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1 | @c -*-texinfo-*- |
2 | @c This is part of the GNU Emacs Lisp Reference Manual. | |
fd897522 GM |
3 | @c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999 |
4 | @c Free Software Foundation, Inc. | |
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5 | @c See the file elisp.texi for copying conditions. |
6 | @setfilename ../info/processes | |
969fe9b5 | 7 | @node Processes, Display, Abbrevs, Top |
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8 | @chapter Processes |
9 | @cindex child process | |
10 | @cindex parent process | |
11 | @cindex subprocess | |
12 | @cindex process | |
13 | ||
14 | In the terminology of operating systems, a @dfn{process} is a space in | |
15 | which a program can execute. Emacs runs in a process. Emacs Lisp | |
16 | programs can invoke other programs in processes of their own. These are | |
17 | called @dfn{subprocesses} or @dfn{child processes} of the Emacs process, | |
18 | which is their @dfn{parent process}. | |
19 | ||
20 | A subprocess of Emacs may be @dfn{synchronous} or @dfn{asynchronous}, | |
21 | depending on how it is created. When you create a synchronous | |
22 | subprocess, the Lisp program waits for the subprocess to terminate | |
23 | before continuing execution. When you create an asynchronous | |
24 | subprocess, it can run in parallel with the Lisp program. This kind of | |
25 | subprocess is represented within Emacs by a Lisp object which is also | |
26 | called a ``process''. Lisp programs can use this object to communicate | |
27 | with the subprocess or to control it. For example, you can send | |
28 | signals, obtain status information, receive output from the process, or | |
29 | send input to it. | |
30 | ||
31 | @defun processp object | |
32 | This function returns @code{t} if @var{object} is a process, | |
33 | @code{nil} otherwise. | |
34 | @end defun | |
35 | ||
36 | @menu | |
37 | * Subprocess Creation:: Functions that start subprocesses. | |
a9f0a989 | 38 | * Shell Arguments:: Quoting an argument to pass it to a shell. |
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39 | * Synchronous Processes:: Details of using synchronous subprocesses. |
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 | ||
8241495d | 62 | Synchronous and asynchronous processes are explained in the following |
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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 | |
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83 | go. It should be a buffer or a buffer name; if it is a buffer name, |
84 | that will create the buffer if it does not already exist. It can also | |
85 | be @code{nil}, which says to discard the output unless a filter function | |
86 | handles it. (@xref{Filter Functions}, and @ref{Read and Print}.) | |
87 | Normally, you should avoid having multiple processes send output to the | |
88 | same buffer because their output would be intermixed randomly. | |
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89 | |
90 | @cindex program arguments | |
91 | All three of the subprocess-creating functions have a @code{&rest} | |
92 | argument, @var{args}. The @var{args} must all be strings, and they are | |
93 | supplied to @var{program} as separate command line arguments. Wildcard | |
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94 | characters and other shell constructs have no special meanings in these |
95 | strings, since the whole strings are passed directly to the specified | |
96 | program. | |
73804d4b | 97 | |
b22f3a19 | 98 | @strong{Please note:} The argument @var{program} contains only the |
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99 | name of the program; it may not contain any command-line arguments. You |
100 | must use @var{args} to provide those. | |
101 | ||
102 | The subprocess gets its current directory from the value of | |
103 | @code{default-directory} (@pxref{File Name Expansion}). | |
104 | ||
105 | @cindex environment variables, subprocesses | |
1911e6e5 | 106 | The subprocess inherits its environment from Emacs, but you can |
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107 | specify overrides for it with @code{process-environment}. @xref{System |
108 | Environment}. | |
109 | ||
110 | @defvar exec-directory | |
a9042418 | 111 | @pindex movemail |
8241495d | 112 | The value of this variable is a string, the name of a directory that |
1911e6e5 | 113 | contains programs that come with GNU Emacs, programs intended for Emacs |
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114 | to invoke. The program @code{movemail} is an example of such a program; |
115 | Rmail uses it to fetch new mail from an inbox. | |
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116 | @end defvar |
117 | ||
118 | @defopt exec-path | |
119 | The value of this variable is a list of directories to search for | |
120 | programs to run in subprocesses. Each element is either the name of a | |
121 | directory (i.e., a string), or @code{nil}, which stands for the default | |
122 | directory (which is the value of @code{default-directory}). | |
123 | @cindex program directories | |
124 | ||
125 | The value of @code{exec-path} is used by @code{call-process} and | |
126 | @code{start-process} when the @var{program} argument is not an absolute | |
127 | file name. | |
128 | @end defopt | |
129 | ||
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130 | @node Shell Arguments |
131 | @section Shell Arguments | |
132 | ||
133 | Lisp programs sometimes need to run a shell and give it a command | |
8241495d | 134 | that contains file names that were specified by the user. These |
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135 | programs ought to be able to support any valid file name. But the shell |
136 | gives special treatment to certain characters, and if these characters | |
137 | occur in the file name, they will confuse the shell. To handle these | |
138 | characters, use the function @code{shell-quote-argument}: | |
139 | ||
140 | @defun shell-quote-argument argument | |
141 | This function returns a string which represents, in shell syntax, | |
142 | an argument whose actual contents are @var{argument}. It should | |
143 | work reliably to concatenate the return value into a shell command | |
144 | and then pass it to a shell for execution. | |
145 | ||
146 | Precisely what this function does depends on your operating system. The | |
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147 | function is designed to work with the syntax of your system's standard |
148 | shell; if you use an unusual shell, you will need to redefine this | |
149 | function. | |
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150 | |
151 | @example | |
152 | ;; @r{This example shows the behavior on GNU and Unix systems.} | |
153 | (shell-quote-argument "foo > bar") | |
154 | @result{} "foo\\ \\>\\ bar" | |
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155 | |
156 | ;; @r{This example shows the behavior on MS-DOS and MS-Windows systems.} | |
157 | (shell-quote-argument "foo > bar") | |
158 | @result{} "\"foo > bar\"" | |
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159 | @end example |
160 | ||
161 | Here's an example of using @code{shell-quote-argument} to construct | |
162 | a shell command: | |
163 | ||
164 | @example | |
165 | (concat "diff -c " | |
166 | (shell-quote-argument oldfile) | |
167 | " " | |
168 | (shell-quote-argument newfile)) | |
169 | @end example | |
170 | @end defun | |
171 | ||
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172 | @node Synchronous Processes |
173 | @section Creating a Synchronous Process | |
174 | @cindex synchronous subprocess | |
175 | ||
176 | After a @dfn{synchronous process} is created, Emacs waits for the | |
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177 | process to terminate before continuing. Starting Dired on GNU or |
178 | Unix@footnote{On other systems, Emacs uses a Lisp emulation of | |
179 | @code{ls}; see @ref{Contents of Directories}.} is an example of this: it | |
180 | runs @code{ls} in a synchronous process, then modifies the output | |
181 | slightly. Because the process is synchronous, the entire directory | |
182 | listing arrives in the buffer before Emacs tries to do anything with it. | |
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183 | |
184 | While Emacs waits for the synchronous subprocess to terminate, the | |
185 | user can quit by typing @kbd{C-g}. The first @kbd{C-g} tries to kill | |
186 | the subprocess with a @code{SIGINT} signal; but it waits until the | |
187 | subprocess actually terminates before quitting. If during that time the | |
188 | user types another @kbd{C-g}, that kills the subprocess instantly with | |
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189 | @code{SIGKILL} and quits immediately (except on MS-DOS, where killing |
190 | other processes doesn't work). @xref{Quitting}. | |
73804d4b | 191 | |
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192 | The synchronous subprocess functions return an indication of how the |
193 | process terminated. | |
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194 | |
195 | The output from a synchronous subprocess is generally decoded using a | |
196 | coding system, much like text read from a file. The input sent to a | |
197 | subprocess by @code{call-process-region} is encoded using a coding | |
198 | system, much like text written into a file. @xref{Coding Systems}. | |
73804d4b | 199 | |
22697dac | 200 | @defun call-process program &optional infile destination display &rest args |
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201 | This function calls @var{program} in a separate process and waits for |
202 | it to finish. | |
203 | ||
204 | The standard input for the process comes from file @var{infile} if | |
8241495d | 205 | @var{infile} is not @code{nil}, and from the null device otherwise. |
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206 | The argument @var{destination} says where to put the process output. |
207 | Here are the possibilities: | |
208 | ||
209 | @table @asis | |
210 | @item a buffer | |
211 | Insert the output in that buffer, before point. This includes both the | |
212 | standard output stream and the standard error stream of the process. | |
213 | ||
214 | @item a string | |
969fe9b5 | 215 | Insert the output in a buffer with that name, before point. |
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216 | |
217 | @item @code{t} | |
218 | Insert the output in the current buffer, before point. | |
219 | ||
220 | @item @code{nil} | |
221 | Discard the output. | |
222 | ||
223 | @item 0 | |
8241495d | 224 | Discard the output, and return @code{nil} immediately without waiting |
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225 | for the subprocess to finish. |
226 | ||
227 | In this case, the process is not truly synchronous, since it can run in | |
228 | parallel with Emacs; but you can think of it as synchronous in that | |
229 | Emacs is essentially finished with the subprocess as soon as this | |
230 | function returns. | |
231 | ||
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232 | MS-DOS doesn't support asynchronous subprocesses, so this option doesn't |
233 | work there. | |
234 | ||
1911e6e5 | 235 | @item @code{(@var{real-destination} @var{error-destination})} |
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236 | Keep the standard output stream separate from the standard error stream; |
237 | deal with the ordinary output as specified by @var{real-destination}, | |
238 | and dispose of the error output according to @var{error-destination}. | |
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239 | If @var{error-destination} is @code{nil}, that means to discard the |
240 | error output, @code{t} means mix it with the ordinary output, and a | |
241 | string specifies a file name to redirect error output into. | |
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242 | |
243 | You can't directly specify a buffer to put the error output in; that is | |
244 | too difficult to implement. But you can achieve this result by sending | |
245 | the error output to a temporary file and then inserting the file into a | |
246 | buffer. | |
247 | @end table | |
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248 | |
249 | If @var{display} is non-@code{nil}, then @code{call-process} redisplays | |
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250 | the buffer as output is inserted. (However, if the coding system chosen |
251 | for decoding output is @code{undecided}, meaning deduce the encoding | |
252 | from the actual data, then redisplay sometimes cannot continue once | |
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253 | non-@sc{ascii} characters are encountered. There are fundamental |
254 | reasons why it is hard to fix this; see @ref{Output from Processes}.) | |
255 | ||
256 | Otherwise the function @code{call-process} does no redisplay, and the | |
257 | results become visible on the screen only when Emacs redisplays that | |
258 | buffer in the normal course of events. | |
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259 | |
260 | The remaining arguments, @var{args}, are strings that specify command | |
261 | line arguments for the program. | |
262 | ||
263 | The value returned by @code{call-process} (unless you told it not to | |
264 | wait) indicates the reason for process termination. A number gives the | |
265 | exit status of the subprocess; 0 means success, and any other value | |
266 | means failure. If the process terminated with a signal, | |
267 | @code{call-process} returns a string describing the signal. | |
268 | ||
269 | In the examples below, the buffer @samp{foo} is current. | |
270 | ||
271 | @smallexample | |
272 | @group | |
273 | (call-process "pwd" nil t) | |
8241495d | 274 | @result{} 0 |
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275 | |
276 | ---------- Buffer: foo ---------- | |
277 | /usr/user/lewis/manual | |
278 | ---------- Buffer: foo ---------- | |
279 | @end group | |
280 | ||
281 | @group | |
282 | (call-process "grep" nil "bar" nil "lewis" "/etc/passwd") | |
8241495d | 283 | @result{} 0 |
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284 | |
285 | ---------- Buffer: bar ---------- | |
286 | lewis:5LTsHm66CSWKg:398:21:Bil Lewis:/user/lewis:/bin/csh | |
287 | ||
288 | ---------- Buffer: bar ---------- | |
289 | @end group | |
290 | @end smallexample | |
291 | ||
969fe9b5 RS |
292 | Here is a good example of the use of @code{call-process}, which used to |
293 | be found in the definition of @code{insert-directory}: | |
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294 | |
295 | @smallexample | |
296 | @group | |
969fe9b5 | 297 | (call-process insert-directory-program nil t nil @var{switches} |
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298 | (if full-directory-p |
299 | (concat (file-name-as-directory file) ".") | |
300 | file)) | |
301 | @end group | |
302 | @end smallexample | |
303 | @end defun | |
304 | ||
22697dac | 305 | @defun call-process-region start end program &optional delete destination display &rest args |
8241495d | 306 | This function sends the text from @var{start} to @var{end} as |
73804d4b | 307 | standard input to a process running @var{program}. It deletes the text |
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308 | sent if @var{delete} is non-@code{nil}; this is useful when |
309 | @var{destination} is @code{t}, to insert the output in the current | |
310 | buffer in place of the input. | |
73804d4b | 311 | |
22697dac | 312 | The arguments @var{destination} and @var{display} control what to do |
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313 | with the output from the subprocess, and whether to update the display |
314 | as it comes in. For details, see the description of | |
22697dac | 315 | @code{call-process}, above. If @var{destination} is the integer 0, |
73804d4b | 316 | @code{call-process-region} discards the output and returns @code{nil} |
8241495d | 317 | immediately, without waiting for the subprocess to finish (this only |
4f939ab8 | 318 | works if asynchronous subprocesses are supported). |
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319 | |
320 | The remaining arguments, @var{args}, are strings that specify command | |
321 | line arguments for the program. | |
322 | ||
323 | The return value of @code{call-process-region} is just like that of | |
324 | @code{call-process}: @code{nil} if you told it to return without | |
325 | waiting; otherwise, a number or string which indicates how the | |
326 | subprocess terminated. | |
327 | ||
328 | In the following example, we use @code{call-process-region} to run the | |
329 | @code{cat} utility, with standard input being the first five characters | |
330 | in buffer @samp{foo} (the word @samp{input}). @code{cat} copies its | |
331 | standard input into its standard output. Since the argument | |
22697dac | 332 | @var{destination} is @code{t}, this output is inserted in the current |
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333 | buffer. |
334 | ||
335 | @smallexample | |
336 | @group | |
337 | ---------- Buffer: foo ---------- | |
338 | input@point{} | |
339 | ---------- Buffer: foo ---------- | |
340 | @end group | |
341 | ||
342 | @group | |
343 | (call-process-region 1 6 "cat" nil t) | |
8241495d | 344 | @result{} 0 |
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345 | |
346 | ---------- Buffer: foo ---------- | |
347 | inputinput@point{} | |
348 | ---------- Buffer: foo ---------- | |
349 | @end group | |
350 | @end smallexample | |
351 | ||
352 | The @code{shell-command-on-region} command uses | |
353 | @code{call-process-region} like this: | |
354 | ||
355 | @smallexample | |
356 | @group | |
357 | (call-process-region | |
358 | start end | |
359 | shell-file-name ; @r{Name of program.} | |
360 | nil ; @r{Do not delete region.} | |
361 | buffer ; @r{Send output to @code{buffer}.} | |
362 | nil ; @r{No redisplay during output.} | |
363 | "-c" command) ; @r{Arguments for the shell.} | |
364 | @end group | |
365 | @end smallexample | |
366 | @end defun | |
367 | ||
f9f59935 RS |
368 | @defun shell-command-to-string command |
369 | This function executes @var{command} (a string) as a shell command, | |
370 | then returns the command's output as a string. | |
371 | @end defun | |
372 | ||
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373 | @node Asynchronous Processes |
374 | @section Creating an Asynchronous Process | |
375 | @cindex asynchronous subprocess | |
376 | ||
1911e6e5 RS |
377 | After an @dfn{asynchronous process} is created, Emacs and the subprocess |
378 | both continue running immediately. The process thereafter runs | |
a9f0a989 | 379 | in parallel with Emacs, and the two can communicate with each other |
8241495d | 380 | using the functions described in the following sections. However, |
a9f0a989 RS |
381 | communication is only partially asynchronous: Emacs sends data to the |
382 | process only when certain functions are called, and Emacs accepts data | |
383 | from the process only when Emacs is waiting for input or for a time | |
384 | delay. | |
385 | ||
386 | Here we describe how to create an asynchronous process. | |
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387 | |
388 | @defun start-process name buffer-or-name program &rest args | |
389 | This function creates a new asynchronous subprocess and starts the | |
390 | program @var{program} running in it. It returns a process object that | |
391 | stands for the new subprocess in Lisp. The argument @var{name} | |
392 | specifies the name for the process object; if a process with this name | |
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393 | already exists, then @var{name} is modified (by appending @samp{<1>}, |
394 | etc.) to be unique. The buffer @var{buffer-or-name} is the buffer to | |
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395 | associate with the process. |
396 | ||
397 | The remaining arguments, @var{args}, are strings that specify command | |
398 | line arguments for the program. | |
399 | ||
400 | In the example below, the first process is started and runs (rather, | |
401 | sleeps) for 100 seconds. Meanwhile, the second process is started, and | |
402 | given the name @samp{my-process<1>} for the sake of uniqueness. It | |
403 | inserts the directory listing at the end of the buffer @samp{foo}, | |
404 | before the first process finishes. Then it finishes, and a message to | |
405 | that effect is inserted in the buffer. Much later, the first process | |
406 | finishes, and another message is inserted in the buffer for it. | |
407 | ||
408 | @smallexample | |
409 | @group | |
410 | (start-process "my-process" "foo" "sleep" "100") | |
411 | @result{} #<process my-process> | |
412 | @end group | |
413 | ||
414 | @group | |
415 | (start-process "my-process" "foo" "ls" "-l" "/user/lewis/bin") | |
416 | @result{} #<process my-process<1>> | |
417 | ||
418 | ---------- Buffer: foo ---------- | |
419 | total 2 | |
420 | lrwxrwxrwx 1 lewis 14 Jul 22 10:12 gnuemacs --> /emacs | |
421 | -rwxrwxrwx 1 lewis 19 Jul 30 21:02 lemon | |
422 | ||
423 | Process my-process<1> finished | |
424 | ||
425 | Process my-process finished | |
426 | ---------- Buffer: foo ---------- | |
427 | @end group | |
428 | @end smallexample | |
429 | @end defun | |
430 | ||
431 | @defun start-process-shell-command name buffer-or-name command &rest command-args | |
432 | This function is like @code{start-process} except that it uses a shell | |
433 | to execute the specified command. The argument @var{command} is a shell | |
434 | command name, and @var{command-args} are the arguments for the shell | |
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435 | command. The variable @code{shell-file-name} specifies which shell to |
436 | use. | |
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437 | |
438 | The point of running a program through the shell, rather than directly | |
439 | with @code{start-process}, is so that you can employ shell features such | |
440 | as wildcards in the arguments. It follows that if you include an | |
8241495d | 441 | arbitrary user-specified arguments in the command, you should quote it |
969fe9b5 | 442 | with @code{shell-quote-argument} first, so that any special shell |
8241495d RS |
443 | characters do @emph{not} have their special shell meanings. @xref{Shell |
444 | Arguments}. | |
73804d4b RS |
445 | @end defun |
446 | ||
447 | @defvar process-connection-type | |
448 | @cindex pipes | |
449 | @cindex @sc{pty}s | |
450 | This variable controls the type of device used to communicate with | |
bfe721d1 KH |
451 | asynchronous subprocesses. If it is non-@code{nil}, then @sc{pty}s are |
452 | used, when available. Otherwise, pipes are used. | |
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453 | |
454 | @sc{pty}s are usually preferable for processes visible to the user, as | |
455 | in Shell mode, because they allow job control (@kbd{C-c}, @kbd{C-z}, | |
f9f59935 RS |
456 | etc.) to work between the process and its children, whereas pipes do |
457 | not. For subprocesses used for internal purposes by programs, it is | |
458 | often better to use a pipe, because they are more efficient. In | |
459 | addition, the total number of @sc{pty}s is limited on many systems and | |
460 | it is good not to waste them. | |
73804d4b | 461 | |
8241495d | 462 | The value of @code{process-connection-type} is used when |
73804d4b RS |
463 | @code{start-process} is called. So you can specify how to communicate |
464 | with one subprocess by binding the variable around the call to | |
465 | @code{start-process}. | |
466 | ||
467 | @smallexample | |
468 | @group | |
469 | (let ((process-connection-type nil)) ; @r{Use a pipe.} | |
470 | (start-process @dots{})) | |
471 | @end group | |
472 | @end smallexample | |
22697dac KH |
473 | |
474 | To determine whether a given subprocess actually got a pipe or a | |
475 | @sc{pty}, use the function @code{process-tty-name} (@pxref{Process | |
476 | Information}). | |
73804d4b RS |
477 | @end defvar |
478 | ||
479 | @node Deleting Processes | |
480 | @section Deleting Processes | |
481 | @cindex deleting processes | |
482 | ||
483 | @dfn{Deleting a process} disconnects Emacs immediately from the | |
484 | subprocess, and removes it from the list of active processes. It sends | |
485 | a signal to the subprocess to make the subprocess terminate, but this is | |
486 | not guaranteed to happen immediately. The process object itself | |
f23af701 RS |
487 | continues to exist as long as other Lisp objects point to it. The |
488 | process mark continues to point to the same place as before (usually | |
489 | into a buffer where output from the process was being inserted). | |
73804d4b RS |
490 | |
491 | You can delete a process explicitly at any time. Processes are | |
492 | deleted automatically after they terminate, but not necessarily right | |
493 | away. If you delete a terminated process explicitly before it is | |
494 | deleted automatically, no harm results. | |
495 | ||
1911e6e5 | 496 | @defopt delete-exited-processes |
73804d4b RS |
497 | This variable controls automatic deletion of processes that have |
498 | terminated (due to calling @code{exit} or to a signal). If it is | |
499 | @code{nil}, then they continue to exist until the user runs | |
500 | @code{list-processes}. Otherwise, they are deleted immediately after | |
501 | they exit. | |
1911e6e5 | 502 | @end defopt |
73804d4b RS |
503 | |
504 | @defun delete-process name | |
505 | This function deletes the process associated with @var{name}, killing it | |
506 | with a @code{SIGHUP} signal. The argument @var{name} may be a process, | |
507 | the name of a process, a buffer, or the name of a buffer. | |
508 | ||
509 | @smallexample | |
510 | @group | |
511 | (delete-process "*shell*") | |
512 | @result{} nil | |
513 | @end group | |
514 | @end smallexample | |
515 | @end defun | |
516 | ||
1911e6e5 RS |
517 | @defun process-kill-without-query process &optional do-query |
518 | This function specifies whether Emacs should query the user if | |
519 | @var{process} is still running when Emacs is exited. If @var{do-query} | |
520 | is @code{nil}, the process will be deleted silently. | |
521 | Otherwise, Emacs will query about killing it. | |
522 | ||
523 | The value is @code{t} if the process was formerly set up to require | |
ebc6903b | 524 | query, @code{nil} otherwise. A newly-created process always requires |
1911e6e5 | 525 | query. |
73804d4b RS |
526 | |
527 | @smallexample | |
528 | @group | |
529 | (process-kill-without-query (get-process "shell")) | |
530 | @result{} t | |
531 | @end group | |
532 | @end smallexample | |
533 | @end defun | |
534 | ||
535 | @node Process Information | |
536 | @section Process Information | |
537 | ||
538 | Several functions return information about processes. | |
539 | @code{list-processes} is provided for interactive use. | |
540 | ||
541 | @deffn Command list-processes | |
542 | This command displays a listing of all living processes. In addition, | |
543 | it finally deletes any process whose status was @samp{Exited} or | |
544 | @samp{Signaled}. It returns @code{nil}. | |
545 | @end deffn | |
546 | ||
547 | @defun process-list | |
548 | This function returns a list of all processes that have not been deleted. | |
549 | ||
550 | @smallexample | |
551 | @group | |
552 | (process-list) | |
553 | @result{} (#<process display-time> #<process shell>) | |
554 | @end group | |
555 | @end smallexample | |
556 | @end defun | |
557 | ||
558 | @defun get-process name | |
559 | This function returns the process named @var{name}, or @code{nil} if | |
560 | there is none. An error is signaled if @var{name} is not a string. | |
561 | ||
562 | @smallexample | |
563 | @group | |
564 | (get-process "shell") | |
565 | @result{} #<process shell> | |
566 | @end group | |
567 | @end smallexample | |
568 | @end defun | |
569 | ||
570 | @defun process-command process | |
571 | This function returns the command that was executed to start | |
572 | @var{process}. This is a list of strings, the first string being the | |
573 | program executed and the rest of the strings being the arguments that | |
574 | were given to the program. | |
575 | ||
576 | @smallexample | |
577 | @group | |
578 | (process-command (get-process "shell")) | |
579 | @result{} ("/bin/csh" "-i") | |
580 | @end group | |
581 | @end smallexample | |
582 | @end defun | |
583 | ||
584 | @defun process-id process | |
585 | This function returns the @sc{pid} of @var{process}. This is an | |
78608595 | 586 | integer that distinguishes the process @var{process} from all other |
73804d4b RS |
587 | processes running on the same computer at the current time. The |
588 | @sc{pid} of a process is chosen by the operating system kernel when the | |
589 | process is started and remains constant as long as the process exists. | |
590 | @end defun | |
591 | ||
592 | @defun process-name process | |
593 | This function returns the name of @var{process}. | |
594 | @end defun | |
595 | ||
f9f59935 RS |
596 | @defun process-contact process |
597 | This function returns @code{t} for an ordinary child process, and | |
598 | @code{(@var{hostname} @var{service})} for a net connection | |
599 | (@pxref{Network}). | |
600 | @end defun | |
601 | ||
73804d4b RS |
602 | @defun process-status process-name |
603 | This function returns the status of @var{process-name} as a symbol. | |
604 | The argument @var{process-name} must be a process, a buffer, a | |
605 | process name (string) or a buffer name (string). | |
606 | ||
607 | The possible values for an actual subprocess are: | |
608 | ||
609 | @table @code | |
610 | @item run | |
611 | for a process that is running. | |
612 | @item stop | |
613 | for a process that is stopped but continuable. | |
614 | @item exit | |
615 | for a process that has exited. | |
616 | @item signal | |
617 | for a process that has received a fatal signal. | |
618 | @item open | |
619 | for a network connection that is open. | |
620 | @item closed | |
621 | for a network connection that is closed. Once a connection | |
622 | is closed, you cannot reopen it, though you might be able to open | |
623 | a new connection to the same place. | |
624 | @item nil | |
625 | if @var{process-name} is not the name of an existing process. | |
626 | @end table | |
627 | ||
628 | @smallexample | |
629 | @group | |
630 | (process-status "shell") | |
631 | @result{} run | |
632 | @end group | |
633 | @group | |
634 | (process-status (get-buffer "*shell*")) | |
635 | @result{} run | |
636 | @end group | |
637 | @group | |
638 | x | |
639 | @result{} #<process xx<1>> | |
640 | (process-status x) | |
641 | @result{} exit | |
642 | @end group | |
643 | @end smallexample | |
644 | ||
645 | For a network connection, @code{process-status} returns one of the symbols | |
646 | @code{open} or @code{closed}. The latter means that the other side | |
647 | closed the connection, or Emacs did @code{delete-process}. | |
73804d4b RS |
648 | @end defun |
649 | ||
650 | @defun process-exit-status process | |
651 | This function returns the exit status of @var{process} or the signal | |
652 | number that killed it. (Use the result of @code{process-status} to | |
653 | determine which of those it is.) If @var{process} has not yet | |
654 | terminated, the value is 0. | |
655 | @end defun | |
656 | ||
22697dac KH |
657 | @defun process-tty-name process |
658 | This function returns the terminal name that @var{process} is using for | |
659 | its communication with Emacs---or @code{nil} if it is using pipes | |
660 | instead of a terminal (see @code{process-connection-type} in | |
661 | @ref{Asynchronous Processes}). | |
662 | @end defun | |
663 | ||
f9f59935 RS |
664 | @defun process-coding-system process |
665 | This function returns a cons cell describing the coding systems in use | |
666 | for decoding output from @var{process} and for encoding input to | |
667 | @var{process} (@pxref{Coding Systems}). The value has this form: | |
668 | ||
669 | @example | |
969fe9b5 | 670 | (@var{coding-system-for-decoding} . @var{coding-system-for-encoding}) |
f9f59935 RS |
671 | @end example |
672 | @end defun | |
673 | ||
f9f59935 RS |
674 | @defun set-process-coding-system process decoding-system encoding-system |
675 | This function specifies the coding systems to use for subsequent output | |
676 | from and input to @var{process}. It will use @var{decoding-system} to | |
677 | decode subprocess output, and @var{encoding-system} to encode subprocess | |
678 | input. | |
679 | @end defun | |
680 | ||
73804d4b RS |
681 | @node Input to Processes |
682 | @section Sending Input to Processes | |
683 | @cindex process input | |
684 | ||
685 | Asynchronous subprocesses receive input when it is sent to them by | |
686 | Emacs, which is done with the functions in this section. You must | |
687 | specify the process to send input to, and the input data to send. The | |
688 | data appears on the ``standard input'' of the subprocess. | |
689 | ||
690 | Some operating systems have limited space for buffered input in a | |
691 | @sc{pty}. On these systems, Emacs sends an @sc{eof} periodically amidst | |
692 | the other characters, to force them through. For most programs, | |
693 | these @sc{eof}s do no harm. | |
694 | ||
f9f59935 | 695 | Subprocess input is normally encoded using a coding system before the |
a9f0a989 RS |
696 | subprocess receives it, much like text written into a file. You can use |
697 | @code{set-process-coding-system} to specify which coding system to use | |
698 | (@pxref{Process Information}). Otherwise, the coding system comes from | |
699 | @code{coding-system-for-write}, if that is non-@code{nil}; or else from | |
700 | the defaulting mechanism (@pxref{Default Coding Systems}). | |
f9f59935 | 701 | |
b6954afd RS |
702 | Sometimes the system is unable to accept input for that process, |
703 | because the input buffer is full. When this happens, the send functions | |
704 | wait a short while, accepting output from subprocesses, and then try | |
705 | again. This gives the subprocess a chance to read more of its pending | |
706 | input and make space in the buffer. It also allows filters, sentinels | |
707 | and timers to run---so take account of that in writing your code. | |
708 | ||
73804d4b RS |
709 | @defun process-send-string process-name string |
710 | This function sends @var{process-name} the contents of @var{string} as | |
711 | standard input. The argument @var{process-name} must be a process or | |
712 | the name of a process. If it is @code{nil}, the current buffer's | |
713 | process is used. | |
714 | ||
715 | The function returns @code{nil}. | |
716 | ||
717 | @smallexample | |
718 | @group | |
719 | (process-send-string "shell<1>" "ls\n") | |
720 | @result{} nil | |
721 | @end group | |
722 | ||
723 | ||
724 | @group | |
725 | ---------- Buffer: *shell* ---------- | |
726 | ... | |
727 | introduction.texi syntax-tables.texi~ | |
728 | introduction.texi~ text.texi | |
729 | introduction.txt text.texi~ | |
730 | ... | |
731 | ---------- Buffer: *shell* ---------- | |
732 | @end group | |
733 | @end smallexample | |
734 | @end defun | |
735 | ||
8241495d | 736 | @defun process-send-region process-name start end |
73804d4b RS |
737 | This function sends the text in the region defined by @var{start} and |
738 | @var{end} as standard input to @var{process-name}, which is a process or | |
739 | a process name. (If it is @code{nil}, the current buffer's process is | |
740 | used.) | |
741 | ||
742 | An error is signaled unless both @var{start} and @var{end} are | |
743 | integers or markers that indicate positions in the current buffer. (It | |
744 | is unimportant which number is larger.) | |
8241495d | 745 | @end defun |
73804d4b RS |
746 | |
747 | @defun process-send-eof &optional process-name | |
748 | This function makes @var{process-name} see an end-of-file in its | |
749 | input. The @sc{eof} comes after any text already sent to it. | |
750 | ||
751 | If @var{process-name} is not supplied, or if it is @code{nil}, then | |
752 | this function sends the @sc{eof} to the current buffer's process. An | |
753 | error is signaled if the current buffer has no process. | |
754 | ||
755 | The function returns @var{process-name}. | |
756 | ||
757 | @smallexample | |
758 | @group | |
759 | (process-send-eof "shell") | |
760 | @result{} "shell" | |
761 | @end group | |
762 | @end smallexample | |
763 | @end defun | |
764 | ||
b6954afd RS |
765 | @defun process-running-child-p process |
766 | @tindex process-running-child-p process | |
767 | This function will tell you whether a subprocess has given control of | |
768 | its terminal to its own child process. The value is @code{t} if this is | |
769 | true, or if Emacs cannot tell; it is @code{nil} if Emacs can be certain | |
770 | that this is not so. | |
771 | @end defun | |
772 | ||
73804d4b RS |
773 | @node Signals to Processes |
774 | @section Sending Signals to Processes | |
775 | @cindex process signals | |
776 | @cindex sending signals | |
777 | @cindex signals | |
778 | ||
779 | @dfn{Sending a signal} to a subprocess is a way of interrupting its | |
780 | activities. There are several different signals, each with its own | |
781 | meaning. The set of signals and their names is defined by the operating | |
782 | system. For example, the signal @code{SIGINT} means that the user has | |
783 | typed @kbd{C-c}, or that some analogous thing has happened. | |
784 | ||
785 | Each signal has a standard effect on the subprocess. Most signals | |
786 | kill the subprocess, but some stop or resume execution instead. Most | |
787 | signals can optionally be handled by programs; if the program handles | |
788 | the signal, then we can say nothing in general about its effects. | |
789 | ||
790 | You can send signals explicitly by calling the functions in this | |
791 | section. Emacs also sends signals automatically at certain times: | |
792 | killing a buffer sends a @code{SIGHUP} signal to all its associated | |
793 | processes; killing Emacs sends a @code{SIGHUP} signal to all remaining | |
794 | processes. (@code{SIGHUP} is a signal that usually indicates that the | |
795 | user hung up the phone.) | |
796 | ||
797 | Each of the signal-sending functions takes two optional arguments: | |
798 | @var{process-name} and @var{current-group}. | |
799 | ||
800 | The argument @var{process-name} must be either a process, the name of | |
801 | one, or @code{nil}. If it is @code{nil}, the process defaults to the | |
802 | process associated with the current buffer. An error is signaled if | |
803 | @var{process-name} does not identify a process. | |
804 | ||
805 | The argument @var{current-group} is a flag that makes a difference | |
806 | when you are running a job-control shell as an Emacs subprocess. If it | |
807 | is non-@code{nil}, then the signal is sent to the current process-group | |
78608595 | 808 | of the terminal that Emacs uses to communicate with the subprocess. If |
73804d4b RS |
809 | the process is a job-control shell, this means the shell's current |
810 | subjob. If it is @code{nil}, the signal is sent to the process group of | |
811 | the immediate subprocess of Emacs. If the subprocess is a job-control | |
812 | shell, this is the shell itself. | |
813 | ||
814 | The flag @var{current-group} has no effect when a pipe is used to | |
815 | communicate with the subprocess, because the operating system does not | |
816 | support the distinction in the case of pipes. For the same reason, | |
817 | job-control shells won't work when a pipe is used. See | |
818 | @code{process-connection-type} in @ref{Asynchronous Processes}. | |
819 | ||
820 | @defun interrupt-process &optional process-name current-group | |
821 | This function interrupts the process @var{process-name} by sending the | |
822 | signal @code{SIGINT}. Outside of Emacs, typing the ``interrupt | |
823 | character'' (normally @kbd{C-c} on some systems, and @code{DEL} on | |
824 | others) sends this signal. When the argument @var{current-group} is | |
825 | non-@code{nil}, you can think of this function as ``typing @kbd{C-c}'' | |
826 | on the terminal by which Emacs talks to the subprocess. | |
827 | @end defun | |
828 | ||
829 | @defun kill-process &optional process-name current-group | |
830 | This function kills the process @var{process-name} by sending the | |
831 | signal @code{SIGKILL}. This signal kills the subprocess immediately, | |
832 | and cannot be handled by the subprocess. | |
833 | @end defun | |
834 | ||
835 | @defun quit-process &optional process-name current-group | |
836 | This function sends the signal @code{SIGQUIT} to the process | |
837 | @var{process-name}. This signal is the one sent by the ``quit | |
838 | character'' (usually @kbd{C-b} or @kbd{C-\}) when you are not inside | |
839 | Emacs. | |
840 | @end defun | |
841 | ||
842 | @defun stop-process &optional process-name current-group | |
843 | This function stops the process @var{process-name} by sending the | |
844 | signal @code{SIGTSTP}. Use @code{continue-process} to resume its | |
845 | execution. | |
846 | ||
969fe9b5 | 847 | Outside of Emacs, on systems with job control, the ``stop character'' |
f9f59935 RS |
848 | (usually @kbd{C-z}) normally sends this signal. When |
849 | @var{current-group} is non-@code{nil}, you can think of this function as | |
850 | ``typing @kbd{C-z}'' on the terminal Emacs uses to communicate with the | |
851 | subprocess. | |
73804d4b RS |
852 | @end defun |
853 | ||
854 | @defun continue-process &optional process-name current-group | |
855 | This function resumes execution of the process @var{process} by sending | |
856 | it the signal @code{SIGCONT}. This presumes that @var{process-name} was | |
857 | stopped previously. | |
858 | @end defun | |
859 | ||
860 | @c Emacs 19 feature | |
861 | @defun signal-process pid signal | |
862 | This function sends a signal to process @var{pid}, which need not be | |
863 | a child of Emacs. The argument @var{signal} specifies which signal | |
864 | to send; it should be an integer. | |
865 | @end defun | |
866 | ||
867 | @node Output from Processes | |
868 | @section Receiving Output from Processes | |
869 | @cindex process output | |
870 | @cindex output from processes | |
871 | ||
872 | There are two ways to receive the output that a subprocess writes to | |
873 | its standard output stream. The output can be inserted in a buffer, | |
874 | which is called the associated buffer of the process, or a function | |
78608595 RS |
875 | called the @dfn{filter function} can be called to act on the output. If |
876 | the process has no buffer and no filter function, its output is | |
877 | discarded. | |
8f3efb4e | 878 | |
a9f0a989 RS |
879 | Output from a subprocess can arrive only while Emacs is waiting: when |
880 | reading terminal input, in @code{sit-for} and @code{sleep-for} | |
881 | (@pxref{Waiting}), and in @code{accept-process-output} (@pxref{Accepting | |
882 | Output}). This minimizes the problem of timing errors that usually | |
883 | plague parallel programming. For example, you can safely create a | |
884 | process and only then specify its buffer or filter function; no output | |
885 | can arrive before you finish, if the code in between does not call any | |
886 | primitive that waits. | |
887 | ||
8f3efb4e RS |
888 | It is impossible to separate the standard output and standard error |
889 | streams of the subprocess, because Emacs normally spawns the subprocess | |
890 | inside a pseudo-TTY, and a pseudo-TTY has only one output channel. If | |
891 | you want to keep the output to those streams separate, you should | |
892 | redirect one of them to a file--for example, by using an appropriate | |
893 | shell command. | |
894 | ||
f9f59935 RS |
895 | Subprocess output is normally decoded using a coding system before the |
896 | buffer or filter function receives it, much like text read from a file. | |
a9f0a989 RS |
897 | You can use @code{set-process-coding-system} to specify which coding |
898 | system to use (@pxref{Process Information}). Otherwise, the coding | |
899 | system comes from @code{coding-system-for-read}, if that is | |
900 | non-@code{nil}; or else from the defaulting mechanism (@pxref{Default | |
901 | Coding Systems}). | |
902 | ||
903 | @strong{Warning:} Coding systems such as @code{undecided} which | |
904 | determine the coding system from the data do not work entirely reliably | |
905 | with asynchronous subprocess output. This is because Emacs has to | |
906 | process asynchronous subprocess output in batches, as it arrives. Emacs | |
907 | must try to detect the proper coding system from one batch at a time, | |
908 | and this does not always work. Therefore, if at all possible, use a | |
909 | coding system which determines both the character code conversion and | |
910 | the end of line conversion---that is, one like @code{latin-1-unix}, | |
911 | rather than @code{undecided} or @code{latin-1}. | |
f9f59935 | 912 | |
73804d4b RS |
913 | @menu |
914 | * Process Buffers:: If no filter, output is put in a buffer. | |
915 | * Filter Functions:: Filter functions accept output from the process. | |
916 | * Accepting Output:: Explicitly permitting subprocess output. | |
917 | Waiting for subprocess output. | |
918 | @end menu | |
919 | ||
920 | @node Process Buffers | |
921 | @subsection Process Buffers | |
922 | ||
923 | A process can (and usually does) have an @dfn{associated buffer}, | |
924 | which is an ordinary Emacs buffer that is used for two purposes: storing | |
925 | the output from the process, and deciding when to kill the process. You | |
926 | can also use the buffer to identify a process to operate on, since in | |
927 | normal practice only one process is associated with any given buffer. | |
928 | Many applications of processes also use the buffer for editing input to | |
929 | be sent to the process, but this is not built into Emacs Lisp. | |
930 | ||
931 | Unless the process has a filter function (@pxref{Filter Functions}), | |
932 | its output is inserted in the associated buffer. The position to insert | |
78608595 RS |
933 | the output is determined by the @code{process-mark}, which is then |
934 | updated to point to the end of the text just inserted. Usually, but not | |
935 | always, the @code{process-mark} is at the end of the buffer. | |
73804d4b RS |
936 | |
937 | @defun process-buffer process | |
938 | This function returns the associated buffer of the process | |
939 | @var{process}. | |
940 | ||
941 | @smallexample | |
942 | @group | |
943 | (process-buffer (get-process "shell")) | |
944 | @result{} #<buffer *shell*> | |
945 | @end group | |
946 | @end smallexample | |
947 | @end defun | |
948 | ||
949 | @defun process-mark process | |
950 | This function returns the process marker for @var{process}, which is the | |
951 | marker that says where to insert output from the process. | |
952 | ||
953 | If @var{process} does not have a buffer, @code{process-mark} returns a | |
954 | marker that points nowhere. | |
955 | ||
956 | Insertion of process output in a buffer uses this marker to decide where | |
957 | to insert, and updates it to point after the inserted text. That is why | |
958 | successive batches of output are inserted consecutively. | |
959 | ||
960 | Filter functions normally should use this marker in the same fashion | |
961 | as is done by direct insertion of output in the buffer. A good | |
962 | example of a filter function that uses @code{process-mark} is found at | |
963 | the end of the following section. | |
964 | ||
965 | When the user is expected to enter input in the process buffer for | |
f9f59935 RS |
966 | transmission to the process, the process marker separates the new input |
967 | from previous output. | |
73804d4b RS |
968 | @end defun |
969 | ||
970 | @defun set-process-buffer process buffer | |
971 | This function sets the buffer associated with @var{process} to | |
972 | @var{buffer}. If @var{buffer} is @code{nil}, the process becomes | |
973 | associated with no buffer. | |
974 | @end defun | |
975 | ||
976 | @defun get-buffer-process buffer-or-name | |
977 | This function returns the process associated with @var{buffer-or-name}. | |
978 | If there are several processes associated with it, then one is chosen. | |
f9f59935 | 979 | (Currently, the one chosen is the one most recently created.) It is |
73804d4b RS |
980 | usually a bad idea to have more than one process associated with the |
981 | same buffer. | |
982 | ||
983 | @smallexample | |
984 | @group | |
985 | (get-buffer-process "*shell*") | |
986 | @result{} #<process shell> | |
987 | @end group | |
988 | @end smallexample | |
989 | ||
990 | Killing the process's buffer deletes the process, which kills the | |
991 | subprocess with a @code{SIGHUP} signal (@pxref{Signals to Processes}). | |
992 | @end defun | |
993 | ||
994 | @node Filter Functions | |
995 | @subsection Process Filter Functions | |
996 | @cindex filter function | |
997 | @cindex process filter | |
998 | ||
999 | A process @dfn{filter function} is a function that receives the | |
1000 | standard output from the associated process. If a process has a filter, | |
78608595 RS |
1001 | then @emph{all} output from that process is passed to the filter. The |
1002 | process buffer is used directly for output from the process only when | |
1003 | there is no filter. | |
73804d4b | 1004 | |
a9f0a989 RS |
1005 | The filter function can only be called when Emacs is waiting for |
1006 | something, because process output arrives only at such times. Emacs | |
1007 | waits when reading terminal input, in @code{sit-for} and | |
1008 | @code{sleep-for} (@pxref{Waiting}), and in @code{accept-process-output} | |
1009 | (@pxref{Accepting Output}). | |
1010 | ||
f9f59935 RS |
1011 | A filter function must accept two arguments: the associated process |
1012 | and a string, which is output just received from it. The function is | |
1013 | then free to do whatever it chooses with the output. | |
73804d4b | 1014 | |
73804d4b RS |
1015 | Quitting is normally inhibited within a filter function---otherwise, |
1016 | the effect of typing @kbd{C-g} at command level or to quit a user | |
1017 | command would be unpredictable. If you want to permit quitting inside a | |
1018 | filter function, bind @code{inhibit-quit} to @code{nil}. | |
1019 | @xref{Quitting}. | |
1020 | ||
22697dac KH |
1021 | If an error happens during execution of a filter function, it is |
1022 | caught automatically, so that it doesn't stop the execution of whatever | |
eaac2be1 | 1023 | program was running when the filter function was started. However, if |
22697dac KH |
1024 | @code{debug-on-error} is non-@code{nil}, the error-catching is turned |
1025 | off. This makes it possible to use the Lisp debugger to debug the | |
1026 | filter function. @xref{Debugger}. | |
1027 | ||
73804d4b RS |
1028 | Many filter functions sometimes or always insert the text in the |
1029 | process's buffer, mimicking the actions of Emacs when there is no | |
1030 | filter. Such filter functions need to use @code{set-buffer} in order to | |
1031 | be sure to insert in that buffer. To avoid setting the current buffer | |
f9f59935 RS |
1032 | semipermanently, these filter functions must save and restore the |
1033 | current buffer. They should also update the process marker, and in some | |
1034 | cases update the value of point. Here is how to do these things: | |
73804d4b RS |
1035 | |
1036 | @smallexample | |
1037 | @group | |
1038 | (defun ordinary-insertion-filter (proc string) | |
f9f59935 RS |
1039 | (with-current-buffer (process-buffer proc) |
1040 | (let ((moving (= (point) (process-mark proc)))) | |
73804d4b RS |
1041 | @end group |
1042 | @group | |
f9f59935 RS |
1043 | (save-excursion |
1044 | ;; @r{Insert the text, advancing the process marker.} | |
1045 | (goto-char (process-mark proc)) | |
1046 | (insert string) | |
1047 | (set-marker (process-mark proc) (point))) | |
1048 | (if moving (goto-char (process-mark proc)))))) | |
73804d4b RS |
1049 | @end group |
1050 | @end smallexample | |
1051 | ||
1052 | @noindent | |
f9f59935 RS |
1053 | The reason to use @code{with-current-buffer}, rather than using |
1054 | @code{save-excursion} to save and restore the current buffer, is so as | |
1055 | to preserve the change in point made by the second call to | |
1056 | @code{goto-char}. | |
73804d4b RS |
1057 | |
1058 | To make the filter force the process buffer to be visible whenever new | |
1059 | text arrives, insert the following line just before the | |
f9f59935 | 1060 | @code{with-current-buffer} construct: |
73804d4b RS |
1061 | |
1062 | @smallexample | |
1063 | (display-buffer (process-buffer proc)) | |
1064 | @end smallexample | |
1065 | ||
f9f59935 RS |
1066 | To force point to the end of the new output, no matter where it was |
1067 | previously, eliminate the variable @code{moving} and call | |
73804d4b RS |
1068 | @code{goto-char} unconditionally. |
1069 | ||
f9f59935 RS |
1070 | In earlier Emacs versions, every filter function that did regular |
1071 | expression searching or matching had to explicitly save and restore the | |
1072 | match data. Now Emacs does this automatically for filter functions; | |
1073 | they never need to do it explicitly. @xref{Match Data}. | |
73804d4b RS |
1074 | |
1075 | A filter function that writes the output into the buffer of the | |
bfe721d1 | 1076 | process should check whether the buffer is still alive. If it tries to |
f9f59935 RS |
1077 | insert into a dead buffer, it will get an error. The expression |
1078 | @code{(buffer-name (process-buffer @var{process}))} returns @code{nil} | |
1079 | if the buffer is dead. | |
73804d4b RS |
1080 | |
1081 | The output to the function may come in chunks of any size. A program | |
f9f59935 RS |
1082 | that produces the same output twice in a row may send it as one batch of |
1083 | 200 characters one time, and five batches of 40 characters the next. If | |
1084 | the filter looks for certain text strings in the subprocess output, make | |
1085 | sure to handle the case where one of these strings is split across two | |
1086 | or more batches of output. | |
73804d4b RS |
1087 | |
1088 | @defun set-process-filter process filter | |
1089 | This function gives @var{process} the filter function @var{filter}. If | |
1090 | @var{filter} is @code{nil}, it gives the process no filter. | |
1091 | @end defun | |
1092 | ||
1093 | @defun process-filter process | |
1094 | This function returns the filter function of @var{process}, or @code{nil} | |
1095 | if it has none. | |
1096 | @end defun | |
1097 | ||
1098 | Here is an example of use of a filter function: | |
1099 | ||
1100 | @smallexample | |
1101 | @group | |
1102 | (defun keep-output (process output) | |
1103 | (setq kept (cons output kept))) | |
1104 | @result{} keep-output | |
1105 | @end group | |
1106 | @group | |
1107 | (setq kept nil) | |
1108 | @result{} nil | |
1109 | @end group | |
1110 | @group | |
1111 | (set-process-filter (get-process "shell") 'keep-output) | |
1112 | @result{} keep-output | |
1113 | @end group | |
1114 | @group | |
1115 | (process-send-string "shell" "ls ~/other\n") | |
1116 | @result{} nil | |
1117 | kept | |
1118 | @result{} ("lewis@@slug[8] % " | |
1119 | @end group | |
1120 | @group | |
1121 | "FINAL-W87-SHORT.MSS backup.otl kolstad.mss~ | |
1122 | address.txt backup.psf kolstad.psf | |
1123 | backup.bib~ david.mss resume-Dec-86.mss~ | |
1124 | backup.err david.psf resume-Dec.psf | |
1125 | backup.mss dland syllabus.mss | |
1126 | " | |
1127 | "#backups.mss# backup.mss~ kolstad.mss | |
1128 | ") | |
1129 | @end group | |
1130 | @end smallexample | |
1131 | ||
1132 | @ignore @c The code in this example doesn't show the right way to do things. | |
1133 | Here is another, more realistic example, which demonstrates how to use | |
1134 | the process mark to do insertion in the same fashion as is done when | |
1135 | there is no filter function: | |
1136 | ||
1137 | @smallexample | |
1138 | @group | |
1139 | ;; @r{Insert input in the buffer specified by @code{my-shell-buffer}} | |
1140 | ;; @r{and make sure that buffer is shown in some window.} | |
1141 | (defun my-process-filter (proc str) | |
f9f59935 RS |
1142 | (let ((cur (selected-window)) |
1143 | (pop-up-windows t)) | |
1144 | (pop-to-buffer my-shell-buffer) | |
73804d4b RS |
1145 | @end group |
1146 | @group | |
f9f59935 RS |
1147 | (goto-char (point-max)) |
1148 | (insert str) | |
1149 | (set-marker (process-mark proc) (point-max)) | |
1150 | (select-window cur))) | |
73804d4b RS |
1151 | @end group |
1152 | @end smallexample | |
1153 | @end ignore | |
1154 | ||
1155 | @node Accepting Output | |
1156 | @subsection Accepting Output from Processes | |
1157 | ||
1158 | Output from asynchronous subprocesses normally arrives only while | |
1159 | Emacs is waiting for some sort of external event, such as elapsed time | |
1160 | or terminal input. Occasionally it is useful in a Lisp program to | |
1161 | explicitly permit output to arrive at a specific point, or even to wait | |
1162 | until output arrives from a process. | |
1163 | ||
1164 | @defun accept-process-output &optional process seconds millisec | |
1165 | This function allows Emacs to read pending output from processes. The | |
1166 | output is inserted in the associated buffers or given to their filter | |
1167 | functions. If @var{process} is non-@code{nil} then this function does | |
1168 | not return until some output has been received from @var{process}. | |
1169 | ||
1170 | @c Emacs 19 feature | |
1171 | The arguments @var{seconds} and @var{millisec} let you specify timeout | |
1172 | periods. The former specifies a period measured in seconds and the | |
1173 | latter specifies one measured in milliseconds. The two time periods | |
1174 | thus specified are added together, and @code{accept-process-output} | |
1175 | returns after that much time whether or not there has been any | |
1176 | subprocess output. | |
1177 | ||
bfe721d1 KH |
1178 | The argument @var{seconds} need not be an integer. If it is a floating |
1179 | point number, this function waits for a fractional number of seconds. | |
1180 | Some systems support only a whole number of seconds; on these systems, | |
1911e6e5 | 1181 | @var{seconds} is rounded down. |
bfe721d1 | 1182 | |
73804d4b RS |
1183 | Not all operating systems support waiting periods other than multiples |
1184 | of a second; on those that do not, you get an error if you specify | |
1185 | nonzero @var{millisec}. | |
1186 | ||
1187 | The function @code{accept-process-output} returns non-@code{nil} if it | |
1188 | did get some output, or @code{nil} if the timeout expired before output | |
1189 | arrived. | |
1190 | @end defun | |
1191 | ||
1192 | @node Sentinels | |
1193 | @section Sentinels: Detecting Process Status Changes | |
1194 | @cindex process sentinel | |
1195 | @cindex sentinel | |
1196 | ||
1197 | A @dfn{process sentinel} is a function that is called whenever the | |
1198 | associated process changes status for any reason, including signals | |
1199 | (whether sent by Emacs or caused by the process's own actions) that | |
1200 | terminate, stop, or continue the process. The process sentinel is also | |
1201 | called if the process exits. The sentinel receives two arguments: the | |
1202 | process for which the event occurred, and a string describing the type | |
1203 | of event. | |
1204 | ||
1205 | The string describing the event looks like one of the following: | |
1206 | ||
1207 | @itemize @bullet | |
1208 | @item | |
1209 | @code{"finished\n"}. | |
1210 | ||
1211 | @item | |
1212 | @code{"exited abnormally with code @var{exitcode}\n"}. | |
1213 | ||
1214 | @item | |
1215 | @code{"@var{name-of-signal}\n"}. | |
1216 | ||
1217 | @item | |
1218 | @code{"@var{name-of-signal} (core dumped)\n"}. | |
1219 | @end itemize | |
1220 | ||
1221 | A sentinel runs only while Emacs is waiting (e.g., for terminal input, | |
1222 | or for time to elapse, or for process output). This avoids the timing | |
1223 | errors that could result from running them at random places in the | |
1224 | middle of other Lisp programs. A program can wait, so that sentinels | |
78608595 RS |
1225 | will run, by calling @code{sit-for} or @code{sleep-for} |
1226 | (@pxref{Waiting}), or @code{accept-process-output} (@pxref{Accepting | |
a9f0a989 RS |
1227 | Output}). Emacs also allows sentinels to run when the command loop is |
1228 | reading input. | |
73804d4b RS |
1229 | |
1230 | Quitting is normally inhibited within a sentinel---otherwise, the | |
1231 | effect of typing @kbd{C-g} at command level or to quit a user command | |
1232 | would be unpredictable. If you want to permit quitting inside a | |
1233 | sentinel, bind @code{inhibit-quit} to @code{nil}. @xref{Quitting}. | |
1234 | ||
1235 | A sentinel that writes the output into the buffer of the process | |
bfe721d1 | 1236 | should check whether the buffer is still alive. If it tries to insert |
73804d4b RS |
1237 | into a dead buffer, it will get an error. If the buffer is dead, |
1238 | @code{(buffer-name (process-buffer @var{process}))} returns @code{nil}. | |
1239 | ||
22697dac KH |
1240 | If an error happens during execution of a sentinel, it is caught |
1241 | automatically, so that it doesn't stop the execution of whatever | |
1242 | programs was running when the sentinel was started. However, if | |
1243 | @code{debug-on-error} is non-@code{nil}, the error-catching is turned | |
1244 | off. This makes it possible to use the Lisp debugger to debug the | |
1245 | sentinel. @xref{Debugger}. | |
1246 | ||
f9f59935 RS |
1247 | In earlier Emacs versions, every sentinel that did regular expression |
1248 | searching or matching had to explicitly save and restore the match data. | |
1249 | Now Emacs does this automatically for sentinels; they never need to do | |
1250 | it explicitly. @xref{Match Data}. | |
bfe721d1 | 1251 | |
73804d4b RS |
1252 | @defun set-process-sentinel process sentinel |
1253 | This function associates @var{sentinel} with @var{process}. If | |
1254 | @var{sentinel} is @code{nil}, then the process will have no sentinel. | |
1255 | The default behavior when there is no sentinel is to insert a message in | |
1256 | the process's buffer when the process status changes. | |
1257 | ||
1258 | @smallexample | |
1259 | @group | |
1260 | (defun msg-me (process event) | |
1261 | (princ | |
1262 | (format "Process: %s had the event `%s'" process event))) | |
1263 | (set-process-sentinel (get-process "shell") 'msg-me) | |
1264 | @result{} msg-me | |
1265 | @end group | |
1266 | @group | |
1267 | (kill-process (get-process "shell")) | |
1268 | @print{} Process: #<process shell> had the event `killed' | |
1269 | @result{} #<process shell> | |
1270 | @end group | |
1271 | @end smallexample | |
1272 | @end defun | |
1273 | ||
1274 | @defun process-sentinel process | |
1275 | This function returns the sentinel of @var{process}, or @code{nil} if it | |
1276 | has none. | |
1277 | @end defun | |
1278 | ||
1279 | @defun waiting-for-user-input-p | |
1280 | While a sentinel or filter function is running, this function returns | |
1281 | non-@code{nil} if Emacs was waiting for keyboard input from the user at | |
1282 | the time the sentinel or filter function was called, @code{nil} if it | |
1283 | was not. | |
1284 | @end defun | |
1285 | ||
1286 | @node Transaction Queues | |
1287 | @section Transaction Queues | |
1288 | @cindex transaction queue | |
1289 | ||
f9f59935 RS |
1290 | You can use a @dfn{transaction queue} to communicate with a subprocess |
1291 | using transactions. First use @code{tq-create} to create a transaction | |
1292 | queue communicating with a specified process. Then you can call | |
1293 | @code{tq-enqueue} to send a transaction. | |
73804d4b RS |
1294 | |
1295 | @defun tq-create process | |
1296 | This function creates and returns a transaction queue communicating with | |
1297 | @var{process}. The argument @var{process} should be a subprocess | |
1298 | capable of sending and receiving streams of bytes. It may be a child | |
78608595 | 1299 | process, or it may be a TCP connection to a server, possibly on another |
73804d4b RS |
1300 | machine. |
1301 | @end defun | |
1302 | ||
1303 | @defun tq-enqueue queue question regexp closure fn | |
1304 | This function sends a transaction to queue @var{queue}. Specifying the | |
1305 | queue has the effect of specifying the subprocess to talk to. | |
1306 | ||
78608595 | 1307 | The argument @var{question} is the outgoing message that starts the |
73804d4b RS |
1308 | transaction. The argument @var{fn} is the function to call when the |
1309 | corresponding answer comes back; it is called with two arguments: | |
1310 | @var{closure}, and the answer received. | |
1311 | ||
6f6fd5ef RS |
1312 | The argument @var{regexp} is a regular expression that should match |
1313 | text at the end of the entire answer, but nothing before; that's how | |
1314 | @code{tq-enqueue} determines where the answer ends. | |
73804d4b RS |
1315 | |
1316 | The return value of @code{tq-enqueue} itself is not meaningful. | |
1317 | @end defun | |
1318 | ||
1319 | @defun tq-close queue | |
1320 | Shut down transaction queue @var{queue}, waiting for all pending transactions | |
1321 | to complete, and then terminate the connection or child process. | |
1322 | @end defun | |
1323 | ||
1324 | Transaction queues are implemented by means of a filter function. | |
1325 | @xref{Filter Functions}. | |
1326 | ||
bfe721d1 KH |
1327 | @node Network |
1328 | @section Network Connections | |
1329 | @cindex network connection | |
73804d4b RS |
1330 | @cindex TCP |
1331 | ||
bfe721d1 KH |
1332 | Emacs Lisp programs can open TCP network connections to other processes on |
1333 | the same machine or other machines. A network connection is handled by Lisp | |
73804d4b RS |
1334 | much like a subprocess, and is represented by a process object. |
1335 | However, the process you are communicating with is not a child of the | |
1336 | Emacs process, so you can't kill it or send it signals. All you can do | |
1337 | is send and receive data. @code{delete-process} closes the connection, | |
1338 | but does not kill the process at the other end; that process must decide | |
1339 | what to do about closure of the connection. | |
1340 | ||
1341 | You can distinguish process objects representing network connections | |
1342 | from those representing subprocesses with the @code{process-status} | |
bfe721d1 KH |
1343 | function. It always returns either @code{open} or @code{closed} for a |
1344 | network connection, and it never returns either of those values for a | |
1345 | real subprocess. @xref{Process Information}. | |
73804d4b RS |
1346 | |
1347 | @defun open-network-stream name buffer-or-name host service | |
1348 | This function opens a TCP connection for a service to a host. It | |
1349 | returns a process object to represent the connection. | |
1350 | ||
1351 | The @var{name} argument specifies the name for the process object. It | |
1352 | is modified as necessary to make it unique. | |
1353 | ||
1354 | The @var{buffer-or-name} argument is the buffer to associate with the | |
1355 | connection. Output from the connection is inserted in the buffer, | |
1356 | unless you specify a filter function to handle the output. If | |
1357 | @var{buffer-or-name} is @code{nil}, it means that the connection is not | |
1358 | associated with any buffer. | |
1359 | ||
1360 | The arguments @var{host} and @var{service} specify where to connect to; | |
1361 | @var{host} is the host name (a string), and @var{service} is the name of | |
1362 | a defined network service (a string) or a port number (an integer). | |
1363 | @end defun |