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1 | @c -*-texinfo-*- |
2 | @c This is part of the GNU Emacs Lisp Reference Manual. | |
3 | @c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2001, | |
6ed161e1 | 4 | @c 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc. |
b8d4c8d0 | 5 | @c See the file elisp.texi for copying conditions. |
6336d8c3 | 6 | @setfilename ../../info/os |
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7 | @node System Interface, Antinews, Display, Top |
8 | @chapter Operating System Interface | |
9 | ||
10 | This chapter is about starting and getting out of Emacs, access to | |
11 | values in the operating system environment, and terminal input, output, | |
12 | and flow control. | |
13 | ||
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14 | @xref{Building Emacs}, for related information. @xref{Display}, for |
15 | additional operating system status information pertaining to the | |
16 | terminal and the screen. | |
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17 | |
18 | @menu | |
19 | * Starting Up:: Customizing Emacs startup processing. | |
20 | * Getting Out:: How exiting works (permanent or temporary). | |
21 | * System Environment:: Distinguish the name and kind of system. | |
22 | * User Identification:: Finding the name and user id of the user. | |
23 | * Time of Day:: Getting the current time. | |
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24 | * Time Conversion:: Converting a time from numeric form to |
25 | calendrical data and vice versa. | |
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26 | * Time Parsing:: Converting a time from numeric form to text |
27 | and vice versa. | |
28 | * Processor Run Time:: Getting the run time used by Emacs. | |
29 | * Time Calculations:: Adding, subtracting, comparing times, etc. | |
30 | * Timers:: Setting a timer to call a function at a certain time. | |
31 | * Idle Timers:: Setting a timer to call a function when Emacs has | |
32 | been idle for a certain length of time. | |
33 | * Terminal Input:: Accessing and recording terminal input. | |
34 | * Terminal Output:: Controlling and recording terminal output. | |
35 | * Sound Output:: Playing sounds on the computer's speaker. | |
36 | * X11 Keysyms:: Operating on key symbols for X Windows | |
37 | * Batch Mode:: Running Emacs without terminal interaction. | |
38 | * Session Management:: Saving and restoring state with X Session Management. | |
39 | @end menu | |
40 | ||
41 | @node Starting Up | |
42 | @section Starting Up Emacs | |
43 | ||
44 | This section describes what Emacs does when it is started, and how you | |
45 | can customize these actions. | |
46 | ||
47 | @menu | |
48 | * Startup Summary:: Sequence of actions Emacs performs at startup. | |
02a89103 | 49 | * Init File:: Details on reading the init file. |
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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 | ||
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61 | When Emacs is started up, it performs the following operations |
62 | (which are defined in @file{startup.el}): | |
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63 | |
64 | @enumerate | |
65 | @item | |
66 | It adds subdirectories to @code{load-path}, by running the file named | |
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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 | |
f36acfd9 | 72 | @vindex before-init-time |
b8d4c8d0 | 73 | @item |
02a89103 | 74 | It sets the variable @code{before-init-time} to the value of |
f36acfd9 | 75 | @code{current-time} (@pxref{Time of Day}). It also sets |
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76 | @code{after-init-time} to @code{nil}, which signals to Lisp programs |
77 | that Emacs is being initialized. | |
b8d4c8d0 | 78 | |
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79 | @vindex initial-window-system@r{, and startup} |
80 | @vindex window-system-initialization-alist | |
b8d4c8d0 | 81 | @item |
f36acfd9 | 82 | It loads the initialization library for the window system specified by |
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83 | the variable @code{initial-window-system} (@pxref{Window Systems, |
84 | initial-window-system}). This library's name is | |
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85 | @file{term/@var{windowsystem}-win.el}, where @var{windowsystem} is the |
86 | value of @code{initial-window-system}. From that library, it calls | |
87 | the appropriate initialization function. The initialization function | |
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88 | for each supported window system is specified by |
89 | @code{window-system-initialization-alist}. | |
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90 | |
91 | @item | |
92 | It sets the language environment and the terminal coding system, | |
93 | if requested by environment variables such as @code{LANG}. | |
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94 | |
95 | @item | |
96 | It processes the initial options. (Some of them are handled | |
97 | even earlier than this.) | |
98 | ||
99 | @item | |
f36acfd9 | 100 | It runs the normal hook @code{before-init-hook}. |
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101 | |
102 | @item | |
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103 | It initializes the window frame and faces, if appropriate, and turns |
104 | on the menu bar and tool bar, if the initial frame needs them. | |
105 | ||
106 | @item | |
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107 | It loads the library @file{site-start}, if it exists. This is not |
108 | done if the options @samp{-Q} or @samp{--no-site-file} were specified. | |
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109 | @cindex @file{site-start.el} |
110 | ||
111 | @item | |
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112 | It loads your init file (@pxref{Init File}). This is not done if the |
113 | options @samp{-q}, @samp{-Q}, or @samp{--batch} were specified. If | |
114 | the @samp{-u} option was specified, Emacs looks for the init file in | |
115 | that user's home directory instead. | |
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116 | |
117 | @item | |
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118 | It loads the library @file{default}, if it exists. This is not done |
119 | if @code{inhibit-default-init} is non-@code{nil}, nor if the options | |
120 | @samp{-q}, @samp{-Q}, or @samp{--batch} were specified. | |
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121 | @cindex @file{default.el} |
122 | ||
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123 | @item |
124 | It loads your abbrevs from the file specified by | |
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125 | @code{abbrev-file-name}, if that file exists and can be read |
126 | (@pxref{Abbrev Files, abbrev-file-name}). This is not done if the | |
127 | option @samp{--batch} was specified. | |
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128 | |
129 | @vindex after-init-time | |
130 | @item | |
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131 | It sets the variable @code{after-init-time} to the value of |
132 | @code{current-time}. This variable was set to @code{nil} earlier; | |
133 | setting it to the current time signals that the initialization phase | |
134 | is over, and, together with @code{before-init-time}, provides the | |
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135 | measurement of how long it took. |
136 | ||
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137 | @item |
138 | It runs the normal hook @code{after-init-hook}. | |
139 | ||
140 | @item | |
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141 | If the buffer @samp{*scratch*} exists and is still in Fundamental mode |
142 | (as it should be by default), it sets its major mode according to | |
143 | @code{initial-major-mode}. | |
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144 | |
145 | @item | |
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146 | If started on a text-only terminal, it loads the terminal-specific |
147 | Lisp library, which is specified by the variable | |
148 | @code{term-file-prefix} (@pxref{Terminal-Specific}). This is not done | |
149 | in @code{--batch} mode, nor if @code{term-file-prefix} is @code{nil}. | |
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150 | |
151 | @item | |
152 | It displays the initial echo area message, unless you have suppressed | |
153 | that with @code{inhibit-startup-echo-area-message}. | |
154 | ||
155 | @item | |
156 | It processes the action arguments from the command line. | |
157 | ||
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158 | @item |
159 | It now exits if the option @code{--batch} was specified. | |
160 | ||
161 | @item | |
162 | If @code{initial-buffer-choice} is a string, it visits the file with | |
163 | that name. Furthermore, if the @samp{*scratch*} buffer exists and is | |
164 | empty, it inserts @code{initial-scratch-message} into that buffer. | |
165 | ||
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166 | @item |
167 | It runs @code{emacs-startup-hook} and then @code{term-setup-hook}. | |
168 | ||
169 | @item | |
170 | It calls @code{frame-notice-user-settings}, which modifies the | |
171 | parameters of the selected frame according to whatever the init files | |
172 | specify. | |
173 | ||
174 | @item | |
175 | It runs @code{window-setup-hook}. @xref{Window Systems}. | |
176 | ||
177 | @item | |
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178 | If the option @code{--daemon} was specified, it calls |
179 | @code{server-start} and detaches from the controlling terminal. | |
180 | @xref{Emacs Server,,, emacs, The GNU Emacs Manual}. | |
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181 | |
182 | @item | |
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183 | It displays the @dfn{startup screen}, which is a special buffer that |
184 | contains information about copyleft and basic Emacs usage. This is | |
185 | not done if @code{initial-buffer-choice} or | |
186 | @code{inhibit-startup-screen} are @code{nil}, nor if the | |
187 | @samp{--no-splash} or @samp{-Q} command-line options were specified. | |
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188 | |
189 | @item | |
190 | If started by the X session manager, it calls | |
191 | @code{emacs-session-restore} passing it as argument the ID of the | |
dca019f8 | 192 | previous session. @xref{Session Management}. |
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193 | @end enumerate |
194 | ||
f36acfd9 | 195 | @defopt inhibit-startup-screen |
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196 | This variable, if non-@code{nil}, inhibits the startup screen. In |
197 | that case, Emacs typically displays the @samp{*scratch*} buffer; but | |
198 | see @code{initial-buffer-choice}, below. | |
b8d4c8d0 | 199 | |
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200 | Do not set this variable in the init file of a new user, or in a way |
201 | that affects more than one user, as that would prevent new users from | |
202 | receiving information about copyleft and basic Emacs usage. | |
f36acfd9 | 203 | |
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204 | @code{inhibit-startup-message} and @code{inhibit-splash-screen} are |
205 | aliases for this variable. | |
206 | @end defopt | |
207 | ||
208 | @defopt initial-buffer-choice | |
209 | This variable, if non-@code{nil}, determines a file or buffer for | |
210 | Emacs to display after starting up, instead of the startup screen. If | |
211 | its value is @code{t}, Emacs displays the @samp{*scratch*} buffer. If | |
212 | its value is a string, that specifies the name of a file for Emacs to | |
213 | visit. | |
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214 | @end defopt |
215 | ||
216 | @defopt inhibit-startup-echo-area-message | |
217 | This variable controls the display of the startup echo area message. | |
218 | You can suppress the startup echo area message by adding text with this | |
219 | form to your init file: | |
220 | ||
221 | @example | |
222 | (setq inhibit-startup-echo-area-message | |
223 | "@var{your-login-name}") | |
224 | @end example | |
225 | ||
226 | Emacs explicitly checks for an expression as shown above in your init | |
227 | file; your login name must appear in the expression as a Lisp string | |
228 | constant. Other methods of setting | |
229 | @code{inhibit-startup-echo-area-message} to the same value do not | |
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230 | inhibit the startup message. This way, you can easily inhibit the |
231 | message for yourself if you wish, but thoughtless copying of your init | |
232 | file will not inhibit the message for someone else. | |
233 | @end defopt | |
b8d4c8d0 | 234 | |
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235 | @defopt initial-scratch-message |
236 | This variable, if non-@code{nil}, should be a string, which is | |
237 | inserted into the @samp{*scratch*} buffer when Emacs starts up. If it | |
238 | is @code{nil}, the @samp{*scratch*} buffer is empty. | |
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239 | @end defopt |
240 | ||
241 | @node Init File | |
242 | @subsection The Init File, @file{.emacs} | |
243 | @cindex init file | |
244 | @cindex @file{.emacs} | |
245 | ||
246 | When you start Emacs, it normally attempts to load your @dfn{init | |
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247 | file}. This is either a file named @file{.emacs} or @file{.emacs.el} |
248 | in your home directory, or a file named @file{init.el} in a | |
249 | subdirectory named @file{.emacs.d} in your home directory. Whichever | |
250 | place you use, you can also compile the file (@pxref{Byte | |
251 | Compilation}); then the actual file loaded will be @file{.emacs.elc} | |
252 | or @file{init.elc}. | |
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253 | |
254 | The command-line switches @samp{-q}, @samp{-Q}, and @samp{-u} | |
255 | control whether and where to find the init file; @samp{-q} (and the | |
256 | stronger @samp{-Q}) says not to load an init file, while @samp{-u | |
257 | @var{user}} says to load @var{user}'s init file instead of yours. | |
258 | @xref{Entering Emacs,,, emacs, The GNU Emacs Manual}. If neither | |
259 | option is specified, Emacs uses the @code{LOGNAME} environment | |
260 | variable, or the @code{USER} (most systems) or @code{USERNAME} (MS | |
261 | systems) variable, to find your home directory and thus your init | |
262 | file; this way, even if you have su'd, Emacs still loads your own init | |
263 | file. If those environment variables are absent, though, Emacs uses | |
264 | your user-id to find your home directory. | |
265 | ||
266 | @cindex default init file | |
267 | A site may have a @dfn{default init file}, which is the library | |
268 | named @file{default.el}. Emacs finds the @file{default.el} file | |
269 | through the standard search path for libraries (@pxref{How Programs Do | |
270 | Loading}). The Emacs distribution does not come with this file; sites | |
271 | may provide one for local customizations. If the default init file | |
272 | exists, it is loaded whenever you start Emacs, except in batch mode or | |
273 | if @samp{-q} (or @samp{-Q}) is specified. But your own personal init | |
274 | file, if any, is loaded first; if it sets @code{inhibit-default-init} | |
275 | to a non-@code{nil} value, then Emacs does not subsequently load the | |
276 | @file{default.el} file. | |
277 | ||
278 | Another file for site-customization is @file{site-start.el}. Emacs | |
279 | loads this @emph{before} the user's init file. You can inhibit the | |
280 | loading of this file with the option @samp{--no-site-file}. | |
281 | ||
282 | @defvar site-run-file | |
283 | This variable specifies the site-customization file to load before the | |
284 | user's init file. Its normal value is @code{"site-start"}. The only | |
285 | way you can change it with real effect is to do so before dumping | |
286 | Emacs. | |
287 | @end defvar | |
288 | ||
289 | @xref{Init Examples,, Init File Examples, emacs, The GNU Emacs Manual}, for | |
290 | examples of how to make various commonly desired customizations in your | |
291 | @file{.emacs} file. | |
292 | ||
293 | @defopt inhibit-default-init | |
294 | This variable prevents Emacs from loading the default initialization | |
295 | library file for your session of Emacs. If its value is non-@code{nil}, | |
296 | then the default library is not loaded. The default value is | |
297 | @code{nil}. | |
298 | @end defopt | |
299 | ||
300 | @defvar before-init-hook | |
301 | This normal hook is run, once, just before loading all the init files | |
302 | (the user's init file, @file{default.el}, and/or @file{site-start.el}). | |
303 | (The only way to change it with real effect is before dumping Emacs.) | |
304 | @end defvar | |
305 | ||
306 | @defvar after-init-hook | |
307 | This normal hook is run, once, just after loading all the init files | |
308 | (the user's init file, @file{default.el}, and/or @file{site-start.el}), | |
309 | before loading the terminal-specific library and processing the | |
310 | command-line action arguments. | |
311 | @end defvar | |
312 | ||
313 | @defvar emacs-startup-hook | |
314 | This normal hook is run, once, just after handling the command line | |
315 | arguments, just before @code{term-setup-hook}. | |
316 | @end defvar | |
317 | ||
318 | @defvar user-init-file | |
319 | This variable holds the absolute file name of the user's init file. If the | |
320 | actual init file loaded is a compiled file, such as @file{.emacs.elc}, | |
321 | the value refers to the corresponding source file. | |
322 | @end defvar | |
323 | ||
324 | @defvar user-emacs-directory | |
325 | This variable holds the name of the @file{.emacs.d} directory. It is | |
326 | ordinarily @file{~/.emacs.d}, but differs on some platforms. | |
327 | @end defvar | |
328 | ||
329 | @node Terminal-Specific | |
330 | @subsection Terminal-Specific Initialization | |
331 | @cindex terminal-specific initialization | |
332 | ||
333 | Each terminal type can have its own Lisp library that Emacs loads when | |
334 | run on that type of terminal. The library's name is constructed by | |
335 | concatenating the value of the variable @code{term-file-prefix} and the | |
336 | terminal type (specified by the environment variable @code{TERM}). | |
337 | Normally, @code{term-file-prefix} has the value | |
338 | @code{"term/"}; changing this is not recommended. Emacs finds the file | |
339 | in the normal manner, by searching the @code{load-path} directories, and | |
340 | trying the @samp{.elc} and @samp{.el} suffixes. | |
341 | ||
342 | @cindex Termcap | |
343 | The usual function of a terminal-specific library is to enable | |
344 | special keys to send sequences that Emacs can recognize. It may also | |
4f4a84ec | 345 | need to set or add to @code{input-decode-map} if the Termcap or |
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346 | Terminfo entry does not specify all the terminal's function keys. |
347 | @xref{Terminal Input}. | |
348 | ||
349 | When the name of the terminal type contains a hyphen, and no library | |
350 | is found whose name is identical to the terminal's name, Emacs strips | |
351 | from the terminal's name the last hyphen and everything that follows | |
352 | it, and tries again. This process is repeated until Emacs finds a | |
353 | matching library or until there are no more hyphens in the name (the | |
354 | latter means the terminal doesn't have any library specific to it). | |
355 | Thus, for example, if there are no @samp{aaa-48} and @samp{aaa-30} | |
356 | libraries, Emacs will try the same library @file{term/aaa.el} for | |
357 | terminal types @samp{aaa-48} and @samp{aaa-30-rv}. If necessary, the | |
358 | library can evaluate @code{(getenv "TERM")} to find the full name of | |
359 | the terminal type.@refill | |
360 | ||
361 | Your init file can prevent the loading of the | |
362 | terminal-specific library by setting the variable | |
363 | @code{term-file-prefix} to @code{nil}. This feature is useful when | |
364 | experimenting with your own peculiar customizations. | |
365 | ||
366 | You can also arrange to override some of the actions of the | |
367 | terminal-specific library by setting the variable | |
368 | @code{term-setup-hook}. This is a normal hook which Emacs runs using | |
369 | @code{run-hooks} at the end of Emacs initialization, after loading both | |
370 | your init file and any terminal-specific libraries. You can | |
371 | use this variable to define initializations for terminals that do not | |
372 | have their own libraries. @xref{Hooks}. | |
373 | ||
374 | @defvar term-file-prefix | |
375 | @cindex @code{TERM} environment variable | |
376 | If the @code{term-file-prefix} variable is non-@code{nil}, Emacs loads | |
377 | a terminal-specific initialization file as follows: | |
378 | ||
379 | @example | |
380 | (load (concat term-file-prefix (getenv "TERM"))) | |
381 | @end example | |
382 | ||
383 | @noindent | |
384 | You may set the @code{term-file-prefix} variable to @code{nil} in your | |
385 | init file if you do not wish to load the | |
386 | terminal-initialization file. To do this, put the following in | |
387 | your init file: @code{(setq term-file-prefix nil)}. | |
388 | ||
389 | On MS-DOS, if the environment variable @code{TERM} is not set, Emacs | |
390 | uses @samp{internal} as the terminal type. | |
391 | @end defvar | |
392 | ||
393 | @defvar term-setup-hook | |
394 | This variable is a normal hook that Emacs runs after loading your | |
395 | init file, the default initialization file (if any) and the | |
396 | terminal-specific Lisp file. | |
397 | ||
398 | You can use @code{term-setup-hook} to override the definitions made by a | |
399 | terminal-specific file. | |
400 | @end defvar | |
401 | ||
402 | See @code{window-setup-hook} in @ref{Window Systems}, for a related | |
403 | feature. | |
404 | ||
405 | @node Command-Line Arguments | |
406 | @subsection Command-Line Arguments | |
407 | @cindex command-line arguments | |
408 | ||
409 | You can use command-line arguments to request various actions when you | |
410 | start Emacs. Since you do not need to start Emacs more than once per | |
411 | day, and will often leave your Emacs session running longer than that, | |
412 | command-line arguments are hardly ever used. As a practical matter, it | |
413 | is best to avoid making the habit of using them, since this habit would | |
414 | encourage you to kill and restart Emacs unnecessarily often. These | |
415 | options exist for two reasons: to be compatible with other editors (for | |
416 | invocation by other programs) and to enable shell scripts to run | |
417 | specific Lisp programs. | |
418 | ||
419 | This section describes how Emacs processes command-line arguments, | |
420 | and how you can customize them. | |
421 | ||
422 | @ignore | |
423 | (Note that some other editors require you to start afresh each time | |
424 | you want to edit a file. With this kind of editor, you will probably | |
425 | specify the file as a command-line argument. The recommended way to | |
426 | use GNU Emacs is to start it only once, just after you log in, and do | |
427 | all your editing in the same Emacs process. Each time you want to edit | |
428 | a different file, you visit it with the existing Emacs, which eventually | |
429 | comes to have many files in it ready for editing. Usually you do not | |
430 | kill the Emacs until you are about to log out.) | |
431 | @end ignore | |
432 | ||
433 | @defun command-line | |
434 | This function parses the command line that Emacs was called with, | |
435 | processes it, loads the user's init file and displays the | |
436 | startup messages. | |
437 | @end defun | |
438 | ||
439 | @defvar command-line-processed | |
440 | The value of this variable is @code{t} once the command line has been | |
441 | processed. | |
442 | ||
443 | If you redump Emacs by calling @code{dump-emacs}, you may wish to set | |
444 | this variable to @code{nil} first in order to cause the new dumped Emacs | |
445 | to process its new command-line arguments. | |
446 | @end defvar | |
447 | ||
448 | @defvar command-switch-alist | |
449 | @cindex switches on command line | |
450 | @cindex options on command line | |
451 | @cindex command-line options | |
452 | The value of this variable is an alist of user-defined command-line | |
453 | options and associated handler functions. This variable exists so you | |
454 | can add elements to it. | |
455 | ||
456 | A @dfn{command-line option} is an argument on the command line, which | |
457 | has the form: | |
458 | ||
459 | @example | |
460 | -@var{option} | |
461 | @end example | |
462 | ||
463 | The elements of the @code{command-switch-alist} look like this: | |
464 | ||
465 | @example | |
466 | (@var{option} . @var{handler-function}) | |
467 | @end example | |
468 | ||
469 | The @sc{car}, @var{option}, is a string, the name of a command-line | |
470 | option (not including the initial hyphen). The @var{handler-function} | |
471 | is called to handle @var{option}, and receives the option name as its | |
472 | sole argument. | |
473 | ||
474 | In some cases, the option is followed in the command line by an | |
475 | argument. In these cases, the @var{handler-function} can find all the | |
476 | remaining command-line arguments in the variable | |
477 | @code{command-line-args-left}. (The entire list of command-line | |
478 | arguments is in @code{command-line-args}.) | |
479 | ||
480 | The command-line arguments are parsed by the @code{command-line-1} | |
481 | function in the @file{startup.el} file. See also @ref{Emacs | |
482 | Invocation, , Command Line Arguments for Emacs Invocation, emacs, The | |
483 | GNU Emacs Manual}. | |
484 | @end defvar | |
485 | ||
486 | @defvar command-line-args | |
487 | The value of this variable is the list of command-line arguments passed | |
488 | to Emacs. | |
489 | @end defvar | |
490 | ||
dca019f8 CY |
491 | @defvar command-line-args-left |
492 | The value of this variable is the list of command-line arguments that | |
493 | have not yet been processed. @code{argv} is an alias for this. | |
494 | @end defvar | |
495 | ||
b8d4c8d0 GM |
496 | @defvar command-line-functions |
497 | This variable's value is a list of functions for handling an | |
498 | unrecognized command-line argument. Each time the next argument to be | |
499 | processed has no special meaning, the functions in this list are called, | |
500 | in order of appearance, until one of them returns a non-@code{nil} | |
501 | value. | |
502 | ||
503 | These functions are called with no arguments. They can access the | |
504 | command-line argument under consideration through the variable | |
505 | @code{argi}, which is bound temporarily at this point. The remaining | |
506 | arguments (not including the current one) are in the variable | |
507 | @code{command-line-args-left}. | |
508 | ||
509 | When a function recognizes and processes the argument in @code{argi}, it | |
510 | should return a non-@code{nil} value to say it has dealt with that | |
511 | argument. If it has also dealt with some of the following arguments, it | |
512 | can indicate that by deleting them from @code{command-line-args-left}. | |
513 | ||
514 | If all of these functions return @code{nil}, then the argument is used | |
515 | as a file name to visit. | |
516 | @end defvar | |
517 | ||
518 | @node Getting Out | |
519 | @section Getting Out of Emacs | |
520 | @cindex exiting Emacs | |
521 | ||
522 | There are two ways to get out of Emacs: you can kill the Emacs job, | |
523 | which exits permanently, or you can suspend it, which permits you to | |
524 | reenter the Emacs process later. As a practical matter, you seldom kill | |
525 | Emacs---only when you are about to log out. Suspending is much more | |
526 | common. | |
527 | ||
528 | @menu | |
529 | * Killing Emacs:: Exiting Emacs irreversibly. | |
530 | * Suspending Emacs:: Exiting Emacs reversibly. | |
531 | @end menu | |
532 | ||
533 | @node Killing Emacs | |
534 | @comment node-name, next, previous, up | |
535 | @subsection Killing Emacs | |
536 | @cindex killing Emacs | |
537 | ||
538 | Killing Emacs means ending the execution of the Emacs process. The | |
539 | parent process normally resumes control. The low-level primitive for | |
540 | killing Emacs is @code{kill-emacs}. | |
541 | ||
106e6894 CY |
542 | @deffn Command kill-emacs &optional exit-data |
543 | This command exits the Emacs process and kills it. | |
b8d4c8d0 GM |
544 | |
545 | If @var{exit-data} is an integer, then it is used as the exit status | |
546 | of the Emacs process. (This is useful primarily in batch operation; see | |
547 | @ref{Batch Mode}.) | |
548 | ||
549 | If @var{exit-data} is a string, its contents are stuffed into the | |
550 | terminal input buffer so that the shell (or whatever program next reads | |
551 | input) can read them. | |
106e6894 | 552 | @end deffn |
b8d4c8d0 GM |
553 | |
554 | All the information in the Emacs process, aside from files that have | |
555 | been saved, is lost when the Emacs process is killed. Because killing | |
556 | Emacs inadvertently can lose a lot of work, Emacs queries for | |
557 | confirmation before actually terminating if you have buffers that need | |
558 | saving or subprocesses that are running. This is done in the function | |
559 | @code{save-buffers-kill-emacs}, the higher level function from which | |
560 | @code{kill-emacs} is usually called. | |
561 | ||
562 | @defvar kill-emacs-query-functions | |
563 | After asking the standard questions, @code{save-buffers-kill-emacs} | |
564 | calls the functions in the list @code{kill-emacs-query-functions}, in | |
565 | order of appearance, with no arguments. These functions can ask for | |
566 | additional confirmation from the user. If any of them returns | |
567 | @code{nil}, @code{save-buffers-kill-emacs} does not kill Emacs, and | |
568 | does not run the remaining functions in this hook. Calling | |
569 | @code{kill-emacs} directly does not run this hook. | |
570 | @end defvar | |
571 | ||
572 | @defvar kill-emacs-hook | |
573 | This variable is a normal hook; once @code{save-buffers-kill-emacs} is | |
574 | finished with all file saving and confirmation, it calls | |
575 | @code{kill-emacs} which runs the functions in this hook. | |
576 | @code{kill-emacs} does not run this hook in batch mode. | |
577 | ||
578 | @code{kill-emacs} may be invoked directly (that is not via | |
579 | @code{save-buffers-kill-emacs}) if the terminal is disconnected, or in | |
580 | similar situations where interaction with the user is not possible. | |
581 | Thus, if your hook needs to interact with the user, put it on | |
582 | @code{kill-emacs-query-functions}; if it needs to run regardless of | |
583 | how Emacs is killed, put it on @code{kill-emacs-hook}. | |
584 | @end defvar | |
585 | ||
586 | @node Suspending Emacs | |
587 | @subsection Suspending Emacs | |
588 | @cindex suspending Emacs | |
589 | ||
dca019f8 CY |
590 | On text-only terminals, it is possible to @dfn{suspend Emacs}, which |
591 | means stopping Emacs temporarily and returning control to its superior | |
592 | process, which is usually the shell. This allows you to resume | |
593 | editing later in the same Emacs process, with the same buffers, the | |
594 | same kill ring, the same undo history, and so on. To resume Emacs, | |
595 | use the appropriate command in the parent shell---most likely | |
596 | @code{fg}. | |
b8d4c8d0 | 597 | |
62a5303f EZ |
598 | @cindex controlling terminal |
599 | Suspending works only on a terminal device from which the Emacs | |
600 | session was started. We call that device the @dfn{controlling | |
dca019f8 CY |
601 | terminal} of the session. Suspending is not allowed if the |
602 | controlling terminal is a graphical terminal. | |
62a5303f | 603 | |
b8d4c8d0 GM |
604 | Some operating systems do not support suspension of jobs; on these |
605 | systems, ``suspension'' actually creates a new shell temporarily as a | |
606 | subprocess of Emacs. Then you would exit the shell to return to Emacs. | |
607 | ||
106e6894 | 608 | @deffn Command suspend-emacs &optional string |
b8d4c8d0 GM |
609 | This function stops Emacs and returns control to the superior process. |
610 | If and when the superior process resumes Emacs, @code{suspend-emacs} | |
611 | returns @code{nil} to its caller in Lisp. | |
612 | ||
62a5303f EZ |
613 | This function works only on the controlling terminal of the Emacs |
614 | session; to relinquish control of other tty devices, use | |
f71de46c | 615 | @code{suspend-tty} (see below). If the Emacs session uses more than |
dca019f8 CY |
616 | one terminal, you must delete the frames on all the other terminals |
617 | before suspending Emacs, or this function signals an error. | |
618 | @xref{Multiple Terminals}. | |
62a5303f | 619 | |
dca019f8 CY |
620 | If @var{string} is non-@code{nil}, its characters are sent to Emacs's |
621 | superior shell, to be read as terminal input. The characters in | |
b8d4c8d0 GM |
622 | @var{string} are not echoed by the superior shell; only the results |
623 | appear. | |
624 | ||
625 | Before suspending, @code{suspend-emacs} runs the normal hook | |
dca019f8 CY |
626 | @code{suspend-hook}. After the user resumes Emacs, |
627 | @code{suspend-emacs} runs the normal hook @code{suspend-resume-hook}. | |
628 | @xref{Hooks}. | |
b8d4c8d0 GM |
629 | |
630 | The next redisplay after resumption will redraw the entire screen, | |
dca019f8 CY |
631 | unless the variable @code{no-redraw-on-reenter} is non-@code{nil}. |
632 | @xref{Refresh Screen}. | |
b8d4c8d0 GM |
633 | |
634 | In the following example, note that @samp{pwd} is not echoed after | |
635 | Emacs is suspended. But it is read and executed by the shell. | |
636 | ||
637 | @smallexample | |
638 | @group | |
639 | (suspend-emacs) | |
640 | @result{} nil | |
641 | @end group | |
642 | ||
643 | @group | |
644 | (add-hook 'suspend-hook | |
645 | (function (lambda () | |
646 | (or (y-or-n-p | |
647 | "Really suspend? ") | |
648 | (error "Suspend canceled"))))) | |
649 | @result{} (lambda nil | |
650 | (or (y-or-n-p "Really suspend? ") | |
651 | (error "Suspend canceled"))) | |
652 | @end group | |
653 | @group | |
654 | (add-hook 'suspend-resume-hook | |
655 | (function (lambda () (message "Resumed!")))) | |
656 | @result{} (lambda nil (message "Resumed!")) | |
657 | @end group | |
658 | @group | |
659 | (suspend-emacs "pwd") | |
660 | @result{} nil | |
661 | @end group | |
662 | @group | |
663 | ---------- Buffer: Minibuffer ---------- | |
664 | Really suspend? @kbd{y} | |
665 | ---------- Buffer: Minibuffer ---------- | |
666 | @end group | |
667 | ||
668 | @group | |
669 | ---------- Parent Shell ---------- | |
670 | lewis@@slug[23] % /user/lewis/manual | |
671 | lewis@@slug[24] % fg | |
672 | @end group | |
673 | ||
674 | @group | |
675 | ---------- Echo Area ---------- | |
676 | Resumed! | |
677 | @end group | |
678 | @end smallexample | |
106e6894 | 679 | @end deffn |
b8d4c8d0 GM |
680 | |
681 | @defvar suspend-hook | |
682 | This variable is a normal hook that Emacs runs before suspending. | |
683 | @end defvar | |
684 | ||
685 | @defvar suspend-resume-hook | |
686 | This variable is a normal hook that Emacs runs on resuming | |
687 | after a suspension. | |
688 | @end defvar | |
689 | ||
62a5303f EZ |
690 | @defun suspend-tty &optional tty |
691 | If @var{tty} specifies a terminal device used by Emacs, this function | |
692 | relinquishes the device and restores it to its prior state. Frames | |
693 | that used the device continue to exist, but are not updated and Emacs | |
dca019f8 CY |
694 | doesn't read input from them. @var{tty} can be a terminal object, a |
695 | frame (meaning the terminal for that frame), or @code{nil} (meaning | |
696 | the terminal for the selected frame). @xref{Multiple Terminals}. | |
697 | ||
698 | If @var{tty} is already suspended, this function does nothing. | |
699 | ||
700 | This function runs the hook @code{suspend-tty-functions}, passing the | |
701 | terminal object as an argument to each function. | |
62a5303f EZ |
702 | @end defun |
703 | ||
704 | @defun resume-tty &optional tty | |
dca019f8 CY |
705 | This function resumes the previously suspended terminal device |
706 | @var{tty}; @var{tty} can be a terminal object, a frame (meaning the | |
707 | terminal for that frame), or @code{nil} (meaning the terminal for the | |
708 | selected frame). | |
62a5303f EZ |
709 | |
710 | This function reopens the terminal device, re-initializes it, and | |
711 | redraws its with that terminal's selected frame. It then runs the | |
dca019f8 CY |
712 | hook @code{resume-tty-functions}, passing the terminal object as an |
713 | argument to each function. | |
62a5303f EZ |
714 | |
715 | If the same device is already used by another Emacs terminal, this | |
716 | function signals an error. | |
717 | @end defun | |
718 | ||
719 | @defun controlling-tty-p &optional terminal | |
720 | This function returns non-@code{nil} if @var{terminal} is the | |
dca019f8 CY |
721 | controlling terminal of the Emacs session; @code{terminal} can be a |
722 | terminal object, a frame (meaning the terminal for that frame), or | |
723 | @code{nil} (meaning the terminal for the selected frame). | |
62a5303f EZ |
724 | @end defun |
725 | ||
726 | @deffn Command suspend-frame | |
727 | This command @dfn{suspends} a frame. For GUI frames, it calls | |
728 | @code{iconify-frame} (@pxref{Visibility of Frames}); for text-only | |
729 | frames, it calls either @code{suspend-emacs} or @code{suspend-tty}, | |
730 | depending on whether the frame is displayed on the controlling | |
731 | terminal device or not. | |
732 | @end deffn | |
733 | ||
b8d4c8d0 GM |
734 | @node System Environment |
735 | @section Operating System Environment | |
736 | @cindex operating system environment | |
737 | ||
738 | Emacs provides access to variables in the operating system environment | |
739 | through various functions. These variables include the name of the | |
740 | system, the user's @acronym{UID}, and so on. | |
741 | ||
742 | @defvar system-configuration | |
743 | This variable holds the standard GNU configuration name for the | |
744 | hardware/software configuration of your system, as a string. The | |
745 | convenient way to test parts of this string is with | |
746 | @code{string-match}. | |
747 | @end defvar | |
748 | ||
749 | @cindex system type and name | |
750 | @defvar system-type | |
751 | The value of this variable is a symbol indicating the type of operating | |
752 | system Emacs is operating on. Here is a table of the possible values: | |
753 | ||
58e3d8e8 | 754 | @table @code |
1213465a EZ |
755 | @item aix |
756 | IBM's AIX. | |
b8d4c8d0 GM |
757 | |
758 | @item berkeley-unix | |
1213465a | 759 | Berkeley BSD and its variants. |
b8d4c8d0 GM |
760 | |
761 | @item cygwin | |
1213465a EZ |
762 | Cygwin, a Posix layer on top of MS-Windows. |
763 | ||
764 | @item darwin | |
765 | Darwin (Mac OS X). | |
b8d4c8d0 | 766 | |
b8d4c8d0 | 767 | @item gnu |
1213465a | 768 | The GNU system (using the GNU kernel, which consists of the HURD and Mach). |
b8d4c8d0 GM |
769 | |
770 | @item gnu/linux | |
771 | A GNU/Linux system---that is, a variant GNU system, using the Linux | |
772 | kernel. (These systems are the ones people often call ``Linux,'' but | |
773 | actually Linux is just the kernel, not the whole system.) | |
774 | ||
1213465a EZ |
775 | @item gnu/kfreebsd |
776 | A GNU (glibc-based) system with a FreeBSD kernel. | |
777 | ||
b8d4c8d0 GM |
778 | @item hpux |
779 | Hewlett-Packard HPUX operating system. | |
780 | ||
781 | @item irix | |
782 | Silicon Graphics Irix system. | |
783 | ||
1213465a EZ |
784 | @item lynxos 3.0.1 |
785 | LynxOS-3.0.1. | |
786 | ||
b8d4c8d0 GM |
787 | @item ms-dos |
788 | Microsoft MS-DOS ``operating system.'' Emacs compiled with DJGPP for | |
789 | MS-DOS binds @code{system-type} to @code{ms-dos} even when you run it on | |
790 | MS-Windows. | |
791 | ||
b8d4c8d0 | 792 | @item usg-unix-v |
1213465a | 793 | AT&T Unix System V. |
b8d4c8d0 | 794 | |
b8d4c8d0 | 795 | @item windows-nt |
200811d6 EZ |
796 | Microsoft Windows NT and later. The same executable supports Windows |
797 | 9X, but the value of @code{system-type} is @code{windows-nt} in either | |
798 | case. | |
b8d4c8d0 | 799 | |
b8d4c8d0 GM |
800 | @end table |
801 | ||
802 | We do not wish to add new symbols to make finer distinctions unless it | |
803 | is absolutely necessary! In fact, we hope to eliminate some of these | |
804 | alternatives in the future. We recommend using | |
805 | @code{system-configuration} to distinguish between different operating | |
806 | systems. | |
807 | @end defvar | |
808 | ||
809 | @defun system-name | |
810 | This function returns the name of the machine you are running on. | |
811 | @example | |
812 | (system-name) | |
813 | @result{} "www.gnu.org" | |
814 | @end example | |
815 | @end defun | |
816 | ||
817 | The symbol @code{system-name} is a variable as well as a function. In | |
818 | fact, the function returns whatever value the variable | |
819 | @code{system-name} currently holds. Thus, you can set the variable | |
820 | @code{system-name} in case Emacs is confused about the name of your | |
821 | system. The variable is also useful for constructing frame titles | |
822 | (@pxref{Frame Titles}). | |
823 | ||
824 | @defvar mail-host-address | |
825 | If this variable is non-@code{nil}, it is used instead of | |
826 | @code{system-name} for purposes of generating email addresses. For | |
827 | example, it is used when constructing the default value of | |
828 | @code{user-mail-address}. @xref{User Identification}. (Since this is | |
829 | done when Emacs starts up, the value actually used is the one saved when | |
830 | Emacs was dumped. @xref{Building Emacs}.) | |
831 | @end defvar | |
832 | ||
106e6894 | 833 | @deffn Command getenv var &optional frame |
b8d4c8d0 GM |
834 | @cindex environment variable access |
835 | This function returns the value of the environment variable @var{var}, | |
836 | as a string. @var{var} should be a string. If @var{var} is undefined | |
837 | in the environment, @code{getenv} returns @code{nil}. If returns | |
838 | @samp{""} if @var{var} is set but null. Within Emacs, the environment | |
839 | variable values are kept in the Lisp variable @code{process-environment}. | |
840 | ||
841 | @example | |
842 | @group | |
843 | (getenv "USER") | |
844 | @result{} "lewis" | |
845 | @end group | |
846 | ||
847 | @group | |
848 | lewis@@slug[10] % printenv | |
849 | PATH=.:/user/lewis/bin:/usr/bin:/usr/local/bin | |
850 | USER=lewis | |
851 | @end group | |
852 | @group | |
853 | TERM=ibmapa16 | |
854 | SHELL=/bin/csh | |
855 | HOME=/user/lewis | |
856 | @end group | |
857 | @end example | |
858 | @end deffn | |
859 | ||
860 | @c Emacs 19 feature | |
861 | @deffn Command setenv variable &optional value | |
862 | This command sets the value of the environment variable named | |
863 | @var{variable} to @var{value}. @var{variable} should be a string. | |
864 | Internally, Emacs Lisp can handle any string. However, normally | |
865 | @var{variable} should be a valid shell identifier, that is, a sequence | |
866 | of letters, digits and underscores, starting with a letter or | |
867 | underscore. Otherwise, errors may occur if subprocesses of Emacs try | |
868 | to access the value of @var{variable}. If @var{value} is omitted or | |
869 | @code{nil}, @code{setenv} removes @var{variable} from the environment. | |
870 | Otherwise, @var{value} should be a string. | |
871 | ||
872 | @code{setenv} works by modifying @code{process-environment}; binding | |
873 | that variable with @code{let} is also reasonable practice. | |
874 | ||
875 | @code{setenv} returns the new value of @var{variable}, or @code{nil} | |
876 | if it removed @var{variable} from the environment. | |
877 | @end deffn | |
878 | ||
879 | @defvar process-environment | |
880 | This variable is a list of strings, each describing one environment | |
881 | variable. The functions @code{getenv} and @code{setenv} work by means | |
882 | of this variable. | |
883 | ||
884 | @smallexample | |
885 | @group | |
886 | process-environment | |
887 | @result{} ("l=/usr/stanford/lib/gnuemacs/lisp" | |
888 | "PATH=.:/user/lewis/bin:/usr/class:/nfsusr/local/bin" | |
889 | "USER=lewis" | |
890 | @end group | |
891 | @group | |
892 | "TERM=ibmapa16" | |
893 | "SHELL=/bin/csh" | |
894 | "HOME=/user/lewis") | |
895 | @end group | |
896 | @end smallexample | |
897 | ||
898 | If @code{process-environment} contains ``duplicate'' elements that | |
899 | specify the same environment variable, the first of these elements | |
900 | specifies the variable, and the other ``duplicates'' are ignored. | |
901 | @end defvar | |
902 | ||
200811d6 EZ |
903 | @defvar initial-environment |
904 | This variable holds the list of environment variables Emacs inherited | |
905 | from its parent process. It is computed during startup, see | |
906 | @ref{Startup Summary}. | |
907 | @end defvar | |
908 | ||
b8d4c8d0 GM |
909 | @defvar path-separator |
910 | This variable holds a string which says which character separates | |
911 | directories in a search path (as found in an environment variable). Its | |
912 | value is @code{":"} for Unix and GNU systems, and @code{";"} for MS-DOS | |
913 | and MS-Windows. | |
914 | @end defvar | |
915 | ||
916 | @defun parse-colon-path path | |
917 | This function takes a search path string such as would be the value of | |
918 | the @code{PATH} environment variable, and splits it at the separators, | |
919 | returning a list of directory names. @code{nil} in this list stands for | |
920 | ``use the current directory.'' Although the function's name says | |
921 | ``colon,'' it actually uses the value of @code{path-separator}. | |
922 | ||
923 | @example | |
924 | (parse-colon-path ":/foo:/bar") | |
925 | @result{} (nil "/foo/" "/bar/") | |
926 | @end example | |
927 | @end defun | |
928 | ||
929 | @defvar invocation-name | |
930 | This variable holds the program name under which Emacs was invoked. The | |
931 | value is a string, and does not include a directory name. | |
932 | @end defvar | |
933 | ||
934 | @defvar invocation-directory | |
935 | This variable holds the directory from which the Emacs executable was | |
936 | invoked, or perhaps @code{nil} if that directory cannot be determined. | |
937 | @end defvar | |
938 | ||
939 | @defvar installation-directory | |
940 | If non-@code{nil}, this is a directory within which to look for the | |
941 | @file{lib-src} and @file{etc} subdirectories. This is non-@code{nil} | |
942 | when Emacs can't find those directories in their standard installed | |
943 | locations, but can find them in a directory related somehow to the one | |
944 | containing the Emacs executable. | |
945 | @end defvar | |
946 | ||
947 | @defun load-average &optional use-float | |
948 | This function returns the current 1-minute, 5-minute, and 15-minute load | |
949 | averages, in a list. | |
950 | ||
951 | By default, the values are integers that are 100 times the system load | |
952 | averages, which indicate the average number of processes trying to run. | |
953 | If @var{use-float} is non-@code{nil}, then they are returned | |
954 | as floating point numbers and without multiplying by 100. | |
955 | ||
956 | If it is impossible to obtain the load average, this function signals | |
957 | an error. On some platforms, access to load averages requires | |
958 | installing Emacs as setuid or setgid so that it can read kernel | |
959 | information, and that usually isn't advisable. | |
960 | ||
961 | If the 1-minute load average is available, but the 5- or 15-minute | |
962 | averages are not, this function returns a shortened list containing | |
963 | the available averages. | |
964 | ||
965 | @example | |
966 | @group | |
967 | (load-average) | |
968 | @result{} (169 48 36) | |
969 | @end group | |
970 | @group | |
971 | (load-average t) | |
972 | @result{} (1.69 0.48 0.36) | |
973 | @end group | |
974 | ||
975 | @group | |
976 | lewis@@rocky[5] % uptime | |
977 | 11:55am up 1 day, 19:37, 3 users, | |
978 | load average: 1.69, 0.48, 0.36 | |
979 | @end group | |
980 | @end example | |
981 | @end defun | |
982 | ||
983 | @defun emacs-pid | |
984 | This function returns the process @acronym{ID} of the Emacs process, | |
985 | as an integer. | |
986 | @end defun | |
987 | ||
988 | @defvar tty-erase-char | |
989 | This variable holds the erase character that was selected | |
990 | in the system's terminal driver, before Emacs was started. | |
991 | The value is @code{nil} if Emacs is running under a window system. | |
992 | @end defvar | |
993 | ||
b8d4c8d0 GM |
994 | @node User Identification |
995 | @section User Identification | |
996 | @cindex user identification | |
997 | ||
998 | @defvar init-file-user | |
999 | This variable says which user's init files should be used by | |
1000 | Emacs---or @code{nil} if none. @code{""} stands for the user who | |
1001 | originally logged in. The value reflects command-line options such as | |
1002 | @samp{-q} or @samp{-u @var{user}}. | |
1003 | ||
1004 | Lisp packages that load files of customizations, or any other sort of | |
1005 | user profile, should obey this variable in deciding where to find it. | |
1006 | They should load the profile of the user name found in this variable. | |
1007 | If @code{init-file-user} is @code{nil}, meaning that the @samp{-q} | |
1008 | option was used, then Lisp packages should not load any customization | |
1009 | files or user profile. | |
1010 | @end defvar | |
1011 | ||
1012 | @defvar user-mail-address | |
1013 | This holds the nominal email address of the user who is using Emacs. | |
1014 | Emacs normally sets this variable to a default value after reading your | |
1015 | init files, but not if you have already set it. So you can set the | |
1016 | variable to some other value in your init file if you do not | |
1017 | want to use the default value. | |
1018 | @end defvar | |
1019 | ||
1020 | @defun user-login-name &optional uid | |
1021 | If you don't specify @var{uid}, this function returns the name under | |
1022 | which the user is logged in. If the environment variable @code{LOGNAME} | |
1023 | is set, that value is used. Otherwise, if the environment variable | |
1024 | @code{USER} is set, that value is used. Otherwise, the value is based | |
1025 | on the effective @acronym{UID}, not the real @acronym{UID}. | |
1026 | ||
1027 | If you specify @var{uid}, the value is the user name that corresponds | |
1028 | to @var{uid} (which should be an integer), or @code{nil} if there is | |
1029 | no such user. | |
1030 | ||
1031 | @example | |
1032 | @group | |
1033 | (user-login-name) | |
1034 | @result{} "lewis" | |
1035 | @end group | |
1036 | @end example | |
1037 | @end defun | |
1038 | ||
1039 | @defun user-real-login-name | |
1040 | This function returns the user name corresponding to Emacs's real | |
1041 | @acronym{UID}. This ignores the effective @acronym{UID} and ignores the | |
1042 | environment variables @code{LOGNAME} and @code{USER}. | |
1043 | @end defun | |
1044 | ||
1045 | @defun user-full-name &optional uid | |
1046 | This function returns the full name of the logged-in user---or the value | |
1047 | of the environment variable @code{NAME}, if that is set. | |
1048 | ||
1049 | @c "Bil" is the correct spelling. | |
1050 | @example | |
1051 | @group | |
1052 | (user-full-name) | |
1053 | @result{} "Bil Lewis" | |
1054 | @end group | |
1055 | @end example | |
1056 | ||
1057 | If the Emacs job's user-id does not correspond to any known user (and | |
1058 | provided @code{NAME} is not set), the value is @code{"unknown"}. | |
1059 | ||
1060 | If @var{uid} is non-@code{nil}, then it should be a number (a user-id) | |
1061 | or a string (a login name). Then @code{user-full-name} returns the full | |
1062 | name corresponding to that user-id or login name. If you specify a | |
1063 | user-id or login name that isn't defined, it returns @code{nil}. | |
1064 | @end defun | |
1065 | ||
1066 | @vindex user-full-name | |
1067 | @vindex user-real-login-name | |
1068 | @vindex user-login-name | |
1069 | The symbols @code{user-login-name}, @code{user-real-login-name} and | |
1070 | @code{user-full-name} are variables as well as functions. The functions | |
1071 | return the same values that the variables hold. These variables allow | |
1072 | you to ``fake out'' Emacs by telling the functions what to return. The | |
1073 | variables are also useful for constructing frame titles (@pxref{Frame | |
1074 | Titles}). | |
1075 | ||
1076 | @defun user-real-uid | |
1077 | This function returns the real @acronym{UID} of the user. | |
1078 | The value may be a floating point number. | |
1079 | ||
1080 | @example | |
1081 | @group | |
1082 | (user-real-uid) | |
1083 | @result{} 19 | |
1084 | @end group | |
1085 | @end example | |
1086 | @end defun | |
1087 | ||
1088 | @defun user-uid | |
1089 | This function returns the effective @acronym{UID} of the user. | |
1090 | The value may be a floating point number. | |
1091 | @end defun | |
1092 | ||
1093 | @node Time of Day | |
1094 | @section Time of Day | |
1095 | ||
1096 | This section explains how to determine the current time and the time | |
1097 | zone. | |
1098 | ||
1099 | @defun current-time-string &optional time-value | |
1100 | This function returns the current time and date as a human-readable | |
1101 | string. The format of the string is unvarying; the number of characters | |
1102 | used for each part is always the same, so you can reliably use | |
1103 | @code{substring} to extract pieces of it. It is wise to count the | |
1104 | characters from the beginning of the string rather than from the end, as | |
1105 | additional information may some day be added at the end. | |
1106 | ||
1107 | @c Emacs 19 feature | |
1108 | The argument @var{time-value}, if given, specifies a time to format | |
1109 | instead of the current time. The argument should be a list whose first | |
1110 | two elements are integers. Thus, you can use times obtained from | |
1111 | @code{current-time} (see below) and from @code{file-attributes} | |
1112 | (@pxref{Definition of file-attributes}). @var{time-value} can also be | |
1113 | a cons of two integers, but this is considered obsolete. | |
1114 | ||
1115 | @example | |
1116 | @group | |
1117 | (current-time-string) | |
1118 | @result{} "Wed Oct 14 22:21:05 1987" | |
1119 | @end group | |
1120 | @end example | |
1121 | @end defun | |
1122 | ||
1123 | @c Emacs 19 feature | |
1124 | @defun current-time | |
1125 | This function returns the system's time value as a list of three | |
1126 | integers: @code{(@var{high} @var{low} @var{microsec})}. The integers | |
1127 | @var{high} and @var{low} combine to give the number of seconds since | |
1128 | 0:00 January 1, 1970 UTC (Coordinated Universal Time), which is | |
1129 | @ifnottex | |
1130 | @var{high} * 2**16 + @var{low}. | |
1131 | @end ifnottex | |
1132 | @tex | |
1133 | $high*2^{16}+low$. | |
1134 | @end tex | |
1135 | ||
1136 | The third element, @var{microsec}, gives the microseconds since the | |
1137 | start of the current second (or 0 for systems that return time with | |
1138 | the resolution of only one second). | |
1139 | ||
1140 | The first two elements can be compared with file time values such as you | |
1141 | get with the function @code{file-attributes}. | |
1142 | @xref{Definition of file-attributes}. | |
1143 | @end defun | |
1144 | ||
1145 | @c Emacs 19 feature | |
1146 | @defun current-time-zone &optional time-value | |
1147 | This function returns a list describing the time zone that the user is | |
1148 | in. | |
1149 | ||
1150 | The value has the form @code{(@var{offset} @var{name})}. Here | |
1151 | @var{offset} is an integer giving the number of seconds ahead of UTC | |
1152 | (east of Greenwich). A negative value means west of Greenwich. The | |
1153 | second element, @var{name}, is a string giving the name of the time | |
1154 | zone. Both elements change when daylight saving time begins or ends; | |
1155 | if the user has specified a time zone that does not use a seasonal time | |
1156 | adjustment, then the value is constant through time. | |
1157 | ||
1158 | If the operating system doesn't supply all the information necessary to | |
1159 | compute the value, the unknown elements of the list are @code{nil}. | |
1160 | ||
1161 | The argument @var{time-value}, if given, specifies a time to analyze | |
1162 | instead of the current time. The argument should have the same form | |
1163 | as for @code{current-time-string} (see above). Thus, you can use | |
1164 | times obtained from @code{current-time} (see above) and from | |
1165 | @code{file-attributes}. @xref{Definition of file-attributes}. | |
1166 | @end defun | |
1167 | ||
1168 | @defun set-time-zone-rule tz | |
1169 | This function specifies the local time zone according to @var{tz}. If | |
1170 | @var{tz} is @code{nil}, that means to use an implementation-defined | |
1171 | default time zone. If @var{tz} is @code{t}, that means to use | |
1172 | Universal Time. Otherwise, @var{tz} should be a string specifying a | |
1173 | time zone rule. | |
1174 | @end defun | |
1175 | ||
1176 | @defun float-time &optional time-value | |
1177 | This function returns the current time as a floating-point number of | |
1178 | seconds since the epoch. The argument @var{time-value}, if given, | |
1179 | specifies a time to convert instead of the current time. The argument | |
1180 | should have the same form as for @code{current-time-string} (see | |
1181 | above). Thus, it accepts the output of @code{current-time} and | |
1182 | @code{file-attributes}. | |
1183 | ||
1184 | @emph{Warning}: Since the result is floating point, it may not be | |
1185 | exact. Do not use this function if precise time stamps are required. | |
1186 | @end defun | |
1187 | ||
1188 | @node Time Conversion | |
1189 | @section Time Conversion | |
1190 | ||
1191 | These functions convert time values (lists of two or three integers) | |
1192 | to calendrical information and vice versa. You can get time values | |
1193 | from the functions @code{current-time} (@pxref{Time of Day}) and | |
1194 | @code{file-attributes} (@pxref{Definition of file-attributes}). | |
1195 | ||
1196 | Many operating systems are limited to time values that contain 32 bits | |
1197 | of information; these systems typically handle only the times from | |
1198 | 1901-12-13 20:45:52 UTC through 2038-01-19 03:14:07 UTC. However, some | |
1199 | operating systems have larger time values, and can represent times far | |
1200 | in the past or future. | |
1201 | ||
1202 | Time conversion functions always use the Gregorian calendar, even | |
1203 | for dates before the Gregorian calendar was introduced. Year numbers | |
1204 | count the number of years since the year 1 B.C., and do not skip zero | |
1205 | as traditional Gregorian years do; for example, the year number | |
1206 | @minus{}37 represents the Gregorian year 38 B.C@. | |
1207 | ||
1208 | @defun decode-time &optional time | |
1209 | This function converts a time value into calendrical information. If | |
1210 | you don't specify @var{time}, it decodes the current time. The return | |
1211 | value is a list of nine elements, as follows: | |
1212 | ||
1213 | @example | |
1214 | (@var{seconds} @var{minutes} @var{hour} @var{day} @var{month} @var{year} @var{dow} @var{dst} @var{zone}) | |
1215 | @end example | |
1216 | ||
1217 | Here is what the elements mean: | |
1218 | ||
1219 | @table @var | |
1220 | @item seconds | |
1221 | The number of seconds past the minute, as an integer between 0 and 59. | |
1222 | On some operating systems, this is 60 for leap seconds. | |
1223 | @item minutes | |
1224 | The number of minutes past the hour, as an integer between 0 and 59. | |
1225 | @item hour | |
1226 | The hour of the day, as an integer between 0 and 23. | |
1227 | @item day | |
1228 | The day of the month, as an integer between 1 and 31. | |
1229 | @item month | |
1230 | The month of the year, as an integer between 1 and 12. | |
1231 | @item year | |
1232 | The year, an integer typically greater than 1900. | |
1233 | @item dow | |
1234 | The day of week, as an integer between 0 and 6, where 0 stands for | |
1235 | Sunday. | |
1236 | @item dst | |
1237 | @code{t} if daylight saving time is effect, otherwise @code{nil}. | |
1238 | @item zone | |
1239 | An integer indicating the time zone, as the number of seconds east of | |
1240 | Greenwich. | |
1241 | @end table | |
1242 | ||
1243 | @strong{Common Lisp Note:} Common Lisp has different meanings for | |
1244 | @var{dow} and @var{zone}. | |
1245 | @end defun | |
1246 | ||
1247 | @defun encode-time seconds minutes hour day month year &optional zone | |
1248 | This function is the inverse of @code{decode-time}. It converts seven | |
1249 | items of calendrical data into a time value. For the meanings of the | |
1250 | arguments, see the table above under @code{decode-time}. | |
1251 | ||
1252 | Year numbers less than 100 are not treated specially. If you want them | |
1253 | to stand for years above 1900, or years above 2000, you must alter them | |
1254 | yourself before you call @code{encode-time}. | |
1255 | ||
1256 | The optional argument @var{zone} defaults to the current time zone and | |
1257 | its daylight saving time rules. If specified, it can be either a list | |
1258 | (as you would get from @code{current-time-zone}), a string as in the | |
1259 | @code{TZ} environment variable, @code{t} for Universal Time, or an | |
1260 | integer (as you would get from @code{decode-time}). The specified | |
1261 | zone is used without any further alteration for daylight saving time. | |
1262 | ||
1263 | If you pass more than seven arguments to @code{encode-time}, the first | |
1264 | six are used as @var{seconds} through @var{year}, the last argument is | |
1265 | used as @var{zone}, and the arguments in between are ignored. This | |
1266 | feature makes it possible to use the elements of a list returned by | |
1267 | @code{decode-time} as the arguments to @code{encode-time}, like this: | |
1268 | ||
1269 | @example | |
1270 | (apply 'encode-time (decode-time @dots{})) | |
1271 | @end example | |
1272 | ||
1273 | You can perform simple date arithmetic by using out-of-range values for | |
1274 | the @var{seconds}, @var{minutes}, @var{hour}, @var{day}, and @var{month} | |
1275 | arguments; for example, day 0 means the day preceding the given month. | |
1276 | ||
1277 | The operating system puts limits on the range of possible time values; | |
1278 | if you try to encode a time that is out of range, an error results. | |
1279 | For instance, years before 1970 do not work on some systems; | |
1280 | on others, years as early as 1901 do work. | |
1281 | @end defun | |
1282 | ||
1283 | @node Time Parsing | |
1284 | @section Parsing and Formatting Times | |
1285 | ||
1286 | These functions convert time values (lists of two or three integers) | |
1287 | to text in a string, and vice versa. | |
1288 | ||
1289 | @defun date-to-time string | |
1290 | This function parses the time-string @var{string} and returns the | |
1291 | corresponding time value. | |
1292 | @end defun | |
1293 | ||
1294 | @defun format-time-string format-string &optional time universal | |
1295 | This function converts @var{time} (or the current time, if @var{time} is | |
1296 | omitted) to a string according to @var{format-string}. The argument | |
1297 | @var{format-string} may contain @samp{%}-sequences which say to | |
1298 | substitute parts of the time. Here is a table of what the | |
1299 | @samp{%}-sequences mean: | |
1300 | ||
1301 | @table @samp | |
1302 | @item %a | |
1303 | This stands for the abbreviated name of the day of week. | |
1304 | @item %A | |
1305 | This stands for the full name of the day of week. | |
1306 | @item %b | |
1307 | This stands for the abbreviated name of the month. | |
1308 | @item %B | |
1309 | This stands for the full name of the month. | |
1310 | @item %c | |
1311 | This is a synonym for @samp{%x %X}. | |
1312 | @item %C | |
1313 | This has a locale-specific meaning. In the default locale (named C), it | |
1314 | is equivalent to @samp{%A, %B %e, %Y}. | |
1315 | @item %d | |
1316 | This stands for the day of month, zero-padded. | |
1317 | @item %D | |
1318 | This is a synonym for @samp{%m/%d/%y}. | |
1319 | @item %e | |
1320 | This stands for the day of month, blank-padded. | |
1321 | @item %h | |
1322 | This is a synonym for @samp{%b}. | |
1323 | @item %H | |
1324 | This stands for the hour (00-23). | |
1325 | @item %I | |
1326 | This stands for the hour (01-12). | |
1327 | @item %j | |
1328 | This stands for the day of the year (001-366). | |
1329 | @item %k | |
1330 | This stands for the hour (0-23), blank padded. | |
1331 | @item %l | |
1332 | This stands for the hour (1-12), blank padded. | |
1333 | @item %m | |
1334 | This stands for the month (01-12). | |
1335 | @item %M | |
1336 | This stands for the minute (00-59). | |
1337 | @item %n | |
1338 | This stands for a newline. | |
1339 | @item %p | |
1340 | This stands for @samp{AM} or @samp{PM}, as appropriate. | |
1341 | @item %r | |
1342 | This is a synonym for @samp{%I:%M:%S %p}. | |
1343 | @item %R | |
1344 | This is a synonym for @samp{%H:%M}. | |
1345 | @item %S | |
1346 | This stands for the seconds (00-59). | |
1347 | @item %t | |
1348 | This stands for a tab character. | |
1349 | @item %T | |
1350 | This is a synonym for @samp{%H:%M:%S}. | |
1351 | @item %U | |
1352 | This stands for the week of the year (01-52), assuming that weeks | |
1353 | start on Sunday. | |
1354 | @item %w | |
1355 | This stands for the numeric day of week (0-6). Sunday is day 0. | |
1356 | @item %W | |
1357 | This stands for the week of the year (01-52), assuming that weeks | |
1358 | start on Monday. | |
1359 | @item %x | |
1360 | This has a locale-specific meaning. In the default locale (named | |
1361 | @samp{C}), it is equivalent to @samp{%D}. | |
1362 | @item %X | |
1363 | This has a locale-specific meaning. In the default locale (named | |
1364 | @samp{C}), it is equivalent to @samp{%T}. | |
1365 | @item %y | |
1366 | This stands for the year without century (00-99). | |
1367 | @item %Y | |
1368 | This stands for the year with century. | |
1369 | @item %Z | |
1370 | This stands for the time zone abbreviation (e.g., @samp{EST}). | |
1371 | @item %z | |
1372 | This stands for the time zone numerical offset (e.g., @samp{-0500}). | |
1373 | @end table | |
1374 | ||
1375 | You can also specify the field width and type of padding for any of | |
1376 | these @samp{%}-sequences. This works as in @code{printf}: you write | |
1377 | the field width as digits in the middle of a @samp{%}-sequences. If you | |
1378 | start the field width with @samp{0}, it means to pad with zeros. If you | |
1379 | start the field width with @samp{_}, it means to pad with spaces. | |
1380 | ||
1381 | For example, @samp{%S} specifies the number of seconds since the minute; | |
1382 | @samp{%03S} means to pad this with zeros to 3 positions, @samp{%_3S} to | |
1383 | pad with spaces to 3 positions. Plain @samp{%3S} pads with zeros, | |
1384 | because that is how @samp{%S} normally pads to two positions. | |
1385 | ||
1386 | The characters @samp{E} and @samp{O} act as modifiers when used between | |
1387 | @samp{%} and one of the letters in the table above. @samp{E} specifies | |
1388 | using the current locale's ``alternative'' version of the date and time. | |
1389 | In a Japanese locale, for example, @code{%Ex} might yield a date format | |
1390 | based on the Japanese Emperors' reigns. @samp{E} is allowed in | |
1391 | @samp{%Ec}, @samp{%EC}, @samp{%Ex}, @samp{%EX}, @samp{%Ey}, and | |
1392 | @samp{%EY}. | |
1393 | ||
1394 | @samp{O} means to use the current locale's ``alternative'' | |
1395 | representation of numbers, instead of the ordinary decimal digits. This | |
1396 | is allowed with most letters, all the ones that output numbers. | |
1397 | ||
1398 | If @var{universal} is non-@code{nil}, that means to describe the time as | |
1399 | Universal Time; @code{nil} means describe it using what Emacs believes | |
1400 | is the local time zone (see @code{current-time-zone}). | |
1401 | ||
1402 | This function uses the C library function @code{strftime} | |
1403 | (@pxref{Formatting Calendar Time,,, libc, The GNU C Library Reference | |
1404 | Manual}) to do most of the work. In order to communicate with that | |
1405 | function, it first encodes its argument using the coding system | |
1406 | specified by @code{locale-coding-system} (@pxref{Locales}); after | |
1407 | @code{strftime} returns the resulting string, | |
1408 | @code{format-time-string} decodes the string using that same coding | |
1409 | system. | |
1410 | @end defun | |
1411 | ||
1412 | @defun seconds-to-time seconds | |
1413 | This function converts @var{seconds}, a floating point number of | |
1414 | seconds since the epoch, to a time value and returns that. To perform | |
1415 | the inverse conversion, use @code{float-time}. | |
1416 | @end defun | |
1417 | ||
53728487 EZ |
1418 | @defun format-seconds format-string seconds |
1419 | This function converts its argument @var{seconds} into a string of | |
1420 | years, days, hours, etc., according to @var{format-string}. The | |
1421 | argument @var{format-string} may contain @samp{%}-sequences which | |
1422 | control the conversion. Here is a table of what the | |
1423 | @samp{%}-sequences mean: | |
1424 | ||
1425 | @table @samp | |
1426 | @item %y | |
1427 | @itemx %Y | |
3051e4bf | 1428 | The integer number of 365-day years. |
53728487 EZ |
1429 | @item %d |
1430 | @itemx %D | |
3051e4bf | 1431 | The integer number of days. |
53728487 EZ |
1432 | @item %h |
1433 | @itemx %H | |
3051e4bf | 1434 | The integer number of hours. |
53728487 EZ |
1435 | @item %m |
1436 | @itemx %M | |
3051e4bf | 1437 | The integer number of minutes. |
53728487 EZ |
1438 | @item %s |
1439 | @itemx %S | |
3051e4bf | 1440 | The integer number of seconds. |
53728487 EZ |
1441 | @item %z |
1442 | Non-printing control flag. When it is used, other specifiers must be | |
1443 | given in the order of decreasing size, i.e.@: years before days, hours | |
1444 | before minutes, etc. Nothing will be produced in the result string to | |
1445 | the left of @samp{%z} until the first non-zero conversion is | |
1446 | encountered. For example, the default format used by | |
1447 | @code{emacs-uptime} (@pxref{Processor Run Time, emacs-uptime}) | |
1448 | @w{@code{"%Y, %D, %H, %M, %z%S"}} means that the number of seconds | |
1449 | will always be produced, but years, days, hours, and minutes will only | |
1450 | be shown if they are non-zero. | |
1451 | @item %% | |
1452 | Produces a literal @samp{%}. | |
1453 | @end table | |
1454 | ||
1455 | Upper-case format sequences produce the units in addition to the | |
1456 | numbers, lower-case formats produce only the numbers. | |
1457 | ||
1458 | You can also specify the field width by following the @samp{%} with a | |
1459 | number; shorter numbers will be padded with blanks. An optional | |
1460 | period before the width requests zero-padding instead. For example, | |
1461 | @code{"%.3Y"} might produce @code{"004 years"}. | |
1462 | ||
1463 | @emph{Warning:} This function works only with values of @var{seconds} | |
1464 | that don't exceed @code{most-positive-fixnum} (@pxref{Integer Basics, | |
1465 | most-positive-fixnum}). | |
1466 | @end defun | |
1467 | ||
b8d4c8d0 GM |
1468 | @node Processor Run Time |
1469 | @section Processor Run time | |
1470 | @cindex processor run time | |
53728487 EZ |
1471 | @cindex Emacs process run time |
1472 | ||
1473 | Emacs provides several functions and primitives that return time, | |
1474 | both elapsed and processor time, used by the Emacs process. | |
1475 | ||
106e6894 | 1476 | @deffn Command emacs-uptime &optional format |
53728487 EZ |
1477 | This function returns a string representing the Emacs |
1478 | @dfn{uptime}---the elapsed wall-clock time this instance of Emacs is | |
3051e4bf EZ |
1479 | running. The string is formatted by @code{format-seconds} according |
1480 | to the optional argument @var{format}. For the available format | |
1481 | descriptors, see @ref{Time Parsing, format-seconds}. If @var{format} | |
e2b7cebb CY |
1482 | is @code{nil} or omitted, it defaults to @code{"%Y, %D, %H, %M, |
1483 | %z%S"}. | |
106e6894 CY |
1484 | |
1485 | When called interactively, it prints the uptime in the echo area. | |
1486 | @end deffn | |
b8d4c8d0 GM |
1487 | |
1488 | @defun get-internal-run-time | |
1489 | This function returns the processor run time used by Emacs as a list | |
1490 | of three integers: @code{(@var{high} @var{low} @var{microsec})}. The | |
1491 | integers @var{high} and @var{low} combine to give the number of | |
1492 | seconds, which is | |
1493 | @ifnottex | |
1494 | @var{high} * 2**16 + @var{low}. | |
1495 | @end ifnottex | |
1496 | @tex | |
1497 | $high*2^{16}+low$. | |
1498 | @end tex | |
1499 | ||
1500 | The third element, @var{microsec}, gives the microseconds (or 0 for | |
1501 | systems that return time with the resolution of only one second). | |
1502 | ||
53728487 EZ |
1503 | Note that the time returned by this function excludes the time Emacs |
1504 | was not using the processor, and if the Emacs process has several | |
1505 | threads, the returned value is the sum of the processor times used up | |
1506 | by all Emacs threads. | |
1507 | ||
b8d4c8d0 | 1508 | If the system doesn't provide a way to determine the processor run |
53728487 EZ |
1509 | time, @code{get-internal-run-time} returns the same time as |
1510 | @code{current-time}. | |
1511 | @end defun | |
1512 | ||
106e6894 | 1513 | @deffn Command emacs-init-time |
53728487 | 1514 | This function returns the duration of the Emacs initialization |
106e6894 CY |
1515 | (@pxref{Startup Summary}) in seconds, as a string. When called |
1516 | interactively, it prints the duration in the echo area. | |
1517 | @end deffn | |
b8d4c8d0 GM |
1518 | |
1519 | @node Time Calculations | |
1520 | @section Time Calculations | |
1521 | ||
1522 | These functions perform calendrical computations using time values | |
1523 | (the kind of list that @code{current-time} returns). | |
1524 | ||
1525 | @defun time-less-p t1 t2 | |
1526 | This returns @code{t} if time value @var{t1} is less than time value | |
1527 | @var{t2}. | |
1528 | @end defun | |
1529 | ||
1530 | @defun time-subtract t1 t2 | |
1531 | This returns the time difference @var{t1} @minus{} @var{t2} between | |
1532 | two time values, in the same format as a time value. | |
1533 | @end defun | |
1534 | ||
1535 | @defun time-add t1 t2 | |
1536 | This returns the sum of two time values, one of which ought to | |
1537 | represent a time difference rather than a point in time. | |
1538 | Here is how to add a number of seconds to a time value: | |
1539 | ||
1540 | @example | |
1541 | (time-add @var{time} (seconds-to-time @var{seconds})) | |
1542 | @end example | |
1543 | @end defun | |
1544 | ||
1545 | @defun time-to-days time | |
1546 | This function returns the number of days between the beginning of year | |
1547 | 1 and @var{time}. | |
1548 | @end defun | |
1549 | ||
1550 | @defun time-to-day-in-year time | |
1551 | This returns the day number within the year corresponding to @var{time}. | |
1552 | @end defun | |
1553 | ||
1554 | @defun date-leap-year-p year | |
1555 | This function returns @code{t} if @var{year} is a leap year. | |
1556 | @end defun | |
1557 | ||
1558 | @node Timers | |
1559 | @section Timers for Delayed Execution | |
1560 | @cindex timer | |
1561 | ||
1562 | You can set up a @dfn{timer} to call a function at a specified | |
1563 | future time or after a certain length of idleness. | |
1564 | ||
1565 | Emacs cannot run timers at any arbitrary point in a Lisp program; it | |
1566 | can run them only when Emacs could accept output from a subprocess: | |
1567 | namely, while waiting or inside certain primitive functions such as | |
1568 | @code{sit-for} or @code{read-event} which @emph{can} wait. Therefore, a | |
1569 | timer's execution may be delayed if Emacs is busy. However, the time of | |
1570 | execution is very precise if Emacs is idle. | |
1571 | ||
1572 | Emacs binds @code{inhibit-quit} to @code{t} before calling the timer | |
1573 | function, because quitting out of many timer functions can leave | |
1574 | things in an inconsistent state. This is normally unproblematical | |
1575 | because most timer functions don't do a lot of work. Indeed, for a | |
1576 | timer to call a function that takes substantial time to run is likely | |
1577 | to be annoying. If a timer function needs to allow quitting, it | |
1578 | should use @code{with-local-quit} (@pxref{Quitting}). For example, if | |
1579 | a timer function calls @code{accept-process-output} to receive output | |
1580 | from an external process, that call should be wrapped inside | |
1581 | @code{with-local-quit}, to ensure that @kbd{C-g} works if the external | |
1582 | process hangs. | |
1583 | ||
1584 | It is usually a bad idea for timer functions to alter buffer | |
1585 | contents. When they do, they usually should call @code{undo-boundary} | |
1586 | both before and after changing the buffer, to separate the timer's | |
1587 | changes from user commands' changes and prevent a single undo entry | |
1588 | from growing to be quite large. | |
1589 | ||
1590 | Timer functions should also avoid calling functions that cause Emacs | |
1591 | to wait, such as @code{sit-for} (@pxref{Waiting}). This can lead to | |
1592 | unpredictable effects, since other timers (or even the same timer) can | |
1593 | run while waiting. If a timer function needs to perform an action | |
1594 | after a certain time has elapsed, it can do this by scheduling a new | |
1595 | timer. | |
1596 | ||
1597 | If a timer function calls functions that can change the match data, | |
1598 | it should save and restore the match data. @xref{Saving Match Data}. | |
1599 | ||
1600 | @deffn Command run-at-time time repeat function &rest args | |
1601 | This sets up a timer that calls the function @var{function} with | |
1602 | arguments @var{args} at time @var{time}. If @var{repeat} is a number | |
1603 | (integer or floating point), the timer is scheduled to run again every | |
1604 | @var{repeat} seconds after @var{time}. If @var{repeat} is @code{nil}, | |
1605 | the timer runs only once. | |
1606 | ||
1607 | @var{time} may specify an absolute or a relative time. | |
1608 | ||
1609 | Absolute times may be specified using a string with a limited variety | |
1610 | of formats, and are taken to be times @emph{today}, even if already in | |
1611 | the past. The recognized forms are @samp{@var{xxxx}}, | |
1612 | @samp{@var{x}:@var{xx}}, or @samp{@var{xx}:@var{xx}} (military time), | |
1613 | and @samp{@var{xx}am}, @samp{@var{xx}AM}, @samp{@var{xx}pm}, | |
1614 | @samp{@var{xx}PM}, @samp{@var{xx}:@var{xx}am}, | |
1615 | @samp{@var{xx}:@var{xx}AM}, @samp{@var{xx}:@var{xx}pm}, or | |
1616 | @samp{@var{xx}:@var{xx}PM}. A period can be used instead of a colon | |
1617 | to separate the hour and minute parts. | |
1618 | ||
1619 | To specify a relative time as a string, use numbers followed by units. | |
1620 | For example: | |
1621 | ||
1622 | @table @samp | |
1623 | @item 1 min | |
1624 | denotes 1 minute from now. | |
1625 | @item 1 min 5 sec | |
1626 | denotes 65 seconds from now. | |
1627 | @item 1 min 2 sec 3 hour 4 day 5 week 6 fortnight 7 month 8 year | |
1628 | denotes exactly 103 months, 123 days, and 10862 seconds from now. | |
1629 | @end table | |
1630 | ||
1631 | For relative time values, Emacs considers a month to be exactly thirty | |
1632 | days, and a year to be exactly 365.25 days. | |
1633 | ||
1634 | Not all convenient formats are strings. If @var{time} is a number | |
1635 | (integer or floating point), that specifies a relative time measured in | |
1636 | seconds. The result of @code{encode-time} can also be used to specify | |
1637 | an absolute value for @var{time}. | |
1638 | ||
1639 | In most cases, @var{repeat} has no effect on when @emph{first} call | |
1640 | takes place---@var{time} alone specifies that. There is one exception: | |
1641 | if @var{time} is @code{t}, then the timer runs whenever the time is a | |
1642 | multiple of @var{repeat} seconds after the epoch. This is useful for | |
1643 | functions like @code{display-time}. | |
1644 | ||
1645 | The function @code{run-at-time} returns a timer value that identifies | |
1646 | the particular scheduled future action. You can use this value to call | |
1647 | @code{cancel-timer} (see below). | |
1648 | @end deffn | |
1649 | ||
1650 | A repeating timer nominally ought to run every @var{repeat} seconds, | |
1651 | but remember that any invocation of a timer can be late. Lateness of | |
1652 | one repetition has no effect on the scheduled time of the next | |
1653 | repetition. For instance, if Emacs is busy computing for long enough | |
1654 | to cover three scheduled repetitions of the timer, and then starts to | |
1655 | wait, it will immediately call the timer function three times in | |
1656 | immediate succession (presuming no other timers trigger before or | |
1657 | between them). If you want a timer to run again no less than @var{n} | |
1658 | seconds after the last invocation, don't use the @var{repeat} argument. | |
1659 | Instead, the timer function should explicitly reschedule the timer. | |
1660 | ||
1661 | @defvar timer-max-repeats | |
1662 | This variable's value specifies the maximum number of times to repeat | |
1663 | calling a timer function in a row, when many previously scheduled | |
1664 | calls were unavoidably delayed. | |
1665 | @end defvar | |
1666 | ||
1667 | @defmac with-timeout (seconds timeout-forms@dots{}) body@dots{} | |
1668 | Execute @var{body}, but give up after @var{seconds} seconds. If | |
1669 | @var{body} finishes before the time is up, @code{with-timeout} returns | |
1670 | the value of the last form in @var{body}. If, however, the execution of | |
1671 | @var{body} is cut short by the timeout, then @code{with-timeout} | |
1672 | executes all the @var{timeout-forms} and returns the value of the last | |
1673 | of them. | |
1674 | ||
1675 | This macro works by setting a timer to run after @var{seconds} seconds. If | |
1676 | @var{body} finishes before that time, it cancels the timer. If the | |
1677 | timer actually runs, it terminates execution of @var{body}, then | |
1678 | executes @var{timeout-forms}. | |
1679 | ||
1680 | Since timers can run within a Lisp program only when the program calls a | |
1681 | primitive that can wait, @code{with-timeout} cannot stop executing | |
1682 | @var{body} while it is in the midst of a computation---only when it | |
1683 | calls one of those primitives. So use @code{with-timeout} only with a | |
1684 | @var{body} that waits for input, not one that does a long computation. | |
1685 | @end defmac | |
1686 | ||
1687 | The function @code{y-or-n-p-with-timeout} provides a simple way to use | |
1688 | a timer to avoid waiting too long for an answer. @xref{Yes-or-No | |
1689 | Queries}. | |
1690 | ||
1691 | @defun cancel-timer timer | |
1692 | This cancels the requested action for @var{timer}, which should be a | |
1693 | timer---usually, one previously returned by @code{run-at-time} or | |
1694 | @code{run-with-idle-timer}. This cancels the effect of that call to | |
1695 | one of these functions; the arrival of the specified time will not | |
1696 | cause anything special to happen. | |
1697 | @end defun | |
1698 | ||
1699 | @node Idle Timers | |
1700 | @section Idle Timers | |
1701 | ||
1702 | Here is how to set up a timer that runs when Emacs is idle for a | |
1703 | certain length of time. Aside from how to set them up, idle timers | |
1704 | work just like ordinary timers. | |
1705 | ||
1706 | @deffn Command run-with-idle-timer secs repeat function &rest args | |
1707 | Set up a timer which runs when Emacs has been idle for @var{secs} | |
1708 | seconds. The value of @var{secs} may be an integer or a floating point | |
1709 | number; a value of the type returned by @code{current-idle-time} | |
1710 | is also allowed. | |
1711 | ||
1712 | If @var{repeat} is @code{nil}, the timer runs just once, the first time | |
1713 | Emacs remains idle for a long enough time. More often @var{repeat} is | |
1714 | non-@code{nil}, which means to run the timer @emph{each time} Emacs | |
1715 | remains idle for @var{secs} seconds. | |
1716 | ||
1717 | The function @code{run-with-idle-timer} returns a timer value which you | |
1718 | can use in calling @code{cancel-timer} (@pxref{Timers}). | |
1719 | @end deffn | |
1720 | ||
1721 | @cindex idleness | |
1722 | Emacs becomes ``idle'' when it starts waiting for user input, and it | |
1723 | remains idle until the user provides some input. If a timer is set for | |
1724 | five seconds of idleness, it runs approximately five seconds after Emacs | |
1725 | first becomes idle. Even if @var{repeat} is non-@code{nil}, this timer | |
1726 | will not run again as long as Emacs remains idle, because the duration | |
1727 | of idleness will continue to increase and will not go down to five | |
1728 | seconds again. | |
1729 | ||
1730 | Emacs can do various things while idle: garbage collect, autosave or | |
1731 | handle data from a subprocess. But these interludes during idleness do | |
1732 | not interfere with idle timers, because they do not reset the clock of | |
1733 | idleness to zero. An idle timer set for 600 seconds will run when ten | |
1734 | minutes have elapsed since the last user command was finished, even if | |
1735 | subprocess output has been accepted thousands of times within those ten | |
1736 | minutes, and even if there have been garbage collections and autosaves. | |
1737 | ||
1738 | When the user supplies input, Emacs becomes non-idle while executing the | |
1739 | input. Then it becomes idle again, and all the idle timers that are | |
1740 | set up to repeat will subsequently run another time, one by one. | |
1741 | ||
1742 | @c Emacs 19 feature | |
1743 | @defun current-idle-time | |
17bec671 RS |
1744 | If Emacs is idle, this function returns the length of time Emacs has |
1745 | been idle, as a list of three integers: @code{(@var{high} @var{low} | |
1746 | @var{microsec})}. The integers @var{high} and @var{low} combine to | |
1747 | give the number of seconds of idleness, which is | |
b8d4c8d0 GM |
1748 | @ifnottex |
1749 | @var{high} * 2**16 + @var{low}. | |
1750 | @end ifnottex | |
1751 | @tex | |
1752 | $high*2^{16}+low$. | |
1753 | @end tex | |
1754 | ||
1755 | The third element, @var{microsec}, gives the microseconds since the | |
1756 | start of the current second (or 0 for systems that return time with | |
1757 | the resolution of only one second). | |
1758 | ||
17bec671 RS |
1759 | When Emacs is not idle, @code{current-idle-time} returns @code{nil}. |
1760 | This is a convenient way to test whether Emacs is idle. | |
1761 | ||
b8d4c8d0 GM |
1762 | The main use of this function is when an idle timer function wants to |
1763 | ``take a break'' for a while. It can set up another idle timer to | |
1764 | call the same function again, after a few seconds more idleness. | |
1765 | Here's an example: | |
1766 | ||
1767 | @smallexample | |
1768 | (defvar resume-timer nil | |
1769 | "Timer that `timer-function' used to reschedule itself, or nil.") | |
1770 | ||
1771 | (defun timer-function () | |
1772 | ;; @r{If the user types a command while @code{resume-timer}} | |
1773 | ;; @r{is active, the next time this function is called from} | |
1774 | ;; @r{its main idle timer, deactivate @code{resume-timer}.} | |
1775 | (when resume-timer | |
1776 | (cancel-timer resume-timer)) | |
1777 | ...@var{do the work for a while}... | |
1778 | (when @var{taking-a-break} | |
1779 | (setq resume-timer | |
1780 | (run-with-idle-timer | |
1781 | ;; Compute an idle time @var{break-length} | |
1782 | ;; more than the current value. | |
1783 | (time-add (current-idle-time) | |
1784 | (seconds-to-time @var{break-length})) | |
1785 | nil | |
1786 | 'timer-function)))) | |
1787 | @end smallexample | |
1788 | @end defun | |
1789 | ||
1790 | Some idle timer functions in user Lisp packages have a loop that | |
1791 | does a certain amount of processing each time around, and exits when | |
1792 | @code{(input-pending-p)} is non-@code{nil}. That approach seems very | |
1793 | natural but has two problems: | |
1794 | ||
1795 | @itemize | |
1796 | @item | |
1797 | It blocks out all process output (since Emacs accepts process output | |
1798 | only while waiting). | |
1799 | ||
1800 | @item | |
1801 | It blocks out any idle timers that ought to run during that time. | |
1802 | @end itemize | |
1803 | ||
1804 | @noindent | |
1805 | To avoid these problems, don't use that technique. Instead, write | |
1806 | such idle timers to reschedule themselves after a brief pause, using | |
1807 | the method in the @code{timer-function} example above. | |
1808 | ||
1809 | @node Terminal Input | |
1810 | @section Terminal Input | |
1811 | @cindex terminal input | |
1812 | ||
1813 | This section describes functions and variables for recording or | |
1814 | manipulating terminal input. See @ref{Display}, for related | |
1815 | functions. | |
1816 | ||
1817 | @menu | |
1818 | * Input Modes:: Options for how input is processed. | |
1819 | * Recording Input:: Saving histories of recent or all input events. | |
1820 | @end menu | |
1821 | ||
1822 | @node Input Modes | |
1823 | @subsection Input Modes | |
1824 | @cindex input modes | |
1825 | @cindex terminal input modes | |
1826 | ||
1827 | @defun set-input-mode interrupt flow meta &optional quit-char | |
1828 | This function sets the mode for reading keyboard input. If | |
1829 | @var{interrupt} is non-null, then Emacs uses input interrupts. If it is | |
1830 | @code{nil}, then it uses @sc{cbreak} mode. The default setting is | |
1831 | system-dependent. Some systems always use @sc{cbreak} mode regardless | |
1832 | of what is specified. | |
1833 | ||
1834 | When Emacs communicates directly with X, it ignores this argument and | |
1835 | uses interrupts if that is the way it knows how to communicate. | |
1836 | ||
1837 | If @var{flow} is non-@code{nil}, then Emacs uses @sc{xon/xoff} | |
1838 | (@kbd{C-q}, @kbd{C-s}) flow control for output to the terminal. This | |
1839 | has no effect except in @sc{cbreak} mode. | |
1840 | ||
1841 | @c Emacs 19 feature | |
1842 | The argument @var{meta} controls support for input character codes | |
1843 | above 127. If @var{meta} is @code{t}, Emacs converts characters with | |
1844 | the 8th bit set into Meta characters. If @var{meta} is @code{nil}, | |
1845 | Emacs disregards the 8th bit; this is necessary when the terminal uses | |
1846 | it as a parity bit. If @var{meta} is neither @code{t} nor @code{nil}, | |
1847 | Emacs uses all 8 bits of input unchanged. This is good for terminals | |
1848 | that use 8-bit character sets. | |
1849 | ||
1850 | @c Emacs 19 feature | |
1851 | If @var{quit-char} is non-@code{nil}, it specifies the character to | |
1852 | use for quitting. Normally this character is @kbd{C-g}. | |
1853 | @xref{Quitting}. | |
1854 | @end defun | |
1855 | ||
1856 | The @code{current-input-mode} function returns the input mode settings | |
1857 | Emacs is currently using. | |
1858 | ||
1859 | @c Emacs 19 feature | |
1860 | @defun current-input-mode | |
1861 | This function returns the current mode for reading keyboard input. It | |
1862 | returns a list, corresponding to the arguments of @code{set-input-mode}, | |
1863 | of the form @code{(@var{interrupt} @var{flow} @var{meta} @var{quit})} in | |
1864 | which: | |
1865 | @table @var | |
1866 | @item interrupt | |
1867 | is non-@code{nil} when Emacs is using interrupt-driven input. If | |
1868 | @code{nil}, Emacs is using @sc{cbreak} mode. | |
1869 | @item flow | |
1870 | is non-@code{nil} if Emacs uses @sc{xon/xoff} (@kbd{C-q}, @kbd{C-s}) | |
1871 | flow control for output to the terminal. This value is meaningful only | |
1872 | when @var{interrupt} is @code{nil}. | |
1873 | @item meta | |
1874 | is @code{t} if Emacs treats the eighth bit of input characters as | |
1875 | the meta bit; @code{nil} means Emacs clears the eighth bit of every | |
1876 | input character; any other value means Emacs uses all eight bits as the | |
1877 | basic character code. | |
1878 | @item quit | |
1879 | is the character Emacs currently uses for quitting, usually @kbd{C-g}. | |
1880 | @end table | |
1881 | @end defun | |
1882 | ||
1883 | @node Recording Input | |
1884 | @subsection Recording Input | |
1885 | @cindex recording input | |
1886 | ||
1887 | @defun recent-keys | |
1888 | This function returns a vector containing the last 300 input events from | |
1889 | the keyboard or mouse. All input events are included, whether or not | |
1890 | they were used as parts of key sequences. Thus, you always get the last | |
1891 | 100 input events, not counting events generated by keyboard macros. | |
1892 | (These are excluded because they are less interesting for debugging; it | |
1893 | should be enough to see the events that invoked the macros.) | |
1894 | ||
1895 | A call to @code{clear-this-command-keys} (@pxref{Command Loop Info}) | |
1896 | causes this function to return an empty vector immediately afterward. | |
1897 | @end defun | |
1898 | ||
1899 | @deffn Command open-dribble-file filename | |
1900 | @cindex dribble file | |
1901 | This function opens a @dfn{dribble file} named @var{filename}. When a | |
1902 | dribble file is open, each input event from the keyboard or mouse (but | |
1903 | not those from keyboard macros) is written in that file. A | |
1904 | non-character event is expressed using its printed representation | |
1905 | surrounded by @samp{<@dots{}>}. | |
1906 | ||
1907 | You close the dribble file by calling this function with an argument | |
1908 | of @code{nil}. | |
1909 | ||
1910 | This function is normally used to record the input necessary to | |
1911 | trigger an Emacs bug, for the sake of a bug report. | |
1912 | ||
1913 | @example | |
1914 | @group | |
1915 | (open-dribble-file "~/dribble") | |
1916 | @result{} nil | |
1917 | @end group | |
1918 | @end example | |
1919 | @end deffn | |
1920 | ||
1921 | See also the @code{open-termscript} function (@pxref{Terminal Output}). | |
1922 | ||
1923 | @node Terminal Output | |
1924 | @section Terminal Output | |
1925 | @cindex terminal output | |
1926 | ||
1927 | The terminal output functions send output to a text terminal, or keep | |
1928 | track of output sent to the terminal. The variable @code{baud-rate} | |
1929 | tells you what Emacs thinks is the output speed of the terminal. | |
1930 | ||
1931 | @defvar baud-rate | |
1932 | This variable's value is the output speed of the terminal, as far as | |
1933 | Emacs knows. Setting this variable does not change the speed of actual | |
1934 | data transmission, but the value is used for calculations such as | |
1935 | padding. | |
1936 | ||
1937 | It also affects decisions about whether to scroll part of the | |
1938 | screen or repaint on text terminals. @xref{Forcing Redisplay}, | |
1939 | for the corresponding functionality on graphical terminals. | |
1940 | ||
1941 | The value is measured in baud. | |
1942 | @end defvar | |
1943 | ||
1944 | If you are running across a network, and different parts of the | |
1945 | network work at different baud rates, the value returned by Emacs may be | |
1946 | different from the value used by your local terminal. Some network | |
1947 | protocols communicate the local terminal speed to the remote machine, so | |
1948 | that Emacs and other programs can get the proper value, but others do | |
1949 | not. If Emacs has the wrong value, it makes decisions that are less | |
1950 | than optimal. To fix the problem, set @code{baud-rate}. | |
1951 | ||
106e6894 CY |
1952 | @defun send-string-to-terminal string &optional terminal |
1953 | This function sends @var{string} to @var{terminal} without alteration. | |
b8d4c8d0 | 1954 | Control characters in @var{string} have terminal-dependent effects. |
106e6894 CY |
1955 | This function operates only on text terminals. @var{terminal} may be |
1956 | a terminal object, a frame, or @code{nil} for the selected frame's | |
1957 | terminal. | |
b8d4c8d0 GM |
1958 | |
1959 | One use of this function is to define function keys on terminals that | |
1960 | have downloadable function key definitions. For example, this is how (on | |
1961 | certain terminals) to define function key 4 to move forward four | |
1962 | characters (by transmitting the characters @kbd{C-u C-f} to the | |
1963 | computer): | |
1964 | ||
1965 | @example | |
1966 | @group | |
1967 | (send-string-to-terminal "\eF4\^U\^F") | |
1968 | @result{} nil | |
1969 | @end group | |
1970 | @end example | |
1971 | @end defun | |
1972 | ||
1973 | @deffn Command open-termscript filename | |
1974 | @cindex termscript file | |
1975 | This function is used to open a @dfn{termscript file} that will record | |
1976 | all the characters sent by Emacs to the terminal. It returns | |
1977 | @code{nil}. Termscript files are useful for investigating problems | |
1978 | where Emacs garbles the screen, problems that are due to incorrect | |
1979 | Termcap entries or to undesirable settings of terminal options more | |
1980 | often than to actual Emacs bugs. Once you are certain which characters | |
1981 | were actually output, you can determine reliably whether they correspond | |
1982 | to the Termcap specifications in use. | |
1983 | ||
1984 | You close the termscript file by calling this function with an | |
1985 | argument of @code{nil}. | |
1986 | ||
1987 | See also @code{open-dribble-file} in @ref{Recording Input}. | |
1988 | ||
1989 | @example | |
1990 | @group | |
1991 | (open-termscript "../junk/termscript") | |
1992 | @result{} nil | |
1993 | @end group | |
1994 | @end example | |
1995 | @end deffn | |
1996 | ||
1997 | @node Sound Output | |
1998 | @section Sound Output | |
1999 | @cindex sound | |
2000 | ||
2001 | To play sound using Emacs, use the function @code{play-sound}. Only | |
2002 | certain systems are supported; if you call @code{play-sound} on a system | |
2003 | which cannot really do the job, it gives an error. Emacs version 20 and | |
2004 | earlier did not support sound at all. | |
2005 | ||
2006 | The sound must be stored as a file in RIFF-WAVE format (@samp{.wav}) | |
2007 | or Sun Audio format (@samp{.au}). | |
2008 | ||
2009 | @defun play-sound sound | |
2010 | This function plays a specified sound. The argument, @var{sound}, has | |
2011 | the form @code{(sound @var{properties}...)}, where the @var{properties} | |
2012 | consist of alternating keywords (particular symbols recognized | |
2013 | specially) and values corresponding to them. | |
2014 | ||
2015 | Here is a table of the keywords that are currently meaningful in | |
2016 | @var{sound}, and their meanings: | |
2017 | ||
2018 | @table @code | |
2019 | @item :file @var{file} | |
2020 | This specifies the file containing the sound to play. | |
2021 | If the file name is not absolute, it is expanded against | |
2022 | the directory @code{data-directory}. | |
2023 | ||
2024 | @item :data @var{data} | |
2025 | This specifies the sound to play without need to refer to a file. The | |
2026 | value, @var{data}, should be a string containing the same bytes as a | |
2027 | sound file. We recommend using a unibyte string. | |
2028 | ||
2029 | @item :volume @var{volume} | |
2030 | This specifies how loud to play the sound. It should be a number in the | |
2031 | range of 0 to 1. The default is to use whatever volume has been | |
2032 | specified before. | |
2033 | ||
2034 | @item :device @var{device} | |
2035 | This specifies the system device on which to play the sound, as a | |
2036 | string. The default device is system-dependent. | |
2037 | @end table | |
2038 | ||
2039 | Before actually playing the sound, @code{play-sound} | |
2040 | calls the functions in the list @code{play-sound-functions}. | |
2041 | Each function is called with one argument, @var{sound}. | |
2042 | @end defun | |
2043 | ||
2044 | @defun play-sound-file file &optional volume device | |
2045 | This function is an alternative interface to playing a sound @var{file} | |
2046 | specifying an optional @var{volume} and @var{device}. | |
2047 | @end defun | |
2048 | ||
2049 | @defvar play-sound-functions | |
2050 | A list of functions to be called before playing a sound. Each function | |
2051 | is called with one argument, a property list that describes the sound. | |
2052 | @end defvar | |
2053 | ||
2054 | @node X11 Keysyms | |
2055 | @section Operating on X11 Keysyms | |
2056 | @cindex X11 keysyms | |
2057 | ||
2058 | To define system-specific X11 keysyms, set the variable | |
2059 | @code{system-key-alist}. | |
2060 | ||
2061 | @defvar system-key-alist | |
2062 | This variable's value should be an alist with one element for each | |
2063 | system-specific keysym. Each element has the form @code{(@var{code} | |
2064 | . @var{symbol})}, where @var{code} is the numeric keysym code (not | |
2065 | including the ``vendor specific'' bit, | |
2066 | @ifnottex | |
2067 | -2**28), | |
2068 | @end ifnottex | |
2069 | @tex | |
2070 | $-2^{28}$), | |
2071 | @end tex | |
2072 | and @var{symbol} is the name for the function key. | |
2073 | ||
2074 | For example @code{(168 . mute-acute)} defines a system-specific key (used | |
2075 | by HP X servers) whose numeric code is | |
2076 | @ifnottex | |
2077 | -2**28 | |
2078 | @end ifnottex | |
2079 | @tex | |
2080 | $-2^{28}$ | |
2081 | @end tex | |
2082 | + 168. | |
2083 | ||
2084 | It is not crucial to exclude from the alist the keysyms of other X | |
2085 | servers; those do no harm, as long as they don't conflict with the ones | |
2086 | used by the X server actually in use. | |
2087 | ||
2088 | The variable is always local to the current terminal, and cannot be | |
3ec61d4e | 2089 | buffer-local. @xref{Multiple Terminals}. |
b8d4c8d0 GM |
2090 | @end defvar |
2091 | ||
2092 | You can specify which keysyms Emacs should use for the Meta, Alt, Hyper, and Super modifiers by setting these variables: | |
2093 | ||
2094 | @defvar x-alt-keysym | |
2095 | @defvarx x-meta-keysym | |
2096 | @defvarx x-hyper-keysym | |
2097 | @defvarx x-super-keysym | |
2098 | The name of the keysym that should stand for the Alt modifier | |
2099 | (respectively, for Meta, Hyper, and Super). For example, here is | |
2100 | how to swap the Meta and Alt modifiers within Emacs: | |
2101 | @lisp | |
2102 | (setq x-alt-keysym 'meta) | |
2103 | (setq x-meta-keysym 'alt) | |
2104 | @end lisp | |
2105 | @end defvar | |
2106 | ||
2107 | @node Batch Mode | |
2108 | @section Batch Mode | |
2109 | @cindex batch mode | |
2110 | ||
2111 | The command-line option @samp{-batch} causes Emacs to run | |
2112 | noninteractively. In this mode, Emacs does not read commands from the | |
2113 | terminal, it does not alter the terminal modes, and it does not expect | |
2114 | to be outputting to an erasable screen. The idea is that you specify | |
2115 | Lisp programs to run; when they are finished, Emacs should exit. The | |
2116 | way to specify the programs to run is with @samp{-l @var{file}}, which | |
2117 | loads the library named @var{file}, or @samp{-f @var{function}}, which | |
2118 | calls @var{function} with no arguments, or @samp{--eval @var{form}}. | |
2119 | ||
2120 | Any Lisp program output that would normally go to the echo area, | |
2121 | either using @code{message}, or using @code{prin1}, etc., with @code{t} | |
2122 | as the stream, goes instead to Emacs's standard error descriptor when | |
2123 | in batch mode. Similarly, input that would normally come from the | |
2124 | minibuffer is read from the standard input descriptor. | |
2125 | Thus, Emacs behaves much like a noninteractive | |
2126 | application program. (The echo area output that Emacs itself normally | |
2127 | generates, such as command echoing, is suppressed entirely.) | |
2128 | ||
2129 | @defvar noninteractive | |
2130 | This variable is non-@code{nil} when Emacs is running in batch mode. | |
2131 | @end defvar | |
2132 | ||
2133 | @node Session Management | |
2134 | @section Session Management | |
2135 | @cindex session manager | |
2136 | ||
dca019f8 CY |
2137 | Emacs supports the X Session Management Protocol, which is used to |
2138 | suspend and restart applications. In the X Window System, a program | |
2139 | called the @dfn{session manager} is responsible for keeping track of | |
2140 | the applications that are running. When the X server shuts down, the | |
2141 | session manager asks applications to save their state, and delays the | |
2142 | actual shutdown until they respond. An application can also cancel | |
2143 | the shutdown. | |
b8d4c8d0 GM |
2144 | |
2145 | When the session manager restarts a suspended session, it directs | |
2146 | these applications to individually reload their saved state. It does | |
2147 | this by specifying a special command-line argument that says what | |
2148 | saved session to restore. For Emacs, this argument is @samp{--smid | |
2149 | @var{session}}. | |
2150 | ||
2151 | @defvar emacs-save-session-functions | |
dca019f8 CY |
2152 | Emacs supports saving state via a hook called |
2153 | @code{emacs-save-session-functions}. Emacs runs this hook when the | |
2154 | session manager tells it that the window system is shutting down. The | |
2155 | functions are called with no arguments, and with the current buffer | |
2156 | set to a temporary buffer. Each function can use @code{insert} to add | |
2157 | Lisp code to this buffer. At the end, Emacs saves the buffer in a | |
2158 | file, called the @dfn{session file}. | |
2159 | ||
2160 | @findex emacs-session-restore | |
2161 | Subsequently, when the session manager restarts Emacs, it loads the | |
2162 | session file automatically (@pxref{Loading}). This is performed by a | |
2163 | function named @code{emacs-session-restore}, which is called during | |
2164 | startup. @xref{Startup Summary}. | |
b8d4c8d0 GM |
2165 | |
2166 | If a function in @code{emacs-save-session-functions} returns | |
2167 | non-@code{nil}, Emacs tells the session manager to cancel the | |
2168 | shutdown. | |
2169 | @end defvar | |
2170 | ||
2171 | Here is an example that just inserts some text into @samp{*scratch*} when | |
2172 | Emacs is restarted by the session manager. | |
2173 | ||
2174 | @example | |
2175 | @group | |
2176 | (add-hook 'emacs-save-session-functions 'save-yourself-test) | |
2177 | @end group | |
2178 | ||
2179 | @group | |
2180 | (defun save-yourself-test () | |
2181 | (insert "(save-excursion | |
2182 | (switch-to-buffer \"*scratch*\") | |
2183 | (insert \"I am restored\"))") | |
2184 | nil) | |
2185 | @end group | |
2186 | @end example | |
2187 | ||
2188 | @ignore | |
2189 | arch-tag: 8378814a-30d7-467c-9615-74a80b9988a7 | |
2190 | @end ignore |