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1 | @c -*-texinfo-*- |
2 | @c This is part of the GNU Emacs Lisp Reference Manual. | |
fd897522 | 3 | @c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999 |
177c0ea7 | 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. | |
edc590bb | 48 | * Query Before Exit:: Whether to query if exiting will kill a process. |
73804d4b | 49 | * Transaction Queues:: Transaction-based communication with subprocesses. |
bfe721d1 | 50 | * Network:: Opening network connections. |
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51 | @end menu |
52 | ||
53 | @node Subprocess Creation | |
54 | @section Functions that Create Subprocesses | |
55 | ||
56 | There are three functions that create a new subprocess in which to run | |
57 | a program. One of them, @code{start-process}, creates an asynchronous | |
58 | process and returns a process object (@pxref{Asynchronous Processes}). | |
59 | The other two, @code{call-process} and @code{call-process-region}, | |
60 | create a synchronous process and do not return a process object | |
61 | (@pxref{Synchronous Processes}). | |
62 | ||
8241495d | 63 | Synchronous and asynchronous processes are explained in the following |
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64 | sections. Since the three functions are all called in a similar |
65 | fashion, their common arguments are described here. | |
66 | ||
67 | @cindex execute program | |
68 | @cindex @code{PATH} environment variable | |
69 | @cindex @code{HOME} environment variable | |
70 | In all cases, the function's @var{program} argument specifies the | |
71 | program to be run. An error is signaled if the file is not found or | |
72 | cannot be executed. If the file name is relative, the variable | |
73 | @code{exec-path} contains a list of directories to search. Emacs | |
74 | initializes @code{exec-path} when it starts up, based on the value of | |
75 | the environment variable @code{PATH}. The standard file name | |
76 | constructs, @samp{~}, @samp{.}, and @samp{..}, are interpreted as usual | |
77 | in @code{exec-path}, but environment variable substitutions | |
78 | (@samp{$HOME}, etc.) are not recognized; use | |
79 | @code{substitute-in-file-name} to perform them (@pxref{File Name | |
80 | Expansion}). | |
81 | ||
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82 | Executing a program can also try adding suffixes to the specified |
83 | name: | |
84 | ||
85 | @defvar exec-suffixes | |
86 | This variable is a list of suffixes (strings) to try adding to the | |
87 | specified program file name. The list should include @code{""} if you | |
88 | want the name to be tried exactly as specified. The default value is | |
89 | system-dependent. | |
90 | @end defvar | |
91 | ||
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92 | Each of the subprocess-creating functions has a @var{buffer-or-name} |
93 | argument which specifies where the standard output from the program will | |
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94 | go. It should be a buffer or a buffer name; if it is a buffer name, |
95 | that will create the buffer if it does not already exist. It can also | |
96 | be @code{nil}, which says to discard the output unless a filter function | |
97 | handles it. (@xref{Filter Functions}, and @ref{Read and Print}.) | |
98 | Normally, you should avoid having multiple processes send output to the | |
99 | same buffer because their output would be intermixed randomly. | |
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100 | |
101 | @cindex program arguments | |
102 | All three of the subprocess-creating functions have a @code{&rest} | |
103 | argument, @var{args}. The @var{args} must all be strings, and they are | |
104 | supplied to @var{program} as separate command line arguments. Wildcard | |
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105 | characters and other shell constructs have no special meanings in these |
106 | strings, since the whole strings are passed directly to the specified | |
107 | program. | |
73804d4b | 108 | |
b22f3a19 | 109 | @strong{Please note:} The argument @var{program} contains only the |
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110 | name of the program; it may not contain any command-line arguments. You |
111 | must use @var{args} to provide those. | |
112 | ||
113 | The subprocess gets its current directory from the value of | |
114 | @code{default-directory} (@pxref{File Name Expansion}). | |
115 | ||
116 | @cindex environment variables, subprocesses | |
1911e6e5 | 117 | The subprocess inherits its environment from Emacs, but you can |
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118 | specify overrides for it with @code{process-environment}. @xref{System |
119 | Environment}. | |
120 | ||
177c0ea7 | 121 | @defvar exec-directory |
a9042418 | 122 | @pindex movemail |
8241495d | 123 | The value of this variable is a string, the name of a directory that |
1911e6e5 | 124 | contains programs that come with GNU Emacs, programs intended for Emacs |
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125 | to invoke. The program @code{movemail} is an example of such a program; |
126 | Rmail uses it to fetch new mail from an inbox. | |
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127 | @end defvar |
128 | ||
129 | @defopt exec-path | |
130 | The value of this variable is a list of directories to search for | |
131 | programs to run in subprocesses. Each element is either the name of a | |
132 | directory (i.e., a string), or @code{nil}, which stands for the default | |
133 | directory (which is the value of @code{default-directory}). | |
134 | @cindex program directories | |
135 | ||
136 | The value of @code{exec-path} is used by @code{call-process} and | |
137 | @code{start-process} when the @var{program} argument is not an absolute | |
138 | file name. | |
139 | @end defopt | |
140 | ||
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141 | @node Shell Arguments |
142 | @section Shell Arguments | |
143 | ||
144 | Lisp programs sometimes need to run a shell and give it a command | |
8241495d | 145 | that contains file names that were specified by the user. These |
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146 | programs ought to be able to support any valid file name. But the shell |
147 | gives special treatment to certain characters, and if these characters | |
148 | occur in the file name, they will confuse the shell. To handle these | |
149 | characters, use the function @code{shell-quote-argument}: | |
150 | ||
151 | @defun shell-quote-argument argument | |
152 | This function returns a string which represents, in shell syntax, | |
153 | an argument whose actual contents are @var{argument}. It should | |
154 | work reliably to concatenate the return value into a shell command | |
155 | and then pass it to a shell for execution. | |
156 | ||
157 | Precisely what this function does depends on your operating system. The | |
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158 | function is designed to work with the syntax of your system's standard |
159 | shell; if you use an unusual shell, you will need to redefine this | |
160 | function. | |
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161 | |
162 | @example | |
163 | ;; @r{This example shows the behavior on GNU and Unix systems.} | |
164 | (shell-quote-argument "foo > bar") | |
165 | @result{} "foo\\ \\>\\ bar" | |
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166 | |
167 | ;; @r{This example shows the behavior on MS-DOS and MS-Windows systems.} | |
168 | (shell-quote-argument "foo > bar") | |
169 | @result{} "\"foo > bar\"" | |
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170 | @end example |
171 | ||
172 | Here's an example of using @code{shell-quote-argument} to construct | |
173 | a shell command: | |
174 | ||
175 | @example | |
176 | (concat "diff -c " | |
177 | (shell-quote-argument oldfile) | |
178 | " " | |
179 | (shell-quote-argument newfile)) | |
180 | @end example | |
181 | @end defun | |
182 | ||
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183 | @node Synchronous Processes |
184 | @section Creating a Synchronous Process | |
185 | @cindex synchronous subprocess | |
186 | ||
187 | After a @dfn{synchronous process} is created, Emacs waits for the | |
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188 | process to terminate before continuing. Starting Dired on GNU or |
189 | Unix@footnote{On other systems, Emacs uses a Lisp emulation of | |
190 | @code{ls}; see @ref{Contents of Directories}.} is an example of this: it | |
191 | runs @code{ls} in a synchronous process, then modifies the output | |
192 | slightly. Because the process is synchronous, the entire directory | |
193 | listing arrives in the buffer before Emacs tries to do anything with it. | |
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194 | |
195 | While Emacs waits for the synchronous subprocess to terminate, the | |
196 | user can quit by typing @kbd{C-g}. The first @kbd{C-g} tries to kill | |
197 | the subprocess with a @code{SIGINT} signal; but it waits until the | |
198 | subprocess actually terminates before quitting. If during that time the | |
199 | user types another @kbd{C-g}, that kills the subprocess instantly with | |
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200 | @code{SIGKILL} and quits immediately (except on MS-DOS, where killing |
201 | other processes doesn't work). @xref{Quitting}. | |
73804d4b | 202 | |
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203 | The synchronous subprocess functions return an indication of how the |
204 | process terminated. | |
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205 | |
206 | The output from a synchronous subprocess is generally decoded using a | |
207 | coding system, much like text read from a file. The input sent to a | |
208 | subprocess by @code{call-process-region} is encoded using a coding | |
209 | system, much like text written into a file. @xref{Coding Systems}. | |
73804d4b | 210 | |
22697dac | 211 | @defun call-process program &optional infile destination display &rest args |
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212 | This function calls @var{program} in a separate process and waits for |
213 | it to finish. | |
214 | ||
215 | The standard input for the process comes from file @var{infile} if | |
8241495d | 216 | @var{infile} is not @code{nil}, and from the null device otherwise. |
22697dac KH |
217 | The argument @var{destination} says where to put the process output. |
218 | Here are the possibilities: | |
219 | ||
220 | @table @asis | |
221 | @item a buffer | |
222 | Insert the output in that buffer, before point. This includes both the | |
223 | standard output stream and the standard error stream of the process. | |
224 | ||
225 | @item a string | |
969fe9b5 | 226 | Insert the output in a buffer with that name, before point. |
22697dac KH |
227 | |
228 | @item @code{t} | |
229 | Insert the output in the current buffer, before point. | |
230 | ||
231 | @item @code{nil} | |
232 | Discard the output. | |
233 | ||
234 | @item 0 | |
8241495d | 235 | Discard the output, and return @code{nil} immediately without waiting |
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236 | for the subprocess to finish. |
237 | ||
238 | In this case, the process is not truly synchronous, since it can run in | |
239 | parallel with Emacs; but you can think of it as synchronous in that | |
240 | Emacs is essentially finished with the subprocess as soon as this | |
241 | function returns. | |
242 | ||
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243 | MS-DOS doesn't support asynchronous subprocesses, so this option doesn't |
244 | work there. | |
245 | ||
1911e6e5 | 246 | @item @code{(@var{real-destination} @var{error-destination})} |
22697dac KH |
247 | Keep the standard output stream separate from the standard error stream; |
248 | deal with the ordinary output as specified by @var{real-destination}, | |
249 | and dispose of the error output according to @var{error-destination}. | |
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250 | If @var{error-destination} is @code{nil}, that means to discard the |
251 | error output, @code{t} means mix it with the ordinary output, and a | |
252 | string specifies a file name to redirect error output into. | |
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253 | |
254 | You can't directly specify a buffer to put the error output in; that is | |
255 | too difficult to implement. But you can achieve this result by sending | |
256 | the error output to a temporary file and then inserting the file into a | |
257 | buffer. | |
258 | @end table | |
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259 | |
260 | If @var{display} is non-@code{nil}, then @code{call-process} redisplays | |
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261 | the buffer as output is inserted. (However, if the coding system chosen |
262 | for decoding output is @code{undecided}, meaning deduce the encoding | |
263 | from the actual data, then redisplay sometimes cannot continue once | |
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264 | non-@sc{ascii} characters are encountered. There are fundamental |
265 | reasons why it is hard to fix this; see @ref{Output from Processes}.) | |
266 | ||
267 | Otherwise the function @code{call-process} does no redisplay, and the | |
268 | results become visible on the screen only when Emacs redisplays that | |
269 | buffer in the normal course of events. | |
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270 | |
271 | The remaining arguments, @var{args}, are strings that specify command | |
272 | line arguments for the program. | |
273 | ||
274 | The value returned by @code{call-process} (unless you told it not to | |
275 | wait) indicates the reason for process termination. A number gives the | |
276 | exit status of the subprocess; 0 means success, and any other value | |
277 | means failure. If the process terminated with a signal, | |
278 | @code{call-process} returns a string describing the signal. | |
279 | ||
280 | In the examples below, the buffer @samp{foo} is current. | |
281 | ||
282 | @smallexample | |
283 | @group | |
284 | (call-process "pwd" nil t) | |
8241495d | 285 | @result{} 0 |
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286 | |
287 | ---------- Buffer: foo ---------- | |
288 | /usr/user/lewis/manual | |
289 | ---------- Buffer: foo ---------- | |
290 | @end group | |
291 | ||
292 | @group | |
293 | (call-process "grep" nil "bar" nil "lewis" "/etc/passwd") | |
8241495d | 294 | @result{} 0 |
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295 | |
296 | ---------- Buffer: bar ---------- | |
297 | lewis:5LTsHm66CSWKg:398:21:Bil Lewis:/user/lewis:/bin/csh | |
298 | ||
299 | ---------- Buffer: bar ---------- | |
300 | @end group | |
301 | @end smallexample | |
302 | ||
969fe9b5 RS |
303 | Here is a good example of the use of @code{call-process}, which used to |
304 | be found in the definition of @code{insert-directory}: | |
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305 | |
306 | @smallexample | |
307 | @group | |
969fe9b5 | 308 | (call-process insert-directory-program nil t nil @var{switches} |
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309 | (if full-directory-p |
310 | (concat (file-name-as-directory file) ".") | |
311 | file)) | |
312 | @end group | |
313 | @end smallexample | |
314 | @end defun | |
315 | ||
22697dac | 316 | @defun call-process-region start end program &optional delete destination display &rest args |
8241495d | 317 | This function sends the text from @var{start} to @var{end} as |
73804d4b | 318 | standard input to a process running @var{program}. It deletes the text |
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319 | sent if @var{delete} is non-@code{nil}; this is useful when |
320 | @var{destination} is @code{t}, to insert the output in the current | |
321 | buffer in place of the input. | |
73804d4b | 322 | |
22697dac | 323 | The arguments @var{destination} and @var{display} control what to do |
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324 | with the output from the subprocess, and whether to update the display |
325 | as it comes in. For details, see the description of | |
22697dac | 326 | @code{call-process}, above. If @var{destination} is the integer 0, |
73804d4b | 327 | @code{call-process-region} discards the output and returns @code{nil} |
8241495d | 328 | immediately, without waiting for the subprocess to finish (this only |
4f939ab8 | 329 | works if asynchronous subprocesses are supported). |
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330 | |
331 | The remaining arguments, @var{args}, are strings that specify command | |
332 | line arguments for the program. | |
333 | ||
334 | The return value of @code{call-process-region} is just like that of | |
335 | @code{call-process}: @code{nil} if you told it to return without | |
336 | waiting; otherwise, a number or string which indicates how the | |
337 | subprocess terminated. | |
338 | ||
339 | In the following example, we use @code{call-process-region} to run the | |
340 | @code{cat} utility, with standard input being the first five characters | |
341 | in buffer @samp{foo} (the word @samp{input}). @code{cat} copies its | |
342 | standard input into its standard output. Since the argument | |
22697dac | 343 | @var{destination} is @code{t}, this output is inserted in the current |
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344 | buffer. |
345 | ||
346 | @smallexample | |
347 | @group | |
348 | ---------- Buffer: foo ---------- | |
349 | input@point{} | |
350 | ---------- Buffer: foo ---------- | |
351 | @end group | |
352 | ||
353 | @group | |
354 | (call-process-region 1 6 "cat" nil t) | |
8241495d | 355 | @result{} 0 |
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356 | |
357 | ---------- Buffer: foo ---------- | |
358 | inputinput@point{} | |
359 | ---------- Buffer: foo ---------- | |
360 | @end group | |
361 | @end smallexample | |
362 | ||
363 | The @code{shell-command-on-region} command uses | |
364 | @code{call-process-region} like this: | |
365 | ||
366 | @smallexample | |
367 | @group | |
177c0ea7 JB |
368 | (call-process-region |
369 | start end | |
73804d4b RS |
370 | shell-file-name ; @r{Name of program.} |
371 | nil ; @r{Do not delete region.} | |
372 | buffer ; @r{Send output to @code{buffer}.} | |
373 | nil ; @r{No redisplay during output.} | |
374 | "-c" command) ; @r{Arguments for the shell.} | |
375 | @end group | |
376 | @end smallexample | |
377 | @end defun | |
378 | ||
f9f59935 RS |
379 | @defun shell-command-to-string command |
380 | This function executes @var{command} (a string) as a shell command, | |
381 | then returns the command's output as a string. | |
382 | @end defun | |
383 | ||
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384 | @node Asynchronous Processes |
385 | @section Creating an Asynchronous Process | |
386 | @cindex asynchronous subprocess | |
387 | ||
1911e6e5 RS |
388 | After an @dfn{asynchronous process} is created, Emacs and the subprocess |
389 | both continue running immediately. The process thereafter runs | |
a9f0a989 | 390 | in parallel with Emacs, and the two can communicate with each other |
8241495d | 391 | using the functions described in the following sections. However, |
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392 | communication is only partially asynchronous: Emacs sends data to the |
393 | process only when certain functions are called, and Emacs accepts data | |
394 | from the process only when Emacs is waiting for input or for a time | |
395 | delay. | |
396 | ||
397 | Here we describe how to create an asynchronous process. | |
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398 | |
399 | @defun start-process name buffer-or-name program &rest args | |
400 | This function creates a new asynchronous subprocess and starts the | |
401 | program @var{program} running in it. It returns a process object that | |
402 | stands for the new subprocess in Lisp. The argument @var{name} | |
403 | specifies the name for the process object; if a process with this name | |
f9f59935 RS |
404 | already exists, then @var{name} is modified (by appending @samp{<1>}, |
405 | etc.) to be unique. The buffer @var{buffer-or-name} is the buffer to | |
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406 | associate with the process. |
407 | ||
408 | The remaining arguments, @var{args}, are strings that specify command | |
409 | line arguments for the program. | |
410 | ||
411 | In the example below, the first process is started and runs (rather, | |
412 | sleeps) for 100 seconds. Meanwhile, the second process is started, and | |
413 | given the name @samp{my-process<1>} for the sake of uniqueness. It | |
414 | inserts the directory listing at the end of the buffer @samp{foo}, | |
415 | before the first process finishes. Then it finishes, and a message to | |
416 | that effect is inserted in the buffer. Much later, the first process | |
417 | finishes, and another message is inserted in the buffer for it. | |
418 | ||
419 | @smallexample | |
420 | @group | |
421 | (start-process "my-process" "foo" "sleep" "100") | |
422 | @result{} #<process my-process> | |
423 | @end group | |
424 | ||
425 | @group | |
426 | (start-process "my-process" "foo" "ls" "-l" "/user/lewis/bin") | |
427 | @result{} #<process my-process<1>> | |
428 | ||
429 | ---------- Buffer: foo ---------- | |
430 | total 2 | |
431 | lrwxrwxrwx 1 lewis 14 Jul 22 10:12 gnuemacs --> /emacs | |
432 | -rwxrwxrwx 1 lewis 19 Jul 30 21:02 lemon | |
433 | ||
434 | Process my-process<1> finished | |
435 | ||
436 | Process my-process finished | |
437 | ---------- Buffer: foo ---------- | |
438 | @end group | |
439 | @end smallexample | |
440 | @end defun | |
441 | ||
442 | @defun start-process-shell-command name buffer-or-name command &rest command-args | |
443 | This function is like @code{start-process} except that it uses a shell | |
444 | to execute the specified command. The argument @var{command} is a shell | |
445 | command name, and @var{command-args} are the arguments for the shell | |
f9f59935 RS |
446 | command. The variable @code{shell-file-name} specifies which shell to |
447 | use. | |
969fe9b5 RS |
448 | |
449 | The point of running a program through the shell, rather than directly | |
450 | with @code{start-process}, is so that you can employ shell features such | |
451 | as wildcards in the arguments. It follows that if you include an | |
8241495d | 452 | arbitrary user-specified arguments in the command, you should quote it |
969fe9b5 | 453 | with @code{shell-quote-argument} first, so that any special shell |
8241495d RS |
454 | characters do @emph{not} have their special shell meanings. @xref{Shell |
455 | Arguments}. | |
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456 | @end defun |
457 | ||
458 | @defvar process-connection-type | |
459 | @cindex pipes | |
460 | @cindex @sc{pty}s | |
461 | This variable controls the type of device used to communicate with | |
bfe721d1 KH |
462 | asynchronous subprocesses. If it is non-@code{nil}, then @sc{pty}s are |
463 | used, when available. Otherwise, pipes are used. | |
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464 | |
465 | @sc{pty}s are usually preferable for processes visible to the user, as | |
466 | in Shell mode, because they allow job control (@kbd{C-c}, @kbd{C-z}, | |
f9f59935 RS |
467 | etc.) to work between the process and its children, whereas pipes do |
468 | not. For subprocesses used for internal purposes by programs, it is | |
469 | often better to use a pipe, because they are more efficient. In | |
470 | addition, the total number of @sc{pty}s is limited on many systems and | |
471 | it is good not to waste them. | |
73804d4b | 472 | |
edc590bb | 473 | The value of @code{process-connection-type} takes effect when |
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474 | @code{start-process} is called. So you can specify how to communicate |
475 | with one subprocess by binding the variable around the call to | |
476 | @code{start-process}. | |
477 | ||
478 | @smallexample | |
479 | @group | |
480 | (let ((process-connection-type nil)) ; @r{Use a pipe.} | |
481 | (start-process @dots{})) | |
482 | @end group | |
483 | @end smallexample | |
22697dac KH |
484 | |
485 | To determine whether a given subprocess actually got a pipe or a | |
486 | @sc{pty}, use the function @code{process-tty-name} (@pxref{Process | |
487 | Information}). | |
73804d4b RS |
488 | @end defvar |
489 | ||
490 | @node Deleting Processes | |
491 | @section Deleting Processes | |
492 | @cindex deleting processes | |
493 | ||
494 | @dfn{Deleting a process} disconnects Emacs immediately from the | |
5517ea8a RS |
495 | subprocess. Processes are deleted automatically after they terminate, |
496 | but not necessarily right away. You can delete a process explicitly | |
497 | at any time. If you delete a terminated process explicitly before it | |
498 | is deleted automatically, no harm results. Deletion of a running | |
edc590bb RS |
499 | process sends a signal to terminate it (and its child processes if |
500 | any), and calls the process sentinel if it has one. | |
5517ea8a RS |
501 | |
502 | @code{get-buffer-process} and @code{process-list} do not remember a | |
503 | deleted process, but the process object itself continues to exist as | |
504 | long as other Lisp objects point to it. All the Lisp primitives that | |
505 | work on process objects accept deleted processes, but those that do | |
506 | I/O or send signals will report an error. The process mark continues | |
507 | to point to the same place as before, usually into a buffer where | |
508 | output from the process was being inserted. | |
73804d4b | 509 | |
1911e6e5 | 510 | @defopt delete-exited-processes |
73804d4b RS |
511 | This variable controls automatic deletion of processes that have |
512 | terminated (due to calling @code{exit} or to a signal). If it is | |
513 | @code{nil}, then they continue to exist until the user runs | |
514 | @code{list-processes}. Otherwise, they are deleted immediately after | |
515 | they exit. | |
1911e6e5 | 516 | @end defopt |
73804d4b RS |
517 | |
518 | @defun delete-process name | |
5517ea8a RS |
519 | This function deletes the process associated with @var{name}, killing |
520 | it with a @code{SIGKILL} signal. The argument @var{name} may be a | |
521 | process, the name of a process, a buffer, or the name of a buffer. | |
522 | Calling @code{delete-process} on a running process terminates it, | |
523 | updates the process status, and runs the sentinel (if any) immediately. | |
524 | If the process has already terminated, calling @code{delete-process} | |
525 | has no effect on its status, or on the running of its sentinel (which | |
526 | will happen sooner or later). | |
73804d4b RS |
527 | |
528 | @smallexample | |
529 | @group | |
530 | (delete-process "*shell*") | |
531 | @result{} nil | |
532 | @end group | |
533 | @end smallexample | |
534 | @end defun | |
535 | ||
73804d4b RS |
536 | @node Process Information |
537 | @section Process Information | |
538 | ||
539 | Several functions return information about processes. | |
540 | @code{list-processes} is provided for interactive use. | |
541 | ||
542 | @deffn Command list-processes | |
543 | This command displays a listing of all living processes. In addition, | |
544 | it finally deletes any process whose status was @samp{Exited} or | |
545 | @samp{Signaled}. It returns @code{nil}. | |
546 | @end deffn | |
547 | ||
548 | @defun process-list | |
549 | This function returns a list of all processes that have not been deleted. | |
550 | ||
551 | @smallexample | |
552 | @group | |
553 | (process-list) | |
554 | @result{} (#<process display-time> #<process shell>) | |
555 | @end group | |
556 | @end smallexample | |
557 | @end defun | |
558 | ||
559 | @defun get-process name | |
560 | This function returns the process named @var{name}, or @code{nil} if | |
561 | there is none. An error is signaled if @var{name} is not a string. | |
562 | ||
563 | @smallexample | |
564 | @group | |
565 | (get-process "shell") | |
566 | @result{} #<process shell> | |
567 | @end group | |
568 | @end smallexample | |
569 | @end defun | |
570 | ||
571 | @defun process-command process | |
572 | This function returns the command that was executed to start | |
573 | @var{process}. This is a list of strings, the first string being the | |
574 | program executed and the rest of the strings being the arguments that | |
575 | were given to the program. | |
576 | ||
577 | @smallexample | |
578 | @group | |
579 | (process-command (get-process "shell")) | |
580 | @result{} ("/bin/csh" "-i") | |
581 | @end group | |
582 | @end smallexample | |
583 | @end defun | |
584 | ||
585 | @defun process-id process | |
586 | This function returns the @sc{pid} of @var{process}. This is an | |
78608595 | 587 | integer that distinguishes the process @var{process} from all other |
73804d4b RS |
588 | processes running on the same computer at the current time. The |
589 | @sc{pid} of a process is chosen by the operating system kernel when the | |
590 | process is started and remains constant as long as the process exists. | |
591 | @end defun | |
592 | ||
593 | @defun process-name process | |
594 | This function returns the name of @var{process}. | |
595 | @end defun | |
596 | ||
f9f59935 RS |
597 | @defun process-contact process |
598 | This function returns @code{t} for an ordinary child process, and | |
599 | @code{(@var{hostname} @var{service})} for a net connection | |
600 | (@pxref{Network}). | |
601 | @end defun | |
602 | ||
73804d4b RS |
603 | @defun process-status process-name |
604 | This function returns the status of @var{process-name} as a symbol. | |
605 | The argument @var{process-name} must be a process, a buffer, a | |
606 | process name (string) or a buffer name (string). | |
607 | ||
608 | The possible values for an actual subprocess are: | |
609 | ||
610 | @table @code | |
611 | @item run | |
612 | for a process that is running. | |
613 | @item stop | |
614 | for a process that is stopped but continuable. | |
615 | @item exit | |
616 | for a process that has exited. | |
617 | @item signal | |
618 | for a process that has received a fatal signal. | |
619 | @item open | |
620 | for a network connection that is open. | |
621 | @item closed | |
622 | for a network connection that is closed. Once a connection | |
623 | is closed, you cannot reopen it, though you might be able to open | |
624 | a new connection to the same place. | |
625 | @item nil | |
626 | if @var{process-name} is not the name of an existing process. | |
627 | @end table | |
628 | ||
629 | @smallexample | |
630 | @group | |
631 | (process-status "shell") | |
632 | @result{} run | |
633 | @end group | |
634 | @group | |
635 | (process-status (get-buffer "*shell*")) | |
636 | @result{} run | |
637 | @end group | |
638 | @group | |
639 | x | |
640 | @result{} #<process xx<1>> | |
641 | (process-status x) | |
642 | @result{} exit | |
643 | @end group | |
644 | @end smallexample | |
645 | ||
646 | For a network connection, @code{process-status} returns one of the symbols | |
647 | @code{open} or @code{closed}. The latter means that the other side | |
648 | closed the connection, or Emacs did @code{delete-process}. | |
73804d4b RS |
649 | @end defun |
650 | ||
651 | @defun process-exit-status process | |
652 | This function returns the exit status of @var{process} or the signal | |
653 | number that killed it. (Use the result of @code{process-status} to | |
654 | determine which of those it is.) If @var{process} has not yet | |
655 | terminated, the value is 0. | |
656 | @end defun | |
657 | ||
22697dac KH |
658 | @defun process-tty-name process |
659 | This function returns the terminal name that @var{process} is using for | |
660 | its communication with Emacs---or @code{nil} if it is using pipes | |
661 | instead of a terminal (see @code{process-connection-type} in | |
662 | @ref{Asynchronous Processes}). | |
663 | @end defun | |
664 | ||
f9f59935 RS |
665 | @defun process-coding-system process |
666 | This function returns a cons cell describing the coding systems in use | |
667 | for decoding output from @var{process} and for encoding input to | |
668 | @var{process} (@pxref{Coding Systems}). The value has this form: | |
669 | ||
670 | @example | |
969fe9b5 | 671 | (@var{coding-system-for-decoding} . @var{coding-system-for-encoding}) |
f9f59935 RS |
672 | @end example |
673 | @end defun | |
674 | ||
f9f59935 RS |
675 | @defun set-process-coding-system process decoding-system encoding-system |
676 | This function specifies the coding systems to use for subsequent output | |
677 | from and input to @var{process}. It will use @var{decoding-system} to | |
678 | decode subprocess output, and @var{encoding-system} to encode subprocess | |
679 | input. | |
680 | @end defun | |
681 | ||
73804d4b RS |
682 | @node Input to Processes |
683 | @section Sending Input to Processes | |
684 | @cindex process input | |
685 | ||
686 | Asynchronous subprocesses receive input when it is sent to them by | |
687 | Emacs, which is done with the functions in this section. You must | |
688 | specify the process to send input to, and the input data to send. The | |
689 | data appears on the ``standard input'' of the subprocess. | |
690 | ||
691 | Some operating systems have limited space for buffered input in a | |
692 | @sc{pty}. On these systems, Emacs sends an @sc{eof} periodically amidst | |
693 | the other characters, to force them through. For most programs, | |
694 | these @sc{eof}s do no harm. | |
695 | ||
f9f59935 | 696 | Subprocess input is normally encoded using a coding system before the |
a9f0a989 RS |
697 | subprocess receives it, much like text written into a file. You can use |
698 | @code{set-process-coding-system} to specify which coding system to use | |
699 | (@pxref{Process Information}). Otherwise, the coding system comes from | |
700 | @code{coding-system-for-write}, if that is non-@code{nil}; or else from | |
701 | the defaulting mechanism (@pxref{Default Coding Systems}). | |
f9f59935 | 702 | |
b6954afd RS |
703 | Sometimes the system is unable to accept input for that process, |
704 | because the input buffer is full. When this happens, the send functions | |
705 | wait a short while, accepting output from subprocesses, and then try | |
706 | again. This gives the subprocess a chance to read more of its pending | |
707 | input and make space in the buffer. It also allows filters, sentinels | |
708 | and timers to run---so take account of that in writing your code. | |
709 | ||
73804d4b RS |
710 | @defun process-send-string process-name string |
711 | This function sends @var{process-name} the contents of @var{string} as | |
712 | standard input. The argument @var{process-name} must be a process or | |
713 | the name of a process. If it is @code{nil}, the current buffer's | |
714 | process is used. | |
715 | ||
716 | The function returns @code{nil}. | |
717 | ||
718 | @smallexample | |
719 | @group | |
720 | (process-send-string "shell<1>" "ls\n") | |
721 | @result{} nil | |
722 | @end group | |
723 | ||
724 | ||
725 | @group | |
726 | ---------- Buffer: *shell* ---------- | |
727 | ... | |
728 | introduction.texi syntax-tables.texi~ | |
729 | introduction.texi~ text.texi | |
730 | introduction.txt text.texi~ | |
731 | ... | |
732 | ---------- Buffer: *shell* ---------- | |
733 | @end group | |
734 | @end smallexample | |
735 | @end defun | |
736 | ||
8241495d | 737 | @defun process-send-region process-name start end |
73804d4b RS |
738 | This function sends the text in the region defined by @var{start} and |
739 | @var{end} as standard input to @var{process-name}, which is a process or | |
740 | a process name. (If it is @code{nil}, the current buffer's process is | |
741 | used.) | |
742 | ||
743 | An error is signaled unless both @var{start} and @var{end} are | |
744 | integers or markers that indicate positions in the current buffer. (It | |
745 | is unimportant which number is larger.) | |
8241495d | 746 | @end defun |
73804d4b RS |
747 | |
748 | @defun process-send-eof &optional process-name | |
749 | This function makes @var{process-name} see an end-of-file in its | |
750 | input. The @sc{eof} comes after any text already sent to it. | |
751 | ||
752 | If @var{process-name} is not supplied, or if it is @code{nil}, then | |
753 | this function sends the @sc{eof} to the current buffer's process. An | |
754 | error is signaled if the current buffer has no process. | |
755 | ||
756 | The function returns @var{process-name}. | |
757 | ||
758 | @smallexample | |
759 | @group | |
760 | (process-send-eof "shell") | |
761 | @result{} "shell" | |
762 | @end group | |
763 | @end smallexample | |
764 | @end defun | |
765 | ||
b6954afd RS |
766 | @defun process-running-child-p process |
767 | @tindex process-running-child-p process | |
768 | This function will tell you whether a subprocess has given control of | |
769 | its terminal to its own child process. The value is @code{t} if this is | |
770 | true, or if Emacs cannot tell; it is @code{nil} if Emacs can be certain | |
771 | that this is not so. | |
772 | @end defun | |
773 | ||
73804d4b RS |
774 | @node Signals to Processes |
775 | @section Sending Signals to Processes | |
776 | @cindex process signals | |
777 | @cindex sending signals | |
778 | @cindex signals | |
779 | ||
780 | @dfn{Sending a signal} to a subprocess is a way of interrupting its | |
781 | activities. There are several different signals, each with its own | |
782 | meaning. The set of signals and their names is defined by the operating | |
783 | system. For example, the signal @code{SIGINT} means that the user has | |
784 | typed @kbd{C-c}, or that some analogous thing has happened. | |
785 | ||
786 | Each signal has a standard effect on the subprocess. Most signals | |
787 | kill the subprocess, but some stop or resume execution instead. Most | |
788 | signals can optionally be handled by programs; if the program handles | |
789 | the signal, then we can say nothing in general about its effects. | |
790 | ||
791 | You can send signals explicitly by calling the functions in this | |
792 | section. Emacs also sends signals automatically at certain times: | |
793 | killing a buffer sends a @code{SIGHUP} signal to all its associated | |
794 | processes; killing Emacs sends a @code{SIGHUP} signal to all remaining | |
795 | processes. (@code{SIGHUP} is a signal that usually indicates that the | |
796 | user hung up the phone.) | |
797 | ||
798 | Each of the signal-sending functions takes two optional arguments: | |
799 | @var{process-name} and @var{current-group}. | |
800 | ||
801 | The argument @var{process-name} must be either a process, the name of | |
802 | one, or @code{nil}. If it is @code{nil}, the process defaults to the | |
803 | process associated with the current buffer. An error is signaled if | |
804 | @var{process-name} does not identify a process. | |
805 | ||
806 | The argument @var{current-group} is a flag that makes a difference | |
807 | when you are running a job-control shell as an Emacs subprocess. If it | |
808 | is non-@code{nil}, then the signal is sent to the current process-group | |
78608595 | 809 | of the terminal that Emacs uses to communicate with the subprocess. If |
73804d4b RS |
810 | the process is a job-control shell, this means the shell's current |
811 | subjob. If it is @code{nil}, the signal is sent to the process group of | |
812 | the immediate subprocess of Emacs. If the subprocess is a job-control | |
813 | shell, this is the shell itself. | |
814 | ||
815 | The flag @var{current-group} has no effect when a pipe is used to | |
816 | communicate with the subprocess, because the operating system does not | |
817 | support the distinction in the case of pipes. For the same reason, | |
818 | job-control shells won't work when a pipe is used. See | |
819 | @code{process-connection-type} in @ref{Asynchronous Processes}. | |
820 | ||
821 | @defun interrupt-process &optional process-name current-group | |
822 | This function interrupts the process @var{process-name} by sending the | |
823 | signal @code{SIGINT}. Outside of Emacs, typing the ``interrupt | |
824 | character'' (normally @kbd{C-c} on some systems, and @code{DEL} on | |
825 | others) sends this signal. When the argument @var{current-group} is | |
826 | non-@code{nil}, you can think of this function as ``typing @kbd{C-c}'' | |
827 | on the terminal by which Emacs talks to the subprocess. | |
828 | @end defun | |
829 | ||
830 | @defun kill-process &optional process-name current-group | |
831 | This function kills the process @var{process-name} by sending the | |
832 | signal @code{SIGKILL}. This signal kills the subprocess immediately, | |
833 | and cannot be handled by the subprocess. | |
834 | @end defun | |
835 | ||
836 | @defun quit-process &optional process-name current-group | |
837 | This function sends the signal @code{SIGQUIT} to the process | |
838 | @var{process-name}. This signal is the one sent by the ``quit | |
839 | character'' (usually @kbd{C-b} or @kbd{C-\}) when you are not inside | |
840 | Emacs. | |
841 | @end defun | |
842 | ||
843 | @defun stop-process &optional process-name current-group | |
844 | This function stops the process @var{process-name} by sending the | |
845 | signal @code{SIGTSTP}. Use @code{continue-process} to resume its | |
846 | execution. | |
847 | ||
969fe9b5 | 848 | Outside of Emacs, on systems with job control, the ``stop character'' |
f9f59935 RS |
849 | (usually @kbd{C-z}) normally sends this signal. When |
850 | @var{current-group} is non-@code{nil}, you can think of this function as | |
851 | ``typing @kbd{C-z}'' on the terminal Emacs uses to communicate with the | |
852 | subprocess. | |
73804d4b RS |
853 | @end defun |
854 | ||
855 | @defun continue-process &optional process-name current-group | |
856 | This function resumes execution of the process @var{process} by sending | |
857 | it the signal @code{SIGCONT}. This presumes that @var{process-name} was | |
858 | stopped previously. | |
859 | @end defun | |
860 | ||
861 | @c Emacs 19 feature | |
862 | @defun signal-process pid signal | |
863 | This function sends a signal to process @var{pid}, which need not be | |
864 | a child of Emacs. The argument @var{signal} specifies which signal | |
865 | to send; it should be an integer. | |
866 | @end defun | |
867 | ||
868 | @node Output from Processes | |
869 | @section Receiving Output from Processes | |
870 | @cindex process output | |
871 | @cindex output from processes | |
872 | ||
873 | There are two ways to receive the output that a subprocess writes to | |
874 | its standard output stream. The output can be inserted in a buffer, | |
875 | which is called the associated buffer of the process, or a function | |
78608595 RS |
876 | called the @dfn{filter function} can be called to act on the output. If |
877 | the process has no buffer and no filter function, its output is | |
878 | discarded. | |
177c0ea7 | 879 | |
edc590bb RS |
880 | When a subprocess terminates, Emacs reads any pending output, |
881 | then stops reading output from that subprocess. Therefore, if the | |
882 | subprocess has children that are still live and still producing | |
883 | output, Emacs won't receive that output. | |
884 | ||
a9f0a989 RS |
885 | Output from a subprocess can arrive only while Emacs is waiting: when |
886 | reading terminal input, in @code{sit-for} and @code{sleep-for} | |
887 | (@pxref{Waiting}), and in @code{accept-process-output} (@pxref{Accepting | |
888 | Output}). This minimizes the problem of timing errors that usually | |
889 | plague parallel programming. For example, you can safely create a | |
890 | process and only then specify its buffer or filter function; no output | |
891 | can arrive before you finish, if the code in between does not call any | |
892 | primitive that waits. | |
893 | ||
8f3efb4e RS |
894 | It is impossible to separate the standard output and standard error |
895 | streams of the subprocess, because Emacs normally spawns the subprocess | |
896 | inside a pseudo-TTY, and a pseudo-TTY has only one output channel. If | |
897 | you want to keep the output to those streams separate, you should | |
898 | redirect one of them to a file--for example, by using an appropriate | |
899 | shell command. | |
900 | ||
73804d4b | 901 | @menu |
582ef186 RS |
902 | * Process Buffers:: If no filter, output is put in a buffer. |
903 | * Filter Functions:: Filter functions accept output from the process. | |
591a3500 | 904 | * Decoding Output:: Filters can get unibyte or multibyte strings. |
582ef186 | 905 | * Accepting Output:: How to wait until process output arrives. |
73804d4b RS |
906 | @end menu |
907 | ||
908 | @node Process Buffers | |
909 | @subsection Process Buffers | |
910 | ||
911 | A process can (and usually does) have an @dfn{associated buffer}, | |
912 | which is an ordinary Emacs buffer that is used for two purposes: storing | |
913 | the output from the process, and deciding when to kill the process. You | |
914 | can also use the buffer to identify a process to operate on, since in | |
915 | normal practice only one process is associated with any given buffer. | |
916 | Many applications of processes also use the buffer for editing input to | |
917 | be sent to the process, but this is not built into Emacs Lisp. | |
918 | ||
919 | Unless the process has a filter function (@pxref{Filter Functions}), | |
920 | its output is inserted in the associated buffer. The position to insert | |
78608595 RS |
921 | the output is determined by the @code{process-mark}, which is then |
922 | updated to point to the end of the text just inserted. Usually, but not | |
923 | always, the @code{process-mark} is at the end of the buffer. | |
73804d4b RS |
924 | |
925 | @defun process-buffer process | |
926 | This function returns the associated buffer of the process | |
927 | @var{process}. | |
928 | ||
929 | @smallexample | |
930 | @group | |
931 | (process-buffer (get-process "shell")) | |
932 | @result{} #<buffer *shell*> | |
933 | @end group | |
934 | @end smallexample | |
935 | @end defun | |
936 | ||
937 | @defun process-mark process | |
938 | This function returns the process marker for @var{process}, which is the | |
939 | marker that says where to insert output from the process. | |
940 | ||
941 | If @var{process} does not have a buffer, @code{process-mark} returns a | |
942 | marker that points nowhere. | |
943 | ||
944 | Insertion of process output in a buffer uses this marker to decide where | |
945 | to insert, and updates it to point after the inserted text. That is why | |
946 | successive batches of output are inserted consecutively. | |
947 | ||
948 | Filter functions normally should use this marker in the same fashion | |
949 | as is done by direct insertion of output in the buffer. A good | |
950 | example of a filter function that uses @code{process-mark} is found at | |
951 | the end of the following section. | |
952 | ||
953 | When the user is expected to enter input in the process buffer for | |
f9f59935 RS |
954 | transmission to the process, the process marker separates the new input |
955 | from previous output. | |
73804d4b RS |
956 | @end defun |
957 | ||
958 | @defun set-process-buffer process buffer | |
959 | This function sets the buffer associated with @var{process} to | |
960 | @var{buffer}. If @var{buffer} is @code{nil}, the process becomes | |
961 | associated with no buffer. | |
962 | @end defun | |
963 | ||
964 | @defun get-buffer-process buffer-or-name | |
5517ea8a RS |
965 | This function returns a nondeleted process associated with the buffer |
966 | specified by @var{buffer-or-name}. If there are several processes | |
967 | associated with it, this function chooses one (currently, the one most | |
968 | recently created, but don't count on that). Deletion of a process | |
969 | (see @code{delete-process}) makes it ineligible for this function to | |
970 | return. | |
971 | ||
972 | It is usually a bad idea to have more than one process associated with | |
973 | the same buffer. | |
73804d4b RS |
974 | |
975 | @smallexample | |
976 | @group | |
977 | (get-buffer-process "*shell*") | |
978 | @result{} #<process shell> | |
979 | @end group | |
980 | @end smallexample | |
981 | ||
982 | Killing the process's buffer deletes the process, which kills the | |
983 | subprocess with a @code{SIGHUP} signal (@pxref{Signals to Processes}). | |
984 | @end defun | |
985 | ||
986 | @node Filter Functions | |
987 | @subsection Process Filter Functions | |
988 | @cindex filter function | |
989 | @cindex process filter | |
990 | ||
991 | A process @dfn{filter function} is a function that receives the | |
992 | standard output from the associated process. If a process has a filter, | |
78608595 RS |
993 | then @emph{all} output from that process is passed to the filter. The |
994 | process buffer is used directly for output from the process only when | |
995 | there is no filter. | |
73804d4b | 996 | |
a9f0a989 RS |
997 | The filter function can only be called when Emacs is waiting for |
998 | something, because process output arrives only at such times. Emacs | |
999 | waits when reading terminal input, in @code{sit-for} and | |
1000 | @code{sleep-for} (@pxref{Waiting}), and in @code{accept-process-output} | |
1001 | (@pxref{Accepting Output}). | |
1002 | ||
f9f59935 RS |
1003 | A filter function must accept two arguments: the associated process |
1004 | and a string, which is output just received from it. The function is | |
1005 | then free to do whatever it chooses with the output. | |
73804d4b | 1006 | |
73804d4b RS |
1007 | Quitting is normally inhibited within a filter function---otherwise, |
1008 | the effect of typing @kbd{C-g} at command level or to quit a user | |
1009 | command would be unpredictable. If you want to permit quitting inside a | |
1010 | filter function, bind @code{inhibit-quit} to @code{nil}. | |
1011 | @xref{Quitting}. | |
1012 | ||
22697dac KH |
1013 | If an error happens during execution of a filter function, it is |
1014 | caught automatically, so that it doesn't stop the execution of whatever | |
eaac2be1 | 1015 | program was running when the filter function was started. However, if |
22697dac KH |
1016 | @code{debug-on-error} is non-@code{nil}, the error-catching is turned |
1017 | off. This makes it possible to use the Lisp debugger to debug the | |
1018 | filter function. @xref{Debugger}. | |
1019 | ||
73804d4b RS |
1020 | Many filter functions sometimes or always insert the text in the |
1021 | process's buffer, mimicking the actions of Emacs when there is no | |
1022 | filter. Such filter functions need to use @code{set-buffer} in order to | |
1023 | be sure to insert in that buffer. To avoid setting the current buffer | |
f9f59935 RS |
1024 | semipermanently, these filter functions must save and restore the |
1025 | current buffer. They should also update the process marker, and in some | |
1026 | cases update the value of point. Here is how to do these things: | |
73804d4b RS |
1027 | |
1028 | @smallexample | |
1029 | @group | |
1030 | (defun ordinary-insertion-filter (proc string) | |
f9f59935 RS |
1031 | (with-current-buffer (process-buffer proc) |
1032 | (let ((moving (= (point) (process-mark proc)))) | |
73804d4b RS |
1033 | @end group |
1034 | @group | |
f9f59935 RS |
1035 | (save-excursion |
1036 | ;; @r{Insert the text, advancing the process marker.} | |
1037 | (goto-char (process-mark proc)) | |
1038 | (insert string) | |
1039 | (set-marker (process-mark proc) (point))) | |
1040 | (if moving (goto-char (process-mark proc)))))) | |
73804d4b RS |
1041 | @end group |
1042 | @end smallexample | |
1043 | ||
1044 | @noindent | |
f9f59935 RS |
1045 | The reason to use @code{with-current-buffer}, rather than using |
1046 | @code{save-excursion} to save and restore the current buffer, is so as | |
1047 | to preserve the change in point made by the second call to | |
1048 | @code{goto-char}. | |
73804d4b RS |
1049 | |
1050 | To make the filter force the process buffer to be visible whenever new | |
1051 | text arrives, insert the following line just before the | |
f9f59935 | 1052 | @code{with-current-buffer} construct: |
73804d4b RS |
1053 | |
1054 | @smallexample | |
1055 | (display-buffer (process-buffer proc)) | |
1056 | @end smallexample | |
1057 | ||
f9f59935 RS |
1058 | To force point to the end of the new output, no matter where it was |
1059 | previously, eliminate the variable @code{moving} and call | |
73804d4b RS |
1060 | @code{goto-char} unconditionally. |
1061 | ||
f9f59935 RS |
1062 | In earlier Emacs versions, every filter function that did regular |
1063 | expression searching or matching had to explicitly save and restore the | |
1064 | match data. Now Emacs does this automatically for filter functions; | |
1065 | they never need to do it explicitly. @xref{Match Data}. | |
73804d4b RS |
1066 | |
1067 | A filter function that writes the output into the buffer of the | |
bfe721d1 | 1068 | process should check whether the buffer is still alive. If it tries to |
f9f59935 RS |
1069 | insert into a dead buffer, it will get an error. The expression |
1070 | @code{(buffer-name (process-buffer @var{process}))} returns @code{nil} | |
1071 | if the buffer is dead. | |
73804d4b RS |
1072 | |
1073 | The output to the function may come in chunks of any size. A program | |
f9f59935 RS |
1074 | that produces the same output twice in a row may send it as one batch of |
1075 | 200 characters one time, and five batches of 40 characters the next. If | |
1076 | the filter looks for certain text strings in the subprocess output, make | |
1077 | sure to handle the case where one of these strings is split across two | |
1078 | or more batches of output. | |
73804d4b RS |
1079 | |
1080 | @defun set-process-filter process filter | |
1081 | This function gives @var{process} the filter function @var{filter}. If | |
1082 | @var{filter} is @code{nil}, it gives the process no filter. | |
1083 | @end defun | |
1084 | ||
1085 | @defun process-filter process | |
1086 | This function returns the filter function of @var{process}, or @code{nil} | |
1087 | if it has none. | |
1088 | @end defun | |
1089 | ||
1090 | Here is an example of use of a filter function: | |
1091 | ||
1092 | @smallexample | |
1093 | @group | |
1094 | (defun keep-output (process output) | |
1095 | (setq kept (cons output kept))) | |
1096 | @result{} keep-output | |
1097 | @end group | |
1098 | @group | |
1099 | (setq kept nil) | |
1100 | @result{} nil | |
1101 | @end group | |
1102 | @group | |
1103 | (set-process-filter (get-process "shell") 'keep-output) | |
1104 | @result{} keep-output | |
1105 | @end group | |
1106 | @group | |
1107 | (process-send-string "shell" "ls ~/other\n") | |
1108 | @result{} nil | |
1109 | kept | |
1110 | @result{} ("lewis@@slug[8] % " | |
1111 | @end group | |
1112 | @group | |
1113 | "FINAL-W87-SHORT.MSS backup.otl kolstad.mss~ | |
1114 | address.txt backup.psf kolstad.psf | |
1115 | backup.bib~ david.mss resume-Dec-86.mss~ | |
1116 | backup.err david.psf resume-Dec.psf | |
1117 | backup.mss dland syllabus.mss | |
1118 | " | |
1119 | "#backups.mss# backup.mss~ kolstad.mss | |
1120 | ") | |
1121 | @end group | |
1122 | @end smallexample | |
1123 | ||
1124 | @ignore @c The code in this example doesn't show the right way to do things. | |
1125 | Here is another, more realistic example, which demonstrates how to use | |
1126 | the process mark to do insertion in the same fashion as is done when | |
1127 | there is no filter function: | |
1128 | ||
1129 | @smallexample | |
1130 | @group | |
1131 | ;; @r{Insert input in the buffer specified by @code{my-shell-buffer}} | |
1132 | ;; @r{and make sure that buffer is shown in some window.} | |
1133 | (defun my-process-filter (proc str) | |
f9f59935 RS |
1134 | (let ((cur (selected-window)) |
1135 | (pop-up-windows t)) | |
1136 | (pop-to-buffer my-shell-buffer) | |
73804d4b RS |
1137 | @end group |
1138 | @group | |
f9f59935 RS |
1139 | (goto-char (point-max)) |
1140 | (insert str) | |
1141 | (set-marker (process-mark proc) (point-max)) | |
1142 | (select-window cur))) | |
73804d4b RS |
1143 | @end group |
1144 | @end smallexample | |
1145 | @end ignore | |
1146 | ||
582ef186 RS |
1147 | @node Decoding Output |
1148 | @subsection Decoding Process Output | |
1149 | ||
1150 | When Emacs writes process output directly into a multibyte buffer, | |
1151 | it decodes the output according to the process output coding system. | |
1152 | If the coding system is @code{raw-text} or @code{no-conversion}, Emacs | |
1153 | converts the unibyte output to multibyte using | |
1154 | @code{string-to-multibyte}, inserts the resulting multibyte text. | |
1155 | ||
1156 | You can use @code{set-process-coding-system} to specify which coding | |
1157 | system to use (@pxref{Process Information}). Otherwise, the coding | |
1158 | system comes from @code{coding-system-for-read}, if that is | |
1159 | non-@code{nil}; or else from the defaulting mechanism (@pxref{Default | |
1160 | Coding Systems}). | |
1161 | ||
1162 | @strong{Warning:} Coding systems such as @code{undecided} which | |
1163 | determine the coding system from the data do not work entirely | |
1164 | reliably with asynchronous subprocess output. This is because Emacs | |
1165 | has to process asynchronous subprocess output in batches, as it | |
1166 | arrives. Emacs must try to detect the proper coding system from one | |
1167 | batch at a time, and this does not always work. Therefore, if at all | |
1168 | possible, specify a coding system that determines both the character | |
1169 | code conversion and the end of line conversion---that is, one like | |
1170 | @code{latin-1-unix}, rather than @code{undecided} or @code{latin-1}. | |
1171 | ||
1172 | @cindex filter multibyte flag, of process | |
1173 | @cindex process filter multibyte flag | |
1174 | When Emacs calls a process filter function, it provides the process | |
1175 | output as a multibyte string or as a unibyte string according to the | |
1176 | process's filter multibyte flag. If the flag is non-@code{nil}, Emacs | |
1177 | decodes the output according to the process output coding system to | |
1178 | produce a multibyte string, and passes that to the process. If the | |
1179 | flag is @code{nil}, Emacs puts the output into a unibyte string, with | |
1180 | no decoding, and passes that. | |
1181 | ||
1182 | When you create a process, the filter multibyte flag takes its | |
1183 | initial value from @code{default-enable-multibyte-characters}. If you | |
1184 | want to change the flag later on, use | |
1185 | @code{set-process-filter-multibyte}. | |
1186 | ||
1187 | @defun set-process-filter-multibyte process multibyte | |
1188 | This function sets the filter multibyte flag of @var{process} | |
1189 | to @var{multibyte}. | |
1190 | @end defun | |
1191 | ||
1192 | @defun process-filter-multibyte-p process | |
1193 | This function returns the filter multibyte flag of @var{process}. | |
1194 | @end defun | |
1195 | ||
73804d4b RS |
1196 | @node Accepting Output |
1197 | @subsection Accepting Output from Processes | |
1198 | ||
1199 | Output from asynchronous subprocesses normally arrives only while | |
1200 | Emacs is waiting for some sort of external event, such as elapsed time | |
1201 | or terminal input. Occasionally it is useful in a Lisp program to | |
1202 | explicitly permit output to arrive at a specific point, or even to wait | |
1203 | until output arrives from a process. | |
1204 | ||
1205 | @defun accept-process-output &optional process seconds millisec | |
1206 | This function allows Emacs to read pending output from processes. The | |
1207 | output is inserted in the associated buffers or given to their filter | |
1208 | functions. If @var{process} is non-@code{nil} then this function does | |
1209 | not return until some output has been received from @var{process}. | |
1210 | ||
1211 | @c Emacs 19 feature | |
1212 | The arguments @var{seconds} and @var{millisec} let you specify timeout | |
1213 | periods. The former specifies a period measured in seconds and the | |
1214 | latter specifies one measured in milliseconds. The two time periods | |
1215 | thus specified are added together, and @code{accept-process-output} | |
1216 | returns after that much time whether or not there has been any | |
1217 | subprocess output. | |
1218 | ||
bfe721d1 KH |
1219 | The argument @var{seconds} need not be an integer. If it is a floating |
1220 | point number, this function waits for a fractional number of seconds. | |
1221 | Some systems support only a whole number of seconds; on these systems, | |
1911e6e5 | 1222 | @var{seconds} is rounded down. |
bfe721d1 | 1223 | |
73804d4b RS |
1224 | Not all operating systems support waiting periods other than multiples |
1225 | of a second; on those that do not, you get an error if you specify | |
1226 | nonzero @var{millisec}. | |
1227 | ||
1228 | The function @code{accept-process-output} returns non-@code{nil} if it | |
1229 | did get some output, or @code{nil} if the timeout expired before output | |
1230 | arrived. | |
1231 | @end defun | |
1232 | ||
1233 | @node Sentinels | |
1234 | @section Sentinels: Detecting Process Status Changes | |
1235 | @cindex process sentinel | |
1236 | @cindex sentinel | |
1237 | ||
1238 | A @dfn{process sentinel} is a function that is called whenever the | |
1239 | associated process changes status for any reason, including signals | |
1240 | (whether sent by Emacs or caused by the process's own actions) that | |
5517ea8a RS |
1241 | terminate, stop, or continue the process. The process sentinel is |
1242 | also called if the process exits. The sentinel receives two | |
1243 | arguments: the process for which the event occurred, and a string | |
1244 | describing the type of event. | |
73804d4b RS |
1245 | |
1246 | The string describing the event looks like one of the following: | |
1247 | ||
1248 | @itemize @bullet | |
177c0ea7 | 1249 | @item |
73804d4b RS |
1250 | @code{"finished\n"}. |
1251 | ||
1252 | @item | |
1253 | @code{"exited abnormally with code @var{exitcode}\n"}. | |
1254 | ||
1255 | @item | |
1256 | @code{"@var{name-of-signal}\n"}. | |
1257 | ||
1258 | @item | |
1259 | @code{"@var{name-of-signal} (core dumped)\n"}. | |
1260 | @end itemize | |
1261 | ||
5517ea8a RS |
1262 | A sentinel runs only while Emacs is waiting (e.g., for terminal |
1263 | input, or for time to elapse, or for process output). This avoids the | |
1264 | timing errors that could result from running them at random places in | |
1265 | the middle of other Lisp programs. A program can wait, so that | |
1266 | sentinels will run, by calling @code{sit-for} or @code{sleep-for} | |
78608595 | 1267 | (@pxref{Waiting}), or @code{accept-process-output} (@pxref{Accepting |
a9f0a989 | 1268 | Output}). Emacs also allows sentinels to run when the command loop is |
5517ea8a RS |
1269 | reading input. @code{delete-process} calls the sentinel when it |
1270 | terminates a running process. | |
1271 | ||
1272 | Emacs does not keep a queue of multiple reasons to call the sentinel | |
1273 | of one process; it records just the current status and the fact that | |
1274 | there has been a change. Therefore two changes in status, coming in | |
1275 | quick succession, can call the sentinel just once. However, process | |
1276 | termination will always run the sentinel exactly once. This is | |
1277 | because the process status can't change again after termination. | |
73804d4b RS |
1278 | |
1279 | Quitting is normally inhibited within a sentinel---otherwise, the | |
1280 | effect of typing @kbd{C-g} at command level or to quit a user command | |
1281 | would be unpredictable. If you want to permit quitting inside a | |
1282 | sentinel, bind @code{inhibit-quit} to @code{nil}. @xref{Quitting}. | |
1283 | ||
1284 | A sentinel that writes the output into the buffer of the process | |
bfe721d1 | 1285 | should check whether the buffer is still alive. If it tries to insert |
73804d4b RS |
1286 | into a dead buffer, it will get an error. If the buffer is dead, |
1287 | @code{(buffer-name (process-buffer @var{process}))} returns @code{nil}. | |
1288 | ||
22697dac KH |
1289 | If an error happens during execution of a sentinel, it is caught |
1290 | automatically, so that it doesn't stop the execution of whatever | |
1291 | programs was running when the sentinel was started. However, if | |
1292 | @code{debug-on-error} is non-@code{nil}, the error-catching is turned | |
1293 | off. This makes it possible to use the Lisp debugger to debug the | |
1294 | sentinel. @xref{Debugger}. | |
1295 | ||
8a56d8ed RS |
1296 | While a sentinel is running, the process sentinel is temporarily |
1297 | set to @code{nil} so that the sentinel won't run recursively. | |
1298 | For this reason it is not possible for a sentinel to specify | |
1299 | a new sentinel. | |
1300 | ||
f9f59935 RS |
1301 | In earlier Emacs versions, every sentinel that did regular expression |
1302 | searching or matching had to explicitly save and restore the match data. | |
1303 | Now Emacs does this automatically for sentinels; they never need to do | |
1304 | it explicitly. @xref{Match Data}. | |
bfe721d1 | 1305 | |
73804d4b RS |
1306 | @defun set-process-sentinel process sentinel |
1307 | This function associates @var{sentinel} with @var{process}. If | |
1308 | @var{sentinel} is @code{nil}, then the process will have no sentinel. | |
1309 | The default behavior when there is no sentinel is to insert a message in | |
1310 | the process's buffer when the process status changes. | |
1311 | ||
5517ea8a RS |
1312 | Changes in process sentinel take effect immediately---if the sentinel |
1313 | is slated to be run but has not been called yet, and you specify a new | |
1314 | sentinel, the eventual call to the sentinel will use the new one. | |
1315 | ||
73804d4b RS |
1316 | @smallexample |
1317 | @group | |
1318 | (defun msg-me (process event) | |
1319 | (princ | |
1320 | (format "Process: %s had the event `%s'" process event))) | |
1321 | (set-process-sentinel (get-process "shell") 'msg-me) | |
1322 | @result{} msg-me | |
1323 | @end group | |
1324 | @group | |
1325 | (kill-process (get-process "shell")) | |
1326 | @print{} Process: #<process shell> had the event `killed' | |
1327 | @result{} #<process shell> | |
1328 | @end group | |
1329 | @end smallexample | |
1330 | @end defun | |
1331 | ||
1332 | @defun process-sentinel process | |
1333 | This function returns the sentinel of @var{process}, or @code{nil} if it | |
1334 | has none. | |
1335 | @end defun | |
1336 | ||
1337 | @defun waiting-for-user-input-p | |
1338 | While a sentinel or filter function is running, this function returns | |
1339 | non-@code{nil} if Emacs was waiting for keyboard input from the user at | |
1340 | the time the sentinel or filter function was called, @code{nil} if it | |
1341 | was not. | |
1342 | @end defun | |
1343 | ||
edc590bb | 1344 | @node Query Before Exit |
177c0ea7 | 1345 | @section Querying Before Exit |
edc590bb RS |
1346 | |
1347 | When Emacs exits, it terminates all its subprocesses by sending them | |
1348 | the @code{SIGHUP} signal. Because some subprocesses are doing | |
1349 | valuable work, Emacs normally asks the user to confirm that it is ok | |
1350 | to terminate them. Each process has a query flag which, if | |
1351 | non-@code{nil}, says that Emacs should ask for confirmation before | |
1352 | exiting and thus killing that process. The default for the query flag | |
1353 | is @code{t}, meaning @emph{do} query. | |
1354 | ||
1355 | @tindex process-query-on-exit-flag | |
1356 | @defun process-query-on-exit-flag process | |
1357 | This returns the query flag of @var{process}. | |
1358 | @end defun | |
1359 | ||
1360 | @tindex set-process-query-on-exit-flag | |
1361 | @defun set-process-query-on-exit-flag process flag | |
1362 | This function sets the query flag of @var{process} to @var{flag}. It | |
1363 | returns @var{flag}. | |
1364 | ||
1365 | @smallexample | |
1366 | @group | |
1367 | ;; @r{Don't query about the shell process} | |
1368 | (set-process-query-on-exit-flag (get-process "shell") nil) | |
1369 | @result{} t | |
1370 | @end group | |
1371 | @end smallexample | |
1372 | @end defun | |
1373 | ||
1374 | @defun process-kill-without-query process &optional do-query | |
1375 | This function clears the query flag of @var{process}, so that | |
1376 | Emacs will not query the user on account of that process. | |
1377 | ||
1378 | Actually, the function does more than that: it returns the old value of | |
1379 | the process's query flag, and sets the query flag to @var{do-query}. | |
1380 | Please don't use this function to do those things any more---please | |
1381 | use the newer, cleaner functions @code{process-query-on-exit-flag} and | |
1382 | @code{set-process-query-on-exit-flag} in all but the simplest cases. | |
1383 | The only way you should use @code{process-kill-without-query} nowadays | |
1384 | is like this: | |
1385 | ||
1386 | @smallexample | |
1387 | @group | |
1388 | ;; @r{Don't query about the shell process} | |
1389 | (process-kill-without-query (get-process "shell")) | |
1390 | @end group | |
1391 | @end smallexample | |
1392 | @end defun | |
1393 | ||
73804d4b RS |
1394 | @node Transaction Queues |
1395 | @section Transaction Queues | |
1396 | @cindex transaction queue | |
1397 | ||
f9f59935 RS |
1398 | You can use a @dfn{transaction queue} to communicate with a subprocess |
1399 | using transactions. First use @code{tq-create} to create a transaction | |
1400 | queue communicating with a specified process. Then you can call | |
1401 | @code{tq-enqueue} to send a transaction. | |
73804d4b RS |
1402 | |
1403 | @defun tq-create process | |
1404 | This function creates and returns a transaction queue communicating with | |
1405 | @var{process}. The argument @var{process} should be a subprocess | |
1406 | capable of sending and receiving streams of bytes. It may be a child | |
78608595 | 1407 | process, or it may be a TCP connection to a server, possibly on another |
73804d4b RS |
1408 | machine. |
1409 | @end defun | |
1410 | ||
1411 | @defun tq-enqueue queue question regexp closure fn | |
1412 | This function sends a transaction to queue @var{queue}. Specifying the | |
1413 | queue has the effect of specifying the subprocess to talk to. | |
1414 | ||
78608595 | 1415 | The argument @var{question} is the outgoing message that starts the |
73804d4b RS |
1416 | transaction. The argument @var{fn} is the function to call when the |
1417 | corresponding answer comes back; it is called with two arguments: | |
1418 | @var{closure}, and the answer received. | |
1419 | ||
6f6fd5ef RS |
1420 | The argument @var{regexp} is a regular expression that should match |
1421 | text at the end of the entire answer, but nothing before; that's how | |
1422 | @code{tq-enqueue} determines where the answer ends. | |
73804d4b RS |
1423 | |
1424 | The return value of @code{tq-enqueue} itself is not meaningful. | |
1425 | @end defun | |
1426 | ||
1427 | @defun tq-close queue | |
1428 | Shut down transaction queue @var{queue}, waiting for all pending transactions | |
1429 | to complete, and then terminate the connection or child process. | |
1430 | @end defun | |
1431 | ||
1432 | Transaction queues are implemented by means of a filter function. | |
1433 | @xref{Filter Functions}. | |
1434 | ||
bfe721d1 KH |
1435 | @node Network |
1436 | @section Network Connections | |
1437 | @cindex network connection | |
73804d4b RS |
1438 | @cindex TCP |
1439 | ||
bfe721d1 KH |
1440 | Emacs Lisp programs can open TCP network connections to other processes on |
1441 | the same machine or other machines. A network connection is handled by Lisp | |
73804d4b RS |
1442 | much like a subprocess, and is represented by a process object. |
1443 | However, the process you are communicating with is not a child of the | |
1444 | Emacs process, so you can't kill it or send it signals. All you can do | |
1445 | is send and receive data. @code{delete-process} closes the connection, | |
1446 | but does not kill the process at the other end; that process must decide | |
1447 | what to do about closure of the connection. | |
1448 | ||
1449 | You can distinguish process objects representing network connections | |
1450 | from those representing subprocesses with the @code{process-status} | |
bfe721d1 KH |
1451 | function. It always returns either @code{open} or @code{closed} for a |
1452 | network connection, and it never returns either of those values for a | |
1453 | real subprocess. @xref{Process Information}. | |
73804d4b RS |
1454 | |
1455 | @defun open-network-stream name buffer-or-name host service | |
1456 | This function opens a TCP connection for a service to a host. It | |
1457 | returns a process object to represent the connection. | |
1458 | ||
1459 | The @var{name} argument specifies the name for the process object. It | |
1460 | is modified as necessary to make it unique. | |
1461 | ||
1462 | The @var{buffer-or-name} argument is the buffer to associate with the | |
1463 | connection. Output from the connection is inserted in the buffer, | |
1464 | unless you specify a filter function to handle the output. If | |
1465 | @var{buffer-or-name} is @code{nil}, it means that the connection is not | |
1466 | associated with any buffer. | |
1467 | ||
1468 | The arguments @var{host} and @var{service} specify where to connect to; | |
1469 | @var{host} is the host name (a string), and @var{service} is the name of | |
1470 | a defined network service (a string) or a port number (an integer). | |
1471 | @end defun | |
ab5796a9 MB |
1472 | |
1473 | @ignore | |
1474 | arch-tag: ba9da253-e65f-4e7f-b727-08fba0a1df7a | |
1475 | @end ignore |