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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 Free Software Foundation, Inc. | |
4 | @c See the file elisp.texi for copying conditions. | |
5 | @setfilename ../info/processes | |
6 | @node Processes, System Interface, Abbrevs, Top | |
7 | @chapter Processes | |
8 | @cindex child process | |
9 | @cindex parent process | |
10 | @cindex subprocess | |
11 | @cindex process | |
12 | ||
13 | In the terminology of operating systems, a @dfn{process} is a space in | |
14 | which a program can execute. Emacs runs in a process. Emacs Lisp | |
15 | programs can invoke other programs in processes of their own. These are | |
16 | called @dfn{subprocesses} or @dfn{child processes} of the Emacs process, | |
17 | which is their @dfn{parent process}. | |
18 | ||
19 | A subprocess of Emacs may be @dfn{synchronous} or @dfn{asynchronous}, | |
20 | depending on how it is created. When you create a synchronous | |
21 | subprocess, the Lisp program waits for the subprocess to terminate | |
22 | before continuing execution. When you create an asynchronous | |
23 | subprocess, it can run in parallel with the Lisp program. This kind of | |
24 | subprocess is represented within Emacs by a Lisp object which is also | |
25 | called a ``process''. Lisp programs can use this object to communicate | |
26 | with the subprocess or to control it. For example, you can send | |
27 | signals, obtain status information, receive output from the process, or | |
28 | send input to it. | |
29 | ||
30 | @defun processp object | |
31 | This function returns @code{t} if @var{object} is a process, | |
32 | @code{nil} otherwise. | |
33 | @end defun | |
34 | ||
35 | @menu | |
36 | * Subprocess Creation:: Functions that start subprocesses. | |
37 | * Synchronous Processes:: Details of using synchronous subprocesses. | |
61cb8162 RS |
38 | * MS-DOS Subprocesses:: On MS-DOS, you must indicate text vs binary |
39 | for data sent to and from a subprocess. | |
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40 | * Asynchronous Processes:: Starting up an asynchronous subprocess. |
41 | * Deleting Processes:: Eliminating an asynchronous subprocess. | |
42 | * Process Information:: Accessing run-status and other attributes. | |
43 | * Input to Processes:: Sending input to an asynchronous subprocess. | |
44 | * Signals to Processes:: Stopping, continuing or interrupting | |
45 | an asynchronous subprocess. | |
46 | * Output from Processes:: Collecting output from an asynchronous subprocess. | |
47 | * Sentinels:: Sentinels run when process run-status changes. | |
48 | * Transaction Queues:: Transaction-based communication with subprocesses. | |
bfe721d1 | 49 | * Network:: Opening network connections. |
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50 | @end menu |
51 | ||
52 | @node Subprocess Creation | |
53 | @section Functions that Create Subprocesses | |
54 | ||
55 | There are three functions that create a new subprocess in which to run | |
56 | a program. One of them, @code{start-process}, creates an asynchronous | |
57 | process and returns a process object (@pxref{Asynchronous Processes}). | |
58 | The other two, @code{call-process} and @code{call-process-region}, | |
59 | create a synchronous process and do not return a process object | |
60 | (@pxref{Synchronous Processes}). | |
61 | ||
62 | Synchronous and asynchronous processes are explained in following | |
63 | sections. Since the three functions are all called in a similar | |
64 | fashion, their common arguments are described here. | |
65 | ||
66 | @cindex execute program | |
67 | @cindex @code{PATH} environment variable | |
68 | @cindex @code{HOME} environment variable | |
69 | In all cases, the function's @var{program} argument specifies the | |
70 | program to be run. An error is signaled if the file is not found or | |
71 | cannot be executed. If the file name is relative, the variable | |
72 | @code{exec-path} contains a list of directories to search. Emacs | |
73 | initializes @code{exec-path} when it starts up, based on the value of | |
74 | the environment variable @code{PATH}. The standard file name | |
75 | constructs, @samp{~}, @samp{.}, and @samp{..}, are interpreted as usual | |
76 | in @code{exec-path}, but environment variable substitutions | |
77 | (@samp{$HOME}, etc.) are not recognized; use | |
78 | @code{substitute-in-file-name} to perform them (@pxref{File Name | |
79 | Expansion}). | |
80 | ||
81 | Each of the subprocess-creating functions has a @var{buffer-or-name} | |
82 | argument which specifies where the standard output from the program will | |
83 | go. If @var{buffer-or-name} is @code{nil}, that says to discard the | |
84 | output unless a filter function handles it. (@xref{Filter Functions}, | |
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85 | and @ref{Read and Print}.) Normally, you should avoid having multiple |
86 | processes send output to the same buffer because their output would be | |
87 | intermixed randomly. | |
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88 | |
89 | @cindex program arguments | |
90 | All three of the subprocess-creating functions have a @code{&rest} | |
91 | argument, @var{args}. The @var{args} must all be strings, and they are | |
92 | supplied to @var{program} as separate command line arguments. Wildcard | |
93 | characters and other shell constructs are not allowed in these strings, | |
94 | since they are passed directly to the specified program. | |
95 | ||
b22f3a19 | 96 | @strong{Please note:} The argument @var{program} contains only the |
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97 | name of the program; it may not contain any command-line arguments. You |
98 | must use @var{args} to provide those. | |
99 | ||
100 | The subprocess gets its current directory from the value of | |
101 | @code{default-directory} (@pxref{File Name Expansion}). | |
102 | ||
103 | @cindex environment variables, subprocesses | |
104 | The subprocess inherits its environment from Emacs; but you can | |
105 | specify overrides for it with @code{process-environment}. @xref{System | |
106 | Environment}. | |
107 | ||
108 | @defvar exec-directory | |
109 | @pindex wakeup | |
110 | The value of this variable is the name of a directory (a string) that | |
111 | contains programs that come with GNU Emacs, that are intended for Emacs | |
112 | to invoke. The program @code{wakeup} is an example of such a program; | |
113 | the @code{display-time} command uses it to get a reminder once per | |
114 | minute. | |
115 | @end defvar | |
116 | ||
117 | @defopt exec-path | |
118 | The value of this variable is a list of directories to search for | |
119 | programs to run in subprocesses. Each element is either the name of a | |
120 | directory (i.e., a string), or @code{nil}, which stands for the default | |
121 | directory (which is the value of @code{default-directory}). | |
122 | @cindex program directories | |
123 | ||
124 | The value of @code{exec-path} is used by @code{call-process} and | |
125 | @code{start-process} when the @var{program} argument is not an absolute | |
126 | file name. | |
127 | @end defopt | |
128 | ||
129 | @node Synchronous Processes | |
130 | @section Creating a Synchronous Process | |
131 | @cindex synchronous subprocess | |
132 | ||
133 | After a @dfn{synchronous process} is created, Emacs waits for the | |
134 | process to terminate before continuing. Starting Dired is an example of | |
135 | this: it runs @code{ls} in a synchronous process, then modifies the | |
136 | output slightly. Because the process is synchronous, the entire | |
137 | directory listing arrives in the buffer before Emacs tries to do | |
138 | anything with it. | |
139 | ||
140 | While Emacs waits for the synchronous subprocess to terminate, the | |
141 | user can quit by typing @kbd{C-g}. The first @kbd{C-g} tries to kill | |
142 | the subprocess with a @code{SIGINT} signal; but it waits until the | |
143 | subprocess actually terminates before quitting. If during that time the | |
144 | user types another @kbd{C-g}, that kills the subprocess instantly with | |
145 | @code{SIGKILL} and quits immediately. @xref{Quitting}. | |
146 | ||
147 | The synchronous subprocess functions returned @code{nil} in version | |
148 | 18. In version 19, they return an indication of how the process | |
149 | terminated. | |
150 | ||
22697dac | 151 | @defun call-process program &optional infile destination display &rest args |
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152 | This function calls @var{program} in a separate process and waits for |
153 | it to finish. | |
154 | ||
155 | The standard input for the process comes from file @var{infile} if | |
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156 | @var{infile} is not @code{nil} and from @file{/dev/null} otherwise. |
157 | The argument @var{destination} says where to put the process output. | |
158 | Here are the possibilities: | |
159 | ||
160 | @table @asis | |
161 | @item a buffer | |
162 | Insert the output in that buffer, before point. This includes both the | |
163 | standard output stream and the standard error stream of the process. | |
164 | ||
165 | @item a string | |
166 | Find or create a buffer with that name, then insert | |
167 | the output in that buffer, before point. | |
168 | ||
169 | @item @code{t} | |
170 | Insert the output in the current buffer, before point. | |
171 | ||
172 | @item @code{nil} | |
173 | Discard the output. | |
174 | ||
175 | @item 0 | |
176 | Discard the output, and return immediately without waiting | |
177 | for the subprocess to finish. | |
178 | ||
179 | In this case, the process is not truly synchronous, since it can run in | |
180 | parallel with Emacs; but you can think of it as synchronous in that | |
181 | Emacs is essentially finished with the subprocess as soon as this | |
182 | function returns. | |
183 | ||
184 | @item (@var{real-destination} @var{error-destination}) | |
185 | Keep the standard output stream separate from the standard error stream; | |
186 | deal with the ordinary output as specified by @var{real-destination}, | |
187 | and dispose of the error output according to @var{error-destination}. | |
188 | The value @code{nil} means discard it, @code{t} means mix it with the | |
189 | ordinary output, and a string specifies a file name to redirect error | |
190 | output into. | |
191 | ||
192 | You can't directly specify a buffer to put the error output in; that is | |
193 | too difficult to implement. But you can achieve this result by sending | |
194 | the error output to a temporary file and then inserting the file into a | |
195 | buffer. | |
196 | @end table | |
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197 | |
198 | If @var{display} is non-@code{nil}, then @code{call-process} redisplays | |
199 | the buffer as output is inserted. Otherwise the function does no | |
200 | redisplay, and the results become visible on the screen only when Emacs | |
201 | redisplays that buffer in the normal course of events. | |
202 | ||
203 | The remaining arguments, @var{args}, are strings that specify command | |
204 | line arguments for the program. | |
205 | ||
206 | The value returned by @code{call-process} (unless you told it not to | |
207 | wait) indicates the reason for process termination. A number gives the | |
208 | exit status of the subprocess; 0 means success, and any other value | |
209 | means failure. If the process terminated with a signal, | |
210 | @code{call-process} returns a string describing the signal. | |
211 | ||
212 | In the examples below, the buffer @samp{foo} is current. | |
213 | ||
214 | @smallexample | |
215 | @group | |
216 | (call-process "pwd" nil t) | |
217 | @result{} nil | |
218 | ||
219 | ---------- Buffer: foo ---------- | |
220 | /usr/user/lewis/manual | |
221 | ---------- Buffer: foo ---------- | |
222 | @end group | |
223 | ||
224 | @group | |
225 | (call-process "grep" nil "bar" nil "lewis" "/etc/passwd") | |
226 | @result{} nil | |
227 | ||
228 | ---------- Buffer: bar ---------- | |
229 | lewis:5LTsHm66CSWKg:398:21:Bil Lewis:/user/lewis:/bin/csh | |
230 | ||
231 | ---------- Buffer: bar ---------- | |
232 | @end group | |
233 | @end smallexample | |
234 | ||
235 | The @code{insert-directory} function contains a good example of the use | |
236 | of @code{call-process}: | |
237 | ||
238 | @smallexample | |
239 | @group | |
240 | (call-process insert-directory-program nil t nil switches | |
241 | (if full-directory-p | |
242 | (concat (file-name-as-directory file) ".") | |
243 | file)) | |
244 | @end group | |
245 | @end smallexample | |
246 | @end defun | |
247 | ||
22697dac | 248 | @defun call-process-region start end program &optional delete destination display &rest args |
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249 | This function sends the text between @var{start} to @var{end} as |
250 | standard input to a process running @var{program}. It deletes the text | |
251 | sent if @var{delete} is non-@code{nil}; this is useful when @var{buffer} | |
252 | is @code{t}, to insert the output in the current buffer. | |
253 | ||
22697dac | 254 | The arguments @var{destination} and @var{display} control what to do |
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255 | with the output from the subprocess, and whether to update the display |
256 | as it comes in. For details, see the description of | |
22697dac | 257 | @code{call-process}, above. If @var{destination} is the integer 0, |
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258 | @code{call-process-region} discards the output and returns @code{nil} |
259 | immediately, without waiting for the subprocess to finish. | |
260 | ||
261 | The remaining arguments, @var{args}, are strings that specify command | |
262 | line arguments for the program. | |
263 | ||
264 | The return value of @code{call-process-region} is just like that of | |
265 | @code{call-process}: @code{nil} if you told it to return without | |
266 | waiting; otherwise, a number or string which indicates how the | |
267 | subprocess terminated. | |
268 | ||
269 | In the following example, we use @code{call-process-region} to run the | |
270 | @code{cat} utility, with standard input being the first five characters | |
271 | in buffer @samp{foo} (the word @samp{input}). @code{cat} copies its | |
272 | standard input into its standard output. Since the argument | |
22697dac | 273 | @var{destination} is @code{t}, this output is inserted in the current |
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274 | buffer. |
275 | ||
276 | @smallexample | |
277 | @group | |
278 | ---------- Buffer: foo ---------- | |
279 | input@point{} | |
280 | ---------- Buffer: foo ---------- | |
281 | @end group | |
282 | ||
283 | @group | |
284 | (call-process-region 1 6 "cat" nil t) | |
285 | @result{} nil | |
286 | ||
287 | ---------- Buffer: foo ---------- | |
288 | inputinput@point{} | |
289 | ---------- Buffer: foo ---------- | |
290 | @end group | |
291 | @end smallexample | |
292 | ||
293 | The @code{shell-command-on-region} command uses | |
294 | @code{call-process-region} like this: | |
295 | ||
296 | @smallexample | |
297 | @group | |
298 | (call-process-region | |
299 | start end | |
300 | shell-file-name ; @r{Name of program.} | |
301 | nil ; @r{Do not delete region.} | |
302 | buffer ; @r{Send output to @code{buffer}.} | |
303 | nil ; @r{No redisplay during output.} | |
304 | "-c" command) ; @r{Arguments for the shell.} | |
305 | @end group | |
306 | @end smallexample | |
307 | @end defun | |
308 | ||
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309 | @node MS-DOS Subprocesses |
310 | @section MS-DOS Subprocesses | |
311 | ||
312 | On MS-DOS, you must indicate whether the data going to and from | |
313 | a synchronous subprocess are text or binary. Text data requires | |
314 | translation between the end-of-line convention used within Emacs | |
315 | (a single newline character) and the convention used outside Emacs | |
bfe721d1 | 316 | (the two-character sequence, @sc{crlf}). |
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317 | |
318 | The variable @code{binary-process-input} applies to input sent to the | |
319 | subprocess, and @code{binary-process-output} applies to output received | |
320 | from it. A non-@code{nil} value means the data is non-text; @code{nil} | |
321 | means the data is text, and calls for conversion. | |
322 | ||
323 | @defvar binary-process-input | |
bfe721d1 | 324 | If this variable is @code{nil}, convert newlines to @sc{crlf} sequences in |
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325 | the input to a synchronous subprocess. |
326 | @end defvar | |
327 | ||
328 | @defvar binary-process-output | |
bfe721d1 | 329 | If this variable is @code{nil}, convert @sc{crlf} sequences to newlines in |
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330 | the output from a synchronous subprocess. |
331 | @end defvar | |
332 | ||
333 | @xref{Files and MS-DOS}, for related information. | |
334 | ||
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335 | @node Asynchronous Processes |
336 | @section Creating an Asynchronous Process | |
337 | @cindex asynchronous subprocess | |
338 | ||
339 | After an @dfn{asynchronous process} is created, Emacs and the Lisp | |
340 | program both continue running immediately. The process may thereafter | |
341 | run in parallel with Emacs, and the two may communicate with each other | |
342 | using the functions described in following sections. Here we describe | |
343 | how to create an asynchronous process with @code{start-process}. | |
344 | ||
345 | @defun start-process name buffer-or-name program &rest args | |
346 | This function creates a new asynchronous subprocess and starts the | |
347 | program @var{program} running in it. It returns a process object that | |
348 | stands for the new subprocess in Lisp. The argument @var{name} | |
349 | specifies the name for the process object; if a process with this name | |
350 | already exists, then @var{name} is modified (by adding @samp{<1>}, etc.) | |
351 | to be unique. The buffer @var{buffer-or-name} is the buffer to | |
352 | associate with the process. | |
353 | ||
354 | The remaining arguments, @var{args}, are strings that specify command | |
355 | line arguments for the program. | |
356 | ||
357 | In the example below, the first process is started and runs (rather, | |
358 | sleeps) for 100 seconds. Meanwhile, the second process is started, and | |
359 | given the name @samp{my-process<1>} for the sake of uniqueness. It | |
360 | inserts the directory listing at the end of the buffer @samp{foo}, | |
361 | before the first process finishes. Then it finishes, and a message to | |
362 | that effect is inserted in the buffer. Much later, the first process | |
363 | finishes, and another message is inserted in the buffer for it. | |
364 | ||
365 | @smallexample | |
366 | @group | |
367 | (start-process "my-process" "foo" "sleep" "100") | |
368 | @result{} #<process my-process> | |
369 | @end group | |
370 | ||
371 | @group | |
372 | (start-process "my-process" "foo" "ls" "-l" "/user/lewis/bin") | |
373 | @result{} #<process my-process<1>> | |
374 | ||
375 | ---------- Buffer: foo ---------- | |
376 | total 2 | |
377 | lrwxrwxrwx 1 lewis 14 Jul 22 10:12 gnuemacs --> /emacs | |
378 | -rwxrwxrwx 1 lewis 19 Jul 30 21:02 lemon | |
379 | ||
380 | Process my-process<1> finished | |
381 | ||
382 | Process my-process finished | |
383 | ---------- Buffer: foo ---------- | |
384 | @end group | |
385 | @end smallexample | |
386 | @end defun | |
387 | ||
388 | @defun start-process-shell-command name buffer-or-name command &rest command-args | |
389 | This function is like @code{start-process} except that it uses a shell | |
390 | to execute the specified command. The argument @var{command} is a shell | |
391 | command name, and @var{command-args} are the arguments for the shell | |
392 | command. | |
393 | @end defun | |
394 | ||
395 | @defvar process-connection-type | |
396 | @cindex pipes | |
397 | @cindex @sc{pty}s | |
398 | This variable controls the type of device used to communicate with | |
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399 | asynchronous subprocesses. If it is non-@code{nil}, then @sc{pty}s are |
400 | used, when available. Otherwise, pipes are used. | |
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401 | |
402 | @sc{pty}s are usually preferable for processes visible to the user, as | |
403 | in Shell mode, because they allow job control (@kbd{C-c}, @kbd{C-z}, | |
404 | etc.) to work between the process and its children whereas pipes do not. | |
405 | For subprocesses used for internal purposes by programs, it is often | |
406 | better to use a pipe, because they are more efficient. In addition, the | |
407 | total number of @sc{pty}s is limited on many systems and it is good not | |
408 | to waste them. | |
409 | ||
410 | The value @code{process-connection-type} is used when | |
411 | @code{start-process} is called. So you can specify how to communicate | |
412 | with one subprocess by binding the variable around the call to | |
413 | @code{start-process}. | |
414 | ||
415 | @smallexample | |
416 | @group | |
417 | (let ((process-connection-type nil)) ; @r{Use a pipe.} | |
418 | (start-process @dots{})) | |
419 | @end group | |
420 | @end smallexample | |
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421 | |
422 | To determine whether a given subprocess actually got a pipe or a | |
423 | @sc{pty}, use the function @code{process-tty-name} (@pxref{Process | |
424 | Information}). | |
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425 | @end defvar |
426 | ||
427 | @node Deleting Processes | |
428 | @section Deleting Processes | |
429 | @cindex deleting processes | |
430 | ||
431 | @dfn{Deleting a process} disconnects Emacs immediately from the | |
432 | subprocess, and removes it from the list of active processes. It sends | |
433 | a signal to the subprocess to make the subprocess terminate, but this is | |
434 | not guaranteed to happen immediately. The process object itself | |
435 | continues to exist as long as other Lisp objects point to it. | |
436 | ||
437 | You can delete a process explicitly at any time. Processes are | |
438 | deleted automatically after they terminate, but not necessarily right | |
439 | away. If you delete a terminated process explicitly before it is | |
440 | deleted automatically, no harm results. | |
441 | ||
442 | @defvar delete-exited-processes | |
443 | This variable controls automatic deletion of processes that have | |
444 | terminated (due to calling @code{exit} or to a signal). If it is | |
445 | @code{nil}, then they continue to exist until the user runs | |
446 | @code{list-processes}. Otherwise, they are deleted immediately after | |
447 | they exit. | |
448 | @end defvar | |
449 | ||
450 | @defun delete-process name | |
451 | This function deletes the process associated with @var{name}, killing it | |
452 | with a @code{SIGHUP} signal. The argument @var{name} may be a process, | |
453 | the name of a process, a buffer, or the name of a buffer. | |
454 | ||
455 | @smallexample | |
456 | @group | |
457 | (delete-process "*shell*") | |
458 | @result{} nil | |
459 | @end group | |
460 | @end smallexample | |
461 | @end defun | |
462 | ||
463 | @defun process-kill-without-query process | |
464 | This function declares that Emacs need not query the user if | |
465 | @var{process} is still running when Emacs is exited. The process will | |
466 | be deleted silently. The value is @code{t}. | |
467 | ||
468 | @smallexample | |
469 | @group | |
470 | (process-kill-without-query (get-process "shell")) | |
471 | @result{} t | |
472 | @end group | |
473 | @end smallexample | |
474 | @end defun | |
475 | ||
476 | @node Process Information | |
477 | @section Process Information | |
478 | ||
479 | Several functions return information about processes. | |
480 | @code{list-processes} is provided for interactive use. | |
481 | ||
482 | @deffn Command list-processes | |
483 | This command displays a listing of all living processes. In addition, | |
484 | it finally deletes any process whose status was @samp{Exited} or | |
485 | @samp{Signaled}. It returns @code{nil}. | |
486 | @end deffn | |
487 | ||
488 | @defun process-list | |
489 | This function returns a list of all processes that have not been deleted. | |
490 | ||
491 | @smallexample | |
492 | @group | |
493 | (process-list) | |
494 | @result{} (#<process display-time> #<process shell>) | |
495 | @end group | |
496 | @end smallexample | |
497 | @end defun | |
498 | ||
499 | @defun get-process name | |
500 | This function returns the process named @var{name}, or @code{nil} if | |
501 | there is none. An error is signaled if @var{name} is not a string. | |
502 | ||
503 | @smallexample | |
504 | @group | |
505 | (get-process "shell") | |
506 | @result{} #<process shell> | |
507 | @end group | |
508 | @end smallexample | |
509 | @end defun | |
510 | ||
511 | @defun process-command process | |
512 | This function returns the command that was executed to start | |
513 | @var{process}. This is a list of strings, the first string being the | |
514 | program executed and the rest of the strings being the arguments that | |
515 | were given to the program. | |
516 | ||
517 | @smallexample | |
518 | @group | |
519 | (process-command (get-process "shell")) | |
520 | @result{} ("/bin/csh" "-i") | |
521 | @end group | |
522 | @end smallexample | |
523 | @end defun | |
524 | ||
525 | @defun process-id process | |
526 | This function returns the @sc{pid} of @var{process}. This is an | |
78608595 | 527 | integer that distinguishes the process @var{process} from all other |
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528 | processes running on the same computer at the current time. The |
529 | @sc{pid} of a process is chosen by the operating system kernel when the | |
530 | process is started and remains constant as long as the process exists. | |
531 | @end defun | |
532 | ||
533 | @defun process-name process | |
534 | This function returns the name of @var{process}. | |
535 | @end defun | |
536 | ||
537 | @defun process-status process-name | |
538 | This function returns the status of @var{process-name} as a symbol. | |
539 | The argument @var{process-name} must be a process, a buffer, a | |
540 | process name (string) or a buffer name (string). | |
541 | ||
542 | The possible values for an actual subprocess are: | |
543 | ||
544 | @table @code | |
545 | @item run | |
546 | for a process that is running. | |
547 | @item stop | |
548 | for a process that is stopped but continuable. | |
549 | @item exit | |
550 | for a process that has exited. | |
551 | @item signal | |
552 | for a process that has received a fatal signal. | |
553 | @item open | |
554 | for a network connection that is open. | |
555 | @item closed | |
556 | for a network connection that is closed. Once a connection | |
557 | is closed, you cannot reopen it, though you might be able to open | |
558 | a new connection to the same place. | |
559 | @item nil | |
560 | if @var{process-name} is not the name of an existing process. | |
561 | @end table | |
562 | ||
563 | @smallexample | |
564 | @group | |
565 | (process-status "shell") | |
566 | @result{} run | |
567 | @end group | |
568 | @group | |
569 | (process-status (get-buffer "*shell*")) | |
570 | @result{} run | |
571 | @end group | |
572 | @group | |
573 | x | |
574 | @result{} #<process xx<1>> | |
575 | (process-status x) | |
576 | @result{} exit | |
577 | @end group | |
578 | @end smallexample | |
579 | ||
580 | For a network connection, @code{process-status} returns one of the symbols | |
581 | @code{open} or @code{closed}. The latter means that the other side | |
582 | closed the connection, or Emacs did @code{delete-process}. | |
583 | ||
584 | In earlier Emacs versions (prior to version 19), the status of a network | |
585 | connection was @code{run} if open, and @code{exit} if closed. | |
586 | @end defun | |
587 | ||
588 | @defun process-exit-status process | |
589 | This function returns the exit status of @var{process} or the signal | |
590 | number that killed it. (Use the result of @code{process-status} to | |
591 | determine which of those it is.) If @var{process} has not yet | |
592 | terminated, the value is 0. | |
593 | @end defun | |
594 | ||
22697dac KH |
595 | @defun process-tty-name process |
596 | This function returns the terminal name that @var{process} is using for | |
597 | its communication with Emacs---or @code{nil} if it is using pipes | |
598 | instead of a terminal (see @code{process-connection-type} in | |
599 | @ref{Asynchronous Processes}). | |
600 | @end defun | |
601 | ||
73804d4b RS |
602 | @node Input to Processes |
603 | @section Sending Input to Processes | |
604 | @cindex process input | |
605 | ||
606 | Asynchronous subprocesses receive input when it is sent to them by | |
607 | Emacs, which is done with the functions in this section. You must | |
608 | specify the process to send input to, and the input data to send. The | |
609 | data appears on the ``standard input'' of the subprocess. | |
610 | ||
611 | Some operating systems have limited space for buffered input in a | |
612 | @sc{pty}. On these systems, Emacs sends an @sc{eof} periodically amidst | |
613 | the other characters, to force them through. For most programs, | |
614 | these @sc{eof}s do no harm. | |
615 | ||
616 | @defun process-send-string process-name string | |
617 | This function sends @var{process-name} the contents of @var{string} as | |
618 | standard input. The argument @var{process-name} must be a process or | |
619 | the name of a process. If it is @code{nil}, the current buffer's | |
620 | process is used. | |
621 | ||
622 | The function returns @code{nil}. | |
623 | ||
624 | @smallexample | |
625 | @group | |
626 | (process-send-string "shell<1>" "ls\n") | |
627 | @result{} nil | |
628 | @end group | |
629 | ||
630 | ||
631 | @group | |
632 | ---------- Buffer: *shell* ---------- | |
633 | ... | |
634 | introduction.texi syntax-tables.texi~ | |
635 | introduction.texi~ text.texi | |
636 | introduction.txt text.texi~ | |
637 | ... | |
638 | ---------- Buffer: *shell* ---------- | |
639 | @end group | |
640 | @end smallexample | |
641 | @end defun | |
642 | ||
643 | @deffn Command process-send-region process-name start end | |
644 | This function sends the text in the region defined by @var{start} and | |
645 | @var{end} as standard input to @var{process-name}, which is a process or | |
646 | a process name. (If it is @code{nil}, the current buffer's process is | |
647 | used.) | |
648 | ||
649 | An error is signaled unless both @var{start} and @var{end} are | |
650 | integers or markers that indicate positions in the current buffer. (It | |
651 | is unimportant which number is larger.) | |
652 | @end deffn | |
653 | ||
654 | @defun process-send-eof &optional process-name | |
655 | This function makes @var{process-name} see an end-of-file in its | |
656 | input. The @sc{eof} comes after any text already sent to it. | |
657 | ||
658 | If @var{process-name} is not supplied, or if it is @code{nil}, then | |
659 | this function sends the @sc{eof} to the current buffer's process. An | |
660 | error is signaled if the current buffer has no process. | |
661 | ||
662 | The function returns @var{process-name}. | |
663 | ||
664 | @smallexample | |
665 | @group | |
666 | (process-send-eof "shell") | |
667 | @result{} "shell" | |
668 | @end group | |
669 | @end smallexample | |
670 | @end defun | |
671 | ||
672 | @node Signals to Processes | |
673 | @section Sending Signals to Processes | |
674 | @cindex process signals | |
675 | @cindex sending signals | |
676 | @cindex signals | |
677 | ||
678 | @dfn{Sending a signal} to a subprocess is a way of interrupting its | |
679 | activities. There are several different signals, each with its own | |
680 | meaning. The set of signals and their names is defined by the operating | |
681 | system. For example, the signal @code{SIGINT} means that the user has | |
682 | typed @kbd{C-c}, or that some analogous thing has happened. | |
683 | ||
684 | Each signal has a standard effect on the subprocess. Most signals | |
685 | kill the subprocess, but some stop or resume execution instead. Most | |
686 | signals can optionally be handled by programs; if the program handles | |
687 | the signal, then we can say nothing in general about its effects. | |
688 | ||
689 | You can send signals explicitly by calling the functions in this | |
690 | section. Emacs also sends signals automatically at certain times: | |
691 | killing a buffer sends a @code{SIGHUP} signal to all its associated | |
692 | processes; killing Emacs sends a @code{SIGHUP} signal to all remaining | |
693 | processes. (@code{SIGHUP} is a signal that usually indicates that the | |
694 | user hung up the phone.) | |
695 | ||
696 | Each of the signal-sending functions takes two optional arguments: | |
697 | @var{process-name} and @var{current-group}. | |
698 | ||
699 | The argument @var{process-name} must be either a process, the name of | |
700 | one, or @code{nil}. If it is @code{nil}, the process defaults to the | |
701 | process associated with the current buffer. An error is signaled if | |
702 | @var{process-name} does not identify a process. | |
703 | ||
704 | The argument @var{current-group} is a flag that makes a difference | |
705 | when you are running a job-control shell as an Emacs subprocess. If it | |
706 | is non-@code{nil}, then the signal is sent to the current process-group | |
78608595 | 707 | of the terminal that Emacs uses to communicate with the subprocess. If |
73804d4b RS |
708 | the process is a job-control shell, this means the shell's current |
709 | subjob. If it is @code{nil}, the signal is sent to the process group of | |
710 | the immediate subprocess of Emacs. If the subprocess is a job-control | |
711 | shell, this is the shell itself. | |
712 | ||
713 | The flag @var{current-group} has no effect when a pipe is used to | |
714 | communicate with the subprocess, because the operating system does not | |
715 | support the distinction in the case of pipes. For the same reason, | |
716 | job-control shells won't work when a pipe is used. See | |
717 | @code{process-connection-type} in @ref{Asynchronous Processes}. | |
718 | ||
719 | @defun interrupt-process &optional process-name current-group | |
720 | This function interrupts the process @var{process-name} by sending the | |
721 | signal @code{SIGINT}. Outside of Emacs, typing the ``interrupt | |
722 | character'' (normally @kbd{C-c} on some systems, and @code{DEL} on | |
723 | others) sends this signal. When the argument @var{current-group} is | |
724 | non-@code{nil}, you can think of this function as ``typing @kbd{C-c}'' | |
725 | on the terminal by which Emacs talks to the subprocess. | |
726 | @end defun | |
727 | ||
728 | @defun kill-process &optional process-name current-group | |
729 | This function kills the process @var{process-name} by sending the | |
730 | signal @code{SIGKILL}. This signal kills the subprocess immediately, | |
731 | and cannot be handled by the subprocess. | |
732 | @end defun | |
733 | ||
734 | @defun quit-process &optional process-name current-group | |
735 | This function sends the signal @code{SIGQUIT} to the process | |
736 | @var{process-name}. This signal is the one sent by the ``quit | |
737 | character'' (usually @kbd{C-b} or @kbd{C-\}) when you are not inside | |
738 | Emacs. | |
739 | @end defun | |
740 | ||
741 | @defun stop-process &optional process-name current-group | |
742 | This function stops the process @var{process-name} by sending the | |
743 | signal @code{SIGTSTP}. Use @code{continue-process} to resume its | |
744 | execution. | |
745 | ||
746 | On systems with job control, the ``stop character'' (usually @kbd{C-z}) | |
747 | sends this signal (outside of Emacs). When @var{current-group} is | |
748 | non-@code{nil}, you can think of this function as ``typing @kbd{C-z}'' | |
749 | on the terminal Emacs uses to communicate with the subprocess. | |
750 | @end defun | |
751 | ||
752 | @defun continue-process &optional process-name current-group | |
753 | This function resumes execution of the process @var{process} by sending | |
754 | it the signal @code{SIGCONT}. This presumes that @var{process-name} was | |
755 | stopped previously. | |
756 | @end defun | |
757 | ||
758 | @c Emacs 19 feature | |
759 | @defun signal-process pid signal | |
760 | This function sends a signal to process @var{pid}, which need not be | |
761 | a child of Emacs. The argument @var{signal} specifies which signal | |
762 | to send; it should be an integer. | |
763 | @end defun | |
764 | ||
765 | @node Output from Processes | |
766 | @section Receiving Output from Processes | |
767 | @cindex process output | |
768 | @cindex output from processes | |
769 | ||
770 | There are two ways to receive the output that a subprocess writes to | |
771 | its standard output stream. The output can be inserted in a buffer, | |
772 | which is called the associated buffer of the process, or a function | |
78608595 RS |
773 | called the @dfn{filter function} can be called to act on the output. If |
774 | the process has no buffer and no filter function, its output is | |
775 | discarded. | |
73804d4b RS |
776 | |
777 | @menu | |
778 | * Process Buffers:: If no filter, output is put in a buffer. | |
779 | * Filter Functions:: Filter functions accept output from the process. | |
780 | * Accepting Output:: Explicitly permitting subprocess output. | |
781 | Waiting for subprocess output. | |
782 | @end menu | |
783 | ||
784 | @node Process Buffers | |
785 | @subsection Process Buffers | |
786 | ||
787 | A process can (and usually does) have an @dfn{associated buffer}, | |
788 | which is an ordinary Emacs buffer that is used for two purposes: storing | |
789 | the output from the process, and deciding when to kill the process. You | |
790 | can also use the buffer to identify a process to operate on, since in | |
791 | normal practice only one process is associated with any given buffer. | |
792 | Many applications of processes also use the buffer for editing input to | |
793 | be sent to the process, but this is not built into Emacs Lisp. | |
794 | ||
795 | Unless the process has a filter function (@pxref{Filter Functions}), | |
796 | its output is inserted in the associated buffer. The position to insert | |
78608595 RS |
797 | the output is determined by the @code{process-mark}, which is then |
798 | updated to point to the end of the text just inserted. Usually, but not | |
799 | always, the @code{process-mark} is at the end of the buffer. | |
73804d4b RS |
800 | |
801 | @defun process-buffer process | |
802 | This function returns the associated buffer of the process | |
803 | @var{process}. | |
804 | ||
805 | @smallexample | |
806 | @group | |
807 | (process-buffer (get-process "shell")) | |
808 | @result{} #<buffer *shell*> | |
809 | @end group | |
810 | @end smallexample | |
811 | @end defun | |
812 | ||
813 | @defun process-mark process | |
814 | This function returns the process marker for @var{process}, which is the | |
815 | marker that says where to insert output from the process. | |
816 | ||
817 | If @var{process} does not have a buffer, @code{process-mark} returns a | |
818 | marker that points nowhere. | |
819 | ||
820 | Insertion of process output in a buffer uses this marker to decide where | |
821 | to insert, and updates it to point after the inserted text. That is why | |
822 | successive batches of output are inserted consecutively. | |
823 | ||
824 | Filter functions normally should use this marker in the same fashion | |
825 | as is done by direct insertion of output in the buffer. A good | |
826 | example of a filter function that uses @code{process-mark} is found at | |
827 | the end of the following section. | |
828 | ||
829 | When the user is expected to enter input in the process buffer for | |
830 | transmission to the process, the process marker is useful for | |
831 | distinguishing the new input from previous output. | |
832 | @end defun | |
833 | ||
834 | @defun set-process-buffer process buffer | |
835 | This function sets the buffer associated with @var{process} to | |
836 | @var{buffer}. If @var{buffer} is @code{nil}, the process becomes | |
837 | associated with no buffer. | |
838 | @end defun | |
839 | ||
840 | @defun get-buffer-process buffer-or-name | |
841 | This function returns the process associated with @var{buffer-or-name}. | |
842 | If there are several processes associated with it, then one is chosen. | |
843 | (Presently, the one chosen is the one most recently created.) It is | |
844 | usually a bad idea to have more than one process associated with the | |
845 | same buffer. | |
846 | ||
847 | @smallexample | |
848 | @group | |
849 | (get-buffer-process "*shell*") | |
850 | @result{} #<process shell> | |
851 | @end group | |
852 | @end smallexample | |
853 | ||
854 | Killing the process's buffer deletes the process, which kills the | |
855 | subprocess with a @code{SIGHUP} signal (@pxref{Signals to Processes}). | |
856 | @end defun | |
857 | ||
858 | @node Filter Functions | |
859 | @subsection Process Filter Functions | |
860 | @cindex filter function | |
861 | @cindex process filter | |
862 | ||
863 | A process @dfn{filter function} is a function that receives the | |
864 | standard output from the associated process. If a process has a filter, | |
78608595 RS |
865 | then @emph{all} output from that process is passed to the filter. The |
866 | process buffer is used directly for output from the process only when | |
867 | there is no filter. | |
73804d4b RS |
868 | |
869 | A filter function must accept two arguments: the associated process and | |
870 | a string, which is the output. The function is then free to do whatever it | |
871 | chooses with the output. | |
872 | ||
873 | A filter function runs only while Emacs is waiting (e.g., for terminal | |
874 | input, or for time to elapse, or for process output). This avoids the | |
875 | timing errors that could result from running filters at random places in | |
876 | the middle of other Lisp programs. You may explicitly cause Emacs to | |
78608595 RS |
877 | wait, so that filter functions will run, by calling @code{sit-for} or |
878 | @code{sleep-for} (@pxref{Waiting}), or @code{accept-process-output} | |
879 | (@pxref{Accepting Output}). Emacs is also waiting when the command loop | |
880 | is reading input. | |
73804d4b RS |
881 | |
882 | Quitting is normally inhibited within a filter function---otherwise, | |
883 | the effect of typing @kbd{C-g} at command level or to quit a user | |
884 | command would be unpredictable. If you want to permit quitting inside a | |
885 | filter function, bind @code{inhibit-quit} to @code{nil}. | |
886 | @xref{Quitting}. | |
887 | ||
22697dac KH |
888 | If an error happens during execution of a filter function, it is |
889 | caught automatically, so that it doesn't stop the execution of whatever | |
eaac2be1 | 890 | program was running when the filter function was started. However, if |
22697dac KH |
891 | @code{debug-on-error} is non-@code{nil}, the error-catching is turned |
892 | off. This makes it possible to use the Lisp debugger to debug the | |
893 | filter function. @xref{Debugger}. | |
894 | ||
73804d4b RS |
895 | Many filter functions sometimes or always insert the text in the |
896 | process's buffer, mimicking the actions of Emacs when there is no | |
897 | filter. Such filter functions need to use @code{set-buffer} in order to | |
898 | be sure to insert in that buffer. To avoid setting the current buffer | |
899 | semipermanently, these filter functions must use @code{unwind-protect} | |
900 | to make sure to restore the previous current buffer. They should also | |
901 | update the process marker, and in some cases update the value of point. | |
902 | Here is how to do these things: | |
903 | ||
904 | @smallexample | |
905 | @group | |
906 | (defun ordinary-insertion-filter (proc string) | |
907 | (let ((old-buffer (current-buffer))) | |
908 | (unwind-protect | |
909 | (let (moving) | |
910 | (set-buffer (process-buffer proc)) | |
911 | (setq moving (= (point) (process-mark proc))) | |
912 | @end group | |
913 | @group | |
914 | (save-excursion | |
915 | ;; @r{Insert the text, moving the process-marker.} | |
916 | (goto-char (process-mark proc)) | |
917 | (insert string) | |
918 | (set-marker (process-mark proc) (point))) | |
919 | (if moving (goto-char (process-mark proc)))) | |
920 | (set-buffer old-buffer)))) | |
921 | @end group | |
922 | @end smallexample | |
923 | ||
924 | @noindent | |
925 | The reason to use an explicit @code{unwind-protect} rather than letting | |
926 | @code{save-excursion} restore the current buffer is so as to preserve | |
927 | the change in point made by @code{goto-char}. | |
928 | ||
929 | To make the filter force the process buffer to be visible whenever new | |
930 | text arrives, insert the following line just before the | |
931 | @code{unwind-protect}: | |
932 | ||
933 | @smallexample | |
934 | (display-buffer (process-buffer proc)) | |
935 | @end smallexample | |
936 | ||
937 | To force point to move to the end of the new output no matter where | |
938 | it was previously, eliminate the variable @code{moving} and call | |
939 | @code{goto-char} unconditionally. | |
940 | ||
4f4265ab RS |
941 | In earlier Emacs versions, every filter function that did regexp |
942 | searching or matching had to explicitly save and restore the match data. | |
943 | Now Emacs does this automatically; filter functions never need to do it | |
944 | explicitly. @xref{Match Data}. | |
73804d4b RS |
945 | |
946 | A filter function that writes the output into the buffer of the | |
bfe721d1 | 947 | process should check whether the buffer is still alive. If it tries to |
73804d4b RS |
948 | insert into a dead buffer, it will get an error. If the buffer is dead, |
949 | @code{(buffer-name (process-buffer @var{process}))} returns @code{nil}. | |
950 | ||
951 | The output to the function may come in chunks of any size. A program | |
952 | that produces the same output twice in a row may send it as one batch | |
953 | of 200 characters one time, and five batches of 40 characters the next. | |
954 | ||
955 | @defun set-process-filter process filter | |
956 | This function gives @var{process} the filter function @var{filter}. If | |
957 | @var{filter} is @code{nil}, it gives the process no filter. | |
958 | @end defun | |
959 | ||
960 | @defun process-filter process | |
961 | This function returns the filter function of @var{process}, or @code{nil} | |
962 | if it has none. | |
963 | @end defun | |
964 | ||
965 | Here is an example of use of a filter function: | |
966 | ||
967 | @smallexample | |
968 | @group | |
969 | (defun keep-output (process output) | |
970 | (setq kept (cons output kept))) | |
971 | @result{} keep-output | |
972 | @end group | |
973 | @group | |
974 | (setq kept nil) | |
975 | @result{} nil | |
976 | @end group | |
977 | @group | |
978 | (set-process-filter (get-process "shell") 'keep-output) | |
979 | @result{} keep-output | |
980 | @end group | |
981 | @group | |
982 | (process-send-string "shell" "ls ~/other\n") | |
983 | @result{} nil | |
984 | kept | |
985 | @result{} ("lewis@@slug[8] % " | |
986 | @end group | |
987 | @group | |
988 | "FINAL-W87-SHORT.MSS backup.otl kolstad.mss~ | |
989 | address.txt backup.psf kolstad.psf | |
990 | backup.bib~ david.mss resume-Dec-86.mss~ | |
991 | backup.err david.psf resume-Dec.psf | |
992 | backup.mss dland syllabus.mss | |
993 | " | |
994 | "#backups.mss# backup.mss~ kolstad.mss | |
995 | ") | |
996 | @end group | |
997 | @end smallexample | |
998 | ||
999 | @ignore @c The code in this example doesn't show the right way to do things. | |
1000 | Here is another, more realistic example, which demonstrates how to use | |
1001 | the process mark to do insertion in the same fashion as is done when | |
1002 | there is no filter function: | |
1003 | ||
1004 | @smallexample | |
1005 | @group | |
1006 | ;; @r{Insert input in the buffer specified by @code{my-shell-buffer}} | |
1007 | ;; @r{and make sure that buffer is shown in some window.} | |
1008 | (defun my-process-filter (proc str) | |
1009 | (let ((cur (selected-window)) | |
1010 | (pop-up-windows t)) | |
1011 | (pop-to-buffer my-shell-buffer) | |
1012 | @end group | |
1013 | @group | |
1014 | (goto-char (point-max)) | |
1015 | (insert str) | |
1016 | (set-marker (process-mark proc) (point-max)) | |
1017 | (select-window cur))) | |
1018 | @end group | |
1019 | @end smallexample | |
1020 | @end ignore | |
1021 | ||
1022 | @node Accepting Output | |
1023 | @subsection Accepting Output from Processes | |
1024 | ||
1025 | Output from asynchronous subprocesses normally arrives only while | |
1026 | Emacs is waiting for some sort of external event, such as elapsed time | |
1027 | or terminal input. Occasionally it is useful in a Lisp program to | |
1028 | explicitly permit output to arrive at a specific point, or even to wait | |
1029 | until output arrives from a process. | |
1030 | ||
1031 | @defun accept-process-output &optional process seconds millisec | |
1032 | This function allows Emacs to read pending output from processes. The | |
1033 | output is inserted in the associated buffers or given to their filter | |
1034 | functions. If @var{process} is non-@code{nil} then this function does | |
1035 | not return until some output has been received from @var{process}. | |
1036 | ||
1037 | @c Emacs 19 feature | |
1038 | The arguments @var{seconds} and @var{millisec} let you specify timeout | |
1039 | periods. The former specifies a period measured in seconds and the | |
1040 | latter specifies one measured in milliseconds. The two time periods | |
1041 | thus specified are added together, and @code{accept-process-output} | |
1042 | returns after that much time whether or not there has been any | |
1043 | subprocess output. | |
1044 | ||
bfe721d1 KH |
1045 | The argument @var{seconds} need not be an integer. If it is a floating |
1046 | point number, this function waits for a fractional number of seconds. | |
1047 | Some systems support only a whole number of seconds; on these systems, | |
1048 | @var{seconds} is rounded down. If the system doesn't support waiting | |
1049 | fractions of a second, you get an error if you specify nonzero | |
1050 | @var{millisec}. | |
1051 | ||
73804d4b RS |
1052 | Not all operating systems support waiting periods other than multiples |
1053 | of a second; on those that do not, you get an error if you specify | |
1054 | nonzero @var{millisec}. | |
1055 | ||
1056 | The function @code{accept-process-output} returns non-@code{nil} if it | |
1057 | did get some output, or @code{nil} if the timeout expired before output | |
1058 | arrived. | |
1059 | @end defun | |
1060 | ||
1061 | @node Sentinels | |
1062 | @section Sentinels: Detecting Process Status Changes | |
1063 | @cindex process sentinel | |
1064 | @cindex sentinel | |
1065 | ||
1066 | A @dfn{process sentinel} is a function that is called whenever the | |
1067 | associated process changes status for any reason, including signals | |
1068 | (whether sent by Emacs or caused by the process's own actions) that | |
1069 | terminate, stop, or continue the process. The process sentinel is also | |
1070 | called if the process exits. The sentinel receives two arguments: the | |
1071 | process for which the event occurred, and a string describing the type | |
1072 | of event. | |
1073 | ||
1074 | The string describing the event looks like one of the following: | |
1075 | ||
1076 | @itemize @bullet | |
1077 | @item | |
1078 | @code{"finished\n"}. | |
1079 | ||
1080 | @item | |
1081 | @code{"exited abnormally with code @var{exitcode}\n"}. | |
1082 | ||
1083 | @item | |
1084 | @code{"@var{name-of-signal}\n"}. | |
1085 | ||
1086 | @item | |
1087 | @code{"@var{name-of-signal} (core dumped)\n"}. | |
1088 | @end itemize | |
1089 | ||
1090 | A sentinel runs only while Emacs is waiting (e.g., for terminal input, | |
1091 | or for time to elapse, or for process output). This avoids the timing | |
1092 | errors that could result from running them at random places in the | |
1093 | middle of other Lisp programs. A program can wait, so that sentinels | |
78608595 RS |
1094 | will run, by calling @code{sit-for} or @code{sleep-for} |
1095 | (@pxref{Waiting}), or @code{accept-process-output} (@pxref{Accepting | |
1096 | Output}). Emacs is also waiting when the command loop is reading input. | |
73804d4b RS |
1097 | |
1098 | Quitting is normally inhibited within a sentinel---otherwise, the | |
1099 | effect of typing @kbd{C-g} at command level or to quit a user command | |
1100 | would be unpredictable. If you want to permit quitting inside a | |
1101 | sentinel, bind @code{inhibit-quit} to @code{nil}. @xref{Quitting}. | |
1102 | ||
1103 | A sentinel that writes the output into the buffer of the process | |
bfe721d1 | 1104 | should check whether the buffer is still alive. If it tries to insert |
73804d4b RS |
1105 | into a dead buffer, it will get an error. If the buffer is dead, |
1106 | @code{(buffer-name (process-buffer @var{process}))} returns @code{nil}. | |
1107 | ||
22697dac KH |
1108 | If an error happens during execution of a sentinel, it is caught |
1109 | automatically, so that it doesn't stop the execution of whatever | |
1110 | programs was running when the sentinel was started. However, if | |
1111 | @code{debug-on-error} is non-@code{nil}, the error-catching is turned | |
1112 | off. This makes it possible to use the Lisp debugger to debug the | |
1113 | sentinel. @xref{Debugger}. | |
1114 | ||
bfe721d1 KH |
1115 | In earlier Emacs versions, every sentinel that did regexp searching or |
1116 | matching had to explicitly save and restore the match data. Now Emacs | |
1117 | does this automatically; sentinels never need to do it explicitly. | |
1118 | @xref{Match Data}. | |
1119 | ||
73804d4b RS |
1120 | @defun set-process-sentinel process sentinel |
1121 | This function associates @var{sentinel} with @var{process}. If | |
1122 | @var{sentinel} is @code{nil}, then the process will have no sentinel. | |
1123 | The default behavior when there is no sentinel is to insert a message in | |
1124 | the process's buffer when the process status changes. | |
1125 | ||
1126 | @smallexample | |
1127 | @group | |
1128 | (defun msg-me (process event) | |
1129 | (princ | |
1130 | (format "Process: %s had the event `%s'" process event))) | |
1131 | (set-process-sentinel (get-process "shell") 'msg-me) | |
1132 | @result{} msg-me | |
1133 | @end group | |
1134 | @group | |
1135 | (kill-process (get-process "shell")) | |
1136 | @print{} Process: #<process shell> had the event `killed' | |
1137 | @result{} #<process shell> | |
1138 | @end group | |
1139 | @end smallexample | |
1140 | @end defun | |
1141 | ||
1142 | @defun process-sentinel process | |
1143 | This function returns the sentinel of @var{process}, or @code{nil} if it | |
1144 | has none. | |
1145 | @end defun | |
1146 | ||
1147 | @defun waiting-for-user-input-p | |
1148 | While a sentinel or filter function is running, this function returns | |
1149 | non-@code{nil} if Emacs was waiting for keyboard input from the user at | |
1150 | the time the sentinel or filter function was called, @code{nil} if it | |
1151 | was not. | |
1152 | @end defun | |
1153 | ||
1154 | @node Transaction Queues | |
1155 | @section Transaction Queues | |
1156 | @cindex transaction queue | |
1157 | ||
1158 | You can use a @dfn{transaction queue} for more convenient communication | |
1159 | with subprocesses using transactions. First use @code{tq-create} to | |
1160 | create a transaction queue communicating with a specified process. Then | |
1161 | you can call @code{tq-enqueue} to send a transaction. | |
1162 | ||
1163 | @defun tq-create process | |
1164 | This function creates and returns a transaction queue communicating with | |
1165 | @var{process}. The argument @var{process} should be a subprocess | |
1166 | capable of sending and receiving streams of bytes. It may be a child | |
78608595 | 1167 | process, or it may be a TCP connection to a server, possibly on another |
73804d4b RS |
1168 | machine. |
1169 | @end defun | |
1170 | ||
1171 | @defun tq-enqueue queue question regexp closure fn | |
1172 | This function sends a transaction to queue @var{queue}. Specifying the | |
1173 | queue has the effect of specifying the subprocess to talk to. | |
1174 | ||
78608595 | 1175 | The argument @var{question} is the outgoing message that starts the |
73804d4b RS |
1176 | transaction. The argument @var{fn} is the function to call when the |
1177 | corresponding answer comes back; it is called with two arguments: | |
1178 | @var{closure}, and the answer received. | |
1179 | ||
1180 | The argument @var{regexp} is a regular expression that should match the | |
1181 | entire answer, but nothing less; that's how @code{tq-enqueue} determines | |
1182 | where the answer ends. | |
1183 | ||
1184 | The return value of @code{tq-enqueue} itself is not meaningful. | |
1185 | @end defun | |
1186 | ||
1187 | @defun tq-close queue | |
1188 | Shut down transaction queue @var{queue}, waiting for all pending transactions | |
1189 | to complete, and then terminate the connection or child process. | |
1190 | @end defun | |
1191 | ||
1192 | Transaction queues are implemented by means of a filter function. | |
1193 | @xref{Filter Functions}. | |
1194 | ||
bfe721d1 KH |
1195 | @node Network |
1196 | @section Network Connections | |
1197 | @cindex network connection | |
73804d4b RS |
1198 | @cindex TCP |
1199 | ||
bfe721d1 KH |
1200 | Emacs Lisp programs can open TCP network connections to other processes on |
1201 | the same machine or other machines. A network connection is handled by Lisp | |
73804d4b RS |
1202 | much like a subprocess, and is represented by a process object. |
1203 | However, the process you are communicating with is not a child of the | |
1204 | Emacs process, so you can't kill it or send it signals. All you can do | |
1205 | is send and receive data. @code{delete-process} closes the connection, | |
1206 | but does not kill the process at the other end; that process must decide | |
1207 | what to do about closure of the connection. | |
1208 | ||
1209 | You can distinguish process objects representing network connections | |
1210 | from those representing subprocesses with the @code{process-status} | |
bfe721d1 KH |
1211 | function. It always returns either @code{open} or @code{closed} for a |
1212 | network connection, and it never returns either of those values for a | |
1213 | real subprocess. @xref{Process Information}. | |
73804d4b RS |
1214 | |
1215 | @defun open-network-stream name buffer-or-name host service | |
1216 | This function opens a TCP connection for a service to a host. It | |
1217 | returns a process object to represent the connection. | |
1218 | ||
1219 | The @var{name} argument specifies the name for the process object. It | |
1220 | is modified as necessary to make it unique. | |
1221 | ||
1222 | The @var{buffer-or-name} argument is the buffer to associate with the | |
1223 | connection. Output from the connection is inserted in the buffer, | |
1224 | unless you specify a filter function to handle the output. If | |
1225 | @var{buffer-or-name} is @code{nil}, it means that the connection is not | |
1226 | associated with any buffer. | |
1227 | ||
1228 | The arguments @var{host} and @var{service} specify where to connect to; | |
1229 | @var{host} is the host name (a string), and @var{service} is the name of | |
1230 | a defined network service (a string) or a port number (an integer). | |
1231 | @end defun |