2 @c This is part of the GNU Emacs Lisp Reference Manual.
3 @c Copyright (C) 1990-1995, 1998-1999, 2001-2011
4 @c Free Software Foundation, Inc.
5 @c See the file elisp.texi for copying conditions.
6 @setfilename ../../info/processes
7 @node Processes, Display, Abbrevs, Top
10 @cindex parent process
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}.
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
31 @defun processp object
32 This function returns @code{t} if @var{object} represents an Emacs
33 subprocess, @code{nil} otherwise.
36 In addition to subprocesses of the current Emacs session, you can
37 also access other processes running on your machine. @xref{System
41 * Subprocess Creation:: Functions that start subprocesses.
42 * Shell Arguments:: Quoting an argument to pass it to a shell.
43 * Synchronous Processes:: Details of using synchronous subprocesses.
44 * Asynchronous Processes:: Starting up an asynchronous subprocess.
45 * Deleting Processes:: Eliminating an asynchronous subprocess.
46 * Process Information:: Accessing run-status and other attributes.
47 * Input to Processes:: Sending input to an asynchronous subprocess.
48 * Signals to Processes:: Stopping, continuing or interrupting
49 an asynchronous subprocess.
50 * Output from Processes:: Collecting output from an asynchronous subprocess.
51 * Sentinels:: Sentinels run when process run-status changes.
52 * Query Before Exit:: Whether to query if exiting will kill a process.
53 * System Processes:: Accessing other processes running on your system.
54 * Transaction Queues:: Transaction-based communication with subprocesses.
55 * Network:: Opening network connections.
56 * Network Servers:: Network servers let Emacs accept net connections.
57 * Datagrams:: UDP network connections.
58 * Low-Level Network:: Lower-level but more general function
59 to create connections and servers.
60 * Misc Network:: Additional relevant functions for net connections.
61 * Serial Ports:: Communicating with serial ports.
62 * Byte Packing:: Using bindat to pack and unpack binary data.
65 @node Subprocess Creation
66 @section Functions that Create Subprocesses
68 There are three primitives that create a new subprocess in which to run
69 a program. One of them, @code{start-process}, creates an asynchronous
70 process and returns a process object (@pxref{Asynchronous Processes}).
71 The other two, @code{call-process} and @code{call-process-region},
72 create a synchronous process and do not return a process object
73 (@pxref{Synchronous Processes}).
75 Synchronous and asynchronous processes are explained in the following
76 sections. Since the three functions are all called in a similar
77 fashion, their common arguments are described here.
79 @cindex execute program
80 @cindex @code{PATH} environment variable
81 @cindex @code{HOME} environment variable
82 In all cases, the function's @var{program} argument specifies the
83 program to be run. An error is signaled if the file is not found or
84 cannot be executed. If the file name is relative, the variable
85 @code{exec-path} contains a list of directories to search. Emacs
86 initializes @code{exec-path} when it starts up, based on the value of
87 the environment variable @code{PATH}. The standard file name
88 constructs, @samp{~}, @samp{.}, and @samp{..}, are interpreted as
89 usual in @code{exec-path}, but environment variable substitutions
90 (@samp{$HOME}, etc.) are not recognized; use
91 @code{substitute-in-file-name} to perform them (@pxref{File Name
92 Expansion}). @code{nil} in this list refers to
93 @code{default-directory}.
95 Executing a program can also try adding suffixes to the specified
99 This variable is a list of suffixes (strings) to try adding to the
100 specified program file name. The list should include @code{""} if you
101 want the name to be tried exactly as specified. The default value is
105 @strong{Please note:} The argument @var{program} contains only the
106 name of the program; it may not contain any command-line arguments. You
107 must use @var{args} to provide those.
109 Each of the subprocess-creating functions has a @var{buffer-or-name}
110 argument which specifies where the standard output from the program will
111 go. It should be a buffer or a buffer name; if it is a buffer name,
112 that will create the buffer if it does not already exist. It can also
113 be @code{nil}, which says to discard the output unless a filter function
114 handles it. (@xref{Filter Functions}, and @ref{Read and Print}.)
115 Normally, you should avoid having multiple processes send output to the
116 same buffer because their output would be intermixed randomly.
118 @cindex program arguments
119 All three of the subprocess-creating functions have a @code{&rest}
120 argument, @var{args}. The @var{args} must all be strings, and they are
121 supplied to @var{program} as separate command line arguments. Wildcard
122 characters and other shell constructs have no special meanings in these
123 strings, since the strings are passed directly to the specified program.
125 The subprocess gets its current directory from the value of
126 @code{default-directory} (@pxref{File Name Expansion}).
128 @cindex environment variables, subprocesses
129 The subprocess inherits its environment from Emacs, but you can
130 specify overrides for it with @code{process-environment}. @xref{System
133 @defvar exec-directory
135 The value of this variable is a string, the name of a directory that
136 contains programs that come with GNU Emacs, programs intended for Emacs
137 to invoke. The program @code{movemail} is an example of such a program;
138 Rmail uses it to fetch new mail from an inbox.
142 The value of this variable is a list of directories to search for
143 programs to run in subprocesses. Each element is either the name of a
144 directory (i.e., a string), or @code{nil}, which stands for the default
145 directory (which is the value of @code{default-directory}).
146 @cindex program directories
148 The value of @code{exec-path} is used by @code{call-process} and
149 @code{start-process} when the @var{program} argument is not an absolute
153 @node Shell Arguments
154 @section Shell Arguments
155 @cindex arguments for shell commands
156 @cindex shell command arguments
158 Lisp programs sometimes need to run a shell and give it a command
159 that contains file names that were specified by the user. These
160 programs ought to be able to support any valid file name. But the shell
161 gives special treatment to certain characters, and if these characters
162 occur in the file name, they will confuse the shell. To handle these
163 characters, use the function @code{shell-quote-argument}:
165 @defun shell-quote-argument argument
166 This function returns a string which represents, in shell syntax,
167 an argument whose actual contents are @var{argument}. It should
168 work reliably to concatenate the return value into a shell command
169 and then pass it to a shell for execution.
171 Precisely what this function does depends on your operating system. The
172 function is designed to work with the syntax of your system's standard
173 shell; if you use an unusual shell, you will need to redefine this
177 ;; @r{This example shows the behavior on GNU and Unix systems.}
178 (shell-quote-argument "foo > bar")
179 @result{} "foo\\ \\>\\ bar"
181 ;; @r{This example shows the behavior on MS-DOS and MS-Windows.}
182 (shell-quote-argument "foo > bar")
183 @result{} "\"foo > bar\""
186 Here's an example of using @code{shell-quote-argument} to construct
191 (shell-quote-argument oldfile)
193 (shell-quote-argument newfile))
197 @cindex quoting and unquoting command-line arguments
198 @cindex minibuffer input, and command-line arguments
199 @cindex @code{call-process}, command-line arguments from minibuffer
200 @cindex @code{start-process}, command-line arguments from minibuffer
201 The following two functions are useful for combining a list of
202 individual command-line argument strings into a single string, and
203 taking a string apart into a list of individual command-line
204 arguments. These functions are mainly intended to be used for
205 converting user input in the minibuffer, a Lisp string, into a list of
206 string arguments to be passed to @code{call-process} or
207 @code{start-process}, or for the converting such lists of arguments in
208 a single Lisp string to be presented in the minibuffer or echo area.
210 @defun split-string-and-unquote string &optional separators
211 This function splits @var{string} into substrings at matches for the
212 regular expression @var{separators}, like @code{split-string} does
213 (@pxref{Creating Strings}); in addition, it removes quoting from the
214 substrings. It then makes a list of the substrings and returns it.
216 If @var{separators} is omitted or @code{nil}, it defaults to
217 @code{"\\s-+"}, which is a regular expression that matches one or more
218 characters with whitespace syntax (@pxref{Syntax Class Table}).
220 This function supports two types of quoting: enclosing a whole string
221 in double quotes @code{"@dots{}"}, and quoting individual characters
222 with a backslash escape @samp{\}. The latter is also used in Lisp
223 strings, so this function can handle those as well.
226 @defun combine-and-quote-strings list-of-strings &optional separator
227 This function concatenates @var{list-of-strings} into a single string,
228 quoting each string as necessary. It also sticks the @var{separator}
229 string between each pair of strings; if @var{separator} is omitted or
230 @code{nil}, it defaults to @code{" "}. The return value is the
233 The strings in @var{list-of-strings} that need quoting are those that
234 include @var{separator} as their substring. Quoting a string encloses
235 it in double quotes @code{"@dots{}"}. In the simplest case, if you
236 are consing a command from the individual command-line arguments,
237 every argument that includes embedded blanks will be quoted.
240 @node Synchronous Processes
241 @section Creating a Synchronous Process
242 @cindex synchronous subprocess
244 After a @dfn{synchronous process} is created, Emacs waits for the
245 process to terminate before continuing. Starting Dired on GNU or
246 Unix@footnote{On other systems, Emacs uses a Lisp emulation of
247 @code{ls}; see @ref{Contents of Directories}.} is an example of this: it
248 runs @code{ls} in a synchronous process, then modifies the output
249 slightly. Because the process is synchronous, the entire directory
250 listing arrives in the buffer before Emacs tries to do anything with it.
252 While Emacs waits for the synchronous subprocess to terminate, the
253 user can quit by typing @kbd{C-g}. The first @kbd{C-g} tries to kill
254 the subprocess with a @code{SIGINT} signal; but it waits until the
255 subprocess actually terminates before quitting. If during that time the
256 user types another @kbd{C-g}, that kills the subprocess instantly with
257 @code{SIGKILL} and quits immediately (except on MS-DOS, where killing
258 other processes doesn't work). @xref{Quitting}.
260 The synchronous subprocess functions return an indication of how the
263 The output from a synchronous subprocess is generally decoded using a
264 coding system, much like text read from a file. The input sent to a
265 subprocess by @code{call-process-region} is encoded using a coding
266 system, much like text written into a file. @xref{Coding Systems}.
268 @defun call-process program &optional infile destination display &rest args
269 This function calls @var{program} in a separate process and waits for
272 The standard input for the process comes from file @var{infile} if
273 @var{infile} is not @code{nil}, and from the null device otherwise.
274 The argument @var{destination} says where to put the process output.
275 Here are the possibilities:
279 Insert the output in that buffer, before point. This includes both the
280 standard output stream and the standard error stream of the process.
283 Insert the output in a buffer with that name, before point.
286 Insert the output in the current buffer, before point.
292 Discard the output, and return @code{nil} immediately without waiting
293 for the subprocess to finish.
295 In this case, the process is not truly synchronous, since it can run in
296 parallel with Emacs; but you can think of it as synchronous in that
297 Emacs is essentially finished with the subprocess as soon as this
300 MS-DOS doesn't support asynchronous subprocesses, so this option doesn't
303 @item @code{(@var{real-destination} @var{error-destination})}
304 Keep the standard output stream separate from the standard error stream;
305 deal with the ordinary output as specified by @var{real-destination},
306 and dispose of the error output according to @var{error-destination}.
307 If @var{error-destination} is @code{nil}, that means to discard the
308 error output, @code{t} means mix it with the ordinary output, and a
309 string specifies a file name to redirect error output into.
311 You can't directly specify a buffer to put the error output in; that is
312 too difficult to implement. But you can achieve this result by sending
313 the error output to a temporary file and then inserting the file into a
317 If @var{display} is non-@code{nil}, then @code{call-process} redisplays
318 the buffer as output is inserted. (However, if the coding system chosen
319 for decoding output is @code{undecided}, meaning deduce the encoding
320 from the actual data, then redisplay sometimes cannot continue once
321 non-@acronym{ASCII} characters are encountered. There are fundamental
322 reasons why it is hard to fix this; see @ref{Output from Processes}.)
324 Otherwise the function @code{call-process} does no redisplay, and the
325 results become visible on the screen only when Emacs redisplays that
326 buffer in the normal course of events.
328 The remaining arguments, @var{args}, are strings that specify command
329 line arguments for the program.
331 The value returned by @code{call-process} (unless you told it not to
332 wait) indicates the reason for process termination. A number gives the
333 exit status of the subprocess; 0 means success, and any other value
334 means failure. If the process terminated with a signal,
335 @code{call-process} returns a string describing the signal.
337 In the examples below, the buffer @samp{foo} is current.
341 (call-process "pwd" nil t)
344 ---------- Buffer: foo ----------
345 /usr/user/lewis/manual
346 ---------- Buffer: foo ----------
350 (call-process "grep" nil "bar" nil "lewis" "/etc/passwd")
353 ---------- Buffer: bar ----------
354 lewis:5LTsHm66CSWKg:398:21:Bil Lewis:/user/lewis:/bin/csh
356 ---------- Buffer: bar ----------
360 Here is a good example of the use of @code{call-process}, which used to
361 be found in the definition of @code{insert-directory}:
365 (call-process insert-directory-program nil t nil @var{switches}
367 (concat (file-name-as-directory file) ".")
373 @defun process-file program &optional infile buffer display &rest args
374 This function processes files synchronously in a separate process. It
375 is similar to @code{call-process} but may invoke a file handler based
376 on the value of the variable @code{default-directory}. The current
377 working directory of the subprocess is @code{default-directory}.
379 The arguments are handled in almost the same way as for
380 @code{call-process}, with the following differences:
382 Some file handlers may not support all combinations and forms of the
383 arguments @var{infile}, @var{buffer}, and @var{display}. For example,
384 some file handlers might behave as if @var{display} were @code{nil},
385 regardless of the value actually passed. As another example, some
386 file handlers might not support separating standard output and error
387 output by way of the @var{buffer} argument.
389 If a file handler is invoked, it determines the program to run based
390 on the first argument @var{program}. For instance, consider that a
391 handler for remote files is invoked. Then the path that is used for
392 searching the program might be different than @code{exec-path}.
394 The second argument @var{infile} may invoke a file handler. The file
395 handler could be different from the handler chosen for the
396 @code{process-file} function itself. (For example,
397 @code{default-directory} could be on a remote host, whereas
398 @var{infile} is on another remote host. Or @code{default-directory}
399 could be non-special, whereas @var{infile} is on a remote host.)
401 If @var{buffer} is a list of the form @code{(@var{real-destination}
402 @var{error-destination})}, and @var{error-destination} names a file,
403 then the same remarks as for @var{infile} apply.
405 The remaining arguments (@var{args}) will be passed to the process
406 verbatim. Emacs is not involved in processing file names that are
407 present in @var{args}. To avoid confusion, it may be best to avoid
408 absolute file names in @var{args}, but rather to specify all file
409 names as relative to @code{default-directory}. The function
410 @code{file-relative-name} is useful for constructing such relative
414 @defvar process-file-side-effects
415 This variable indicates, whether a call of @code{process-file} changes
418 Per default, this variable is always set to @code{t}, meaning that a
419 call of @code{process-file} could potentially change any file on a
420 remote host. When set to @code{nil}, a file handler could optimize
421 its behaviour with respect to remote file attributes caching.
423 This variable should never be changed by @code{setq}. Instead of, it
424 shall be set only by let-binding.
427 @defun call-process-region start end program &optional delete destination display &rest args
428 This function sends the text from @var{start} to @var{end} as
429 standard input to a process running @var{program}. It deletes the text
430 sent if @var{delete} is non-@code{nil}; this is useful when
431 @var{destination} is @code{t}, to insert the output in the current
432 buffer in place of the input.
434 The arguments @var{destination} and @var{display} control what to do
435 with the output from the subprocess, and whether to update the display
436 as it comes in. For details, see the description of
437 @code{call-process}, above. If @var{destination} is the integer 0,
438 @code{call-process-region} discards the output and returns @code{nil}
439 immediately, without waiting for the subprocess to finish (this only
440 works if asynchronous subprocesses are supported).
442 The remaining arguments, @var{args}, are strings that specify command
443 line arguments for the program.
445 The return value of @code{call-process-region} is just like that of
446 @code{call-process}: @code{nil} if you told it to return without
447 waiting; otherwise, a number or string which indicates how the
448 subprocess terminated.
450 In the following example, we use @code{call-process-region} to run the
451 @code{cat} utility, with standard input being the first five characters
452 in buffer @samp{foo} (the word @samp{input}). @code{cat} copies its
453 standard input into its standard output. Since the argument
454 @var{destination} is @code{t}, this output is inserted in the current
459 ---------- Buffer: foo ----------
461 ---------- Buffer: foo ----------
465 (call-process-region 1 6 "cat" nil t)
468 ---------- Buffer: foo ----------
470 ---------- Buffer: foo ----------
474 The @code{shell-command-on-region} command uses
475 @code{call-process-region} like this:
481 shell-file-name ; @r{Name of program.}
482 nil ; @r{Do not delete region.}
483 buffer ; @r{Send output to @code{buffer}.}
484 nil ; @r{No redisplay during output.}
485 "-c" command) ; @r{Arguments for the shell.}
490 @defun call-process-shell-command command &optional infile destination display &rest args
491 This function executes the shell command @var{command} synchronously
492 in a separate process. The final arguments @var{args} are additional
493 arguments to add at the end of @var{command}. The other arguments
494 are handled as in @code{call-process}.
497 @defun process-file-shell-command command &optional infile destination display &rest args
498 This function is like @code{call-process-shell-command}, but uses
499 @code{process-file} internally. Depending on @code{default-directory},
500 @var{command} can be executed also on remote hosts.
503 @defun shell-command-to-string command
504 This function executes @var{command} (a string) as a shell command,
505 then returns the command's output as a string.
508 @defun process-lines program &rest args
509 This function runs @var{program} in a separate process, waits for it
510 to finish, and returns its output as a list of strings. Each string
511 in the list holds a single line of text output by the program; the
512 end-of-line characters are stripped from each line. The arguments
513 beyond @var{program}, @var{args}, are strings that specify
514 command-line arguments with which to run the program.
516 If @var{program} exits with a non-zero exit status, this function
519 This function works by calling @code{call-process}, so program output
520 is decoded in the same way as for @code{call-process}.
523 @node Asynchronous Processes
524 @section Creating an Asynchronous Process
525 @cindex asynchronous subprocess
527 After an @dfn{asynchronous process} is created, Emacs and the subprocess
528 both continue running immediately. The process thereafter runs
529 in parallel with Emacs, and the two can communicate with each other
530 using the functions described in the following sections. However,
531 communication is only partially asynchronous: Emacs sends data to the
532 process only when certain functions are called, and Emacs accepts data
533 from the process only when Emacs is waiting for input or for a time
536 Here we describe how to create an asynchronous process.
538 @defun start-process name buffer-or-name program &rest args
539 This function creates a new asynchronous subprocess and starts the
540 program @var{program} running in it. It returns a process object that
541 stands for the new subprocess in Lisp. The argument @var{name}
542 specifies the name for the process object; if a process with this name
543 already exists, then @var{name} is modified (by appending @samp{<1>},
544 etc.) to be unique. The buffer @var{buffer-or-name} is the buffer to
545 associate with the process.
547 The remaining arguments, @var{args}, are strings that specify command
548 line arguments for the program.
550 In the example below, the first process is started and runs (rather,
551 sleeps) for 100 seconds. Meanwhile, the second process is started, and
552 given the name @samp{my-process<1>} for the sake of uniqueness. It
553 inserts the directory listing at the end of the buffer @samp{foo},
554 before the first process finishes. Then it finishes, and a message to
555 that effect is inserted in the buffer. Much later, the first process
556 finishes, and another message is inserted in the buffer for it.
560 (start-process "my-process" "foo" "sleep" "100")
561 @result{} #<process my-process>
565 (start-process "my-process" "foo" "ls" "-l" "/user/lewis/bin")
566 @result{} #<process my-process<1>>
568 ---------- Buffer: foo ----------
570 lrwxrwxrwx 1 lewis 14 Jul 22 10:12 gnuemacs --> /emacs
571 -rwxrwxrwx 1 lewis 19 Jul 30 21:02 lemon
573 Process my-process<1> finished
575 Process my-process finished
576 ---------- Buffer: foo ----------
581 @defun start-file-process name buffer-or-name program &rest args
582 Like @code{start-process}, this function starts a new asynchronous
583 subprocess running @var{program} in it, and returns its process
584 object---when @code{default-directory} is not a magic file name.
586 If @code{default-directory} is magic, the function invokes its file
587 handler instead. This handler ought to run @var{program}, perhaps on
588 the local host, perhaps on a remote host that corresponds to
589 @code{default-directory}. In the latter case, the local part of
590 @code{default-directory} becomes the working directory of the process.
592 This function does not try to invoke file name handlers for
593 @var{program} or for the @var{program-args}.
595 Depending on the implementation of the file handler, it might not be
596 possible to apply @code{process-filter} or @code{process-sentinel} to
597 the resulting process object (@pxref{Filter Functions}, @pxref{Sentinels}).
599 Some file handlers may not support @code{start-file-process} (for
600 example @code{ange-ftp-hook-function}). In such cases, the function
601 does nothing and returns @code{nil}.
604 @defun start-process-shell-command name buffer-or-name command
605 This function is like @code{start-process} except that it uses a shell
606 to execute the specified command. The argument @var{command} is a shell
607 command name. The variable @code{shell-file-name} specifies which shell to
610 The point of running a program through the shell, rather than directly
611 with @code{start-process}, is so that you can employ shell features such
612 as wildcards in the arguments. It follows that if you include an
613 arbitrary user-specified arguments in the command, you should quote it
614 with @code{shell-quote-argument} first, so that any special shell
615 characters do @emph{not} have their special shell meanings. @xref{Shell
619 @defun start-file-process-shell-command name buffer-or-name command
620 This function is like @code{start-process-shell-command}, but uses
621 @code{start-file-process} internally. By this, @var{command} can be
622 executed also on remote hosts, depending on @code{default-directory}.
625 @defvar process-connection-type
627 @cindex @acronym{PTY}s
628 This variable controls the type of device used to communicate with
629 asynchronous subprocesses. If it is non-@code{nil}, then @acronym{PTY}s are
630 used, when available. Otherwise, pipes are used.
632 @acronym{PTY}s are usually preferable for processes visible to the user, as
633 in Shell mode, because they allow job control (@kbd{C-c}, @kbd{C-z},
634 etc.) to work between the process and its children, whereas pipes do
635 not. For subprocesses used for internal purposes by programs, it is
636 often better to use a pipe, because they are more efficient. In
637 addition, the total number of @acronym{PTY}s is limited on many systems and
638 it is good not to waste them.
640 The value of @code{process-connection-type} takes effect when
641 @code{start-process} is called. So you can specify how to communicate
642 with one subprocess by binding the variable around the call to
643 @code{start-process}.
647 (let ((process-connection-type nil)) ; @r{Use a pipe.}
648 (start-process @dots{}))
652 To determine whether a given subprocess actually got a pipe or a
653 @acronym{PTY}, use the function @code{process-tty-name} (@pxref{Process
657 @node Deleting Processes
658 @section Deleting Processes
659 @cindex deleting processes
661 @dfn{Deleting a process} disconnects Emacs immediately from the
662 subprocess. Processes are deleted automatically after they terminate,
663 but not necessarily right away. You can delete a process explicitly
664 at any time. If you delete a terminated process explicitly before it
665 is deleted automatically, no harm results. Deleting a running
666 process sends a signal to terminate it (and its child processes if
667 any), and calls the process sentinel if it has one. @xref{Sentinels}.
669 When a process is deleted, the process object itself continues to
670 exist as long as other Lisp objects point to it. All the Lisp
671 primitives that work on process objects accept deleted processes, but
672 those that do I/O or send signals will report an error. The process
673 mark continues to point to the same place as before, usually into a
674 buffer where output from the process was being inserted.
676 @defopt delete-exited-processes
677 This variable controls automatic deletion of processes that have
678 terminated (due to calling @code{exit} or to a signal). If it is
679 @code{nil}, then they continue to exist until the user runs
680 @code{list-processes}. Otherwise, they are deleted immediately after
684 @defun delete-process process
685 This function deletes a process, killing it with a @code{SIGKILL}
686 signal. The argument may be a process, the name of a process, a
687 buffer, or the name of a buffer. (A buffer or buffer-name stands for
688 the process that @code{get-buffer-process} returns.) Calling
689 @code{delete-process} on a running process terminates it, updates the
690 process status, and runs the sentinel (if any) immediately. If the
691 process has already terminated, calling @code{delete-process} has no
692 effect on its status, or on the running of its sentinel (which will
693 happen sooner or later).
697 (delete-process "*shell*")
703 @node Process Information
704 @section Process Information
706 Several functions return information about processes.
707 @code{list-processes} is provided for interactive use.
709 @deffn Command list-processes &optional query-only
710 This command displays a listing of all living processes. In addition,
711 it finally deletes any process whose status was @samp{Exited} or
712 @samp{Signaled}. It returns @code{nil}.
714 If @var{query-only} is non-@code{nil} then it lists only processes
715 whose query flag is non-@code{nil}. @xref{Query Before Exit}.
719 This function returns a list of all processes that have not been deleted.
724 @result{} (#<process display-time> #<process shell>)
729 @defun get-process name
730 This function returns the process named @var{name}, or @code{nil} if
731 there is none. An error is signaled if @var{name} is not a string.
735 (get-process "shell")
736 @result{} #<process shell>
741 @defun process-command process
742 This function returns the command that was executed to start
743 @var{process}. This is a list of strings, the first string being the
744 program executed and the rest of the strings being the arguments that
745 were given to the program.
749 (process-command (get-process "shell"))
750 @result{} ("/bin/csh" "-i")
755 @defun process-contact process &optional key
757 This function returns information about how a network or serial
758 process was set up. For a network process, when @var{key} is
759 @code{nil}, it returns @code{(@var{hostname} @var{service})} which
760 specifies what you connected to. For a serial process, when @var{key}
761 is @code{nil}, it returns @code{(@var{port} @var{speed})}. For an
762 ordinary child process, this function always returns @code{t}.
764 If @var{key} is @code{t}, the value is the complete status information
765 for the connection, server, or serial port; that is, the list of
766 keywords and values specified in @code{make-network-process} or
767 @code{make-serial-process}, except that some of the values represent
768 the current status instead of what you specified.
770 For a network process:
774 The associated value is the process buffer.
776 The associated value is the process filter function.
778 The associated value is the process sentinel function.
780 In a connection, the address in internal format of the remote peer.
782 The local address, in internal format.
784 In a server, if you specified @code{t} for @var{service},
785 this value is the actual port number.
788 @code{:local} and @code{:remote} are included even if they were not
789 specified explicitly in @code{make-network-process}.
791 For a serial process, see @code{make-serial-process} and
792 @code{serial-process-configure} for a list of keys.
794 If @var{key} is a keyword, the function returns the value corresponding
798 @defun process-id process
799 This function returns the @acronym{PID} of @var{process}. This is an
800 integer that distinguishes the process @var{process} from all other
801 processes running on the same computer at the current time. The
802 @acronym{PID} of a process is chosen by the operating system kernel when the
803 process is started and remains constant as long as the process exists.
806 @defun process-name process
807 This function returns the name of @var{process}.
810 @defun process-status process-name
811 This function returns the status of @var{process-name} as a symbol.
812 The argument @var{process-name} must be a process, a buffer, or a
813 process name (a string).
815 The possible values for an actual subprocess are:
819 for a process that is running.
821 for a process that is stopped but continuable.
823 for a process that has exited.
825 for a process that has received a fatal signal.
827 for a network connection that is open.
829 for a network connection that is closed. Once a connection
830 is closed, you cannot reopen it, though you might be able to open
831 a new connection to the same place.
833 for a non-blocking connection that is waiting to complete.
835 for a non-blocking connection that has failed to complete.
837 for a network server that is listening.
839 if @var{process-name} is not the name of an existing process.
844 (process-status (get-buffer "*shell*"))
849 @result{} #<process xx<1>>
855 For a network connection, @code{process-status} returns one of the symbols
856 @code{open} or @code{closed}. The latter means that the other side
857 closed the connection, or Emacs did @code{delete-process}.
860 @defun process-type process
861 This function returns the symbol @code{network} for a network
862 connection or server, @code{serial} for a serial port connection, or
863 @code{real} for a real subprocess.
866 @defun process-exit-status process
867 This function returns the exit status of @var{process} or the signal
868 number that killed it. (Use the result of @code{process-status} to
869 determine which of those it is.) If @var{process} has not yet
870 terminated, the value is 0.
873 @defun process-tty-name process
874 This function returns the terminal name that @var{process} is using for
875 its communication with Emacs---or @code{nil} if it is using pipes
876 instead of a terminal (see @code{process-connection-type} in
877 @ref{Asynchronous Processes}). If @var{process} represents a program
878 running on a remote host, the terminal name used by that program on
879 the remote host is provided as process property @code{remote-tty}.
882 @defun process-coding-system process
883 @anchor{Coding systems for a subprocess}
884 This function returns a cons cell describing the coding systems in use
885 for decoding output from @var{process} and for encoding input to
886 @var{process} (@pxref{Coding Systems}). The value has this form:
889 (@var{coding-system-for-decoding} . @var{coding-system-for-encoding})
893 @defun set-process-coding-system process &optional decoding-system encoding-system
894 This function specifies the coding systems to use for subsequent output
895 from and input to @var{process}. It will use @var{decoding-system} to
896 decode subprocess output, and @var{encoding-system} to encode subprocess
900 Every process also has a property list that you can use to store
901 miscellaneous values associated with the process.
903 @defun process-get process propname
904 This function returns the value of the @var{propname} property
908 @defun process-put process propname value
909 This function sets the value of the @var{propname} property
910 of @var{process} to @var{value}.
913 @defun process-plist process
914 This function returns the process plist of @var{process}.
917 @defun set-process-plist process plist
918 This function sets the process plist of @var{process} to @var{plist}.
921 @node Input to Processes
922 @section Sending Input to Processes
923 @cindex process input
925 Asynchronous subprocesses receive input when it is sent to them by
926 Emacs, which is done with the functions in this section. You must
927 specify the process to send input to, and the input data to send. The
928 data appears on the ``standard input'' of the subprocess.
930 Some operating systems have limited space for buffered input in a
931 @acronym{PTY}. On these systems, Emacs sends an @acronym{EOF}
932 periodically amidst the other characters, to force them through. For
933 most programs, these @acronym{EOF}s do no harm.
935 Subprocess input is normally encoded using a coding system before the
936 subprocess receives it, much like text written into a file. You can use
937 @code{set-process-coding-system} to specify which coding system to use
938 (@pxref{Process Information}). Otherwise, the coding system comes from
939 @code{coding-system-for-write}, if that is non-@code{nil}; or else from
940 the defaulting mechanism (@pxref{Default Coding Systems}).
942 Sometimes the system is unable to accept input for that process,
943 because the input buffer is full. When this happens, the send functions
944 wait a short while, accepting output from subprocesses, and then try
945 again. This gives the subprocess a chance to read more of its pending
946 input and make space in the buffer. It also allows filters, sentinels
947 and timers to run---so take account of that in writing your code.
949 In these functions, the @var{process} argument can be a process or
950 the name of a process, or a buffer or buffer name (which stands
951 for a process via @code{get-buffer-process}). @code{nil} means
952 the current buffer's process.
954 @defun process-send-string process string
955 This function sends @var{process} the contents of @var{string} as
956 standard input. If it is @code{nil}, the current buffer's process is used.
958 The function returns @code{nil}.
962 (process-send-string "shell<1>" "ls\n")
968 ---------- Buffer: *shell* ----------
970 introduction.texi syntax-tables.texi~
971 introduction.texi~ text.texi
972 introduction.txt text.texi~
974 ---------- Buffer: *shell* ----------
979 @defun process-send-region process start end
980 This function sends the text in the region defined by @var{start} and
981 @var{end} as standard input to @var{process}.
983 An error is signaled unless both @var{start} and @var{end} are
984 integers or markers that indicate positions in the current buffer. (It
985 is unimportant which number is larger.)
988 @defun process-send-eof &optional process
989 This function makes @var{process} see an end-of-file in its
990 input. The @acronym{EOF} comes after any text already sent to it.
992 The function returns @var{process}.
996 (process-send-eof "shell")
1002 @defun process-running-child-p &optional process
1003 This function will tell you whether a @var{process} has given control of
1004 its terminal to its own child process. The value is @code{t} if this is
1005 true, or if Emacs cannot tell; it is @code{nil} if Emacs can be certain
1006 that this is not so.
1009 @node Signals to Processes
1010 @section Sending Signals to Processes
1011 @cindex process signals
1012 @cindex sending signals
1015 @dfn{Sending a signal} to a subprocess is a way of interrupting its
1016 activities. There are several different signals, each with its own
1017 meaning. The set of signals and their names is defined by the operating
1018 system. For example, the signal @code{SIGINT} means that the user has
1019 typed @kbd{C-c}, or that some analogous thing has happened.
1021 Each signal has a standard effect on the subprocess. Most signals
1022 kill the subprocess, but some stop or resume execution instead. Most
1023 signals can optionally be handled by programs; if the program handles
1024 the signal, then we can say nothing in general about its effects.
1026 You can send signals explicitly by calling the functions in this
1027 section. Emacs also sends signals automatically at certain times:
1028 killing a buffer sends a @code{SIGHUP} signal to all its associated
1029 processes; killing Emacs sends a @code{SIGHUP} signal to all remaining
1030 processes. (@code{SIGHUP} is a signal that usually indicates that the
1031 user hung up the phone.)
1033 Each of the signal-sending functions takes two optional arguments:
1034 @var{process} and @var{current-group}.
1036 The argument @var{process} must be either a process, a process
1037 name, a buffer, a buffer name, or @code{nil}. A buffer or buffer name
1038 stands for a process through @code{get-buffer-process}. @code{nil}
1039 stands for the process associated with the current buffer. An error
1040 is signaled if @var{process} does not identify a process.
1042 The argument @var{current-group} is a flag that makes a difference
1043 when you are running a job-control shell as an Emacs subprocess. If it
1044 is non-@code{nil}, then the signal is sent to the current process-group
1045 of the terminal that Emacs uses to communicate with the subprocess. If
1046 the process is a job-control shell, this means the shell's current
1047 subjob. If it is @code{nil}, the signal is sent to the process group of
1048 the immediate subprocess of Emacs. If the subprocess is a job-control
1049 shell, this is the shell itself.
1051 The flag @var{current-group} has no effect when a pipe is used to
1052 communicate with the subprocess, because the operating system does not
1053 support the distinction in the case of pipes. For the same reason,
1054 job-control shells won't work when a pipe is used. See
1055 @code{process-connection-type} in @ref{Asynchronous Processes}.
1057 @defun interrupt-process &optional process current-group
1058 This function interrupts the process @var{process} by sending the
1059 signal @code{SIGINT}. Outside of Emacs, typing the ``interrupt
1060 character'' (normally @kbd{C-c} on some systems, and @code{DEL} on
1061 others) sends this signal. When the argument @var{current-group} is
1062 non-@code{nil}, you can think of this function as ``typing @kbd{C-c}''
1063 on the terminal by which Emacs talks to the subprocess.
1066 @defun kill-process &optional process current-group
1067 This function kills the process @var{process} by sending the
1068 signal @code{SIGKILL}. This signal kills the subprocess immediately,
1069 and cannot be handled by the subprocess.
1072 @defun quit-process &optional process current-group
1073 This function sends the signal @code{SIGQUIT} to the process
1074 @var{process}. This signal is the one sent by the ``quit
1075 character'' (usually @kbd{C-b} or @kbd{C-\}) when you are not inside
1079 @defun stop-process &optional process current-group
1080 This function stops the process @var{process} by sending the
1081 signal @code{SIGTSTP}. Use @code{continue-process} to resume its
1084 Outside of Emacs, on systems with job control, the ``stop character''
1085 (usually @kbd{C-z}) normally sends this signal. When
1086 @var{current-group} is non-@code{nil}, you can think of this function as
1087 ``typing @kbd{C-z}'' on the terminal Emacs uses to communicate with the
1091 @defun continue-process &optional process current-group
1092 This function resumes execution of the process @var{process} by sending
1093 it the signal @code{SIGCONT}. This presumes that @var{process} was
1097 @defun signal-process process signal
1098 This function sends a signal to process @var{process}. The argument
1099 @var{signal} specifies which signal to send; it should be an integer.
1101 The @var{process} argument can be a system process @acronym{ID}; that
1102 allows you to send signals to processes that are not children of
1103 Emacs. @xref{System Processes}.
1106 @node Output from Processes
1107 @section Receiving Output from Processes
1108 @cindex process output
1109 @cindex output from processes
1111 There are two ways to receive the output that a subprocess writes to
1112 its standard output stream. The output can be inserted in a buffer,
1113 which is called the associated buffer of the process, or a function
1114 called the @dfn{filter function} can be called to act on the output. If
1115 the process has no buffer and no filter function, its output is
1118 When a subprocess terminates, Emacs reads any pending output,
1119 then stops reading output from that subprocess. Therefore, if the
1120 subprocess has children that are still live and still producing
1121 output, Emacs won't receive that output.
1123 Output from a subprocess can arrive only while Emacs is waiting: when
1124 reading terminal input, in @code{sit-for} and @code{sleep-for}
1125 (@pxref{Waiting}), and in @code{accept-process-output} (@pxref{Accepting
1126 Output}). This minimizes the problem of timing errors that usually
1127 plague parallel programming. For example, you can safely create a
1128 process and only then specify its buffer or filter function; no output
1129 can arrive before you finish, if the code in between does not call any
1130 primitive that waits.
1132 @defvar process-adaptive-read-buffering
1133 On some systems, when Emacs reads the output from a subprocess, the
1134 output data is read in very small blocks, potentially resulting in
1135 very poor performance. This behavior can be remedied to some extent
1136 by setting the variable @var{process-adaptive-read-buffering} to a
1137 non-@code{nil} value (the default), as it will automatically delay reading
1138 from such processes, thus allowing them to produce more output before
1139 Emacs tries to read it.
1142 It is impossible to separate the standard output and standard error
1143 streams of the subprocess, because Emacs normally spawns the subprocess
1144 inside a pseudo-TTY, and a pseudo-TTY has only one output channel. If
1145 you want to keep the output to those streams separate, you should
1146 redirect one of them to a file---for example, by using an appropriate
1150 * Process Buffers:: If no filter, output is put in a buffer.
1151 * Filter Functions:: Filter functions accept output from the process.
1152 * Decoding Output:: Filters can get unibyte or multibyte strings.
1153 * Accepting Output:: How to wait until process output arrives.
1156 @node Process Buffers
1157 @subsection Process Buffers
1159 A process can (and usually does) have an @dfn{associated buffer},
1160 which is an ordinary Emacs buffer that is used for two purposes: storing
1161 the output from the process, and deciding when to kill the process. You
1162 can also use the buffer to identify a process to operate on, since in
1163 normal practice only one process is associated with any given buffer.
1164 Many applications of processes also use the buffer for editing input to
1165 be sent to the process, but this is not built into Emacs Lisp.
1167 Unless the process has a filter function (@pxref{Filter Functions}),
1168 its output is inserted in the associated buffer. The position to insert
1169 the output is determined by the @code{process-mark}, which is then
1170 updated to point to the end of the text just inserted. Usually, but not
1171 always, the @code{process-mark} is at the end of the buffer.
1173 @findex process-kill-buffer-query-function
1174 Killing the associated buffer of a process also kills the process.
1175 Emacs asks for confirmation first, if the process's
1176 @code{process-query-on-exit-flag} is non-@code{nil} (@pxref{Query
1177 Before Exit}). This confirmation is done by the function
1178 @code{process-kill-buffer-query-function}, which is run from
1179 @code{kill-buffer-query-functions} (@pxref{Killing Buffers}).
1181 @defun process-buffer process
1182 This function returns the associated buffer of the process
1187 (process-buffer (get-process "shell"))
1188 @result{} #<buffer *shell*>
1193 @defun process-mark process
1194 This function returns the process marker for @var{process}, which is the
1195 marker that says where to insert output from the process.
1197 If @var{process} does not have a buffer, @code{process-mark} returns a
1198 marker that points nowhere.
1200 Insertion of process output in a buffer uses this marker to decide where
1201 to insert, and updates it to point after the inserted text. That is why
1202 successive batches of output are inserted consecutively.
1204 Filter functions normally should use this marker in the same fashion
1205 as is done by direct insertion of output in the buffer. A good
1206 example of a filter function that uses @code{process-mark} is found at
1207 the end of the following section.
1209 When the user is expected to enter input in the process buffer for
1210 transmission to the process, the process marker separates the new input
1211 from previous output.
1214 @defun set-process-buffer process buffer
1215 This function sets the buffer associated with @var{process} to
1216 @var{buffer}. If @var{buffer} is @code{nil}, the process becomes
1217 associated with no buffer.
1220 @defun get-buffer-process buffer-or-name
1221 This function returns a nondeleted process associated with the buffer
1222 specified by @var{buffer-or-name}. If there are several processes
1223 associated with it, this function chooses one (currently, the one most
1224 recently created, but don't count on that). Deletion of a process
1225 (see @code{delete-process}) makes it ineligible for this function to
1228 It is usually a bad idea to have more than one process associated with
1233 (get-buffer-process "*shell*")
1234 @result{} #<process shell>
1238 Killing the process's buffer deletes the process, which kills the
1239 subprocess with a @code{SIGHUP} signal (@pxref{Signals to Processes}).
1242 @node Filter Functions
1243 @subsection Process Filter Functions
1244 @cindex filter function
1245 @cindex process filter
1247 A process @dfn{filter function} is a function that receives the
1248 standard output from the associated process. If a process has a filter,
1249 then @emph{all} output from that process is passed to the filter. The
1250 process buffer is used directly for output from the process only when
1253 The filter function can only be called when Emacs is waiting for
1254 something, because process output arrives only at such times. Emacs
1255 waits when reading terminal input, in @code{sit-for} and
1256 @code{sleep-for} (@pxref{Waiting}), and in @code{accept-process-output}
1257 (@pxref{Accepting Output}).
1259 A filter function must accept two arguments: the associated process
1260 and a string, which is output just received from it. The function is
1261 then free to do whatever it chooses with the output.
1263 Quitting is normally inhibited within a filter function---otherwise,
1264 the effect of typing @kbd{C-g} at command level or to quit a user
1265 command would be unpredictable. If you want to permit quitting inside
1266 a filter function, bind @code{inhibit-quit} to @code{nil}. In most
1267 cases, the right way to do this is with the macro
1268 @code{with-local-quit}. @xref{Quitting}.
1270 If an error happens during execution of a filter function, it is
1271 caught automatically, so that it doesn't stop the execution of whatever
1272 program was running when the filter function was started. However, if
1273 @code{debug-on-error} is non-@code{nil}, the error-catching is turned
1274 off. This makes it possible to use the Lisp debugger to debug the
1275 filter function. @xref{Debugger}.
1277 Many filter functions sometimes or always insert the text in the
1278 process's buffer, mimicking the actions of Emacs when there is no
1279 filter. Such filter functions need to use @code{set-buffer} in order to
1280 be sure to insert in that buffer. To avoid setting the current buffer
1281 semipermanently, these filter functions must save and restore the
1282 current buffer. They should also check whether the buffer is still
1283 alive, update the process marker, and in some cases update the value
1284 of point. Here is how to do these things:
1288 (defun ordinary-insertion-filter (proc string)
1289 (when (buffer-live-p (process-buffer proc))
1290 (with-current-buffer (process-buffer proc)
1291 (let ((moving (= (point) (process-mark proc))))
1295 ;; @r{Insert the text, advancing the process marker.}
1296 (goto-char (process-mark proc))
1298 (set-marker (process-mark proc) (point)))
1299 (if moving (goto-char (process-mark proc)))))))
1304 The reason to use @code{with-current-buffer}, rather than using
1305 @code{save-excursion} to save and restore the current buffer, is so as
1306 to preserve the change in point made by the second call to
1309 To make the filter force the process buffer to be visible whenever new
1310 text arrives, insert the following line just before the
1311 @code{with-current-buffer} construct:
1314 (display-buffer (process-buffer proc))
1317 To force point to the end of the new output, no matter where it was
1318 previously, eliminate the variable @code{moving} and call
1319 @code{goto-char} unconditionally.
1321 In earlier Emacs versions, every filter function that did regular
1322 expression searching or matching had to explicitly save and restore the
1323 match data. Now Emacs does this automatically for filter functions;
1324 they never need to do it explicitly. @xref{Match Data}.
1326 The output to the function may come in chunks of any size. A program
1327 that produces the same output twice in a row may send it as one batch of
1328 200 characters one time, and five batches of 40 characters the next. If
1329 the filter looks for certain text strings in the subprocess output, make
1330 sure to handle the case where one of these strings is split across two
1331 or more batches of output; one way to do this is to insert the
1332 received text into a temporary buffer, which can then be searched.
1334 @defun set-process-filter process filter
1335 This function gives @var{process} the filter function @var{filter}. If
1336 @var{filter} is @code{nil}, it gives the process no filter.
1339 @defun process-filter process
1340 This function returns the filter function of @var{process}, or @code{nil}
1344 Here is an example of use of a filter function:
1348 (defun keep-output (process output)
1349 (setq kept (cons output kept)))
1350 @result{} keep-output
1357 (set-process-filter (get-process "shell") 'keep-output)
1358 @result{} keep-output
1361 (process-send-string "shell" "ls ~/other\n")
1364 @result{} ("lewis@@slug[8] % "
1367 "FINAL-W87-SHORT.MSS backup.otl kolstad.mss~
1368 address.txt backup.psf kolstad.psf
1369 backup.bib~ david.mss resume-Dec-86.mss~
1370 backup.err david.psf resume-Dec.psf
1371 backup.mss dland syllabus.mss
1373 "#backups.mss# backup.mss~ kolstad.mss
1378 @ignore @c The code in this example doesn't show the right way to do things.
1379 Here is another, more realistic example, which demonstrates how to use
1380 the process mark to do insertion in the same fashion as is done when
1381 there is no filter function:
1385 ;; @r{Insert input in the buffer specified by @code{my-shell-buffer}}
1386 ;; @r{and make sure that buffer is shown in some window.}
1387 (defun my-process-filter (proc str)
1388 (let ((cur (selected-window))
1390 (pop-to-buffer my-shell-buffer)
1393 (goto-char (point-max))
1395 (set-marker (process-mark proc) (point-max))
1396 (select-window cur)))
1401 @node Decoding Output
1402 @subsection Decoding Process Output
1403 @cindex decode process output
1405 When Emacs writes process output directly into a multibyte buffer,
1406 it decodes the output according to the process output coding system.
1407 If the coding system is @code{raw-text} or @code{no-conversion}, Emacs
1408 converts the unibyte output to multibyte using
1409 @code{string-to-multibyte}, and inserts the resulting multibyte text.
1411 You can use @code{set-process-coding-system} to specify which coding
1412 system to use (@pxref{Process Information}). Otherwise, the coding
1413 system comes from @code{coding-system-for-read}, if that is
1414 non-@code{nil}; or else from the defaulting mechanism (@pxref{Default
1415 Coding Systems}). If the text output by a process contains null
1416 bytes, Emacs by default uses @code{no-conversion} for it; see
1417 @ref{Lisp and Coding Systems, inhibit-null-byte-detection}, for how to
1418 control this behavior.
1420 @strong{Warning:} Coding systems such as @code{undecided} which
1421 determine the coding system from the data do not work entirely
1422 reliably with asynchronous subprocess output. This is because Emacs
1423 has to process asynchronous subprocess output in batches, as it
1424 arrives. Emacs must try to detect the proper coding system from one
1425 batch at a time, and this does not always work. Therefore, if at all
1426 possible, specify a coding system that determines both the character
1427 code conversion and the end of line conversion---that is, one like
1428 @code{latin-1-unix}, rather than @code{undecided} or @code{latin-1}.
1430 @c Let's keep the index entries that were there for
1431 @c set-process-filter-multibyte and process-filter-multibyte-p,
1432 @cindex filter multibyte flag, of process
1433 @cindex process filter multibyte flag
1434 When Emacs calls a process filter function, it provides the process
1435 output as a multibyte string or as a unibyte string according to the
1436 process's filter coding system. Emacs
1437 decodes the output according to the process output coding system,
1438 which usually produces a multibyte string, except for coding systems
1439 such as @code{binary} and @code{raw-text}
1441 @node Accepting Output
1442 @subsection Accepting Output from Processes
1443 @cindex accept input from processes
1445 Output from asynchronous subprocesses normally arrives only while
1446 Emacs is waiting for some sort of external event, such as elapsed time
1447 or terminal input. Occasionally it is useful in a Lisp program to
1448 explicitly permit output to arrive at a specific point, or even to wait
1449 until output arrives from a process.
1451 @defun accept-process-output &optional process seconds millisec just-this-one
1452 This function allows Emacs to read pending output from processes. The
1453 output is inserted in the associated buffers or given to their filter
1454 functions. If @var{process} is non-@code{nil} then this function does
1455 not return until some output has been received from @var{process}.
1458 The arguments @var{seconds} and @var{millisec} let you specify timeout
1459 periods. The former specifies a period measured in seconds and the
1460 latter specifies one measured in milliseconds. The two time periods
1461 thus specified are added together, and @code{accept-process-output}
1462 returns after that much time, whether or not there has been any
1465 The argument @var{millisec} is semi-obsolete nowadays because
1466 @var{seconds} can be a floating point number to specify waiting a
1467 fractional number of seconds. If @var{seconds} is 0, the function
1468 accepts whatever output is pending but does not wait.
1470 @c Emacs 22.1 feature
1471 If @var{process} is a process, and the argument @var{just-this-one} is
1472 non-@code{nil}, only output from that process is handled, suspending output
1473 from other processes until some output has been received from that
1474 process or the timeout expires. If @var{just-this-one} is an integer,
1475 also inhibit running timers. This feature is generally not
1476 recommended, but may be necessary for specific applications, such as
1479 The function @code{accept-process-output} returns non-@code{nil} if it
1480 did get some output, or @code{nil} if the timeout expired before output
1485 @section Sentinels: Detecting Process Status Changes
1486 @cindex process sentinel
1487 @cindex sentinel (of process)
1489 A @dfn{process sentinel} is a function that is called whenever the
1490 associated process changes status for any reason, including signals
1491 (whether sent by Emacs or caused by the process's own actions) that
1492 terminate, stop, or continue the process. The process sentinel is
1493 also called if the process exits. The sentinel receives two
1494 arguments: the process for which the event occurred, and a string
1495 describing the type of event.
1497 The string describing the event looks like one of the following:
1501 @code{"finished\n"}.
1504 @code{"exited abnormally with code @var{exitcode}\n"}.
1507 @code{"@var{name-of-signal}\n"}.
1510 @code{"@var{name-of-signal} (core dumped)\n"}.
1513 A sentinel runs only while Emacs is waiting (e.g., for terminal
1514 input, or for time to elapse, or for process output). This avoids the
1515 timing errors that could result from running them at random places in
1516 the middle of other Lisp programs. A program can wait, so that
1517 sentinels will run, by calling @code{sit-for} or @code{sleep-for}
1518 (@pxref{Waiting}), or @code{accept-process-output} (@pxref{Accepting
1519 Output}). Emacs also allows sentinels to run when the command loop is
1520 reading input. @code{delete-process} calls the sentinel when it
1521 terminates a running process.
1523 Emacs does not keep a queue of multiple reasons to call the sentinel
1524 of one process; it records just the current status and the fact that
1525 there has been a change. Therefore two changes in status, coming in
1526 quick succession, can call the sentinel just once. However, process
1527 termination will always run the sentinel exactly once. This is
1528 because the process status can't change again after termination.
1530 Emacs explicitly checks for output from the process before running
1531 the process sentinel. Once the sentinel runs due to process
1532 termination, no further output can arrive from the process.
1534 A sentinel that writes the output into the buffer of the process
1535 should check whether the buffer is still alive. If it tries to insert
1536 into a dead buffer, it will get an error. If the buffer is dead,
1537 @code{(buffer-name (process-buffer @var{process}))} returns @code{nil}.
1539 Quitting is normally inhibited within a sentinel---otherwise, the
1540 effect of typing @kbd{C-g} at command level or to quit a user command
1541 would be unpredictable. If you want to permit quitting inside a
1542 sentinel, bind @code{inhibit-quit} to @code{nil}. In most cases, the
1543 right way to do this is with the macro @code{with-local-quit}.
1546 If an error happens during execution of a sentinel, it is caught
1547 automatically, so that it doesn't stop the execution of whatever
1548 programs was running when the sentinel was started. However, if
1549 @code{debug-on-error} is non-@code{nil}, the error-catching is turned
1550 off. This makes it possible to use the Lisp debugger to debug the
1551 sentinel. @xref{Debugger}.
1553 While a sentinel is running, the process sentinel is temporarily
1554 set to @code{nil} so that the sentinel won't run recursively.
1555 For this reason it is not possible for a sentinel to specify
1558 In earlier Emacs versions, every sentinel that did regular expression
1559 searching or matching had to explicitly save and restore the match data.
1560 Now Emacs does this automatically for sentinels; they never need to do
1561 it explicitly. @xref{Match Data}.
1563 @defun set-process-sentinel process sentinel
1564 This function associates @var{sentinel} with @var{process}. If
1565 @var{sentinel} is @code{nil}, then the process will have no sentinel.
1566 The default behavior when there is no sentinel is to insert a message in
1567 the process's buffer when the process status changes.
1569 Changes in process sentinel take effect immediately---if the sentinel
1570 is slated to be run but has not been called yet, and you specify a new
1571 sentinel, the eventual call to the sentinel will use the new one.
1575 (defun msg-me (process event)
1577 (format "Process: %s had the event `%s'" process event)))
1578 (set-process-sentinel (get-process "shell") 'msg-me)
1582 (kill-process (get-process "shell"))
1583 @print{} Process: #<process shell> had the event `killed'
1584 @result{} #<process shell>
1589 @defun process-sentinel process
1590 This function returns the sentinel of @var{process}, or @code{nil} if it
1594 @defun waiting-for-user-input-p
1595 While a sentinel or filter function is running, this function returns
1596 non-@code{nil} if Emacs was waiting for keyboard input from the user at
1597 the time the sentinel or filter function was called, @code{nil} if it
1601 @node Query Before Exit
1602 @section Querying Before Exit
1604 When Emacs exits, it terminates all its subprocesses by sending them
1605 the @code{SIGHUP} signal. Because subprocesses may be doing
1606 valuable work, Emacs normally asks the user to confirm that it is ok
1607 to terminate them. Each process has a query flag which, if
1608 non-@code{nil}, says that Emacs should ask for confirmation before
1609 exiting and thus killing that process. The default for the query flag
1610 is @code{t}, meaning @emph{do} query.
1612 @defun process-query-on-exit-flag process
1613 This returns the query flag of @var{process}.
1616 @defun set-process-query-on-exit-flag process flag
1617 This function sets the query flag of @var{process} to @var{flag}. It
1622 ;; @r{Don't query about the shell process}
1623 (set-process-query-on-exit-flag (get-process "shell") nil)
1629 @defun process-kill-without-query process &optional do-query
1630 This function clears the query flag of @var{process}, so that
1631 Emacs will not query the user on account of that process.
1633 Actually, the function does more than that: it returns the old value of
1634 the process's query flag, and sets the query flag to @var{do-query}.
1635 Please don't use this function to do those things any more---please
1636 use the newer, cleaner functions @code{process-query-on-exit-flag} and
1637 @code{set-process-query-on-exit-flag} in all but the simplest cases.
1638 The only way you should use @code{process-kill-without-query} nowadays
1643 ;; @r{Don't query about the shell process}
1644 (process-kill-without-query (get-process "shell"))
1649 @node System Processes
1650 @section Accessing Other Processes
1651 @cindex system processes
1653 In addition to accessing and manipulating processes that are
1654 subprocesses of the current Emacs session, Emacs Lisp programs can
1655 also access other processes running on the same machine. We call
1656 these @dfn{system processes}, to distinguish between them and Emacs
1659 Emacs provides several primitives for accessing system processes.
1660 Not all platforms support these primitives; on those which don't,
1661 these primitives return @code{nil}.
1663 @defun list-system-processes
1664 This function returns a list of all the processes running on the
1665 system. Each process is identified by its @acronym{PID}, a numerical
1666 process ID that is assigned by the OS and distinguishes the process
1667 from all the other processes running on the same machine at the same
1671 @defun process-attributes pid
1672 This function returns an alist of attributes for the process specified
1673 by its process ID @var{pid}. Each association in the alist is of the
1674 form @code{(@var{key} . @var{value})}, where @var{key} designates the
1675 attribute and @var{value} is the value of that attribute. The various
1676 attribute @var{key}'s that this function can return are listed below.
1677 Not all platforms support all of these attributes; if an attribute is
1678 not supported, its association will not appear in the returned alist.
1679 Values that are numbers can be either integer or floating-point,
1680 depending on the magnitude of the value.
1684 The effective user ID of the user who invoked the process. The
1685 corresponding @var{value} is a number. If the process was invoked by
1686 the same user who runs the current Emacs session, the value is
1687 identical to what @code{user-uid} returns (@pxref{User
1691 User name corresponding to the process's effective user ID, a string.
1694 The group ID of the effective user ID, a number.
1697 Group name corresponding to the effective user's group ID, a string.
1700 The name of the command that runs in the process. This is a string
1701 that usually specifies the name of the executable file of the process,
1702 without the leading directories. However, some special system
1703 processes can report strings that do not correspond to an executable
1707 The state code of the process. This is a short string that encodes
1708 the scheduling state of the process. Here's a list of the most
1709 frequently seen codes:
1713 uninterruptible sleep (usually I/O)
1717 interruptible sleep (waiting for some event)
1719 stopped, e.g., by a job control signal
1721 ``zombie'': a process that terminated, but was not reaped by its parent
1725 For the full list of the possible states, see the manual page of the
1726 @command{ps} command.
1729 The process ID of the parent process, a number.
1732 The process group ID of the process, a number.
1735 The session ID of the process. This is a number that is the process
1736 ID of the process's @dfn{session leader}.
1739 A string that is the name of the process's controlling terminal. On
1740 Unix and GNU systems, this is normally the file name of the
1741 corresponding terminal device, such as @file{/dev/pts65}.
1744 The numerical process group ID of the foreground process group that
1745 uses the process's terminal.
1748 The number of minor page faults caused by the process since its
1749 beginning. (Minor page faults are those that don't involve reading
1753 The number of major page faults caused by the process since its
1754 beginning. (Major page faults require a disk to be read, and are thus
1755 more expensive than minor page faults.)
1759 Like @code{minflt} and @code{majflt}, but include the number of page
1760 faults for all the child processes of the given process.
1763 Time spent by the process in the user context, for running the
1764 application's code. The corresponding @var{value} is in the
1765 @w{@code{(@var{high} @var{low} @var{microsec})}} format, the same
1766 format used by functions @code{current-time} (@pxref{Time of Day,
1767 current-time}) and @code{file-attributes} (@pxref{File Attributes}).
1770 Time spent by the process in the system (kernel) context, for
1771 processing system calls. The corresponding @var{value} is in the same
1772 format as for @code{utime}.
1775 The sum of @code{utime} and @code{stime}. The corresponding
1776 @var{value} is in the same format as for @code{utime}.
1781 Like @code{utime}, @code{stime}, and @code{time}, but include the
1782 times of all the child processes of the given process.
1785 The numerical priority of the process.
1788 The @dfn{nice value} of the process, a number. (Processes with smaller
1789 nice values get scheduled more favorably.)
1792 The number of threads in the process.
1795 The time the process was started, in the @w{@code{(@var{high}
1796 @var{low} @var{microsec})}} format used by @code{current-time} and
1797 @code{file-attributes}.
1800 The time elapsed since the process started, in the @w{@code{(@var{high}
1801 @var{low} @var{microsec})}} format.
1804 The virtual memory size of the process, measured in kilobytes.
1807 The size of the process's @dfn{resident set}, the number of kilobytes
1808 occupied by the process in the machine's physical memory.
1811 The percentage of the CPU time used by the process since it started.
1812 The corresponding @var{value} is a floating-point number between 0 and
1816 The percentage of the total physical memory installed on the machine
1817 used by the process's resident set. The value is a floating-point
1818 number between 0 and 100.
1821 The command-line with which the process was invoked. This is a string
1822 in which individual command-line arguments are separated by blanks;
1823 whitespace characters that are embedded in the arguments are quoted as
1824 appropriate for the system's shell: escaped by backslash characters on
1825 GNU and Unix, and enclosed in double quote characters on Windows.
1826 Thus, this command-line string can be directly used in primitives such
1827 as @code{shell-command}.
1833 @node Transaction Queues
1834 @section Transaction Queues
1835 @cindex transaction queue
1837 You can use a @dfn{transaction queue} to communicate with a subprocess
1838 using transactions. First use @code{tq-create} to create a transaction
1839 queue communicating with a specified process. Then you can call
1840 @code{tq-enqueue} to send a transaction.
1842 @defun tq-create process
1843 This function creates and returns a transaction queue communicating with
1844 @var{process}. The argument @var{process} should be a subprocess
1845 capable of sending and receiving streams of bytes. It may be a child
1846 process, or it may be a TCP connection to a server, possibly on another
1850 @defun tq-enqueue queue question regexp closure fn &optional delay-question
1851 This function sends a transaction to queue @var{queue}. Specifying the
1852 queue has the effect of specifying the subprocess to talk to.
1854 The argument @var{question} is the outgoing message that starts the
1855 transaction. The argument @var{fn} is the function to call when the
1856 corresponding answer comes back; it is called with two arguments:
1857 @var{closure}, and the answer received.
1859 The argument @var{regexp} is a regular expression that should match
1860 text at the end of the entire answer, but nothing before; that's how
1861 @code{tq-enqueue} determines where the answer ends.
1863 If the argument @var{delay-question} is non-@code{nil}, delay sending
1864 this question until the process has finished replying to any previous
1865 questions. This produces more reliable results with some processes.
1867 The return value of @code{tq-enqueue} itself is not meaningful.
1870 @defun tq-close queue
1871 Shut down transaction queue @var{queue}, waiting for all pending transactions
1872 to complete, and then terminate the connection or child process.
1875 Transaction queues are implemented by means of a filter function.
1876 @xref{Filter Functions}.
1879 @section Network Connections
1880 @cindex network connection
1884 Emacs Lisp programs can open stream (TCP) and datagram (UDP) network
1885 connections to other processes on the same machine or other machines.
1886 A network connection is handled by Lisp much like a subprocess, and is
1887 represented by a process object. However, the process you are
1888 communicating with is not a child of the Emacs process, so it has no
1889 process @acronym{ID}, and you can't kill it or send it signals. All you
1890 can do is send and receive data. @code{delete-process} closes the
1891 connection, but does not kill the program at the other end; that
1892 program must decide what to do about closure of the connection.
1894 Lisp programs can listen for connections by creating network
1895 servers. A network server is also represented by a kind of process
1896 object, but unlike a network connection, the network server never
1897 transfers data itself. When it receives a connection request, it
1898 creates a new network connection to represent the connection just
1899 made. (The network connection inherits certain information, including
1900 the process plist, from the server.) The network server then goes
1901 back to listening for more connection requests.
1903 Network connections and servers are created by calling
1904 @code{make-network-process} with an argument list consisting of
1905 keyword/argument pairs, for example @code{:server t} to create a
1906 server process, or @code{:type 'datagram} to create a datagram
1907 connection. @xref{Low-Level Network}, for details. You can also use
1908 the @code{open-network-stream} function described below.
1910 To distinguish the different types of processes, the
1911 @code{process-type} function returns the symbol @code{network} for a
1912 network connection or server, @code{serial} for a serial port
1913 connection, or @code{real} for a real subprocess.
1915 The @code{process-status} function returns @code{open},
1916 @code{closed}, @code{connect}, and @code{failed} for network
1917 connections. For a network server, the status is always
1918 @code{listen}. None of those values is possible for a real
1919 subprocess. @xref{Process Information}.
1921 You can stop and resume operation of a network process by calling
1922 @code{stop-process} and @code{continue-process}. For a server
1923 process, being stopped means not accepting new connections. (Up to 5
1924 connection requests will be queued for when you resume the server; you
1925 can increase this limit, unless it is imposed by the operating
1926 system.) For a network stream connection, being stopped means not
1927 processing input (any arriving input waits until you resume the
1928 connection). For a datagram connection, some number of packets may be
1929 queued but input may be lost. You can use the function
1930 @code{process-command} to determine whether a network connection or
1931 server is stopped; a non-@code{nil} value means yes.
1933 @defun open-network-stream name buffer-or-name host service
1934 This function opens a TCP connection, and returns a process object
1935 that represents the connection.
1937 The @var{name} argument specifies the name for the process object. It
1938 is modified as necessary to make it unique.
1940 The @var{buffer-or-name} argument is the buffer to associate with the
1941 connection. Output from the connection is inserted in the buffer,
1942 unless you specify a filter function to handle the output. If
1943 @var{buffer-or-name} is @code{nil}, it means that the connection is not
1944 associated with any buffer.
1946 The arguments @var{host} and @var{service} specify where to connect to;
1947 @var{host} is the host name (a string), and @var{service} is the name of
1948 a defined network service (a string) or a port number (an integer).
1951 @node Network Servers
1952 @section Network Servers
1953 @cindex network servers
1955 You create a server by calling @code{make-network-process} with
1956 @code{:server t}. The server will listen for connection requests from
1957 clients. When it accepts a client connection request, that creates a
1958 new network connection, itself a process object, with the following
1963 The connection's process name is constructed by concatenating the
1964 server process' @var{name} with a client identification string. The
1965 client identification string for an IPv4 connection looks like
1966 @samp{<@var{a}.@var{b}.@var{c}.@var{d}:@var{p}>}. Otherwise, it is a
1967 unique number in brackets, as in @samp{<@var{nnn}>}. The number
1968 is unique for each connection in the Emacs session.
1971 If the server's filter is non-@code{nil}, the connection process does
1972 not get a separate process buffer; otherwise, Emacs creates a new
1973 buffer for the purpose. The buffer name is the server's buffer name
1974 or process name, concatenated with the client identification string.
1976 The server's process buffer value is never used directly by Emacs, but
1977 it is passed to the log function, which can log connections by
1978 inserting text there.
1981 The communication type and the process filter and sentinel are
1982 inherited from those of the server. The server never directly
1983 uses its filter and sentinel; their sole purpose is to initialize
1984 connections made to the server.
1987 The connection's process contact info is set according to the client's
1988 addressing information (typically an IP address and a port number).
1989 This information is associated with the @code{process-contact}
1990 keywords @code{:host}, @code{:service}, @code{:remote}.
1993 The connection's local address is set up according to the port
1994 number used for the connection.
1997 The client process' plist is initialized from the server's plist.
2004 A datagram connection communicates with individual packets rather
2005 than streams of data. Each call to @code{process-send} sends one
2006 datagram packet (@pxref{Input to Processes}), and each datagram
2007 received results in one call to the filter function.
2009 The datagram connection doesn't have to talk with the same remote
2010 peer all the time. It has a @dfn{remote peer address} which specifies
2011 where to send datagrams to. Each time an incoming datagram is passed
2012 to the filter function, the peer address is set to the address that
2013 datagram came from; that way, if the filter function sends a datagram,
2014 it will go back to that place. You can specify the remote peer
2015 address when you create the datagram connection using the
2016 @code{:remote} keyword. You can change it later on by calling
2017 @code{set-process-datagram-address}.
2019 @defun process-datagram-address process
2020 If @var{process} is a datagram connection or server, this function
2021 returns its remote peer address.
2024 @defun set-process-datagram-address process address
2025 If @var{process} is a datagram connection or server, this function
2026 sets its remote peer address to @var{address}.
2029 @node Low-Level Network
2030 @section Low-Level Network Access
2032 You can also create network connections by operating at a lower
2033 level than that of @code{open-network-stream}, using
2034 @code{make-network-process}.
2037 * Proc: Network Processes. Using @code{make-network-process}.
2038 * Options: Network Options. Further control over network connections.
2039 * Features: Network Feature Testing.
2040 Determining which network features work on
2041 the machine you are using.
2044 @node Network Processes
2045 @subsection @code{make-network-process}
2047 The basic function for creating network connections and network
2048 servers is @code{make-network-process}. It can do either of those
2049 jobs, depending on the arguments you give it.
2051 @defun make-network-process &rest args
2052 This function creates a network connection or server and returns the
2053 process object that represents it. The arguments @var{args} are a
2054 list of keyword/argument pairs. Omitting a keyword is always
2055 equivalent to specifying it with value @code{nil}, except for
2056 @code{:coding}, @code{:filter-multibyte}, and @code{:reuseaddr}. Here
2057 are the meaningful keywords:
2060 @item :name @var{name}
2061 Use the string @var{name} as the process name. It is modified if
2062 necessary to make it unique.
2064 @item :type @var{type}
2065 Specify the communication type. A value of @code{nil} specifies a
2066 stream connection (the default); @code{datagram} specifies a datagram
2067 connection; @code{seqpacket} specifies a ``sequenced packet stream''
2068 connection. Both connections and servers can be of these types.
2070 @item :server @var{server-flag}
2071 If @var{server-flag} is non-@code{nil}, create a server. Otherwise,
2072 create a connection. For a stream type server, @var{server-flag} may
2073 be an integer which then specifies the length of the queue of pending
2074 connections to the server. The default queue length is 5.
2076 @item :host @var{host}
2077 Specify the host to connect to. @var{host} should be a host name or
2078 Internet address, as a string, or the symbol @code{local} to specify
2079 the local host. If you specify @var{host} for a server, it must
2080 specify a valid address for the local host, and only clients
2081 connecting to that address will be accepted.
2083 @item :service @var{service}
2084 @var{service} specifies a port number to connect to, or, for a server,
2085 the port number to listen on. It should be a service name that
2086 translates to a port number, or an integer specifying the port number
2087 directly. For a server, it can also be @code{t}, which means to let
2088 the system select an unused port number.
2090 @item :family @var{family}
2091 @var{family} specifies the address (and protocol) family for
2092 communication. @code{nil} means determine the proper address family
2093 automatically for the given @var{host} and @var{service}.
2094 @code{local} specifies a Unix socket, in which case @var{host} is
2095 ignored. @code{ipv4} and @code{ipv6} specify to use IPv4 and IPv6
2098 @item :local @var{local-address}
2099 For a server process, @var{local-address} is the address to listen on.
2100 It overrides @var{family}, @var{host} and @var{service}, and you
2101 may as well not specify them.
2103 @item :remote @var{remote-address}
2104 For a connection, @var{remote-address} is the address to connect to.
2105 It overrides @var{family}, @var{host} and @var{service}, and you
2106 may as well not specify them.
2108 For a datagram server, @var{remote-address} specifies the initial
2109 setting of the remote datagram address.
2111 The format of @var{local-address} or @var{remote-address} depends on
2116 An IPv4 address is represented as a five-element vector of four 8-bit
2117 integers and one 16-bit integer
2118 @code{[@var{a} @var{b} @var{c} @var{d} @var{p}]} corresponding to
2119 numeric IPv4 address @var{a}.@var{b}.@var{c}.@var{d} and port number
2123 An IPv6 address is represented as a nine-element vector of 16-bit
2124 integers @code{[@var{a} @var{b} @var{c} @var{d} @var{e} @var{f}
2125 @var{g} @var{h} @var{p}]} corresponding to numeric IPv6 address
2126 @var{a}:@var{b}:@var{c}:@var{d}:@var{e}:@var{f}:@var{g}:@var{h} and
2127 port number @var{p}.
2130 A local address is represented as a string which specifies the address
2131 in the local address space.
2134 An ``unsupported family'' address is represented by a cons
2135 @code{(@var{f} . @var{av})}, where @var{f} is the family number and
2136 @var{av} is a vector specifying the socket address using one element
2137 per address data byte. Do not rely on this format in portable code,
2138 as it may depend on implementation defined constants, data sizes, and
2139 data structure alignment.
2142 @item :nowait @var{bool}
2143 If @var{bool} is non-@code{nil} for a stream connection, return
2144 without waiting for the connection to complete. When the connection
2145 succeeds or fails, Emacs will call the sentinel function, with a
2146 second argument matching @code{"open"} (if successful) or
2147 @code{"failed"}. The default is to block, so that
2148 @code{make-network-process} does not return until the connection
2149 has succeeded or failed.
2151 @item :stop @var{stopped}
2152 Start the network connection or server in the `stopped' state if
2153 @var{stopped} is non-@code{nil}.
2155 @item :buffer @var{buffer}
2156 Use @var{buffer} as the process buffer.
2158 @item :coding @var{coding}
2159 Use @var{coding} as the coding system for this process. To specify
2160 different coding systems for decoding data from the connection and for
2161 encoding data sent to it, specify @code{(@var{decoding} .
2162 @var{encoding})} for @var{coding}.
2164 If you don't specify this keyword at all, the default
2165 is to determine the coding systems from the data.
2167 @item :noquery @var{query-flag}
2168 Initialize the process query flag to @var{query-flag}.
2169 @xref{Query Before Exit}.
2171 @item :filter @var{filter}
2172 Initialize the process filter to @var{filter}.
2174 @item :sentinel @var{sentinel}
2175 Initialize the process sentinel to @var{sentinel}.
2177 @item :log @var{log}
2178 Initialize the log function of a server process to @var{log}. The log
2179 function is called each time the server accepts a network connection
2180 from a client. The arguments passed to the log function are
2181 @var{server}, @var{connection}, and @var{message}, where @var{server}
2182 is the server process, @var{connection} is the new process for the
2183 connection, and @var{message} is a string describing what has
2186 @item :plist @var{plist}
2187 Initialize the process plist to @var{plist}.
2190 The original argument list, modified with the actual connection
2191 information, is available via the @code{process-contact} function.
2194 @node Network Options
2195 @subsection Network Options
2197 The following network options can be specified when you create a
2198 network process. Except for @code{:reuseaddr}, you can also set or
2199 modify these options later, using @code{set-network-process-option}.
2201 For a server process, the options specified with
2202 @code{make-network-process} are not inherited by the client
2203 connections, so you will need to set the necessary options for each
2204 child connection as it is created.
2207 @item :bindtodevice @var{device-name}
2208 If @var{device-name} is a non-empty string identifying a network
2209 interface name (see @code{network-interface-list}), only handle
2210 packets received on that interface. If @var{device-name} is @code{nil}
2211 (the default), handle packets received on any interface.
2213 Using this option may require special privileges on some systems.
2215 @item :broadcast @var{broadcast-flag}
2216 If @var{broadcast-flag} is non-@code{nil} for a datagram process, the
2217 process will receive datagram packet sent to a broadcast address, and
2218 be able to send packets to a broadcast address. Ignored for a stream
2221 @item :dontroute @var{dontroute-flag}
2222 If @var{dontroute-flag} is non-@code{nil}, the process can only send
2223 to hosts on the same network as the local host.
2225 @item :keepalive @var{keepalive-flag}
2226 If @var{keepalive-flag} is non-@code{nil} for a stream connection,
2227 enable exchange of low-level keep-alive messages.
2229 @item :linger @var{linger-arg}
2230 If @var{linger-arg} is non-@code{nil}, wait for successful
2231 transmission of all queued packets on the connection before it is
2232 deleted (see @code{delete-process}). If @var{linger-arg} is an
2233 integer, it specifies the maximum time in seconds to wait for queued
2234 packets to be sent before closing the connection. Default is
2235 @code{nil} which means to discard unsent queued packets when the
2238 @item :oobinline @var{oobinline-flag}
2239 If @var{oobinline-flag} is non-@code{nil} for a stream connection,
2240 receive out-of-band data in the normal data stream. Otherwise, ignore
2243 @item :priority @var{priority}
2244 Set the priority for packets sent on this connection to the integer
2245 @var{priority}. The interpretation of this number is protocol
2246 specific, such as setting the TOS (type of service) field on IP
2247 packets sent on this connection. It may also have system dependent
2248 effects, such as selecting a specific output queue on the network
2251 @item :reuseaddr @var{reuseaddr-flag}
2252 If @var{reuseaddr-flag} is non-@code{nil} (the default) for a stream
2253 server process, allow this server to reuse a specific port number (see
2254 @code{:service}) unless another process on this host is already
2255 listening on that port. If @var{reuseaddr-flag} is @code{nil}, there
2256 may be a period of time after the last use of that port (by any
2257 process on the host), where it is not possible to make a new server on
2261 @defun set-network-process-option process option value &optional no-error
2262 This function sets or modifies a network option for network process
2263 @var{process}. See @code{make-network-process} for details of options
2264 @var{option} and their corresponding values @var{value}. If
2265 @var{no-error} is non-@code{nil}, this function returns @code{nil}
2266 instead of signaling an error if @var{option} is not a supported
2267 option. If the function successfully completes, it returns @code{t}.
2269 The current setting of an option is available via the
2270 @code{process-contact} function.
2273 @node Network Feature Testing
2274 @subsection Testing Availability of Network Features
2276 To test for the availability of a given network feature, use
2277 @code{featurep} like this:
2280 (featurep 'make-network-process '(@var{keyword} @var{value}))
2284 The result of the first form is @code{t} if it works to specify
2285 @var{keyword} with value @var{value} in @code{make-network-process}.
2286 The result of the second form is @code{t} if @var{keyword} is
2287 supported by @code{make-network-process}. Here are some of the
2288 @var{keyword}---@var{value} pairs you can test in
2293 Non-@code{nil} if non-blocking connect is supported.
2294 @item (:type datagram)
2295 Non-@code{nil} if datagrams are supported.
2296 @item (:family local)
2297 Non-@code{nil} if local (a.k.a.@: ``UNIX domain'') sockets are supported.
2298 @item (:family ipv6)
2299 Non-@code{nil} if IPv6 is supported.
2301 Non-@code{nil} if the system can select the port for a server.
2304 To test for the availability of a given network option, use
2305 @code{featurep} like this:
2308 (featurep 'make-network-process '@var{keyword})
2312 Here are some of the options you can test in this way.
2323 That particular network option is supported by
2324 @code{make-network-process} and @code{set-network-process-option}.
2328 @section Misc Network Facilities
2330 These additional functions are useful for creating and operating
2331 on network connections. Note that they are supported only on some
2334 @defun network-interface-list
2335 This function returns a list describing the network interfaces
2336 of the machine you are using. The value is an alist whose
2337 elements have the form @code{(@var{name} . @var{address})}.
2338 @var{address} has the same form as the @var{local-address}
2339 and @var{remote-address} arguments to @code{make-network-process}.
2342 @defun network-interface-info ifname
2343 This function returns information about the network interface named
2344 @var{ifname}. The value is a list of the form
2345 @code{(@var{addr} @var{bcast} @var{netmask} @var{hwaddr} @var{flags})}.
2349 The Internet protocol address.
2351 The broadcast address.
2355 The layer 2 address (Ethernet MAC address, for instance).
2357 The current flags of the interface.
2361 @defun format-network-address address &optional omit-port
2362 This function converts the Lisp representation of a network address to
2365 A five-element vector @code{[@var{a} @var{b} @var{c} @var{d} @var{p}]}
2366 represents an IPv4 address @var{a}.@var{b}.@var{c}.@var{d} and port
2367 number @var{p}. @code{format-network-address} converts that to the
2368 string @code{"@var{a}.@var{b}.@var{c}.@var{d}:@var{p}"}.
2370 A nine-element vector @code{[@var{a} @var{b} @var{c} @var{d} @var{e}
2371 @var{f} @var{g} @var{h} @var{p}]} represents an IPv6 address along
2372 with a port number. @code{format-network-address} converts that to
2374 @code{"[@var{a}:@var{b}:@var{c}:@var{d}:@var{e}:@var{f}:@var{g}:@var{h}]:@var{p}"}.
2376 If the vector does not include the port number, @var{p}, or if
2377 @var{omit-port} is non-@code{nil}, the result does not include the
2378 @code{:@var{p}} suffix.
2382 @section Communicating with Serial Ports
2383 @cindex @file{/dev/tty}
2385 @cindex serial connections
2387 Emacs can communicate with serial ports. For interactive use,
2388 @kbd{M-x serial-term} opens a terminal window. In a Lisp program,
2389 @code{make-serial-process} creates a process object.
2391 The serial port can be configured at run-time, without having to
2392 close and re-open it. The function @code{serial-process-configure}
2393 lets you change the speed, bytesize, and other parameters. In a
2394 terminal window created by @code{serial-term}, you can click on the
2395 mode line for configuration.
2397 A serial connection is represented by a process object which can be
2398 used similar to a subprocess or network process. You can send and
2399 receive data and configure the serial port. A serial process object
2400 has no process ID, you can't send signals to it, and the status codes
2401 are different from other types of processes.
2402 @code{delete-process} on the process object or @code{kill-buffer} on
2403 the process buffer close the connection, but this does not affect the
2404 device connected to the serial port.
2406 The function @code{process-type} returns the symbol @code{serial}
2407 for a process object representing a serial port connection.
2409 Serial ports are available on GNU/Linux, Unix, and Windows systems.
2411 @deffn Command serial-term port speed
2412 Start a terminal-emulator for a serial port in a new buffer.
2413 @var{port} is the name of the serial port to which to connect. For
2414 example, this could be @file{/dev/ttyS0} on Unix. On Windows, this
2415 could be @file{COM1}, or @file{\\.\COM10} (double the backslashes in
2418 @var{speed} is the speed of the serial port in bits per second. 9600
2419 is a common value. The buffer is in Term mode; see @ref{Term Mode,,,
2420 emacs, The GNU Emacs Manual}, for the commands to use in that buffer.
2421 You can change the speed and the configuration in the mode line menu.
2424 @defun make-serial-process &rest args
2425 This function creates a process and a buffer. Arguments are specified
2426 as keyword/argument pairs. Here's the list of the meaningful keywords:
2429 @item :port @var{port}@r{ (mandatory)}
2430 This is the name of the serial port. On Unix and GNU systems, this is
2431 a file name such as @file{/dev/ttyS0}. On Windows, this could be
2432 @file{COM1}, or @file{\\.\COM10} for ports higher than @file{COM9}
2433 (double the backslashes in Lisp strings).
2435 @item :speed @var{speed}@r{ (mandatory)}
2436 The speed of the serial port in bits per second. This function calls
2437 @code{serial-process-configure} to handle the speed.
2439 @item :name @var{name}
2440 The name of the process. If @var{name} is not given, @var{port} will
2441 serve as the process name as well.
2443 @item :buffer @var{buffer}
2444 The buffer to associate with the process. The value could be either a
2445 buffer or a string that names a buffer. Process output goes at the
2446 end of that buffer, unless you specify an output stream or filter
2447 function to handle the output. If @var{buffer} is not given, the
2448 process buffer's name is taken from the value of the @code{:name}
2451 @item :coding @var{coding}
2452 If @var{coding} is a symbol, it specifies the coding system used for
2453 both reading and writing for this process. If @var{coding} is a cons
2454 @code{(decoding . encoding)}, @var{decoding} is used for reading, and
2455 @var{encoding} is used for writing. If not specified, the default is
2456 to determine the coding systems from data itself.
2458 @item :noquery @var{query-flag}
2459 Initialize the process query flag to @var{query-flag}. @xref{Query
2460 Before Exit}. The flags defaults to @code{nil} if unspecified.
2462 @item :stop @var{bool}
2463 Start process in the @code{stopped} state if @var{bool} is
2464 non-@code{nil}. In the stopped state, a serial process does not
2465 accept incoming data, but you can send outgoing data. The stopped
2466 state is cleared by @code{continue-process} and set by
2467 @code{stop-process}.
2469 @item :filter @var{filter}
2470 Install @var{filter} as the process filter.
2472 @item :sentinel @var{sentinel}
2473 Install @var{sentinel} as the process sentinel.
2475 @item :plist @var{plist}
2476 Install @var{plist} as the initial plist of the process.
2483 These arguments are handled by @code{serial-process-configure}, which
2484 is called by @code{make-serial-process}.
2487 The original argument list, possibly modified by later configuration,
2488 is available via the function @code{process-contact}.
2493 (make-serial-process :port "/dev/ttyS0" :speed 9600)
2495 (make-serial-process :port "COM1" :speed 115200 :stopbits 2)
2497 (make-serial-process :port "\\\\.\\COM13" :speed 1200
2498 :bytesize 7 :parity 'odd)
2500 (make-serial-process :port "/dev/tty.BlueConsole-SPP-1"
2505 @defun serial-process-configure &rest args
2506 @cindex baud, in serial connections
2507 @cindex bytesize, in serial connections
2508 @cindex parity, in serial connections
2509 @cindex stopbits, in serial connections
2510 @cindex flowcontrol, in serial connections
2512 This functions configures a serial port connection. Arguments are
2513 specified as keyword/argument pairs. Attributes that are not given
2514 are re-initialized from the process's current configuration (available
2515 via the function @code{process-contact}) or set to reasonable default
2516 values. The following arguments are defined:
2519 @item :process @var{process}
2520 @itemx :name @var{name}
2521 @itemx :buffer @var{buffer}
2522 @itemx :port @var{port}
2523 Any of these arguments can be given to identify the process that is to
2524 be configured. If none of these arguments is given, the current
2525 buffer's process is used.
2527 @item :speed @var{speed}
2528 The speed of the serial port in bits per second, a.k.a.@: @dfn{baud
2529 rate}. The value can be any number, but most serial ports work only
2530 at a few defined values between 1200 and 115200, with 9600 being the
2531 most common value. If @var{speed} is @code{nil}, the function ignores
2532 all other arguments and does not configure the port. This may be
2533 useful for special serial ports such as Bluetooth-to-serial converters
2534 which can only be configured through AT commands sent through the
2535 connection. The value of @code{nil} for @var{speed} is valid only for
2536 connections that were already opened by a previous call to
2537 @code{make-serial-process} or @code{serial-term}.
2539 @item :bytesize @var{bytesize}
2540 The number of bits per byte, which can be 7 or 8. If @var{bytesize}
2541 is not given or @code{nil}, it defaults to 8.
2543 @item :parity @var{parity}
2544 The value can be @code{nil} (don't use parity), the symbol
2545 @code{odd} (use odd parity), or the symbol @code{even} (use even
2546 parity). If @var{parity} is not given, it defaults to no parity.
2548 @item :stopbits @var{stopbits}
2549 The number of stopbits used to terminate a transmission
2550 of each byte. @var{stopbits} can be 1 or 2. If @var{stopbits} is not
2551 given or @code{nil}, it defaults to 1.
2553 @item :flowcontrol @var{flowcontrol}
2554 The type of flow control to use for this connection, which is either
2555 @code{nil} (don't use flow control), the symbol @code{hw} (use RTS/CTS
2556 hardware flow control), or the symbol @code{sw} (use XON/XOFF software
2557 flow control). If @var{flowcontrol} is not given, it defaults to no
2561 @code{serial-process-configure} is called by @code{make-serial-process} for the
2562 initial configuration of the serial port.
2567 (serial-process-configure :process "/dev/ttyS0" :speed 1200)
2569 (serial-process-configure :buffer "COM1" :stopbits 1
2570 :parity 'odd :flowcontrol 'hw)
2572 (serial-process-configure :port "\\\\.\\COM13" :bytesize 7)
2577 @section Packing and Unpacking Byte Arrays
2578 @cindex byte packing and unpacking
2580 This section describes how to pack and unpack arrays of bytes,
2581 usually for binary network protocols. These functions convert byte arrays
2582 to alists, and vice versa. The byte array can be represented as a
2583 unibyte string or as a vector of integers, while the alist associates
2584 symbols either with fixed-size objects or with recursive sub-alists.
2587 @cindex deserializing
2590 Conversion from byte arrays to nested alists is also known as
2591 @dfn{deserializing} or @dfn{unpacking}, while going in the opposite
2592 direction is also known as @dfn{serializing} or @dfn{packing}.
2595 * Bindat Spec:: Describing data layout.
2596 * Bindat Functions:: Doing the unpacking and packing.
2597 * Bindat Examples:: Samples of what bindat.el can do for you!
2601 @subsection Describing Data Layout
2603 To control unpacking and packing, you write a @dfn{data layout
2604 specification}, a special nested list describing named and typed
2605 @dfn{fields}. This specification controls length of each field to be
2606 processed, and how to pack or unpack it. We normally keep bindat specs
2607 in variables whose names end in @samp{-bindat-spec}; that kind of name
2608 is automatically recognized as ``risky.''
2612 @cindex little endian
2613 @cindex network byte ordering
2614 A field's @dfn{type} describes the size (in bytes) of the object
2615 that the field represents and, in the case of multibyte fields, how
2616 the bytes are ordered within the field. The two possible orderings
2617 are ``big endian'' (also known as ``network byte ordering'') and
2618 ``little endian.'' For instance, the number @code{#x23cd} (decimal
2619 9165) in big endian would be the two bytes @code{#x23} @code{#xcd};
2620 and in little endian, @code{#xcd} @code{#x23}. Here are the possible
2626 Unsigned byte, with length 1.
2631 Unsigned integer in network byte order, with length 2.
2634 Unsigned integer in network byte order, with length 3.
2639 Unsigned integer in network byte order, with length 4.
2640 Note: These values may be limited by Emacs' integer implementation limits.
2645 Unsigned integer in little endian order, with length 2, 3 and 4, respectively.
2648 String of length @var{len}.
2650 @item strz @var{len}
2651 Zero-terminated string, in a fixed-size field with length @var{len}.
2653 @item vec @var{len} [@var{type}]
2654 Vector of @var{len} elements of type @var{type}, or bytes if not
2655 @var{type} is specified.
2656 The @var{type} is any of the simple types above, or another vector
2657 specified as a list @code{(vec @var{len} [@var{type}])}.
2660 Four-byte vector representing an Internet address. For example:
2661 @code{[127 0 0 1]} for localhost.
2663 @item bits @var{len}
2664 List of set bits in @var{len} bytes. The bytes are taken in big
2665 endian order and the bits are numbered starting with @code{8 *
2666 @var{len} @minus{} 1} and ending with zero. For example: @code{bits
2667 2} unpacks @code{#x28} @code{#x1c} to @code{(2 3 4 11 13)} and
2668 @code{#x1c} @code{#x28} to @code{(3 5 10 11 12)}.
2670 @item (eval @var{form})
2671 @var{form} is a Lisp expression evaluated at the moment the field is
2672 unpacked or packed. The result of the evaluation should be one of the
2673 above-listed type specifications.
2676 For a fixed-size field, the length @var{len} is given as an integer
2677 specifying the number of bytes in the field.
2679 When the length of a field is not fixed, it typically depends on the
2680 value of a preceding field. In this case, the length @var{len} can be
2681 given either as a list @code{(@var{name} ...)} identifying a
2682 @dfn{field name} in the format specified for @code{bindat-get-field}
2683 below, or by an expression @code{(eval @var{form})} where @var{form}
2684 should evaluate to an integer, specifying the field length.
2686 A field specification generally has the form @code{([@var{name}]
2687 @var{handler})}. The square braces indicate that @var{name} is
2688 optional. (Don't use names that are symbols meaningful as type
2689 specifications (above) or handler specifications (below), since that
2690 would be ambiguous.) @var{name} can be a symbol or the expression
2691 @code{(eval @var{form})}, in which case @var{form} should evaluate to
2694 @var{handler} describes how to unpack or pack the field and can be one
2699 Unpack/pack this field according to the type specification @var{type}.
2701 @item eval @var{form}
2702 Evaluate @var{form}, a Lisp expression, for side-effect only. If the
2703 field name is specified, the value is bound to that field name.
2705 @item fill @var{len}
2706 Skip @var{len} bytes. In packing, this leaves them unchanged,
2707 which normally means they remain zero. In unpacking, this means
2710 @item align @var{len}
2711 Skip to the next multiple of @var{len} bytes.
2713 @item struct @var{spec-name}
2714 Process @var{spec-name} as a sub-specification. This describes a
2715 structure nested within another structure.
2717 @item union @var{form} (@var{tag} @var{spec})@dots{}
2718 @c ??? I don't see how one would actually use this.
2719 @c ??? what kind of expression would be useful for @var{form}?
2720 Evaluate @var{form}, a Lisp expression, find the first @var{tag}
2721 that matches it, and process its associated data layout specification
2722 @var{spec}. Matching can occur in one of three ways:
2726 If a @var{tag} has the form @code{(eval @var{expr})}, evaluate
2727 @var{expr} with the variable @code{tag} dynamically bound to the value
2728 of @var{form}. A non-@code{nil} result indicates a match.
2731 @var{tag} matches if it is @code{equal} to the value of @var{form}.
2734 @var{tag} matches unconditionally if it is @code{t}.
2737 @item repeat @var{count} @var{field-specs}@dots{}
2738 Process the @var{field-specs} recursively, in order, then repeat
2739 starting from the first one, processing all the specs @var{count}
2740 times overall. The @var{count} is given using the same formats as a
2741 field length---if an @code{eval} form is used, it is evaluated just once.
2742 For correct operation, each spec in @var{field-specs} must include a name.
2745 For the @code{(eval @var{form})} forms used in a bindat specification,
2746 the @var{form} can access and update these dynamically bound variables
2751 Value of the last field processed.
2754 The data as a byte array.
2757 Current index (within @code{bindat-raw}) for unpacking or packing.
2760 The alist containing the structured data that have been unpacked so
2761 far, or the entire structure being packed. You can use
2762 @code{bindat-get-field} to access specific fields of this structure.
2766 Inside a @code{repeat} block, these contain the maximum number of
2767 repetitions (as specified by the @var{count} parameter), and the
2768 current repetition number (counting from 0). Setting @code{count} to
2769 zero will terminate the inner-most repeat block after the current
2770 repetition has completed.
2773 @node Bindat Functions
2774 @subsection Functions to Unpack and Pack Bytes
2776 In the following documentation, @var{spec} refers to a data layout
2777 specification, @code{bindat-raw} to a byte array, and @var{struct} to an
2778 alist representing unpacked field data.
2780 @defun bindat-unpack spec bindat-raw &optional bindat-idx
2781 This function unpacks data from the unibyte string or byte
2782 array @code{bindat-raw}
2783 according to @var{spec}. Normally this starts unpacking at the
2784 beginning of the byte array, but if @var{bindat-idx} is non-@code{nil}, it
2785 specifies a zero-based starting position to use instead.
2787 The value is an alist or nested alist in which each element describes
2791 @defun bindat-get-field struct &rest name
2792 This function selects a field's data from the nested alist
2793 @var{struct}. Usually @var{struct} was returned by
2794 @code{bindat-unpack}. If @var{name} corresponds to just one argument,
2795 that means to extract a top-level field value. Multiple @var{name}
2796 arguments specify repeated lookup of sub-structures. An integer name
2797 acts as an array index.
2799 For example, if @var{name} is @code{(a b 2 c)}, that means to find
2800 field @code{c} in the third element of subfield @code{b} of field
2801 @code{a}. (This corresponds to @code{struct.a.b[2].c} in C.)
2804 Although packing and unpacking operations change the organization of
2805 data (in memory), they preserve the data's @dfn{total length}, which is
2806 the sum of all the fields' lengths, in bytes. This value is not
2807 generally inherent in either the specification or alist alone; instead,
2808 both pieces of information contribute to its calculation. Likewise, the
2809 length of a string or array being unpacked may be longer than the data's
2810 total length as described by the specification.
2812 @defun bindat-length spec struct
2813 This function returns the total length of the data in @var{struct},
2814 according to @var{spec}.
2817 @defun bindat-pack spec struct &optional bindat-raw bindat-idx
2818 This function returns a byte array packed according to @var{spec} from
2819 the data in the alist @var{struct}. Normally it creates and fills a
2820 new byte array starting at the beginning. However, if @var{bindat-raw}
2821 is non-@code{nil}, it specifies a pre-allocated unibyte string or vector to
2822 pack into. If @var{bindat-idx} is non-@code{nil}, it specifies the starting
2823 offset for packing into @code{bindat-raw}.
2825 When pre-allocating, you should make sure @code{(length @var{bindat-raw})}
2826 meets or exceeds the total length to avoid an out-of-range error.
2829 @defun bindat-ip-to-string ip
2830 Convert the Internet address vector @var{ip} to a string in the usual
2834 (bindat-ip-to-string [127 0 0 1])
2835 @result{} "127.0.0.1"
2839 @node Bindat Examples
2840 @subsection Examples of Byte Unpacking and Packing
2842 Here is a complete example of byte unpacking and packing:
2845 (defvar fcookie-index-spec
2853 (:offset repeat (:count)
2855 "Description of a fortune cookie index file's contents.")
2857 (defun fcookie (cookies &optional index)
2858 "Display a random fortune cookie from file COOKIES.
2859 Optional second arg INDEX specifies the associated index
2860 filename, which is by default constructed by appending
2861 \".dat\" to COOKIES. Display cookie text in possibly
2862 new buffer \"*Fortune Cookie: BASENAME*\" where BASENAME
2863 is COOKIES without the directory part."
2864 (interactive "fCookies file: ")
2865 (let* ((info (with-temp-buffer
2866 (insert-file-contents-literally
2867 (or index (concat cookies ".dat")))
2868 (bindat-unpack fcookie-index-spec
2870 (sel (random (bindat-get-field info :count)))
2871 (beg (cdar (bindat-get-field info :offset sel)))
2872 (end (or (cdar (bindat-get-field info
2874 (nth 7 (file-attributes cookies)))))
2877 (format "*Fortune Cookie: %s*"
2878 (file-name-nondirectory cookies))))
2880 (insert-file-contents-literally
2881 cookies nil beg (- end 3))))
2883 (defun fcookie-create-index (cookies &optional index delim)
2884 "Scan file COOKIES, and write out its index file.
2885 Optional second arg INDEX specifies the index filename,
2886 which is by default constructed by appending \".dat\" to
2887 COOKIES. Optional third arg DELIM specifies the unibyte
2888 character which, when found on a line of its own in
2889 COOKIES, indicates the border between entries."
2890 (interactive "fCookies file: ")
2891 (setq delim (or delim ?%))
2892 (let ((delim-line (format "\n%c\n" delim))
2895 min p q len offsets)
2896 (unless (= 3 (string-bytes delim-line))
2897 (error "Delimiter cannot be represented in one byte"))
2899 (insert-file-contents-literally cookies)
2900 (while (and (setq p (point))
2901 (search-forward delim-line (point-max) t)
2902 (setq len (- (point) 3 p)))
2903 (setq count (1+ count)
2905 min (min (or min max) len)
2906 offsets (cons (1- p) offsets))))
2908 (set-buffer-multibyte nil)
2918 (:offset . ,(mapcar (lambda (o)
2919 (list (cons :foo o)))
2920 (nreverse offsets))))))
2921 (let ((coding-system-for-write 'raw-text-unix))
2922 (write-file (or index (concat cookies ".dat")))))))
2925 Following is an example of defining and unpacking a complex structure.
2926 Consider the following C structures:
2930 unsigned long dest_ip;
2931 unsigned long src_ip;
2932 unsigned short dest_port;
2933 unsigned short src_port;
2938 unsigned char opcode;
2939 unsigned short length; /* In network byte order */
2940 unsigned char id[8]; /* null-terminated string */
2941 unsigned char data[/* (length + 3) & ~3 */];
2945 struct header header;
2946 unsigned long counters[2]; /* In little endian order */
2947 unsigned char items;
2948 unsigned char filler[3];
2949 struct data item[/* items */];
2954 The corresponding data layout specification:
2966 (length u16) ;; network byte order
2972 '((header struct header-spec)
2973 (counters vec 2 u32r) ;; little endian order
2976 (item repeat (items)
2977 (struct data-spec))))
2980 A binary data representation:
2984 [ 192 168 1 100 192 168 1 101 01 28 21 32
2985 160 134 1 0 5 1 0 0 2 0 0 0
2986 2 3 0 5 ?A ?B ?C ?D ?E ?F 0 0 1 2 3 4 5 0 0 0
2987 1 4 0 7 ?B ?C ?D ?E ?F ?G 0 0 6 7 8 9 10 11 12 0 ])
2990 The corresponding decoded structure:
2993 (setq decoded (bindat-unpack packet-spec binary-data))
2996 (dest-ip . [192 168 1 100])
2997 (src-ip . [192 168 1 101])
3000 (counters . [100000 261])
3002 (item ((data . [1 2 3 4 5])
3007 ((data . [6 7 8 9 10 11 12])
3014 Fetching data from this structure:
3017 (bindat-get-field decoded 'item 1 'id)