysyms:: Operating on key symbols for X Windows. |
b8d4c8d0 GM |
36 | * Batch Mode:: Running Emacs without terminal interaction. |
37 | * Session Management:: Saving and restoring state with X Session Management. | |
00f113eb | 38 | * Dynamic Libraries:: On-demand loading of support libraries. |
b8d4c8d0 GM |
39 | @end menu |
40 | ||
41 | @node Starting Up | |
42 | @section Starting Up Emacs | |
43 | ||
44 | This section describes what Emacs does when it is started, and how you | |
45 | can customize these actions. | |
46 | ||
47 | @menu | |
48 | * Startup Summary:: Sequence of actions Emacs performs at startup. | |
02a89103 | 49 | * Init File:: Details on reading the init file. |
b8d4c8d0 GM |
50 | * Terminal-Specific:: How the terminal-specific Lisp file is read. |
51 | * Command-Line Arguments:: How command-line arguments are processed, | |
52 | and how you can customize them. | |
53 | @end menu | |
54 | ||
55 | @node Startup Summary | |
56 | @subsection Summary: Sequence of Actions at Startup | |
57 | @cindex initialization of Emacs | |
58 | @cindex startup of Emacs | |
59 | @cindex @file{startup.el} | |
60 | ||
02a89103 | 61 | When Emacs is started up, it performs the following operations |
b59af549 | 62 | (see @code{normal-top-level} in @file{startup.el}): |
b8d4c8d0 GM |
63 | |
64 | @enumerate | |
65 | @item | |
66 | It adds subdirectories to @code{load-path}, by running the file named | |
02a89103 CY |
67 | @file{subdirs.el} in each directory in the list. Normally, this file |
68 | adds the directory's subdirectories to the list, and those are scanned | |
69 | in their turn. The files @file{subdirs.el} are normally generated | |
70 | automatically when Emacs is installed. | |
b8d4c8d0 | 71 | |
b59af549 GM |
72 | @item |
73 | It registers input methods by loading any @file{leim-list.el} file | |
74 | found in the @code{load-path}. | |
75 | ||
76 | @c It removes PWD from the environment if it is not accurate. | |
77 | @c It abbreviates default-directory. | |
78 | ||
79 | @c Now normal-top-level calls command-line. | |
80 | ||
f36acfd9 | 81 | @vindex before-init-time |
b8d4c8d0 | 82 | @item |
02a89103 | 83 | It sets the variable @code{before-init-time} to the value of |
f36acfd9 | 84 | @code{current-time} (@pxref{Time of Day}). It also sets |
02a89103 CY |
85 | @code{after-init-time} to @code{nil}, which signals to Lisp programs |
86 | that Emacs is being initialized. | |
b8d4c8d0 | 87 | |
b59af549 GM |
88 | @c set-locale-environment |
89 | @item | |
90 | It sets the language environment and the terminal coding system, | |
91 | if requested by environment variables such as @code{LANG}. | |
92 | ||
93 | @item | |
94 | It does some basic parsing of the command-line arguments. | |
95 | ||
f36acfd9 EZ |
96 | @vindex initial-window-system@r{, and startup} |
97 | @vindex window-system-initialization-alist | |
b8d4c8d0 | 98 | @item |
b59af549 GM |
99 | If not running in batch mode, it initializes the window system that |
100 | the variable @code{initial-window-system} specifies (@pxref{Window | |
101 | Systems, initial-window-system}). The initialization function for | |
102 | each supported window system is specified by | |
103 | @code{window-system-initialization-alist}. If the value | |
104 | of @code{initial-window-system} is @var{windowsystem}, then the | |
105 | appropriate initialization function is defined in the file | |
106 | @file{term/@var{windowsystem}-win.el}. This file should have been | |
107 | compiled into the Emacs executable when it was built. | |
f36acfd9 EZ |
108 | |
109 | @item | |
b59af549 | 110 | It runs the normal hook @code{before-init-hook}. |
b8d4c8d0 GM |
111 | |
112 | @item | |
33da7b16 GM |
113 | If appropriate, it creates a graphical frame. This is not done if the |
114 | options @samp{--batch} or @samp{--daemon} were specified. | |
b8d4c8d0 GM |
115 | |
116 | @item | |
b59af549 GM |
117 | It initializes the initial frame's faces, and sets up the menu bar |
118 | and tool bar if needed. If graphical frames are supported, it sets up | |
119 | the tool bar even if the current frame is not a graphical one, since a | |
120 | graphical frame may be created later on. | |
b8d4c8d0 GM |
121 | |
122 | @item | |
b59af549 GM |
123 | It use @code{custom-reevaluate-setting} to re-initialize the members |
124 | of the list @code{custom-delayed-init-variables}. These are any | |
125 | pre-loaded user options whose default value depends on the run-time, | |
126 | rather than build-time, context. | |
127 | @xref{Building Emacs, custom-initialize-delay}. | |
128 | ||
129 | @c @item | |
130 | @c It registers the colors available for tty frames. | |
f36acfd9 EZ |
131 | |
132 | @item | |
02a89103 CY |
133 | It loads the library @file{site-start}, if it exists. This is not |
134 | done if the options @samp{-Q} or @samp{--no-site-file} were specified. | |
b8d4c8d0 GM |
135 | @cindex @file{site-start.el} |
136 | ||
137 | @item | |
02a89103 CY |
138 | It loads your init file (@pxref{Init File}). This is not done if the |
139 | options @samp{-q}, @samp{-Q}, or @samp{--batch} were specified. If | |
140 | the @samp{-u} option was specified, Emacs looks for the init file in | |
141 | that user's home directory instead. | |
b8d4c8d0 GM |
142 | |
143 | @item | |
02a89103 CY |
144 | It loads the library @file{default}, if it exists. This is not done |
145 | if @code{inhibit-default-init} is non-@code{nil}, nor if the options | |
146 | @samp{-q}, @samp{-Q}, or @samp{--batch} were specified. | |
b8d4c8d0 GM |
147 | @cindex @file{default.el} |
148 | ||
f36acfd9 EZ |
149 | @item |
150 | It loads your abbrevs from the file specified by | |
02a89103 CY |
151 | @code{abbrev-file-name}, if that file exists and can be read |
152 | (@pxref{Abbrev Files, abbrev-file-name}). This is not done if the | |
153 | option @samp{--batch} was specified. | |
f36acfd9 | 154 | |
986bd52a CY |
155 | @item |
156 | If @code{package-enable-at-startup} is non-@code{nil}, it calls the | |
157 | function @code{package-initialize} to activate any optional Emacs Lisp | |
158 | package that has been installed. @xref{Packaging Basics}. | |
159 | ||
f36acfd9 EZ |
160 | @vindex after-init-time |
161 | @item | |
02a89103 CY |
162 | It sets the variable @code{after-init-time} to the value of |
163 | @code{current-time}. This variable was set to @code{nil} earlier; | |
164 | setting it to the current time signals that the initialization phase | |
165 | is over, and, together with @code{before-init-time}, provides the | |
f36acfd9 EZ |
166 | measurement of how long it took. |
167 | ||
b8d4c8d0 GM |
168 | @item |
169 | It runs the normal hook @code{after-init-hook}. | |
170 | ||
171 | @item | |
02a89103 CY |
172 | If the buffer @samp{*scratch*} exists and is still in Fundamental mode |
173 | (as it should be by default), it sets its major mode according to | |
174 | @code{initial-major-mode}. | |
b8d4c8d0 GM |
175 | |
176 | @item | |
a08a07e3 | 177 | If started on a text terminal, it loads the terminal-specific |
02a89103 CY |
178 | Lisp library, which is specified by the variable |
179 | @code{term-file-prefix} (@pxref{Terminal-Specific}). This is not done | |
180 | in @code{--batch} mode, nor if @code{term-file-prefix} is @code{nil}. | |
b8d4c8d0 | 181 | |
b59af549 GM |
182 | @c Now command-line calls command-line-1. |
183 | ||
b8d4c8d0 GM |
184 | @item |
185 | It displays the initial echo area message, unless you have suppressed | |
186 | that with @code{inhibit-startup-echo-area-message}. | |
187 | ||
188 | @item | |
b59af549 | 189 | It processes any command-line options that were not handled earlier. |
b8d4c8d0 | 190 | |
b59af549 GM |
191 | @c This next one is back in command-line, but the remaining bits of |
192 | @c command-line-1 are not done if noninteractive. | |
02a89103 CY |
193 | @item |
194 | It now exits if the option @code{--batch} was specified. | |
195 | ||
196 | @item | |
197 | If @code{initial-buffer-choice} is a string, it visits the file with | |
33da7b16 | 198 | that name. If the @samp{*scratch*} buffer exists and is |
02a89103 CY |
199 | empty, it inserts @code{initial-scratch-message} into that buffer. |
200 | ||
b59af549 GM |
201 | @c To make things nice and confusing, the next three items can be |
202 | @c called from two places. If displaying a startup screen, they are | |
203 | @c called in command-line-1 before the startup screen is shown. | |
204 | @c inhibit-startup-hooks is then set and window-setup-hook set to nil. | |
205 | @c If not displaying a startup screen, they are are called in | |
206 | @c normal-top-level. | |
207 | @c FIXME? So it seems they can be called before or after the | |
208 | @c daemon/session restore step? | |
209 | ||
b8d4c8d0 GM |
210 | @item |
211 | It runs @code{emacs-startup-hook} and then @code{term-setup-hook}. | |
212 | ||
213 | @item | |
214 | It calls @code{frame-notice-user-settings}, which modifies the | |
215 | parameters of the selected frame according to whatever the init files | |
216 | specify. | |
217 | ||
218 | @item | |
219 | It runs @code{window-setup-hook}. @xref{Window Systems}. | |
220 | ||
f36acfd9 | 221 | @item |
02a89103 CY |
222 | It displays the @dfn{startup screen}, which is a special buffer that |
223 | contains information about copyleft and basic Emacs usage. This is | |
33da7b16 GM |
224 | not done if @code{inhibit-startup-screen} or @code{initial-buffer-choice} |
225 | are non-@code{nil}, or if the @samp{--no-splash} or @samp{-Q} command-line | |
226 | options were specified. | |
f36acfd9 | 227 | |
b59af549 GM |
228 | @c End of command-line-1. |
229 | ||
230 | @c Back to command-line from command-line-1. | |
231 | ||
232 | @c This is the point at which we actually exit in batch mode, but the | |
233 | @c last few bits of command-line-1 are not done in batch mode. | |
234 | ||
235 | @item | |
236 | If the option @code{--daemon} was specified, it calls | |
237 | @code{server-start} and detaches from the controlling terminal. | |
238 | @xref{Emacs Server,,, emacs, The GNU Emacs Manual}. | |
239 | ||
f36acfd9 EZ |
240 | @item |
241 | If started by the X session manager, it calls | |
242 | @code{emacs-session-restore} passing it as argument the ID of the | |
dca019f8 | 243 | previous session. @xref{Session Management}. |
b59af549 GM |
244 | |
245 | @c End of command-line. | |
246 | ||
247 | @c Back to normal-top-level from command-line. | |
248 | ||
b8d4c8d0 GM |
249 | @end enumerate |
250 | ||
a5656eae GM |
251 | @noindent |
252 | The following options affect some aspects of the startup sequence. | |
253 | ||
f36acfd9 | 254 | @defopt inhibit-startup-screen |
02a89103 CY |
255 | This variable, if non-@code{nil}, inhibits the startup screen. In |
256 | that case, Emacs typically displays the @samp{*scratch*} buffer; but | |
257 | see @code{initial-buffer-choice}, below. | |
b8d4c8d0 | 258 | |
02a89103 CY |
259 | Do not set this variable in the init file of a new user, or in a way |
260 | that affects more than one user, as that would prevent new users from | |
261 | receiving information about copyleft and basic Emacs usage. | |
f36acfd9 | 262 | |
d3d97050 KR |
263 | @vindex inhibit-startup-message |
264 | @vindex inhibit-splash-screen | |
02a89103 CY |
265 | @code{inhibit-startup-message} and @code{inhibit-splash-screen} are |
266 | aliases for this variable. | |
267 | @end defopt | |
268 | ||
269 | @defopt initial-buffer-choice | |
33da7b16 GM |
270 | If non-@code{nil}, this variable is a string that specifies a file or |
271 | directory for Emacs to display after starting up, instead of the | |
272 | startup screen. | |
a5656eae GM |
273 | @ignore |
274 | @c I do not think this should be mentioned. AFAICS it is just a dodge | |
275 | @c around inhibit-startup-screen not being settable on a site-wide basis. | |
276 | If its value is @code{t}, Emacs displays the @samp{*scratch*} buffer. | |
277 | @end ignore | |
b8d4c8d0 GM |
278 | @end defopt |
279 | ||
280 | @defopt inhibit-startup-echo-area-message | |
281 | This variable controls the display of the startup echo area message. | |
282 | You can suppress the startup echo area message by adding text with this | |
283 | form to your init file: | |
284 | ||
285 | @example | |
286 | (setq inhibit-startup-echo-area-message | |
287 | "@var{your-login-name}") | |
288 | @end example | |
289 | ||
290 | Emacs explicitly checks for an expression as shown above in your init | |
291 | file; your login name must appear in the expression as a Lisp string | |
a5656eae | 292 | constant. You can also use the Custom interface. Other methods of setting |
b8d4c8d0 | 293 | @code{inhibit-startup-echo-area-message} to the same value do not |
02a89103 CY |
294 | inhibit the startup message. This way, you can easily inhibit the |
295 | message for yourself if you wish, but thoughtless copying of your init | |
296 | file will not inhibit the message for someone else. | |
297 | @end defopt | |
b8d4c8d0 | 298 | |
02a89103 CY |
299 | @defopt initial-scratch-message |
300 | This variable, if non-@code{nil}, should be a string, which is | |
301 | inserted into the @samp{*scratch*} buffer when Emacs starts up. If it | |
302 | is @code{nil}, the @samp{*scratch*} buffer is empty. | |
b8d4c8d0 GM |
303 | @end defopt |
304 | ||
a5656eae GM |
305 | @noindent |
306 | The following command-line options affect some aspects of the startup | |
307 | sequence. @xref{Initial Options,,, emacs, The GNU Emacs Manual}. | |
308 | ||
309 | @table @code | |
310 | @item --no-splash | |
311 | Do not display a splash screen. | |
312 | ||
313 | @item --batch | |
314 | Run without an interactive terminal. @xref{Batch Mode}. | |
315 | ||
316 | @item --daemon | |
317 | Do not initialize any display; just start a server in the background. | |
318 | ||
319 | @item --no-init-file | |
320 | @itemx -Q | |
321 | Do not load either the init file, or the @file{default} library. | |
322 | ||
323 | @item --no-site-file | |
324 | Do not load the @file{site-start} library. | |
325 | ||
326 | @item --quick | |
327 | @itemx -Q | |
328 | Equivalent to @samp{-q --no-site-file --no-splash}. | |
329 | @c and --no-site-lisp, but let's not mention that here. | |
330 | @end table | |
331 | ||
332 | ||
b8d4c8d0 | 333 | @node Init File |
986bd52a | 334 | @subsection The Init File |
b8d4c8d0 GM |
335 | @cindex init file |
336 | @cindex @file{.emacs} | |
986bd52a | 337 | @cindex @file{init.el} |
b8d4c8d0 GM |
338 | |
339 | When you start Emacs, it normally attempts to load your @dfn{init | |
02a89103 CY |
340 | file}. This is either a file named @file{.emacs} or @file{.emacs.el} |
341 | in your home directory, or a file named @file{init.el} in a | |
b59af549 GM |
342 | subdirectory named @file{.emacs.d} in your home directory. |
343 | @ignore | |
344 | Whichever place you use, you can also compile the file (@pxref{Byte | |
02a89103 CY |
345 | Compilation}); then the actual file loaded will be @file{.emacs.elc} |
346 | or @file{init.elc}. | |
b59af549 | 347 | @end ignore |
b8d4c8d0 GM |
348 | |
349 | The command-line switches @samp{-q}, @samp{-Q}, and @samp{-u} | |
350 | control whether and where to find the init file; @samp{-q} (and the | |
351 | stronger @samp{-Q}) says not to load an init file, while @samp{-u | |
352 | @var{user}} says to load @var{user}'s init file instead of yours. | |
353 | @xref{Entering Emacs,,, emacs, The GNU Emacs Manual}. If neither | |
354 | option is specified, Emacs uses the @code{LOGNAME} environment | |
355 | variable, or the @code{USER} (most systems) or @code{USERNAME} (MS | |
356 | systems) variable, to find your home directory and thus your init | |
357 | file; this way, even if you have su'd, Emacs still loads your own init | |
358 | file. If those environment variables are absent, though, Emacs uses | |
359 | your user-id to find your home directory. | |
360 | ||
361 | @cindex default init file | |
986bd52a CY |
362 | An Emacs installation may have a @dfn{default init file}, which is a |
363 | Lisp library named @file{default.el}. Emacs finds this file through | |
364 | the standard search path for libraries (@pxref{How Programs Do | |
365 | Loading}). The Emacs distribution does not come with this file; it is | |
366 | intended for local customizations. If the default init file exists, | |
33da7b16 | 367 | it is loaded whenever you start Emacs. But your own personal init |
b8d4c8d0 GM |
368 | file, if any, is loaded first; if it sets @code{inhibit-default-init} |
369 | to a non-@code{nil} value, then Emacs does not subsequently load the | |
33da7b16 GM |
370 | @file{default.el} file. In batch mode, or if you specify @samp{-q} |
371 | (or @samp{-Q}), Emacs loads neither your personal init file nor | |
372 | the default init file. | |
b8d4c8d0 GM |
373 | |
374 | Another file for site-customization is @file{site-start.el}. Emacs | |
375 | loads this @emph{before} the user's init file. You can inhibit the | |
376 | loading of this file with the option @samp{--no-site-file}. | |
377 | ||
01f17ae2 | 378 | @defopt site-run-file |
b8d4c8d0 GM |
379 | This variable specifies the site-customization file to load before the |
380 | user's init file. Its normal value is @code{"site-start"}. The only | |
381 | way you can change it with real effect is to do so before dumping | |
382 | Emacs. | |
33da7b16 | 383 | @c So why even mention it here. I imagine it is almost never changed. |
01f17ae2 | 384 | @end defopt |
b8d4c8d0 GM |
385 | |
386 | @xref{Init Examples,, Init File Examples, emacs, The GNU Emacs Manual}, for | |
387 | examples of how to make various commonly desired customizations in your | |
388 | @file{.emacs} file. | |
389 | ||
390 | @defopt inhibit-default-init | |
33da7b16 GM |
391 | If this variable is non-@code{nil}, it prevents Emacs from loading the |
392 | default initialization library file. The default value is @code{nil}. | |
b8d4c8d0 GM |
393 | @end defopt |
394 | ||
395 | @defvar before-init-hook | |
396 | This normal hook is run, once, just before loading all the init files | |
33da7b16 | 397 | (@file{site-start.el}, your init file, and @file{default.el}). |
b8d4c8d0 GM |
398 | (The only way to change it with real effect is before dumping Emacs.) |
399 | @end defvar | |
400 | ||
401 | @defvar after-init-hook | |
402 | This normal hook is run, once, just after loading all the init files | |
33da7b16 GM |
403 | (@file{site-start.el}, your init file, and @file{default.el}), |
404 | before loading the terminal-specific library (if started on a text | |
405 | terminal) and processing the command-line action arguments. | |
b8d4c8d0 GM |
406 | @end defvar |
407 | ||
408 | @defvar emacs-startup-hook | |
409 | This normal hook is run, once, just after handling the command line | |
33da7b16 GM |
410 | arguments, just before @code{term-setup-hook}. In batch mode, Emacs |
411 | does not run either of these hooks. | |
b8d4c8d0 GM |
412 | @end defvar |
413 | ||
414 | @defvar user-init-file | |
415 | This variable holds the absolute file name of the user's init file. If the | |
416 | actual init file loaded is a compiled file, such as @file{.emacs.elc}, | |
417 | the value refers to the corresponding source file. | |
418 | @end defvar | |
419 | ||
420 | @defvar user-emacs-directory | |
421 | This variable holds the name of the @file{.emacs.d} directory. It is | |
33da7b16 | 422 | @file{~/.emacs.d} on all platforms but MS-DOS. |
b8d4c8d0 GM |
423 | @end defvar |
424 | ||
425 | @node Terminal-Specific | |
426 | @subsection Terminal-Specific Initialization | |
427 | @cindex terminal-specific initialization | |
428 | ||
429 | Each terminal type can have its own Lisp library that Emacs loads when | |
430 | run on that type of terminal. The library's name is constructed by | |
431 | concatenating the value of the variable @code{term-file-prefix} and the | |
432 | terminal type (specified by the environment variable @code{TERM}). | |
433 | Normally, @code{term-file-prefix} has the value | |
434 | @code{"term/"}; changing this is not recommended. Emacs finds the file | |
435 | in the normal manner, by searching the @code{load-path} directories, and | |
436 | trying the @samp{.elc} and @samp{.el} suffixes. | |
437 | ||
438 | @cindex Termcap | |
986bd52a CY |
439 | The usual role of a terminal-specific library is to enable special |
440 | keys to send sequences that Emacs can recognize. It may also need to | |
441 | set or add to @code{input-decode-map} if the Termcap or Terminfo entry | |
442 | does not specify all the terminal's function keys. @xref{Terminal | |
443 | Input}. | |
b8d4c8d0 | 444 | |
33da7b16 | 445 | When the name of the terminal type contains a hyphen or underscore, and no library |
b8d4c8d0 | 446 | is found whose name is identical to the terminal's name, Emacs strips |
33da7b16 | 447 | from the terminal's name the last hyphen or underscore and everything that follows |
b8d4c8d0 | 448 | it, and tries again. This process is repeated until Emacs finds a |
33da7b16 GM |
449 | matching library, or until there are no more hyphens or underscores in the name |
450 | (i.e.@: there is no terminal-specific library). For example, if the | |
986bd52a CY |
451 | terminal name is @samp{xterm-256color} and there is no |
452 | @file{term/xterm-256color.el} library, Emacs tries to load | |
453 | @file{term/xterm.el}. If necessary, the terminal library can evaluate | |
454 | @code{(getenv "TERM")} to find the full name of the terminal type. | |
b8d4c8d0 GM |
455 | |
456 | Your init file can prevent the loading of the | |
457 | terminal-specific library by setting the variable | |
458 | @code{term-file-prefix} to @code{nil}. This feature is useful when | |
459 | experimenting with your own peculiar customizations. | |
460 | ||
461 | You can also arrange to override some of the actions of the | |
462 | terminal-specific library by setting the variable | |
33da7b16 GM |
463 | @code{term-setup-hook}. This is a normal hook that Emacs runs |
464 | at the end its initialization, after loading both | |
465 | your init file and any terminal-specific libraries. You could | |
466 | use this hook to define initializations for terminals that do not | |
b8d4c8d0 GM |
467 | have their own libraries. @xref{Hooks}. |
468 | ||
469 | @defvar term-file-prefix | |
470 | @cindex @code{TERM} environment variable | |
986bd52a CY |
471 | If the value of this variable is non-@code{nil}, Emacs loads a |
472 | terminal-specific initialization file as follows: | |
b8d4c8d0 GM |
473 | |
474 | @example | |
475 | (load (concat term-file-prefix (getenv "TERM"))) | |
476 | @end example | |
477 | ||
478 | @noindent | |
479 | You may set the @code{term-file-prefix} variable to @code{nil} in your | |
480 | init file if you do not wish to load the | |
33da7b16 | 481 | terminal-initialization file. |
b8d4c8d0 | 482 | |
33da7b16 | 483 | On MS-DOS, Emacs sets the @code{TERM} environment variable to @samp{internal}. |
b8d4c8d0 GM |
484 | @end defvar |
485 | ||
486 | @defvar term-setup-hook | |
487 | This variable is a normal hook that Emacs runs after loading your | |
488 | init file, the default initialization file (if any) and the | |
489 | terminal-specific Lisp file. | |
490 | ||
491 | You can use @code{term-setup-hook} to override the definitions made by a | |
492 | terminal-specific file. | |
b8d4c8d0 | 493 | |
33da7b16 GM |
494 | For a related feature, @pxref{Window Systems, window-setup-hook}. |
495 | @end defvar | |
b8d4c8d0 GM |
496 | |
497 | @node Command-Line Arguments | |
498 | @subsection Command-Line Arguments | |
499 | @cindex command-line arguments | |
500 | ||
986bd52a | 501 | You can use command-line arguments to request various actions when |
33da7b16 GM |
502 | you start Emacs. Note that the recommended way of using Emacs is to |
503 | start it just once, after logging in, and then do all editing in the same | |
504 | Emacs session (@pxref{Entering Emacs,,, emacs, The GNU Emacs Manual}). | |
505 | For this reason, you might not use command-line arguments very often; | |
506 | nonetheless, they can be useful when invoking Emacs from session | |
507 | scripts or debugging Emacs. This section describes how Emacs | |
508 | processes command-line arguments. | |
b8d4c8d0 GM |
509 | |
510 | @defun command-line | |
511 | This function parses the command line that Emacs was called with, | |
33da7b16 GM |
512 | processes it, and (amongst other things) loads the user's init file and |
513 | displays the startup messages. | |
b8d4c8d0 GM |
514 | @end defun |
515 | ||
516 | @defvar command-line-processed | |
517 | The value of this variable is @code{t} once the command line has been | |
518 | processed. | |
519 | ||
520 | If you redump Emacs by calling @code{dump-emacs}, you may wish to set | |
521 | this variable to @code{nil} first in order to cause the new dumped Emacs | |
522 | to process its new command-line arguments. | |
523 | @end defvar | |
524 | ||
525 | @defvar command-switch-alist | |
526 | @cindex switches on command line | |
527 | @cindex options on command line | |
528 | @cindex command-line options | |
33da7b16 GM |
529 | This variable is an alist of user-defined command-line options and |
530 | associated handler functions. By default it is empty, but you can | |
531 | add elements if you wish. | |
b8d4c8d0 GM |
532 | |
533 | A @dfn{command-line option} is an argument on the command line, which | |
534 | has the form: | |
535 | ||
536 | @example | |
537 | -@var{option} | |
538 | @end example | |
539 | ||
540 | The elements of the @code{command-switch-alist} look like this: | |
541 | ||
542 | @example | |
543 | (@var{option} . @var{handler-function}) | |
544 | @end example | |
545 | ||
546 | The @sc{car}, @var{option}, is a string, the name of a command-line | |
547 | option (not including the initial hyphen). The @var{handler-function} | |
548 | is called to handle @var{option}, and receives the option name as its | |
549 | sole argument. | |
550 | ||
551 | In some cases, the option is followed in the command line by an | |
552 | argument. In these cases, the @var{handler-function} can find all the | |
553 | remaining command-line arguments in the variable | |
554 | @code{command-line-args-left}. (The entire list of command-line | |
555 | arguments is in @code{command-line-args}.) | |
556 | ||
557 | The command-line arguments are parsed by the @code{command-line-1} | |
558 | function in the @file{startup.el} file. See also @ref{Emacs | |
559 | Invocation, , Command Line Arguments for Emacs Invocation, emacs, The | |
560 | GNU Emacs Manual}. | |
561 | @end defvar | |
562 | ||
563 | @defvar command-line-args | |
564 | The value of this variable is the list of command-line arguments passed | |
565 | to Emacs. | |
566 | @end defvar | |
567 | ||
dca019f8 | 568 | @defvar command-line-args-left |
d3d97050 | 569 | @vindex argv |
dca019f8 | 570 | The value of this variable is the list of command-line arguments that |
33da7b16 GM |
571 | have not yet been processed. |
572 | @c Don't mention this, since it is a "bad name for a dynamically bound variable" | |
573 | @c @code{argv} is an alias for this. | |
dca019f8 CY |
574 | @end defvar |
575 | ||
b8d4c8d0 GM |
576 | @defvar command-line-functions |
577 | This variable's value is a list of functions for handling an | |
578 | unrecognized command-line argument. Each time the next argument to be | |
579 | processed has no special meaning, the functions in this list are called, | |
580 | in order of appearance, until one of them returns a non-@code{nil} | |
581 | value. | |
582 | ||
583 | These functions are called with no arguments. They can access the | |
584 | command-line argument under consideration through the variable | |
585 | @code{argi}, which is bound temporarily at this point. The remaining | |
586 | arguments (not including the current one) are in the variable | |
587 | @code{command-line-args-left}. | |
588 | ||
589 | When a function recognizes and processes the argument in @code{argi}, it | |
590 | should return a non-@code{nil} value to say it has dealt with that | |
591 | argument. If it has also dealt with some of the following arguments, it | |
592 | can indicate that by deleting them from @code{command-line-args-left}. | |
593 | ||
33da7b16 | 594 | If all of these functions return @code{nil}, then the argument is treated |
b8d4c8d0 GM |
595 | as a file name to visit. |
596 | @end defvar | |
597 | ||
598 | @node Getting Out | |
599 | @section Getting Out of Emacs | |
600 | @cindex exiting Emacs | |
601 | ||
602 | There are two ways to get out of Emacs: you can kill the Emacs job, | |
603 | which exits permanently, or you can suspend it, which permits you to | |
02243d9d GM |
604 | reenter the Emacs process later. (In a graphical environment, you can |
605 | of course simply switch to another application without doing anything | |
606 | special to Emacs, then switch back to Emacs when you want.) | |
b8d4c8d0 GM |
607 | |
608 | @menu | |
609 | * Killing Emacs:: Exiting Emacs irreversibly. | |
610 | * Suspending Emacs:: Exiting Emacs reversibly. | |
611 | @end menu | |
612 | ||
613 | @node Killing Emacs | |
614 | @comment node-name, next, previous, up | |
615 | @subsection Killing Emacs | |
616 | @cindex killing Emacs | |
617 | ||
02243d9d GM |
618 | Killing Emacs means ending the execution of the Emacs process. |
619 | If you started Emacs from a terminal, the parent process normally | |
620 | resumes control. The low-level primitive for killing Emacs is | |
621 | @code{kill-emacs}. | |
b8d4c8d0 | 622 | |
106e6894 | 623 | @deffn Command kill-emacs &optional exit-data |
ddb54206 CY |
624 | This command calls the hook @code{kill-emacs-hook}, then exits the |
625 | Emacs process and kills it. | |
b8d4c8d0 | 626 | |
ddb54206 CY |
627 | If @var{exit-data} is an integer, that is used as the exit status of |
628 | the Emacs process. (This is useful primarily in batch operation; see | |
b8d4c8d0 GM |
629 | @ref{Batch Mode}.) |
630 | ||
631 | If @var{exit-data} is a string, its contents are stuffed into the | |
632 | terminal input buffer so that the shell (or whatever program next reads | |
633 | input) can read them. | |
106e6894 | 634 | @end deffn |
b8d4c8d0 | 635 | |
ddb54206 CY |
636 | @cindex SIGTERM |
637 | @cindex SIGHUP | |
638 | @cindex SIGINT | |
639 | @cindex operating system signal | |
640 | The @code{kill-emacs} function is normally called via the | |
641 | higher-level command @kbd{C-x C-c} | |
642 | (@code{save-buffers-kill-terminal}). @xref{Exiting,,, emacs, The GNU | |
643 | Emacs Manual}. It is also called automatically if Emacs receives a | |
644 | @code{SIGTERM} or @code{SIGHUP} operating system signal (e.g. when the | |
645 | controlling terminal is disconnected), or if it receives a | |
646 | @code{SIGINT} signal while running in batch mode (@pxref{Batch Mode}). | |
b8d4c8d0 | 647 | |
ddb54206 CY |
648 | @defvar kill-emacs-hook |
649 | This normal hook is run by @code{kill-emacs}, before it kills Emacs. | |
650 | ||
651 | Because @code{kill-emacs} can be called in situations where user | |
652 | interaction is impossible (e.g. when the terminal is disconnected), | |
653 | functions on this hook should not attempt to interact with the user. | |
654 | If you want to interact with the user when Emacs is shutting down, use | |
655 | @code{kill-emacs-query-functions}, described below. | |
b8d4c8d0 GM |
656 | @end defvar |
657 | ||
ddb54206 CY |
658 | When Emacs is killed, all the information in the Emacs process, |
659 | aside from files that have been saved, is lost. Because killing Emacs | |
660 | inadvertently can lose a lot of work, the | |
661 | @code{save-buffers-kill-terminal} command queries for confirmation if | |
662 | you have buffers that need saving or subprocesses that are running. | |
663 | It also runs the abnormal hook @code{kill-emacs-query-functions}: | |
664 | ||
665 | @defvar kill-emacs-query-functions | |
666 | When @code{save-buffers-kill-terminal} is killing Emacs, it calls the | |
667 | functions in this hook, after asking the standard questions and before | |
668 | calling @code{kill-emacs}. The functions are called in order of | |
669 | appearance, with no arguments. Each function can ask for additional | |
670 | confirmation from the user. If any of them returns @code{nil}, | |
671 | @code{save-buffers-kill-emacs} does not kill Emacs, and does not run | |
672 | the remaining functions in this hook. Calling @code{kill-emacs} | |
673 | directly does not run this hook. | |
b8d4c8d0 GM |
674 | @end defvar |
675 | ||
676 | @node Suspending Emacs | |
677 | @subsection Suspending Emacs | |
678 | @cindex suspending Emacs | |
679 | ||
a08a07e3 | 680 | On text terminals, it is possible to @dfn{suspend Emacs}, which |
dca019f8 CY |
681 | means stopping Emacs temporarily and returning control to its superior |
682 | process, which is usually the shell. This allows you to resume | |
683 | editing later in the same Emacs process, with the same buffers, the | |
684 | same kill ring, the same undo history, and so on. To resume Emacs, | |
685 | use the appropriate command in the parent shell---most likely | |
686 | @code{fg}. | |
b8d4c8d0 | 687 | |
62a5303f EZ |
688 | @cindex controlling terminal |
689 | Suspending works only on a terminal device from which the Emacs | |
690 | session was started. We call that device the @dfn{controlling | |
dca019f8 | 691 | terminal} of the session. Suspending is not allowed if the |
02243d9d GM |
692 | controlling terminal is a graphical terminal. Suspending is usually |
693 | not relevant in graphical environments, since you can simply switch to | |
694 | another application without doing anything special to Emacs. | |
695 | ||
696 | @c FIXME? Are there any systems Emacs still supports that do not | |
697 | @c have SIGTSTP? | |
698 | @cindex SIGTSTP | |
699 | Some operating systems (those without @code{SIGTSTP}, or MS-DOS) do | |
700 | not support suspension of jobs; on these systems, ``suspension'' | |
701 | actually creates a new shell temporarily as a subprocess of Emacs. | |
702 | Then you would exit the shell to return to Emacs. | |
b8d4c8d0 | 703 | |
106e6894 | 704 | @deffn Command suspend-emacs &optional string |
b8d4c8d0 GM |
705 | This function stops Emacs and returns control to the superior process. |
706 | If and when the superior process resumes Emacs, @code{suspend-emacs} | |
707 | returns @code{nil} to its caller in Lisp. | |
708 | ||
62a5303f EZ |
709 | This function works only on the controlling terminal of the Emacs |
710 | session; to relinquish control of other tty devices, use | |
f71de46c | 711 | @code{suspend-tty} (see below). If the Emacs session uses more than |
dca019f8 CY |
712 | one terminal, you must delete the frames on all the other terminals |
713 | before suspending Emacs, or this function signals an error. | |
714 | @xref{Multiple Terminals}. | |
62a5303f | 715 | |
dca019f8 | 716 | If @var{string} is non-@code{nil}, its characters are sent to Emacs's |
02243d9d GM |
717 | superior shell, to be read as terminal input. |
718 | @c FIXME? It seems to me that shell does echo STRING. | |
719 | The characters in @var{string} are not echoed by the superior shell; | |
720 | only the results appear. | |
b8d4c8d0 GM |
721 | |
722 | Before suspending, @code{suspend-emacs} runs the normal hook | |
dca019f8 CY |
723 | @code{suspend-hook}. After the user resumes Emacs, |
724 | @code{suspend-emacs} runs the normal hook @code{suspend-resume-hook}. | |
725 | @xref{Hooks}. | |
b8d4c8d0 GM |
726 | |
727 | The next redisplay after resumption will redraw the entire screen, | |
dca019f8 CY |
728 | unless the variable @code{no-redraw-on-reenter} is non-@code{nil}. |
729 | @xref{Refresh Screen}. | |
b8d4c8d0 | 730 | |
02243d9d | 731 | Here is an example of how you could use these hooks: |
b8d4c8d0 GM |
732 | |
733 | @smallexample | |
b8d4c8d0 GM |
734 | @group |
735 | (add-hook 'suspend-hook | |
02243d9d GM |
736 | (lambda () (or (y-or-n-p "Really suspend? ") |
737 | (error "Suspend canceled")))) | |
b8d4c8d0 | 738 | @end group |
02243d9d GM |
739 | (add-hook 'suspend-resume-hook (lambda () (message "Resumed!") |
740 | (sit-for 2))) | |
741 | @end smallexample | |
742 | @c The sit-for prevents the ``nil'' that suspend-emacs returns | |
743 | @c hiding the message. | |
744 | ||
745 | Here is what you would see upon evaluating @code{(suspend-emacs "pwd")}: | |
746 | ||
747 | @smallexample | |
b8d4c8d0 GM |
748 | @group |
749 | ---------- Buffer: Minibuffer ---------- | |
750 | Really suspend? @kbd{y} | |
751 | ---------- Buffer: Minibuffer ---------- | |
752 | @end group | |
753 | ||
754 | @group | |
755 | ---------- Parent Shell ---------- | |
02243d9d GM |
756 | bash$ /home/username |
757 | bash$ fg | |
b8d4c8d0 GM |
758 | @end group |
759 | ||
760 | @group | |
761 | ---------- Echo Area ---------- | |
762 | Resumed! | |
763 | @end group | |
764 | @end smallexample | |
02243d9d GM |
765 | |
766 | @c FIXME? AFAICS, it is echoed. | |
767 | Note that @samp{pwd} is not echoed after Emacs is suspended. But it | |
768 | is read and executed by the shell. | |
106e6894 | 769 | @end deffn |
b8d4c8d0 GM |
770 | |
771 | @defvar suspend-hook | |
772 | This variable is a normal hook that Emacs runs before suspending. | |
773 | @end defvar | |
774 | ||
775 | @defvar suspend-resume-hook | |
776 | This variable is a normal hook that Emacs runs on resuming | |
777 | after a suspension. | |
778 | @end defvar | |
779 | ||
62a5303f EZ |
780 | @defun suspend-tty &optional tty |
781 | If @var{tty} specifies a terminal device used by Emacs, this function | |
782 | relinquishes the device and restores it to its prior state. Frames | |
783 | that used the device continue to exist, but are not updated and Emacs | |
dca019f8 CY |
784 | doesn't read input from them. @var{tty} can be a terminal object, a |
785 | frame (meaning the terminal for that frame), or @code{nil} (meaning | |
786 | the terminal for the selected frame). @xref{Multiple Terminals}. | |
787 | ||
788 | If @var{tty} is already suspended, this function does nothing. | |
789 | ||
d3d97050 | 790 | @vindex suspend-tty-functions |
dca019f8 CY |
791 | This function runs the hook @code{suspend-tty-functions}, passing the |
792 | terminal object as an argument to each function. | |
62a5303f EZ |
793 | @end defun |
794 | ||
795 | @defun resume-tty &optional tty | |
dca019f8 | 796 | This function resumes the previously suspended terminal device |
02243d9d GM |
797 | @var{tty}; where @var{tty} has the same possible values as it does |
798 | for @code{suspend-tty}. | |
62a5303f | 799 | |
d3d97050 | 800 | @vindex resume-tty-functions |
62a5303f | 801 | This function reopens the terminal device, re-initializes it, and |
02243d9d | 802 | redraws it with that terminal's selected frame. It then runs the |
dca019f8 CY |
803 | hook @code{resume-tty-functions}, passing the terminal object as an |
804 | argument to each function. | |
62a5303f EZ |
805 | |
806 | If the same device is already used by another Emacs terminal, this | |
02243d9d GM |
807 | function signals an error. If @var{tty} is not suspended, this |
808 | function does nothing. | |
62a5303f EZ |
809 | @end defun |
810 | ||
02243d9d GM |
811 | @defun controlling-tty-p &optional tty |
812 | This function returns non-@code{nil} if @var{tty} is the | |
813 | controlling terminal of the Emacs session; @var{tty} can be a | |
dca019f8 CY |
814 | terminal object, a frame (meaning the terminal for that frame), or |
815 | @code{nil} (meaning the terminal for the selected frame). | |
62a5303f EZ |
816 | @end defun |
817 | ||
818 | @deffn Command suspend-frame | |
819 | This command @dfn{suspends} a frame. For GUI frames, it calls | |
a08a07e3 CY |
820 | @code{iconify-frame} (@pxref{Visibility of Frames}); for frames on |
821 | text terminals, it calls either @code{suspend-emacs} or | |
822 | @code{suspend-tty}, depending on whether the frame is displayed on the | |
823 | controlling terminal device or not. | |
62a5303f EZ |
824 | @end deffn |
825 | ||
b8d4c8d0 GM |
826 | @node System Environment |
827 | @section Operating System Environment | |
828 | @cindex operating system environment | |
829 | ||
830 | Emacs provides access to variables in the operating system environment | |
831 | through various functions. These variables include the name of the | |
832 | system, the user's @acronym{UID}, and so on. | |
833 | ||
834 | @defvar system-configuration | |
835 | This variable holds the standard GNU configuration name for the | |
cf0495f2 GM |
836 | hardware/software configuration of your system, as a string. For |
837 | example, a typical value for a 64-bit GNU/Linux system is | |
838 | @samp{"x86_64-unknown-linux-gnu"}. | |
b8d4c8d0 GM |
839 | @end defvar |
840 | ||
841 | @cindex system type and name | |
842 | @defvar system-type | |
843 | The value of this variable is a symbol indicating the type of operating | |
cf0495f2 | 844 | system Emacs is running on. The possible values are: |
b8d4c8d0 | 845 | |
58e3d8e8 | 846 | @table @code |
1213465a EZ |
847 | @item aix |
848 | IBM's AIX. | |
b8d4c8d0 GM |
849 | |
850 | @item berkeley-unix | |
1213465a | 851 | Berkeley BSD and its variants. |
b8d4c8d0 GM |
852 | |
853 | @item cygwin | |
1213465a EZ |
854 | Cygwin, a Posix layer on top of MS-Windows. |
855 | ||
856 | @item darwin | |
857 | Darwin (Mac OS X). | |
b8d4c8d0 | 858 | |
b8d4c8d0 | 859 | @item gnu |
1213465a | 860 | The GNU system (using the GNU kernel, which consists of the HURD and Mach). |
b8d4c8d0 GM |
861 | |
862 | @item gnu/linux | |
863 | A GNU/Linux system---that is, a variant GNU system, using the Linux | |
cf0495f2 | 864 | kernel. (These systems are the ones people often call ``Linux'', but |
b8d4c8d0 GM |
865 | actually Linux is just the kernel, not the whole system.) |
866 | ||
1213465a EZ |
867 | @item gnu/kfreebsd |
868 | A GNU (glibc-based) system with a FreeBSD kernel. | |
869 | ||
b8d4c8d0 GM |
870 | @item hpux |
871 | Hewlett-Packard HPUX operating system. | |
872 | ||
873 | @item irix | |
874 | Silicon Graphics Irix system. | |
875 | ||
876 | @item ms-dos | |
cf0495f2 GM |
877 | Microsoft's DOS. Emacs compiled with DJGPP for MS-DOS binds |
878 | @code{system-type} to @code{ms-dos} even when you run it on MS-Windows. | |
b8d4c8d0 | 879 | |
b8d4c8d0 | 880 | @item usg-unix-v |
1213465a | 881 | AT&T Unix System V. |
b8d4c8d0 | 882 | |
b8d4c8d0 | 883 | @item windows-nt |
cf0495f2 GM |
884 | Microsoft Windows NT, 9X and later. The value of @code{system-type} |
885 | is always @code{windows-nt}, e.g. even on Windows 7. | |
b8d4c8d0 | 886 | |
b8d4c8d0 GM |
887 | @end table |
888 | ||
889 | We do not wish to add new symbols to make finer distinctions unless it | |
890 | is absolutely necessary! In fact, we hope to eliminate some of these | |
cf0495f2 GM |
891 | alternatives in the future. If you need to make a finer distinction |
892 | than @code{system-type} allows for, you can test | |
893 | @code{system-configuration}, e.g. against a regexp. | |
b8d4c8d0 GM |
894 | @end defvar |
895 | ||
896 | @defun system-name | |
cf0495f2 GM |
897 | This function returns the name of the machine you are running on, as a |
898 | string. | |
b8d4c8d0 GM |
899 | @end defun |
900 | ||
901 | The symbol @code{system-name} is a variable as well as a function. In | |
902 | fact, the function returns whatever value the variable | |
903 | @code{system-name} currently holds. Thus, you can set the variable | |
904 | @code{system-name} in case Emacs is confused about the name of your | |
905 | system. The variable is also useful for constructing frame titles | |
906 | (@pxref{Frame Titles}). | |
907 | ||
cf0495f2 | 908 | @c FIXME seems like this section is not the best place for this option? |
01f17ae2 | 909 | @defopt mail-host-address |
b8d4c8d0 GM |
910 | If this variable is non-@code{nil}, it is used instead of |
911 | @code{system-name} for purposes of generating email addresses. For | |
912 | example, it is used when constructing the default value of | |
913 | @code{user-mail-address}. @xref{User Identification}. (Since this is | |
914 | done when Emacs starts up, the value actually used is the one saved when | |
915 | Emacs was dumped. @xref{Building Emacs}.) | |
cf0495f2 GM |
916 | @c FIXME sounds like should probably give this a :set-after and some |
917 | @c custom-initialize-delay voodoo. | |
01f17ae2 | 918 | @end defopt |
b8d4c8d0 | 919 | |
106e6894 | 920 | @deffn Command getenv var &optional frame |
b8d4c8d0 GM |
921 | @cindex environment variable access |
922 | This function returns the value of the environment variable @var{var}, | |
923 | as a string. @var{var} should be a string. If @var{var} is undefined | |
cf0495f2 GM |
924 | in the environment, @code{getenv} returns @code{nil}. It returns |
925 | @samp{""} if @var{var} is set but null. Within Emacs, a list of environment | |
926 | variables and their values is kept in the variable @code{process-environment}. | |
b8d4c8d0 GM |
927 | |
928 | @example | |
929 | @group | |
930 | (getenv "USER") | |
931 | @result{} "lewis" | |
932 | @end group | |
cf0495f2 GM |
933 | @end example |
934 | ||
935 | The shell command @code{printenv} prints all or part of the environment: | |
b8d4c8d0 | 936 | |
cf0495f2 | 937 | @example |
b8d4c8d0 | 938 | @group |
cf0495f2 GM |
939 | bash$ printenv |
940 | PATH=/usr/local/bin:/usr/bin:/bin | |
b8d4c8d0 GM |
941 | USER=lewis |
942 | @end group | |
943 | @group | |
cf0495f2 GM |
944 | TERM=xterm |
945 | SHELL=/bin/bash | |
946 | HOME=/home/lewis | |
b8d4c8d0 | 947 | @end group |
cf0495f2 | 948 | @dots{} |
b8d4c8d0 GM |
949 | @end example |
950 | @end deffn | |
951 | ||
cf0495f2 | 952 | @deffn Command setenv variable &optional value substitute |
b8d4c8d0 GM |
953 | This command sets the value of the environment variable named |
954 | @var{variable} to @var{value}. @var{variable} should be a string. | |
955 | Internally, Emacs Lisp can handle any string. However, normally | |
956 | @var{variable} should be a valid shell identifier, that is, a sequence | |
957 | of letters, digits and underscores, starting with a letter or | |
958 | underscore. Otherwise, errors may occur if subprocesses of Emacs try | |
959 | to access the value of @var{variable}. If @var{value} is omitted or | |
cf0495f2 GM |
960 | @code{nil} (or, interactively, with a prefix argument), @code{setenv} |
961 | removes @var{variable} from the environment. Otherwise, @var{value} | |
962 | should be a string. | |
963 | ||
964 | If the optional argument @var{substitute} is non-@code{nil}, Emacs | |
965 | calls the function @code{substitute-env-vars} to expand any | |
966 | environment variables in @var{value}. | |
b8d4c8d0 GM |
967 | |
968 | @code{setenv} works by modifying @code{process-environment}; binding | |
969 | that variable with @code{let} is also reasonable practice. | |
970 | ||
971 | @code{setenv} returns the new value of @var{variable}, or @code{nil} | |
972 | if it removed @var{variable} from the environment. | |
973 | @end deffn | |
974 | ||
975 | @defvar process-environment | |
976 | This variable is a list of strings, each describing one environment | |
977 | variable. The functions @code{getenv} and @code{setenv} work by means | |
978 | of this variable. | |
979 | ||
980 | @smallexample | |
981 | @group | |
982 | process-environment | |
cf0495f2 | 983 | @result{} ("PATH=/usr/local/bin:/usr/bin:/bin" |
b8d4c8d0 GM |
984 | "USER=lewis" |
985 | @end group | |
986 | @group | |
cf0495f2 GM |
987 | "TERM=xterm" |
988 | "SHELL=/bin/bash" | |
989 | "HOME=/home/lewis" | |
990 | @dots{}) | |
b8d4c8d0 GM |
991 | @end group |
992 | @end smallexample | |
993 | ||
994 | If @code{process-environment} contains ``duplicate'' elements that | |
995 | specify the same environment variable, the first of these elements | |
996 | specifies the variable, and the other ``duplicates'' are ignored. | |
997 | @end defvar | |
998 | ||
200811d6 EZ |
999 | @defvar initial-environment |
1000 | This variable holds the list of environment variables Emacs inherited | |
cf0495f2 | 1001 | from its parent process when Emacs started. |
200811d6 EZ |
1002 | @end defvar |
1003 | ||
b8d4c8d0 | 1004 | @defvar path-separator |
cf0495f2 | 1005 | This variable holds a string that says which character separates |
b8d4c8d0 | 1006 | directories in a search path (as found in an environment variable). Its |
cf0495f2 | 1007 | value is @code{":"} for Unix and GNU systems, and @code{";"} for MS systems. |
b8d4c8d0 GM |
1008 | @end defvar |
1009 | ||
1010 | @defun parse-colon-path path | |
cf0495f2 | 1011 | This function takes a search path string such as the value of |
b8d4c8d0 | 1012 | the @code{PATH} environment variable, and splits it at the separators, |
cf0495f2 GM |
1013 | returning a list of directory names. @code{nil} in this list means |
1014 | the current directory. Although the function's name says | |
1015 | ``colon'', it actually uses the value of @code{path-separator}. | |
b8d4c8d0 GM |
1016 | |
1017 | @example | |
1018 | (parse-colon-path ":/foo:/bar") | |
1019 | @result{} (nil "/foo/" "/bar/") | |
1020 | @end example | |
1021 | @end defun | |
1022 | ||
1023 | @defvar invocation-name | |
1024 | This variable holds the program name under which Emacs was invoked. The | |
1025 | value is a string, and does not include a directory name. | |
1026 | @end defvar | |
1027 | ||
1028 | @defvar invocation-directory | |
1029 | This variable holds the directory from which the Emacs executable was | |
cf0495f2 | 1030 | invoked, or @code{nil} if that directory cannot be determined. |
b8d4c8d0 GM |
1031 | @end defvar |
1032 | ||
1033 | @defvar installation-directory | |
1034 | If non-@code{nil}, this is a directory within which to look for the | |
cf0495f2 GM |
1035 | @file{lib-src} and @file{etc} subdirectories. In an installed Emacs, |
1036 | it is normally @code{nil}. It is non-@code{nil} | |
b8d4c8d0 GM |
1037 | when Emacs can't find those directories in their standard installed |
1038 | locations, but can find them in a directory related somehow to the one | |
cf0495f2 | 1039 | containing the Emacs executable (i.e., @code{invocation-directory}). |
b8d4c8d0 GM |
1040 | @end defvar |
1041 | ||
1042 | @defun load-average &optional use-float | |
cf0495f2 GM |
1043 | This function returns the current 1-minute, 5-minute, and 15-minute |
1044 | system load averages, in a list. The load average indicates the | |
1045 | number of processes trying to run on the system. | |
b8d4c8d0 GM |
1046 | |
1047 | By default, the values are integers that are 100 times the system load | |
cf0495f2 GM |
1048 | averages, but if @var{use-float} is non-@code{nil}, then they are |
1049 | returned as floating point numbers without multiplying by 100. | |
b8d4c8d0 GM |
1050 | |
1051 | If it is impossible to obtain the load average, this function signals | |
1052 | an error. On some platforms, access to load averages requires | |
1053 | installing Emacs as setuid or setgid so that it can read kernel | |
1054 | information, and that usually isn't advisable. | |
cf0495f2 | 1055 | @c FIXME which platforms are these? Are they still relevant? |
b8d4c8d0 GM |
1056 | |
1057 | If the 1-minute load average is available, but the 5- or 15-minute | |
1058 | averages are not, this function returns a shortened list containing | |
1059 | the available averages. | |
1060 | ||
1061 | @example | |
1062 | @group | |
1063 | (load-average) | |
1064 | @result{} (169 48 36) | |
1065 | @end group | |
1066 | @group | |
1067 | (load-average t) | |
1068 | @result{} (1.69 0.48 0.36) | |
1069 | @end group | |
b8d4c8d0 | 1070 | @end example |
cf0495f2 GM |
1071 | |
1072 | The shell command @code{uptime} returns similar information. | |
b8d4c8d0 GM |
1073 | @end defun |
1074 | ||
1075 | @defun emacs-pid | |
1076 | This function returns the process @acronym{ID} of the Emacs process, | |
1077 | as an integer. | |
1078 | @end defun | |
1079 | ||
1080 | @defvar tty-erase-char | |
1081 | This variable holds the erase character that was selected | |
1082 | in the system's terminal driver, before Emacs was started. | |
cf0495f2 GM |
1083 | @c FIXME? Seems untrue since 23.1. For me, it is 0. |
1084 | @c The value is @code{nil} if Emacs is running under a window system. | |
b8d4c8d0 GM |
1085 | @end defvar |
1086 | ||
b8d4c8d0 GM |
1087 | @node User Identification |
1088 | @section User Identification | |
1089 | @cindex user identification | |
1090 | ||
1091 | @defvar init-file-user | |
1092 | This variable says which user's init files should be used by | |
1093 | Emacs---or @code{nil} if none. @code{""} stands for the user who | |
1094 | originally logged in. The value reflects command-line options such as | |
1095 | @samp{-q} or @samp{-u @var{user}}. | |
1096 | ||
1097 | Lisp packages that load files of customizations, or any other sort of | |
1098 | user profile, should obey this variable in deciding where to find it. | |
1099 | They should load the profile of the user name found in this variable. | |
1100 | If @code{init-file-user} is @code{nil}, meaning that the @samp{-q} | |
1101 | option was used, then Lisp packages should not load any customization | |
1102 | files or user profile. | |
1103 | @end defvar | |
1104 | ||
01f17ae2 | 1105 | @defopt user-mail-address |
b8d4c8d0 GM |
1106 | This holds the nominal email address of the user who is using Emacs. |
1107 | Emacs normally sets this variable to a default value after reading your | |
1108 | init files, but not if you have already set it. So you can set the | |
1109 | variable to some other value in your init file if you do not | |
1110 | want to use the default value. | |
01f17ae2 | 1111 | @end defopt |
b8d4c8d0 GM |
1112 | |
1113 | @defun user-login-name &optional uid | |
cf0495f2 GM |
1114 | This function returns the name under which the user is logged in. |
1115 | It uses the environment variables @code{LOGNAME} or @code{USER} if | |
1116 | either is set. Otherwise, the value is based on the effective | |
1117 | @acronym{UID}, not the real @acronym{UID}. | |
b8d4c8d0 | 1118 | |
cf0495f2 GM |
1119 | If you specify @var{uid} (a number), the result is the user name that |
1120 | corresponds to @var{uid}, or @code{nil} if there is no such user. | |
b8d4c8d0 GM |
1121 | @end defun |
1122 | ||
1123 | @defun user-real-login-name | |
1124 | This function returns the user name corresponding to Emacs's real | |
cf0495f2 | 1125 | @acronym{UID}. This ignores the effective @acronym{UID}, and the |
b8d4c8d0 GM |
1126 | environment variables @code{LOGNAME} and @code{USER}. |
1127 | @end defun | |
1128 | ||
1129 | @defun user-full-name &optional uid | |
1130 | This function returns the full name of the logged-in user---or the value | |
1131 | of the environment variable @code{NAME}, if that is set. | |
1132 | ||
cf0495f2 GM |
1133 | If the Emacs process's user-id does not correspond to any known user (and |
1134 | provided @code{NAME} is not set), the result is @code{"unknown"}. | |
b8d4c8d0 GM |
1135 | |
1136 | If @var{uid} is non-@code{nil}, then it should be a number (a user-id) | |
1137 | or a string (a login name). Then @code{user-full-name} returns the full | |
1138 | name corresponding to that user-id or login name. If you specify a | |
1139 | user-id or login name that isn't defined, it returns @code{nil}. | |
1140 | @end defun | |
1141 | ||
1142 | @vindex user-full-name | |
1143 | @vindex user-real-login-name | |
1144 | @vindex user-login-name | |
1145 | The symbols @code{user-login-name}, @code{user-real-login-name} and | |
1146 | @code{user-full-name} are variables as well as functions. The functions | |
1147 | return the same values that the variables hold. These variables allow | |
1148 | you to ``fake out'' Emacs by telling the functions what to return. The | |
1149 | variables are also useful for constructing frame titles (@pxref{Frame | |
1150 | Titles}). | |
1151 | ||
1152 | @defun user-real-uid | |
1153 | This function returns the real @acronym{UID} of the user. | |
cf0495f2 GM |
1154 | The value may be a floating point number, in the (unlikely) event that |
1155 | the UID is too large to fit in a Lisp integer. | |
b8d4c8d0 GM |
1156 | @end defun |
1157 | ||
1158 | @defun user-uid | |
1159 | This function returns the effective @acronym{UID} of the user. | |
1160 | The value may be a floating point number. | |
1161 | @end defun | |
1162 | ||
1163 | @node Time of Day | |
1164 | @section Time of Day | |
1165 | ||
986bd52a | 1166 | This section explains how to determine the current time and time |
b8d4c8d0 GM |
1167 | zone. |
1168 | ||
986bd52a CY |
1169 | @cindex epoch |
1170 | Most of these functions represent time as a list of either three | |
1171 | integers, @code{(@var{sec-high} @var{sec-low} @var{microsec})}, or of | |
1172 | two integers, @code{(@var{sec-high} @var{sec-low})}. The integers | |
1173 | @var{sec-high} and @var{sec-low} give the high and low bits of an | |
1174 | integer number of seconds. This integer number, | |
1175 | @ifnottex | |
1176 | @var{high} * 2**16 + @var{low}, | |
1177 | @end ifnottex | |
1178 | @tex | |
1179 | $high*2^{16}+low$, | |
1180 | @end tex | |
1181 | is the number of seconds from the @dfn{epoch} (0:00 January 1, 1970 | |
1182 | UTC) to the specified time. The third list element @var{microsec}, if | |
1183 | present, gives the number of microseconds from the start of that | |
1184 | second to the specified time. | |
1185 | ||
1186 | The return value of @code{current-time} represents time using three | |
1187 | integers, while the timestamps in the return value of | |
1188 | @code{file-attributes} use two integers (@pxref{Definition of | |
1189 | file-attributes}). In function arguments, e.g.@: the @var{time-value} | |
1190 | argument to @code{current-time-string}, both two- and three-integer | |
1191 | lists are accepted. You can convert times from the list | |
1192 | representation into standard human-readable strings using | |
1193 | @code{current-time}, or to other forms using the @code{decode-time} | |
1194 | and @code{format-time-string} functions documented in the following | |
1195 | sections. | |
1196 | ||
b8d4c8d0 GM |
1197 | @defun current-time-string &optional time-value |
1198 | This function returns the current time and date as a human-readable | |
986bd52a CY |
1199 | string. The format of the string is unvarying; the number of |
1200 | characters used for each part is always the same, so you can reliably | |
1201 | use @code{substring} to extract pieces of it. You should count | |
1202 | characters from the beginning of the string rather than from the end, | |
1203 | as additional information may some day be added at the end. | |
b8d4c8d0 | 1204 | |
b8d4c8d0 | 1205 | The argument @var{time-value}, if given, specifies a time to format |
986bd52a | 1206 | (represented as a list of integers), instead of the current time. |
b8d4c8d0 GM |
1207 | |
1208 | @example | |
1209 | @group | |
1210 | (current-time-string) | |
1211 | @result{} "Wed Oct 14 22:21:05 1987" | |
1212 | @end group | |
1213 | @end example | |
1214 | @end defun | |
1215 | ||
b8d4c8d0 | 1216 | @defun current-time |
986bd52a CY |
1217 | This function returns the current time, represented as a list of three |
1218 | integers @code{(@var{sec-high} @var{sec-low} @var{microsec})}. On | |
1219 | systems with only one-second time resolutions, @var{microsec} is 0. | |
b8d4c8d0 GM |
1220 | @end defun |
1221 | ||
51a714e1 CY |
1222 | @defun float-time &optional time-value |
1223 | This function returns the current time as a floating-point number of | |
986bd52a CY |
1224 | seconds since the epoch. The optional argument @var{time-value}, if |
1225 | given, specifies a time (represented as a list of integers) to convert | |
1226 | instead of the current time. | |
51a714e1 CY |
1227 | |
1228 | @emph{Warning}: Since the result is floating point, it may not be | |
1229 | exact. Do not use this function if precise time stamps are required. | |
1230 | @end defun | |
1231 | ||
b8d4c8d0 GM |
1232 | @defun current-time-zone &optional time-value |
1233 | This function returns a list describing the time zone that the user is | |
1234 | in. | |
1235 | ||
1236 | The value has the form @code{(@var{offset} @var{name})}. Here | |
1237 | @var{offset} is an integer giving the number of seconds ahead of UTC | |
1238 | (east of Greenwich). A negative value means west of Greenwich. The | |
1239 | second element, @var{name}, is a string giving the name of the time | |
1240 | zone. Both elements change when daylight saving time begins or ends; | |
1241 | if the user has specified a time zone that does not use a seasonal time | |
1242 | adjustment, then the value is constant through time. | |
1243 | ||
1244 | If the operating system doesn't supply all the information necessary to | |
1245 | compute the value, the unknown elements of the list are @code{nil}. | |
1246 | ||
986bd52a CY |
1247 | The argument @var{time-value}, if given, specifies a time (represented |
1248 | as a list of integers) to analyze instead of the current time. | |
b8d4c8d0 GM |
1249 | @end defun |
1250 | ||
51a714e1 CY |
1251 | The current time zone is determined by the @samp{TZ} environment |
1252 | variable. @xref{System Environment}. For example, you can tell Emacs | |
1253 | to use universal time with @code{(setenv "TZ" "UTC0")}. If @samp{TZ} | |
1254 | is not in the environment, Emacs uses a platform-dependent default | |
1255 | time zone. | |
b8d4c8d0 GM |
1256 | |
1257 | @node Time Conversion | |
1258 | @section Time Conversion | |
1259 | ||
986bd52a CY |
1260 | These functions convert time values (lists of two or three integers, |
1261 | as explained in the previous section) into calendrical information and | |
1262 | vice versa. | |
b8d4c8d0 | 1263 | |
986bd52a CY |
1264 | Many 32-bit operating systems are limited to time values containing |
1265 | 32 bits of information; these systems typically handle only the times | |
1266 | from 1901-12-13 20:45:52 UTC through 2038-01-19 03:14:07 UTC. | |
1267 | However, 64-bit and some 32-bit operating systems have larger time | |
1268 | values, and can represent times far in the past or future. | |
b8d4c8d0 GM |
1269 | |
1270 | Time conversion functions always use the Gregorian calendar, even | |
1271 | for dates before the Gregorian calendar was introduced. Year numbers | |
1272 | count the number of years since the year 1 B.C., and do not skip zero | |
1273 | as traditional Gregorian years do; for example, the year number | |
1274 | @minus{}37 represents the Gregorian year 38 B.C@. | |
1275 | ||
1276 | @defun decode-time &optional time | |
1277 | This function converts a time value into calendrical information. If | |
1278 | you don't specify @var{time}, it decodes the current time. The return | |
1279 | value is a list of nine elements, as follows: | |
1280 | ||
1281 | @example | |
1282 | (@var{seconds} @var{minutes} @var{hour} @var{day} @var{month} @var{year} @var{dow} @var{dst} @var{zone}) | |
1283 | @end example | |
1284 | ||
1285 | Here is what the elements mean: | |
1286 | ||
1287 | @table @var | |
1288 | @item seconds | |
1289 | The number of seconds past the minute, as an integer between 0 and 59. | |
1290 | On some operating systems, this is 60 for leap seconds. | |
1291 | @item minutes | |
1292 | The number of minutes past the hour, as an integer between 0 and 59. | |
1293 | @item hour | |
1294 | The hour of the day, as an integer between 0 and 23. | |
1295 | @item day | |
1296 | The day of the month, as an integer between 1 and 31. | |
1297 | @item month | |
1298 | The month of the year, as an integer between 1 and 12. | |
1299 | @item year | |
1300 | The year, an integer typically greater than 1900. | |
1301 | @item dow | |
1302 | The day of week, as an integer between 0 and 6, where 0 stands for | |
1303 | Sunday. | |
1304 | @item dst | |
1305 | @code{t} if daylight saving time is effect, otherwise @code{nil}. | |
1306 | @item zone | |
1307 | An integer indicating the time zone, as the number of seconds east of | |
1308 | Greenwich. | |
1309 | @end table | |
1310 | ||
1311 | @strong{Common Lisp Note:} Common Lisp has different meanings for | |
1312 | @var{dow} and @var{zone}. | |
1313 | @end defun | |
1314 | ||
1315 | @defun encode-time seconds minutes hour day month year &optional zone | |
1316 | This function is the inverse of @code{decode-time}. It converts seven | |
1317 | items of calendrical data into a time value. For the meanings of the | |
1318 | arguments, see the table above under @code{decode-time}. | |
1319 | ||
1320 | Year numbers less than 100 are not treated specially. If you want them | |
1321 | to stand for years above 1900, or years above 2000, you must alter them | |
1322 | yourself before you call @code{encode-time}. | |
1323 | ||
1324 | The optional argument @var{zone} defaults to the current time zone and | |
1325 | its daylight saving time rules. If specified, it can be either a list | |
1326 | (as you would get from @code{current-time-zone}), a string as in the | |
1327 | @code{TZ} environment variable, @code{t} for Universal Time, or an | |
1328 | integer (as you would get from @code{decode-time}). The specified | |
1329 | zone is used without any further alteration for daylight saving time. | |
1330 | ||
1331 | If you pass more than seven arguments to @code{encode-time}, the first | |
1332 | six are used as @var{seconds} through @var{year}, the last argument is | |
1333 | used as @var{zone}, and the arguments in between are ignored. This | |
1334 | feature makes it possible to use the elements of a list returned by | |
1335 | @code{decode-time} as the arguments to @code{encode-time}, like this: | |
1336 | ||
1337 | @example | |
1338 | (apply 'encode-time (decode-time @dots{})) | |
1339 | @end example | |
1340 | ||
1341 | You can perform simple date arithmetic by using out-of-range values for | |
1342 | the @var{seconds}, @var{minutes}, @var{hour}, @var{day}, and @var{month} | |
1343 | arguments; for example, day 0 means the day preceding the given month. | |
1344 | ||
1345 | The operating system puts limits on the range of possible time values; | |
1346 | if you try to encode a time that is out of range, an error results. | |
1347 | For instance, years before 1970 do not work on some systems; | |
1348 | on others, years as early as 1901 do work. | |
1349 | @end defun | |
1350 | ||
1351 | @node Time Parsing | |
1352 | @section Parsing and Formatting Times | |
1353 | ||
1354 | These functions convert time values (lists of two or three integers) | |
1355 | to text in a string, and vice versa. | |
1356 | ||
1357 | @defun date-to-time string | |
1358 | This function parses the time-string @var{string} and returns the | |
1359 | corresponding time value. | |
1360 | @end defun | |
1361 | ||
1362 | @defun format-time-string format-string &optional time universal | |
1363 | This function converts @var{time} (or the current time, if @var{time} is | |
1364 | omitted) to a string according to @var{format-string}. The argument | |
1365 | @var{format-string} may contain @samp{%}-sequences which say to | |
1366 | substitute parts of the time. Here is a table of what the | |
1367 | @samp{%}-sequences mean: | |
1368 | ||
1369 | @table @samp | |
1370 | @item %a | |
1371 | This stands for the abbreviated name of the day of week. | |
1372 | @item %A | |
1373 | This stands for the full name of the day of week. | |
1374 | @item %b | |
1375 | This stands for the abbreviated name of the month. | |
1376 | @item %B | |
1377 | This stands for the full name of the month. | |
1378 | @item %c | |
1379 | This is a synonym for @samp{%x %X}. | |
1380 | @item %C | |
1381 | This has a locale-specific meaning. In the default locale (named C), it | |
1382 | is equivalent to @samp{%A, %B %e, %Y}. | |
1383 | @item %d | |
1384 | This stands for the day of month, zero-padded. | |
1385 | @item %D | |
1386 | This is a synonym for @samp{%m/%d/%y}. | |
1387 | @item %e | |
1388 | This stands for the day of month, blank-padded. | |
1389 | @item %h | |
1390 | This is a synonym for @samp{%b}. | |
1391 | @item %H | |
1392 | This stands for the hour (00-23). | |
1393 | @item %I | |
1394 | This stands for the hour (01-12). | |
1395 | @item %j | |
1396 | This stands for the day of the year (001-366). | |
1397 | @item %k | |
1398 | This stands for the hour (0-23), blank padded. | |
1399 | @item %l | |
1400 | This stands for the hour (1-12), blank padded. | |
1401 | @item %m | |
1402 | This stands for the month (01-12). | |
1403 | @item %M | |
1404 | This stands for the minute (00-59). | |
1405 | @item %n | |
1406 | This stands for a newline. | |
a4180391 PE |
1407 | @item %N |
1408 | This stands for the nanoseconds (000000000-999999999). To ask for | |
1409 | fewer digits, use @samp{%3N} for milliseconds, @samp{%6N} for | |
1410 | microseconds, etc. Any excess digits are discarded, without rounding. | |
1411 | Currently Emacs time stamps are at best microsecond resolution so the | |
1412 | last three digits generated by plain @samp{%N} are always zero. | |
b8d4c8d0 GM |
1413 | @item %p |
1414 | This stands for @samp{AM} or @samp{PM}, as appropriate. | |
1415 | @item %r | |
1416 | This is a synonym for @samp{%I:%M:%S %p}. | |
1417 | @item %R | |
1418 | This is a synonym for @samp{%H:%M}. | |
1419 | @item %S | |
1420 | This stands for the seconds (00-59). | |
1421 | @item %t | |
1422 | This stands for a tab character. | |
1423 | @item %T | |
1424 | This is a synonym for @samp{%H:%M:%S}. | |
1425 | @item %U | |
1426 | This stands for the week of the year (01-52), assuming that weeks | |
1427 | start on Sunday. | |
1428 | @item %w | |
1429 | This stands for the numeric day of week (0-6). Sunday is day 0. | |
1430 | @item %W | |
1431 | This stands for the week of the year (01-52), assuming that weeks | |
1432 | start on Monday. | |
1433 | @item %x | |
1434 | This has a locale-specific meaning. In the default locale (named | |
1435 | @samp{C}), it is equivalent to @samp{%D}. | |
1436 | @item %X | |
1437 | This has a locale-specific meaning. In the default locale (named | |
1438 | @samp{C}), it is equivalent to @samp{%T}. | |
1439 | @item %y | |
1440 | This stands for the year without century (00-99). | |
1441 | @item %Y | |
1442 | This stands for the year with century. | |
1443 | @item %Z | |
1444 | This stands for the time zone abbreviation (e.g., @samp{EST}). | |
1445 | @item %z | |
1446 | This stands for the time zone numerical offset (e.g., @samp{-0500}). | |
1447 | @end table | |
1448 | ||
1449 | You can also specify the field width and type of padding for any of | |
1450 | these @samp{%}-sequences. This works as in @code{printf}: you write | |
1451 | the field width as digits in the middle of a @samp{%}-sequences. If you | |
1452 | start the field width with @samp{0}, it means to pad with zeros. If you | |
1453 | start the field width with @samp{_}, it means to pad with spaces. | |
1454 | ||
1455 | For example, @samp{%S} specifies the number of seconds since the minute; | |
1456 | @samp{%03S} means to pad this with zeros to 3 positions, @samp{%_3S} to | |
1457 | pad with spaces to 3 positions. Plain @samp{%3S} pads with zeros, | |
1458 | because that is how @samp{%S} normally pads to two positions. | |
1459 | ||
1460 | The characters @samp{E} and @samp{O} act as modifiers when used between | |
1461 | @samp{%} and one of the letters in the table above. @samp{E} specifies | |
1462 | using the current locale's ``alternative'' version of the date and time. | |
1463 | In a Japanese locale, for example, @code{%Ex} might yield a date format | |
1464 | based on the Japanese Emperors' reigns. @samp{E} is allowed in | |
1465 | @samp{%Ec}, @samp{%EC}, @samp{%Ex}, @samp{%EX}, @samp{%Ey}, and | |
1466 | @samp{%EY}. | |
1467 | ||
1468 | @samp{O} means to use the current locale's ``alternative'' | |
1469 | representation of numbers, instead of the ordinary decimal digits. This | |
1470 | is allowed with most letters, all the ones that output numbers. | |
1471 | ||
1472 | If @var{universal} is non-@code{nil}, that means to describe the time as | |
1473 | Universal Time; @code{nil} means describe it using what Emacs believes | |
1474 | is the local time zone (see @code{current-time-zone}). | |
1475 | ||
1476 | This function uses the C library function @code{strftime} | |
1477 | (@pxref{Formatting Calendar Time,,, libc, The GNU C Library Reference | |
1478 | Manual}) to do most of the work. In order to communicate with that | |
1479 | function, it first encodes its argument using the coding system | |
1480 | specified by @code{locale-coding-system} (@pxref{Locales}); after | |
1481 | @code{strftime} returns the resulting string, | |
1482 | @code{format-time-string} decodes the string using that same coding | |
1483 | system. | |
1484 | @end defun | |
1485 | ||
1486 | @defun seconds-to-time seconds | |
1487 | This function converts @var{seconds}, a floating point number of | |
1488 | seconds since the epoch, to a time value and returns that. To perform | |
1489 | the inverse conversion, use @code{float-time}. | |
1490 | @end defun | |
1491 | ||
53728487 EZ |
1492 | @defun format-seconds format-string seconds |
1493 | This function converts its argument @var{seconds} into a string of | |
1494 | years, days, hours, etc., according to @var{format-string}. The | |
1495 | argument @var{format-string} may contain @samp{%}-sequences which | |
1496 | control the conversion. Here is a table of what the | |
1497 | @samp{%}-sequences mean: | |
1498 | ||
1499 | @table @samp | |
1500 | @item %y | |
1501 | @itemx %Y | |
3051e4bf | 1502 | The integer number of 365-day years. |
53728487 EZ |
1503 | @item %d |
1504 | @itemx %D | |
3051e4bf | 1505 | The integer number of days. |
53728487 EZ |
1506 | @item %h |
1507 | @itemx %H | |
3051e4bf | 1508 | The integer number of hours. |
53728487 EZ |
1509 | @item %m |
1510 | @itemx %M | |
3051e4bf | 1511 | The integer number of minutes. |
53728487 EZ |
1512 | @item %s |
1513 | @itemx %S | |
3051e4bf | 1514 | The integer number of seconds. |
53728487 EZ |
1515 | @item %z |
1516 | Non-printing control flag. When it is used, other specifiers must be | |
1517 | given in the order of decreasing size, i.e.@: years before days, hours | |
1518 | before minutes, etc. Nothing will be produced in the result string to | |
1519 | the left of @samp{%z} until the first non-zero conversion is | |
1520 | encountered. For example, the default format used by | |
1521 | @code{emacs-uptime} (@pxref{Processor Run Time, emacs-uptime}) | |
1522 | @w{@code{"%Y, %D, %H, %M, %z%S"}} means that the number of seconds | |
1523 | will always be produced, but years, days, hours, and minutes will only | |
1524 | be shown if they are non-zero. | |
1525 | @item %% | |
1526 | Produces a literal @samp{%}. | |
1527 | @end table | |
1528 | ||
1529 | Upper-case format sequences produce the units in addition to the | |
1530 | numbers, lower-case formats produce only the numbers. | |
1531 | ||
1532 | You can also specify the field width by following the @samp{%} with a | |
1533 | number; shorter numbers will be padded with blanks. An optional | |
1534 | period before the width requests zero-padding instead. For example, | |
1535 | @code{"%.3Y"} might produce @code{"004 years"}. | |
1536 | ||
1537 | @emph{Warning:} This function works only with values of @var{seconds} | |
1538 | that don't exceed @code{most-positive-fixnum} (@pxref{Integer Basics, | |
1539 | most-positive-fixnum}). | |
1540 | @end defun | |
1541 | ||
b8d4c8d0 GM |
1542 | @node Processor Run Time |
1543 | @section Processor Run time | |
1544 | @cindex processor run time | |
53728487 EZ |
1545 | @cindex Emacs process run time |
1546 | ||
1547 | Emacs provides several functions and primitives that return time, | |
1548 | both elapsed and processor time, used by the Emacs process. | |
1549 | ||
106e6894 | 1550 | @deffn Command emacs-uptime &optional format |
53728487 EZ |
1551 | This function returns a string representing the Emacs |
1552 | @dfn{uptime}---the elapsed wall-clock time this instance of Emacs is | |
3051e4bf EZ |
1553 | running. The string is formatted by @code{format-seconds} according |
1554 | to the optional argument @var{format}. For the available format | |
1555 | descriptors, see @ref{Time Parsing, format-seconds}. If @var{format} | |
e2b7cebb CY |
1556 | is @code{nil} or omitted, it defaults to @code{"%Y, %D, %H, %M, |
1557 | %z%S"}. | |
106e6894 CY |
1558 | |
1559 | When called interactively, it prints the uptime in the echo area. | |
1560 | @end deffn | |
b8d4c8d0 GM |
1561 | |
1562 | @defun get-internal-run-time | |
1563 | This function returns the processor run time used by Emacs as a list | |
1564 | of three integers: @code{(@var{high} @var{low} @var{microsec})}. The | |
1565 | integers @var{high} and @var{low} combine to give the number of | |
1566 | seconds, which is | |
1567 | @ifnottex | |
1568 | @var{high} * 2**16 + @var{low}. | |
1569 | @end ifnottex | |
1570 | @tex | |
1571 | $high*2^{16}+low$. | |
1572 | @end tex | |
1573 | ||
1574 | The third element, @var{microsec}, gives the microseconds (or 0 for | |
1575 | systems that return time with the resolution of only one second). | |
1576 | ||
53728487 EZ |
1577 | Note that the time returned by this function excludes the time Emacs |
1578 | was not using the processor, and if the Emacs process has several | |
1579 | threads, the returned value is the sum of the processor times used up | |
1580 | by all Emacs threads. | |
1581 | ||
b8d4c8d0 | 1582 | If the system doesn't provide a way to determine the processor run |
53728487 EZ |
1583 | time, @code{get-internal-run-time} returns the same time as |
1584 | @code{current-time}. | |
1585 | @end defun | |
1586 | ||
106e6894 | 1587 | @deffn Command emacs-init-time |
53728487 | 1588 | This function returns the duration of the Emacs initialization |
106e6894 CY |
1589 | (@pxref{Startup Summary}) in seconds, as a string. When called |
1590 | interactively, it prints the duration in the echo area. | |
1591 | @end deffn | |
b8d4c8d0 GM |
1592 | |
1593 | @node Time Calculations | |
1594 | @section Time Calculations | |
1595 | ||
1596 | These functions perform calendrical computations using time values | |
1597 | (the kind of list that @code{current-time} returns). | |
1598 | ||
1599 | @defun time-less-p t1 t2 | |
1600 | This returns @code{t} if time value @var{t1} is less than time value | |
1601 | @var{t2}. | |
1602 | @end defun | |
1603 | ||
1604 | @defun time-subtract t1 t2 | |
1605 | This returns the time difference @var{t1} @minus{} @var{t2} between | |
1606 | two time values, in the same format as a time value. | |
1607 | @end defun | |
1608 | ||
1609 | @defun time-add t1 t2 | |
1610 | This returns the sum of two time values, one of which ought to | |
1611 | represent a time difference rather than a point in time. | |
1612 | Here is how to add a number of seconds to a time value: | |
1613 | ||
1614 | @example | |
1615 | (time-add @var{time} (seconds-to-time @var{seconds})) | |
1616 | @end example | |
1617 | @end defun | |
1618 | ||
1619 | @defun time-to-days time | |
1620 | This function returns the number of days between the beginning of year | |
1621 | 1 and @var{time}. | |
1622 | @end defun | |
1623 | ||
1624 | @defun time-to-day-in-year time | |
1625 | This returns the day number within the year corresponding to @var{time}. | |
1626 | @end defun | |
1627 | ||
1628 | @defun date-leap-year-p year | |
1629 | This function returns @code{t} if @var{year} is a leap year. | |
1630 | @end defun | |
1631 | ||
1632 | @node Timers | |
1633 | @section Timers for Delayed Execution | |
1634 | @cindex timer | |
1635 | ||
1636 | You can set up a @dfn{timer} to call a function at a specified | |
1637 | future time or after a certain length of idleness. | |
1638 | ||
1639 | Emacs cannot run timers at any arbitrary point in a Lisp program; it | |
1640 | can run them only when Emacs could accept output from a subprocess: | |
1641 | namely, while waiting or inside certain primitive functions such as | |
1642 | @code{sit-for} or @code{read-event} which @emph{can} wait. Therefore, a | |
1643 | timer's execution may be delayed if Emacs is busy. However, the time of | |
1644 | execution is very precise if Emacs is idle. | |
1645 | ||
1646 | Emacs binds @code{inhibit-quit} to @code{t} before calling the timer | |
1647 | function, because quitting out of many timer functions can leave | |
1648 | things in an inconsistent state. This is normally unproblematical | |
1649 | because most timer functions don't do a lot of work. Indeed, for a | |
1650 | timer to call a function that takes substantial time to run is likely | |
1651 | to be annoying. If a timer function needs to allow quitting, it | |
1652 | should use @code{with-local-quit} (@pxref{Quitting}). For example, if | |
1653 | a timer function calls @code{accept-process-output} to receive output | |
1654 | from an external process, that call should be wrapped inside | |
1655 | @code{with-local-quit}, to ensure that @kbd{C-g} works if the external | |
1656 | process hangs. | |
1657 | ||
1658 | It is usually a bad idea for timer functions to alter buffer | |
1659 | contents. When they do, they usually should call @code{undo-boundary} | |
1660 | both before and after changing the buffer, to separate the timer's | |
1661 | changes from user commands' changes and prevent a single undo entry | |
1662 | from growing to be quite large. | |
1663 | ||
1664 | Timer functions should also avoid calling functions that cause Emacs | |
1665 | to wait, such as @code{sit-for} (@pxref{Waiting}). This can lead to | |
1666 | unpredictable effects, since other timers (or even the same timer) can | |
1667 | run while waiting. If a timer function needs to perform an action | |
1668 | after a certain time has elapsed, it can do this by scheduling a new | |
1669 | timer. | |
1670 | ||
1671 | If a timer function calls functions that can change the match data, | |
1672 | it should save and restore the match data. @xref{Saving Match Data}. | |
1673 | ||
1674 | @deffn Command run-at-time time repeat function &rest args | |
1675 | This sets up a timer that calls the function @var{function} with | |
1676 | arguments @var{args} at time @var{time}. If @var{repeat} is a number | |
1677 | (integer or floating point), the timer is scheduled to run again every | |
1678 | @var{repeat} seconds after @var{time}. If @var{repeat} is @code{nil}, | |
1679 | the timer runs only once. | |
1680 | ||
1681 | @var{time} may specify an absolute or a relative time. | |
1682 | ||
1683 | Absolute times may be specified using a string with a limited variety | |
1684 | of formats, and are taken to be times @emph{today}, even if already in | |
1685 | the past. The recognized forms are @samp{@var{xxxx}}, | |
1686 | @samp{@var{x}:@var{xx}}, or @samp{@var{xx}:@var{xx}} (military time), | |
1687 | and @samp{@var{xx}am}, @samp{@var{xx}AM}, @samp{@var{xx}pm}, | |
1688 | @samp{@var{xx}PM}, @samp{@var{xx}:@var{xx}am}, | |
1689 | @samp{@var{xx}:@var{xx}AM}, @samp{@var{xx}:@var{xx}pm}, or | |
1690 | @samp{@var{xx}:@var{xx}PM}. A period can be used instead of a colon | |
1691 | to separate the hour and minute parts. | |
1692 | ||
1693 | To specify a relative time as a string, use numbers followed by units. | |
1694 | For example: | |
1695 | ||
1696 | @table @samp | |
1697 | @item 1 min | |
1698 | denotes 1 minute from now. | |
1699 | @item 1 min 5 sec | |
1700 | denotes 65 seconds from now. | |
1701 | @item 1 min 2 sec 3 hour 4 day 5 week 6 fortnight 7 month 8 year | |
1702 | denotes exactly 103 months, 123 days, and 10862 seconds from now. | |
1703 | @end table | |
1704 | ||
1705 | For relative time values, Emacs considers a month to be exactly thirty | |
1706 | days, and a year to be exactly 365.25 days. | |
1707 | ||
1708 | Not all convenient formats are strings. If @var{time} is a number | |
1709 | (integer or floating point), that specifies a relative time measured in | |
1710 | seconds. The result of @code{encode-time} can also be used to specify | |
1711 | an absolute value for @var{time}. | |
1712 | ||
1713 | In most cases, @var{repeat} has no effect on when @emph{first} call | |
1714 | takes place---@var{time} alone specifies that. There is one exception: | |
1715 | if @var{time} is @code{t}, then the timer runs whenever the time is a | |
1716 | multiple of @var{repeat} seconds after the epoch. This is useful for | |
1717 | functions like @code{display-time}. | |
1718 | ||
1719 | The function @code{run-at-time} returns a timer value that identifies | |
1720 | the particular scheduled future action. You can use this value to call | |
1721 | @code{cancel-timer} (see below). | |
1722 | @end deffn | |
1723 | ||
1724 | A repeating timer nominally ought to run every @var{repeat} seconds, | |
1725 | but remember that any invocation of a timer can be late. Lateness of | |
1726 | one repetition has no effect on the scheduled time of the next | |
1727 | repetition. For instance, if Emacs is busy computing for long enough | |
1728 | to cover three scheduled repetitions of the timer, and then starts to | |
1729 | wait, it will immediately call the timer function three times in | |
1730 | immediate succession (presuming no other timers trigger before or | |
1731 | between them). If you want a timer to run again no less than @var{n} | |
1732 | seconds after the last invocation, don't use the @var{repeat} argument. | |
1733 | Instead, the timer function should explicitly reschedule the timer. | |
1734 | ||
1735 | @defvar timer-max-repeats | |
1736 | This variable's value specifies the maximum number of times to repeat | |
1737 | calling a timer function in a row, when many previously scheduled | |
1738 | calls were unavoidably delayed. | |
1739 | @end defvar | |
1740 | ||
1741 | @defmac with-timeout (seconds timeout-forms@dots{}) body@dots{} | |
1742 | Execute @var{body}, but give up after @var{seconds} seconds. If | |
1743 | @var{body} finishes before the time is up, @code{with-timeout} returns | |
1744 | the value of the last form in @var{body}. If, however, the execution of | |
1745 | @var{body} is cut short by the timeout, then @code{with-timeout} | |
1746 | executes all the @var{timeout-forms} and returns the value of the last | |
1747 | of them. | |
1748 | ||
1749 | This macro works by setting a timer to run after @var{seconds} seconds. If | |
1750 | @var{body} finishes before that time, it cancels the timer. If the | |
1751 | timer actually runs, it terminates execution of @var{body}, then | |
1752 | executes @var{timeout-forms}. | |
1753 | ||
1754 | Since timers can run within a Lisp program only when the program calls a | |
1755 | primitive that can wait, @code{with-timeout} cannot stop executing | |
1756 | @var{body} while it is in the midst of a computation---only when it | |
1757 | calls one of those primitives. So use @code{with-timeout} only with a | |
1758 | @var{body} that waits for input, not one that does a long computation. | |
1759 | @end defmac | |
1760 | ||
1761 | The function @code{y-or-n-p-with-timeout} provides a simple way to use | |
1762 | a timer to avoid waiting too long for an answer. @xref{Yes-or-No | |
1763 | Queries}. | |
1764 | ||
1765 | @defun cancel-timer timer | |
1766 | This cancels the requested action for @var{timer}, which should be a | |
1767 | timer---usually, one previously returned by @code{run-at-time} or | |
1768 | @code{run-with-idle-timer}. This cancels the effect of that call to | |
1769 | one of these functions; the arrival of the specified time will not | |
1770 | cause anything special to happen. | |
1771 | @end defun | |
1772 | ||
1773 | @node Idle Timers | |
1774 | @section Idle Timers | |
1775 | ||
1776 | Here is how to set up a timer that runs when Emacs is idle for a | |
1777 | certain length of time. Aside from how to set them up, idle timers | |
1778 | work just like ordinary timers. | |
1779 | ||
1780 | @deffn Command run-with-idle-timer secs repeat function &rest args | |
d15aac68 CY |
1781 | Set up a timer which runs the next time Emacs is idle for @var{secs} |
1782 | seconds. The value of @var{secs} may be an integer or a floating | |
1783 | point number; a value of the type returned by @code{current-idle-time} | |
b8d4c8d0 GM |
1784 | is also allowed. |
1785 | ||
1786 | If @var{repeat} is @code{nil}, the timer runs just once, the first time | |
1787 | Emacs remains idle for a long enough time. More often @var{repeat} is | |
1788 | non-@code{nil}, which means to run the timer @emph{each time} Emacs | |
1789 | remains idle for @var{secs} seconds. | |
1790 | ||
1791 | The function @code{run-with-idle-timer} returns a timer value which you | |
1792 | can use in calling @code{cancel-timer} (@pxref{Timers}). | |
1793 | @end deffn | |
1794 | ||
1795 | @cindex idleness | |
d15aac68 CY |
1796 | Emacs becomes @dfn{idle} when it starts waiting for user input, and |
1797 | it remains idle until the user provides some input. If a timer is set | |
1798 | for five seconds of idleness, it runs approximately five seconds after | |
1799 | Emacs first becomes idle. Even if @var{repeat} is non-@code{nil}, | |
1800 | this timer will not run again as long as Emacs remains idle, because | |
1801 | the duration of idleness will continue to increase and will not go | |
1802 | down to five seconds again. | |
b8d4c8d0 GM |
1803 | |
1804 | Emacs can do various things while idle: garbage collect, autosave or | |
1805 | handle data from a subprocess. But these interludes during idleness do | |
1806 | not interfere with idle timers, because they do not reset the clock of | |
1807 | idleness to zero. An idle timer set for 600 seconds will run when ten | |
1808 | minutes have elapsed since the last user command was finished, even if | |
1809 | subprocess output has been accepted thousands of times within those ten | |
1810 | minutes, and even if there have been garbage collections and autosaves. | |
1811 | ||
1812 | When the user supplies input, Emacs becomes non-idle while executing the | |
1813 | input. Then it becomes idle again, and all the idle timers that are | |
1814 | set up to repeat will subsequently run another time, one by one. | |
1815 | ||
b8d4c8d0 | 1816 | @defun current-idle-time |
17bec671 | 1817 | If Emacs is idle, this function returns the length of time Emacs has |
d15aac68 CY |
1818 | been idle, as a list of three integers: @code{(@var{sec-high} |
1819 | @var{sec-low} @var{microsec})}, where @var{high} and @var{low} are the | |
1820 | high and low bits for the number of seconds and @var{microsec} is the | |
1821 | additional number of microseconds (@pxref{Time of Day}). | |
b8d4c8d0 | 1822 | |
17bec671 RS |
1823 | When Emacs is not idle, @code{current-idle-time} returns @code{nil}. |
1824 | This is a convenient way to test whether Emacs is idle. | |
1825 | ||
b8d4c8d0 GM |
1826 | The main use of this function is when an idle timer function wants to |
1827 | ``take a break'' for a while. It can set up another idle timer to | |
1828 | call the same function again, after a few seconds more idleness. | |
1829 | Here's an example: | |
1830 | ||
1831 | @smallexample | |
1832 | (defvar resume-timer nil | |
1833 | "Timer that `timer-function' used to reschedule itself, or nil.") | |
1834 | ||
1835 | (defun timer-function () | |
1836 | ;; @r{If the user types a command while @code{resume-timer}} | |
1837 | ;; @r{is active, the next time this function is called from} | |
1838 | ;; @r{its main idle timer, deactivate @code{resume-timer}.} | |
1839 | (when resume-timer | |
1840 | (cancel-timer resume-timer)) | |
1841 | ...@var{do the work for a while}... | |
1842 | (when @var{taking-a-break} | |
1843 | (setq resume-timer | |
1844 | (run-with-idle-timer | |
1845 | ;; Compute an idle time @var{break-length} | |
1846 | ;; more than the current value. | |
1847 | (time-add (current-idle-time) | |
1848 | (seconds-to-time @var{break-length})) | |
1849 | nil | |
1850 | 'timer-function)))) | |
1851 | @end smallexample | |
1852 | @end defun | |
1853 | ||
d15aac68 CY |
1854 | Do not write an idle timer function containing a loop which does a |
1855 | certain amount of processing each time around, and exits when | |
1856 | @code{(input-pending-p)} is non-@code{nil}. This approach seems very | |
b8d4c8d0 GM |
1857 | natural but has two problems: |
1858 | ||
1859 | @itemize | |
1860 | @item | |
1861 | It blocks out all process output (since Emacs accepts process output | |
1862 | only while waiting). | |
1863 | ||
1864 | @item | |
1865 | It blocks out any idle timers that ought to run during that time. | |
1866 | @end itemize | |
1867 | ||
1868 | @noindent | |
d15aac68 CY |
1869 | The correct approach is for the idle timer to reschedule itself after |
1870 | a brief pause, using the method in the @code{timer-function} example | |
1871 | above. | |
b8d4c8d0 GM |
1872 | |
1873 | @node Terminal Input | |
1874 | @section Terminal Input | |
1875 | @cindex terminal input | |
1876 | ||
1877 | This section describes functions and variables for recording or | |
1878 | manipulating terminal input. See @ref{Display}, for related | |
1879 | functions. | |
1880 | ||
1881 | @menu | |
d24880de GM |
1882 | * Input Modes:: Options for how input is processed. |
1883 | * Recording Input:: Saving histories of recent or all input events. | |
b8d4c8d0 GM |
1884 | @end menu |
1885 | ||
1886 | @node Input Modes | |
1887 | @subsection Input Modes | |
1888 | @cindex input modes | |
1889 | @cindex terminal input modes | |
1890 | ||
1891 | @defun set-input-mode interrupt flow meta &optional quit-char | |
1892 | This function sets the mode for reading keyboard input. If | |
1893 | @var{interrupt} is non-null, then Emacs uses input interrupts. If it is | |
1894 | @code{nil}, then it uses @sc{cbreak} mode. The default setting is | |
1895 | system-dependent. Some systems always use @sc{cbreak} mode regardless | |
1896 | of what is specified. | |
1897 | ||
1898 | When Emacs communicates directly with X, it ignores this argument and | |
1899 | uses interrupts if that is the way it knows how to communicate. | |
1900 | ||
1901 | If @var{flow} is non-@code{nil}, then Emacs uses @sc{xon/xoff} | |
1902 | (@kbd{C-q}, @kbd{C-s}) flow control for output to the terminal. This | |
1903 | has no effect except in @sc{cbreak} mode. | |
1904 | ||
1905 | @c Emacs 19 feature | |
1906 | The argument @var{meta} controls support for input character codes | |
1907 | above 127. If @var{meta} is @code{t}, Emacs converts characters with | |
1908 | the 8th bit set into Meta characters. If @var{meta} is @code{nil}, | |
1909 | Emacs disregards the 8th bit; this is necessary when the terminal uses | |
1910 | it as a parity bit. If @var{meta} is neither @code{t} nor @code{nil}, | |
1911 | Emacs uses all 8 bits of input unchanged. This is good for terminals | |
1912 | that use 8-bit character sets. | |
1913 | ||
1914 | @c Emacs 19 feature | |
1915 | If @var{quit-char} is non-@code{nil}, it specifies the character to | |
1916 | use for quitting. Normally this character is @kbd{C-g}. | |
1917 | @xref{Quitting}. | |
1918 | @end defun | |
1919 | ||
1920 | The @code{current-input-mode} function returns the input mode settings | |
1921 | Emacs is currently using. | |
1922 | ||
1923 | @c Emacs 19 feature | |
1924 | @defun current-input-mode | |
1925 | This function returns the current mode for reading keyboard input. It | |
1926 | returns a list, corresponding to the arguments of @code{set-input-mode}, | |
1927 | of the form @code{(@var{interrupt} @var{flow} @var{meta} @var{quit})} in | |
1928 | which: | |
1929 | @table @var | |
1930 | @item interrupt | |
1931 | is non-@code{nil} when Emacs is using interrupt-driven input. If | |
1932 | @code{nil}, Emacs is using @sc{cbreak} mode. | |
1933 | @item flow | |
1934 | is non-@code{nil} if Emacs uses @sc{xon/xoff} (@kbd{C-q}, @kbd{C-s}) | |
1935 | flow control for output to the terminal. This value is meaningful only | |
1936 | when @var{interrupt} is @code{nil}. | |
1937 | @item meta | |
1938 | is @code{t} if Emacs treats the eighth bit of input characters as | |
1939 | the meta bit; @code{nil} means Emacs clears the eighth bit of every | |
1940 | input character; any other value means Emacs uses all eight bits as the | |
1941 | basic character code. | |
1942 | @item quit | |
1943 | is the character Emacs currently uses for quitting, usually @kbd{C-g}. | |
1944 | @end table | |
1945 | @end defun | |
1946 | ||
1947 | @node Recording Input | |
1948 | @subsection Recording Input | |
1949 | @cindex recording input | |
1950 | ||
1951 | @defun recent-keys | |
1952 | This function returns a vector containing the last 300 input events from | |
1953 | the keyboard or mouse. All input events are included, whether or not | |
1954 | they were used as parts of key sequences. Thus, you always get the last | |
1955 | 100 input events, not counting events generated by keyboard macros. | |
1956 | (These are excluded because they are less interesting for debugging; it | |
1957 | should be enough to see the events that invoked the macros.) | |
1958 | ||
1959 | A call to @code{clear-this-command-keys} (@pxref{Command Loop Info}) | |
1960 | causes this function to return an empty vector immediately afterward. | |
1961 | @end defun | |
1962 | ||
1963 | @deffn Command open-dribble-file filename | |
1964 | @cindex dribble file | |
1965 | This function opens a @dfn{dribble file} named @var{filename}. When a | |
1966 | dribble file is open, each input event from the keyboard or mouse (but | |
1967 | not those from keyboard macros) is written in that file. A | |
1968 | non-character event is expressed using its printed representation | |
1969 | surrounded by @samp{<@dots{}>}. | |
1970 | ||
1971 | You close the dribble file by calling this function with an argument | |
1972 | of @code{nil}. | |
1973 | ||
1974 | This function is normally used to record the input necessary to | |
1975 | trigger an Emacs bug, for the sake of a bug report. | |
1976 | ||
1977 | @example | |
1978 | @group | |
1979 | (open-dribble-file "~/dribble") | |
1980 | @result{} nil | |
1981 | @end group | |
1982 | @end example | |
1983 | @end deffn | |
1984 | ||
1985 | See also the @code{open-termscript} function (@pxref{Terminal Output}). | |
1986 | ||
1987 | @node Terminal Output | |
1988 | @section Terminal Output | |
1989 | @cindex terminal output | |
1990 | ||
1991 | The terminal output functions send output to a text terminal, or keep | |
1992 | track of output sent to the terminal. The variable @code{baud-rate} | |
1993 | tells you what Emacs thinks is the output speed of the terminal. | |
1994 | ||
01f17ae2 | 1995 | @defopt baud-rate |
b8d4c8d0 GM |
1996 | This variable's value is the output speed of the terminal, as far as |
1997 | Emacs knows. Setting this variable does not change the speed of actual | |
1998 | data transmission, but the value is used for calculations such as | |
1999 | padding. | |
2000 | ||
2001 | It also affects decisions about whether to scroll part of the | |
2002 | screen or repaint on text terminals. @xref{Forcing Redisplay}, | |
2003 | for the corresponding functionality on graphical terminals. | |
2004 | ||
2005 | The value is measured in baud. | |
01f17ae2 | 2006 | @end defopt |
b8d4c8d0 GM |
2007 | |
2008 | If you are running across a network, and different parts of the | |
2009 | network work at different baud rates, the value returned by Emacs may be | |
2010 | different from the value used by your local terminal. Some network | |
2011 | protocols communicate the local terminal speed to the remote machine, so | |
2012 | that Emacs and other programs can get the proper value, but others do | |
2013 | not. If Emacs has the wrong value, it makes decisions that are less | |
2014 | than optimal. To fix the problem, set @code{baud-rate}. | |
2015 | ||
106e6894 CY |
2016 | @defun send-string-to-terminal string &optional terminal |
2017 | This function sends @var{string} to @var{terminal} without alteration. | |
b8d4c8d0 | 2018 | Control characters in @var{string} have terminal-dependent effects. |
106e6894 CY |
2019 | This function operates only on text terminals. @var{terminal} may be |
2020 | a terminal object, a frame, or @code{nil} for the selected frame's | |
f804f446 | 2021 | terminal. In batch mode, @var{string} is sent to @code{stdout} when |
f58a7c7e | 2022 | @var{terminal} is @code{nil}. |
b8d4c8d0 GM |
2023 | |
2024 | One use of this function is to define function keys on terminals that | |
2025 | have downloadable function key definitions. For example, this is how (on | |
2026 | certain terminals) to define function key 4 to move forward four | |
2027 | characters (by transmitting the characters @kbd{C-u C-f} to the | |
2028 | computer): | |
2029 | ||
2030 | @example | |
2031 | @group | |
2032 | (send-string-to-terminal "\eF4\^U\^F") | |
2033 | @result{} nil | |
2034 | @end group | |
2035 | @end example | |
2036 | @end defun | |
2037 | ||
2038 | @deffn Command open-termscript filename | |
2039 | @cindex termscript file | |
2040 | This function is used to open a @dfn{termscript file} that will record | |
2041 | all the characters sent by Emacs to the terminal. It returns | |
2042 | @code{nil}. Termscript files are useful for investigating problems | |
2043 | where Emacs garbles the screen, problems that are due to incorrect | |
2044 | Termcap entries or to undesirable settings of terminal options more | |
2045 | often than to actual Emacs bugs. Once you are certain which characters | |
2046 | were actually output, you can determine reliably whether they correspond | |
2047 | to the Termcap specifications in use. | |
2048 | ||
2049 | You close the termscript file by calling this function with an | |
2050 | argument of @code{nil}. | |
2051 | ||
2052 | See also @code{open-dribble-file} in @ref{Recording Input}. | |
2053 | ||
2054 | @example | |
2055 | @group | |
2056 | (open-termscript "../junk/termscript") | |
2057 | @result{} nil | |
2058 | @end group | |
2059 | @end example | |
2060 | @end deffn | |
2061 | ||
2062 | @node Sound Output | |
2063 | @section Sound Output | |
2064 | @cindex sound | |
2065 | ||
2066 | To play sound using Emacs, use the function @code{play-sound}. Only | |
986bd52a CY |
2067 | certain systems are supported; if you call @code{play-sound} on a |
2068 | system which cannot really do the job, it gives an error. | |
b8d4c8d0 GM |
2069 | |
2070 | The sound must be stored as a file in RIFF-WAVE format (@samp{.wav}) | |
2071 | or Sun Audio format (@samp{.au}). | |
2072 | ||
2073 | @defun play-sound sound | |
2074 | This function plays a specified sound. The argument, @var{sound}, has | |
2075 | the form @code{(sound @var{properties}...)}, where the @var{properties} | |
2076 | consist of alternating keywords (particular symbols recognized | |
2077 | specially) and values corresponding to them. | |
2078 | ||
2079 | Here is a table of the keywords that are currently meaningful in | |
2080 | @var{sound}, and their meanings: | |
2081 | ||
2082 | @table @code | |
2083 | @item :file @var{file} | |
2084 | This specifies the file containing the sound to play. | |
2085 | If the file name is not absolute, it is expanded against | |
2086 | the directory @code{data-directory}. | |
2087 | ||
2088 | @item :data @var{data} | |
2089 | This specifies the sound to play without need to refer to a file. The | |
2090 | value, @var{data}, should be a string containing the same bytes as a | |
2091 | sound file. We recommend using a unibyte string. | |
2092 | ||
2093 | @item :volume @var{volume} | |
2094 | This specifies how loud to play the sound. It should be a number in the | |
2095 | range of 0 to 1. The default is to use whatever volume has been | |
2096 | specified before. | |
2097 | ||
2098 | @item :device @var{device} | |
2099 | This specifies the system device on which to play the sound, as a | |
2100 | string. The default device is system-dependent. | |
2101 | @end table | |
2102 | ||
2103 | Before actually playing the sound, @code{play-sound} | |
2104 | calls the functions in the list @code{play-sound-functions}. | |
2105 | Each function is called with one argument, @var{sound}. | |
2106 | @end defun | |
2107 | ||
2108 | @defun play-sound-file file &optional volume device | |
2109 | This function is an alternative interface to playing a sound @var{file} | |
2110 | specifying an optional @var{volume} and @var{device}. | |
2111 | @end defun | |
2112 | ||
2113 | @defvar play-sound-functions | |
2114 | A list of functions to be called before playing a sound. Each function | |
2115 | is called with one argument, a property list that describes the sound. | |
2116 | @end defvar | |
2117 | ||
2118 | @node X11 Keysyms | |
2119 | @section Operating on X11 Keysyms | |
2120 | @cindex X11 keysyms | |
2121 | ||
2122 | To define system-specific X11 keysyms, set the variable | |
2123 | @code{system-key-alist}. | |
2124 | ||
2125 | @defvar system-key-alist | |
2126 | This variable's value should be an alist with one element for each | |
2127 | system-specific keysym. Each element has the form @code{(@var{code} | |
2128 | . @var{symbol})}, where @var{code} is the numeric keysym code (not | |
2129 | including the ``vendor specific'' bit, | |
2130 | @ifnottex | |
2131 | -2**28), | |
2132 | @end ifnottex | |
2133 | @tex | |
2134 | $-2^{28}$), | |
2135 | @end tex | |
2136 | and @var{symbol} is the name for the function key. | |
2137 | ||
2138 | For example @code{(168 . mute-acute)} defines a system-specific key (used | |
2139 | by HP X servers) whose numeric code is | |
2140 | @ifnottex | |
2141 | -2**28 | |
2142 | @end ifnottex | |
2143 | @tex | |
2144 | $-2^{28}$ | |
2145 | @end tex | |
2146 | + 168. | |
2147 | ||
2148 | It is not crucial to exclude from the alist the keysyms of other X | |
2149 | servers; those do no harm, as long as they don't conflict with the ones | |
2150 | used by the X server actually in use. | |
2151 | ||
2152 | The variable is always local to the current terminal, and cannot be | |
3ec61d4e | 2153 | buffer-local. @xref{Multiple Terminals}. |
b8d4c8d0 GM |
2154 | @end defvar |
2155 | ||
2156 | You can specify which keysyms Emacs should use for the Meta, Alt, Hyper, and Super modifiers by setting these variables: | |
2157 | ||
2158 | @defvar x-alt-keysym | |
2159 | @defvarx x-meta-keysym | |
2160 | @defvarx x-hyper-keysym | |
2161 | @defvarx x-super-keysym | |
2162 | The name of the keysym that should stand for the Alt modifier | |
2163 | (respectively, for Meta, Hyper, and Super). For example, here is | |
2164 | how to swap the Meta and Alt modifiers within Emacs: | |
2165 | @lisp | |
2166 | (setq x-alt-keysym 'meta) | |
2167 | (setq x-meta-keysym 'alt) | |
2168 | @end lisp | |
2169 | @end defvar | |
2170 | ||
2171 | @node Batch Mode | |
2172 | @section Batch Mode | |
2173 | @cindex batch mode | |
2174 | ||
2175 | The command-line option @samp{-batch} causes Emacs to run | |
2176 | noninteractively. In this mode, Emacs does not read commands from the | |
2177 | terminal, it does not alter the terminal modes, and it does not expect | |
2178 | to be outputting to an erasable screen. The idea is that you specify | |
2179 | Lisp programs to run; when they are finished, Emacs should exit. The | |
2180 | way to specify the programs to run is with @samp{-l @var{file}}, which | |
2181 | loads the library named @var{file}, or @samp{-f @var{function}}, which | |
2182 | calls @var{function} with no arguments, or @samp{--eval @var{form}}. | |
2183 | ||
2184 | Any Lisp program output that would normally go to the echo area, | |
2185 | either using @code{message}, or using @code{prin1}, etc., with @code{t} | |
2186 | as the stream, goes instead to Emacs's standard error descriptor when | |
2187 | in batch mode. Similarly, input that would normally come from the | |
2188 | minibuffer is read from the standard input descriptor. | |
2189 | Thus, Emacs behaves much like a noninteractive | |
2190 | application program. (The echo area output that Emacs itself normally | |
2191 | generates, such as command echoing, is suppressed entirely.) | |
2192 | ||
2193 | @defvar noninteractive | |
2194 | This variable is non-@code{nil} when Emacs is running in batch mode. | |
2195 | @end defvar | |
2196 | ||
2197 | @node Session Management | |
2198 | @section Session Management | |
2199 | @cindex session manager | |
2200 | ||
dca019f8 CY |
2201 | Emacs supports the X Session Management Protocol, which is used to |
2202 | suspend and restart applications. In the X Window System, a program | |
2203 | called the @dfn{session manager} is responsible for keeping track of | |
2204 | the applications that are running. When the X server shuts down, the | |
2205 | session manager asks applications to save their state, and delays the | |
2206 | actual shutdown until they respond. An application can also cancel | |
2207 | the shutdown. | |
b8d4c8d0 GM |
2208 | |
2209 | When the session manager restarts a suspended session, it directs | |
2210 | these applications to individually reload their saved state. It does | |
2211 | this by specifying a special command-line argument that says what | |
2212 | saved session to restore. For Emacs, this argument is @samp{--smid | |
2213 | @var{session}}. | |
2214 | ||
2215 | @defvar emacs-save-session-functions | |
dca019f8 CY |
2216 | Emacs supports saving state via a hook called |
2217 | @code{emacs-save-session-functions}. Emacs runs this hook when the | |
2218 | session manager tells it that the window system is shutting down. The | |
2219 | functions are called with no arguments, and with the current buffer | |
2220 | set to a temporary buffer. Each function can use @code{insert} to add | |
2221 | Lisp code to this buffer. At the end, Emacs saves the buffer in a | |
2222 | file, called the @dfn{session file}. | |
2223 | ||
2224 | @findex emacs-session-restore | |
2225 | Subsequently, when the session manager restarts Emacs, it loads the | |
2226 | session file automatically (@pxref{Loading}). This is performed by a | |
2227 | function named @code{emacs-session-restore}, which is called during | |
2228 | startup. @xref{Startup Summary}. | |
b8d4c8d0 GM |
2229 | |
2230 | If a function in @code{emacs-save-session-functions} returns | |
2231 | non-@code{nil}, Emacs tells the session manager to cancel the | |
2232 | shutdown. | |
2233 | @end defvar | |
2234 | ||
2235 | Here is an example that just inserts some text into @samp{*scratch*} when | |
2236 | Emacs is restarted by the session manager. | |
2237 | ||
2238 | @example | |
2239 | @group | |
2240 | (add-hook 'emacs-save-session-functions 'save-yourself-test) | |
2241 | @end group | |
2242 | ||
2243 | @group | |
2244 | (defun save-yourself-test () | |
c57008f6 | 2245 | (insert "(save-current-buffer |
b8d4c8d0 GM |
2246 | (switch-to-buffer \"*scratch*\") |
2247 | (insert \"I am restored\"))") | |
2248 | nil) | |
2249 | @end group | |
2250 | @end example | |
2251 | ||
00f113eb JB |
2252 | @node Dynamic Libraries |
2253 | @section Dynamically Loaded Libraries | |
2254 | @cindex dynamic libraries | |
2255 | ||
2256 | A @dfn{dynamically loaded library} is a library that is loaded on | |
2257 | demand, when its facilities are first needed. Emacs supports such | |
2258 | on-demand loading of support libraries for some of its features. | |
2259 | ||
2260 | @defvar dynamic-library-alist | |
2261 | This is an alist of dynamic libraries and external library files | |
2262 | implementing them. | |
2263 | ||
2264 | Each element is a list of the form | |
2265 | @w{@code{(@var{library} @var{files}@dots{})}}, where the @code{car} is | |
2266 | a symbol representing a supported external library, and the rest are | |
2267 | strings giving alternate filenames for that library. | |
2268 | ||
2269 | Emacs tries to load the library from the files in the order they | |
2270 | appear in the list; if none is found, the running session of Emacs | |
2271 | won't have access to that library, and the features that depend on the | |
2272 | library will be unavailable. | |
2273 | ||
2274 | Image support on some platforms uses this facility. Here's an example | |
2275 | of setting this variable for supporting images on MS-Windows: | |
2276 | ||
2277 | @lisp | |
2278 | (setq dynamic-library-alist | |
2279 | '((xpm "libxpm.dll" "xpm4.dll" "libXpm-nox4.dll") | |
2280 | (png "libpng12d.dll" "libpng12.dll" "libpng.dll" | |
2281 | "libpng13d.dll" "libpng13.dll") | |
2282 | (jpeg "jpeg62.dll" "libjpeg.dll" "jpeg-62.dll" "jpeg.dll") | |
2283 | (tiff "libtiff3.dll" "libtiff.dll") | |
2284 | (gif "giflib4.dll" "libungif4.dll" "libungif.dll") | |
2285 | (svg "librsvg-2-2.dll") | |
2286 | (gdk-pixbuf "libgdk_pixbuf-2.0-0.dll") | |
2287 | (glib "libglib-2.0-0.dll") | |
2288 | (gobject "libgobject-2.0-0.dll"))) | |
2289 | @end lisp | |
2290 | ||
2291 | Note that image types @code{pbm} and @code{xbm} do not need entries in | |
2292 | this variable because they do not depend on external libraries and are | |
2293 | always available in Emacs. | |
2294 | ||
2295 | Also note that this variable is not meant to be a generic facility for | |
2296 | accessing external libraries; only those already known by Emacs can | |
2297 | be loaded through it. | |
2298 | ||
2299 | This variable is ignored if the given @var{library} is statically | |
2300 | linked into Emacs. | |
2301 | @end defvar |