2 @c This is part of the GNU Emacs Lisp Reference Manual.
3 @c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2001,
4 @c 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 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 network 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 shell command line
198 The following two functions help creating shell commands from
199 individual argument strings and taking shell command lines apart into
200 individual arguments.
202 @defun split-string-and-unquote string &optional separators
203 This function splits @var{string} into substrings at matches for the
204 regular expression @var{separators}, like @code{split-string} does
205 (@pxref{Creating Strings}), but it additionally removes quoting from
206 the substrings. It then makes a list of the substrings and returns
209 If @var{separators} is omitted or @code{nil}, it defaults to
210 @code{"\\s-+"}, which is a regular expression that matches one or more
211 characters with whitespace syntax (@pxref{Syntax Class Table}).
213 The quoting this function supports is of 2 styles: by enclosing a
214 whole string in double quotes @code{"@dots{}"}, or by quoting
215 individual characters with a backslash escape @samp{\}. The latter is
216 also used in Lisp strings, so this function can handle those as well.
219 @defun combine-and-quote-strings list-of-strings &optional separator
220 This function concatenates @var{list-of-strings} into a single string,
221 quoting each string in the list that needs quoting as it goes. It
222 also sticks the @var{separator} string in between each pair of strings
223 in the result, and returns that result. If @var{separator} is omitted
224 or @code{nil}, it defaults to a blank @code{" "}.
226 The strings in @var{list-of-strings} that need quoting are those that
227 include @var{separator} as their substring. Quoting a string encloses
228 it in double quotes @code{"@dots{}"}. In the simplest case, if you
229 are consing a shell command from the individual command-line
230 arguments, every argument that includes embedded blanks will be
234 @node Synchronous Processes
235 @section Creating a Synchronous Process
236 @cindex synchronous subprocess
238 After a @dfn{synchronous process} is created, Emacs waits for the
239 process to terminate before continuing. Starting Dired on GNU or
240 Unix@footnote{On other systems, Emacs uses a Lisp emulation of
241 @code{ls}; see @ref{Contents of Directories}.} is an example of this: it
242 runs @code{ls} in a synchronous process, then modifies the output
243 slightly. Because the process is synchronous, the entire directory
244 listing arrives in the buffer before Emacs tries to do anything with it.
246 While Emacs waits for the synchronous subprocess to terminate, the
247 user can quit by typing @kbd{C-g}. The first @kbd{C-g} tries to kill
248 the subprocess with a @code{SIGINT} signal; but it waits until the
249 subprocess actually terminates before quitting. If during that time the
250 user types another @kbd{C-g}, that kills the subprocess instantly with
251 @code{SIGKILL} and quits immediately (except on MS-DOS, where killing
252 other processes doesn't work). @xref{Quitting}.
254 The synchronous subprocess functions return an indication of how the
257 The output from a synchronous subprocess is generally decoded using a
258 coding system, much like text read from a file. The input sent to a
259 subprocess by @code{call-process-region} is encoded using a coding
260 system, much like text written into a file. @xref{Coding Systems}.
262 @defun call-process program &optional infile destination display &rest args
263 This function calls @var{program} in a separate process and waits for
266 The standard input for the process comes from file @var{infile} if
267 @var{infile} is not @code{nil}, and from the null device otherwise.
268 The argument @var{destination} says where to put the process output.
269 Here are the possibilities:
273 Insert the output in that buffer, before point. This includes both the
274 standard output stream and the standard error stream of the process.
277 Insert the output in a buffer with that name, before point.
280 Insert the output in the current buffer, before point.
286 Discard the output, and return @code{nil} immediately without waiting
287 for the subprocess to finish.
289 In this case, the process is not truly synchronous, since it can run in
290 parallel with Emacs; but you can think of it as synchronous in that
291 Emacs is essentially finished with the subprocess as soon as this
294 MS-DOS doesn't support asynchronous subprocesses, so this option doesn't
297 @item @code{(@var{real-destination} @var{error-destination})}
298 Keep the standard output stream separate from the standard error stream;
299 deal with the ordinary output as specified by @var{real-destination},
300 and dispose of the error output according to @var{error-destination}.
301 If @var{error-destination} is @code{nil}, that means to discard the
302 error output, @code{t} means mix it with the ordinary output, and a
303 string specifies a file name to redirect error output into.
305 You can't directly specify a buffer to put the error output in; that is
306 too difficult to implement. But you can achieve this result by sending
307 the error output to a temporary file and then inserting the file into a
311 If @var{display} is non-@code{nil}, then @code{call-process} redisplays
312 the buffer as output is inserted. (However, if the coding system chosen
313 for decoding output is @code{undecided}, meaning deduce the encoding
314 from the actual data, then redisplay sometimes cannot continue once
315 non-@acronym{ASCII} characters are encountered. There are fundamental
316 reasons why it is hard to fix this; see @ref{Output from Processes}.)
318 Otherwise the function @code{call-process} does no redisplay, and the
319 results become visible on the screen only when Emacs redisplays that
320 buffer in the normal course of events.
322 The remaining arguments, @var{args}, are strings that specify command
323 line arguments for the program.
325 The value returned by @code{call-process} (unless you told it not to
326 wait) indicates the reason for process termination. A number gives the
327 exit status of the subprocess; 0 means success, and any other value
328 means failure. If the process terminated with a signal,
329 @code{call-process} returns a string describing the signal.
331 In the examples below, the buffer @samp{foo} is current.
335 (call-process "pwd" nil t)
338 ---------- Buffer: foo ----------
339 /usr/user/lewis/manual
340 ---------- Buffer: foo ----------
344 (call-process "grep" nil "bar" nil "lewis" "/etc/passwd")
347 ---------- Buffer: bar ----------
348 lewis:5LTsHm66CSWKg:398:21:Bil Lewis:/user/lewis:/bin/csh
350 ---------- Buffer: bar ----------
354 Here is a good example of the use of @code{call-process}, which used to
355 be found in the definition of @code{insert-directory}:
359 (call-process insert-directory-program nil t nil @var{switches}
361 (concat (file-name-as-directory file) ".")
367 @defun process-file program &optional infile buffer display &rest args
368 This function processes files synchronously in a separate process. It
369 is similar to @code{call-process} but may invoke a file handler based
370 on the value of the variable @code{default-directory}. The current
371 working directory of the subprocess is @code{default-directory}.
373 The arguments are handled in almost the same way as for
374 @code{call-process}, with the following differences:
376 Some file handlers may not support all combinations and forms of the
377 arguments @var{infile}, @var{buffer}, and @var{display}. For example,
378 some file handlers might behave as if @var{display} were @code{nil},
379 regardless of the value actually passed. As another example, some
380 file handlers might not support separating standard output and error
381 output by way of the @var{buffer} argument.
383 If a file handler is invoked, it determines the program to run based
384 on the first argument @var{program}. For instance, consider that a
385 handler for remote files is invoked. Then the path that is used for
386 searching the program might be different than @code{exec-path}.
388 The second argument @var{infile} may invoke a file handler. The file
389 handler could be different from the handler chosen for the
390 @code{process-file} function itself. (For example,
391 @code{default-directory} could be on a remote host, whereas
392 @var{infile} is on another remote host. Or @code{default-directory}
393 could be non-special, whereas @var{infile} is on a remote host.)
395 If @var{buffer} is a list of the form @code{(@var{real-destination}
396 @var{error-destination})}, and @var{error-destination} names a file,
397 then the same remarks as for @var{infile} apply.
399 The remaining arguments (@var{args}) will be passed to the process
400 verbatim. Emacs is not involved in processing file names that are
401 present in @var{args}. To avoid confusion, it may be best to avoid
402 absolute file names in @var{args}, but rather to specify all file
403 names as relative to @code{default-directory}. The function
404 @code{file-relative-name} is useful for constructing such relative
408 @defun call-process-region start end program &optional delete destination display &rest args
409 This function sends the text from @var{start} to @var{end} as
410 standard input to a process running @var{program}. It deletes the text
411 sent if @var{delete} is non-@code{nil}; this is useful when
412 @var{destination} is @code{t}, to insert the output in the current
413 buffer in place of the input.
415 The arguments @var{destination} and @var{display} control what to do
416 with the output from the subprocess, and whether to update the display
417 as it comes in. For details, see the description of
418 @code{call-process}, above. If @var{destination} is the integer 0,
419 @code{call-process-region} discards the output and returns @code{nil}
420 immediately, without waiting for the subprocess to finish (this only
421 works if asynchronous subprocesses are supported).
423 The remaining arguments, @var{args}, are strings that specify command
424 line arguments for the program.
426 The return value of @code{call-process-region} is just like that of
427 @code{call-process}: @code{nil} if you told it to return without
428 waiting; otherwise, a number or string which indicates how the
429 subprocess terminated.
431 In the following example, we use @code{call-process-region} to run the
432 @code{cat} utility, with standard input being the first five characters
433 in buffer @samp{foo} (the word @samp{input}). @code{cat} copies its
434 standard input into its standard output. Since the argument
435 @var{destination} is @code{t}, this output is inserted in the current
440 ---------- Buffer: foo ----------
442 ---------- Buffer: foo ----------
446 (call-process-region 1 6 "cat" nil t)
449 ---------- Buffer: foo ----------
451 ---------- Buffer: foo ----------
455 The @code{shell-command-on-region} command uses
456 @code{call-process-region} like this:
462 shell-file-name ; @r{Name of program.}
463 nil ; @r{Do not delete region.}
464 buffer ; @r{Send output to @code{buffer}.}
465 nil ; @r{No redisplay during output.}
466 "-c" command) ; @r{Arguments for the shell.}
471 @defun call-process-shell-command command &optional infile destination display &rest args
472 This function executes the shell command @var{command} synchronously
473 in a separate process. The final arguments @var{args} are additional
474 arguments to add at the end of @var{command}. The other arguments
475 are handled as in @code{call-process}.
478 @defun process-file-shell-command command &optional infile destination display &rest args
479 This function is like @code{call-process-shell-command}, but uses
480 @code{process-file} internally. Depending on @code{default-directory},
481 @var{command} can be executed also on remote hosts.
484 @defun shell-command-to-string command
485 This function executes @var{command} (a string) as a shell command,
486 then returns the command's output as a string.
489 @defun process-lines program &rest args
490 This function runs @var{program} in a separate process, waits for it
491 to finish, and returns its output as a list of strings. Each string
492 in the list holds a single line of text output by the program; the
493 end-of-line characters are stripped from each line. The arguments
494 beyond @var{program}, @var{args}, are strings that specify
495 command-line arguments with which to run the program.
497 If @var{program} exits with a non-zero exit status, this function
500 This function works by calling @code{call-process}, so program output
501 is decoded in the same way as for @code{call-process}.
504 @node Asynchronous Processes
505 @section Creating an Asynchronous Process
506 @cindex asynchronous subprocess
508 After an @dfn{asynchronous process} is created, Emacs and the subprocess
509 both continue running immediately. The process thereafter runs
510 in parallel with Emacs, and the two can communicate with each other
511 using the functions described in the following sections. However,
512 communication is only partially asynchronous: Emacs sends data to the
513 process only when certain functions are called, and Emacs accepts data
514 from the process only when Emacs is waiting for input or for a time
517 Here we describe how to create an asynchronous process.
519 @defun start-process name buffer-or-name program &rest args
520 This function creates a new asynchronous subprocess and starts the
521 program @var{program} running in it. It returns a process object that
522 stands for the new subprocess in Lisp. The argument @var{name}
523 specifies the name for the process object; if a process with this name
524 already exists, then @var{name} is modified (by appending @samp{<1>},
525 etc.) to be unique. The buffer @var{buffer-or-name} is the buffer to
526 associate with the process.
528 The remaining arguments, @var{args}, are strings that specify command
529 line arguments for the program.
531 In the example below, the first process is started and runs (rather,
532 sleeps) for 100 seconds. Meanwhile, the second process is started, and
533 given the name @samp{my-process<1>} for the sake of uniqueness. It
534 inserts the directory listing at the end of the buffer @samp{foo},
535 before the first process finishes. Then it finishes, and a message to
536 that effect is inserted in the buffer. Much later, the first process
537 finishes, and another message is inserted in the buffer for it.
541 (start-process "my-process" "foo" "sleep" "100")
542 @result{} #<process my-process>
546 (start-process "my-process" "foo" "ls" "-l" "/user/lewis/bin")
547 @result{} #<process my-process<1>>
549 ---------- Buffer: foo ----------
551 lrwxrwxrwx 1 lewis 14 Jul 22 10:12 gnuemacs --> /emacs
552 -rwxrwxrwx 1 lewis 19 Jul 30 21:02 lemon
554 Process my-process<1> finished
556 Process my-process finished
557 ---------- Buffer: foo ----------
562 @defun start-file-process name buffer-or-name program &rest args
563 Like @code{start-process}, this function starts a new asynchronous
564 subprocess running @var{program} in it, and returns its process
565 object---when @code{default-directory} is not a magic file name.
567 If @code{default-directory} is magic, the function invokes its file
568 handler instead. This handler ought to run @var{program}, perhaps on
569 the local host, perhaps on a remote host that corresponds to
570 @code{default-directory}. In the latter case, the local part of
571 @code{default-directory} becomes the working directory of the process.
573 This function does not try to invoke file name handlers for
574 @var{program} or for the @var{program-args}.
576 Depending on the implementation of the file handler, it might not be
577 possible to apply @code{process-filter} or @code{process-sentinel} to
578 the resulting process object (@pxref{Filter Functions}, @pxref{Sentinels}).
580 Some file handlers may not support @code{start-file-process} (for
581 example @code{ange-ftp-hook-function}). In such cases, the function
582 does nothing and returns @code{nil}.
585 @defun start-process-shell-command name buffer-or-name command &rest command-args
586 This function is like @code{start-process} except that it uses a shell
587 to execute the specified command. The argument @var{command} is a shell
588 command name, and @var{command-args} are the arguments for the shell
589 command. The variable @code{shell-file-name} specifies which shell to
592 The point of running a program through the shell, rather than directly
593 with @code{start-process}, is so that you can employ shell features such
594 as wildcards in the arguments. It follows that if you include an
595 arbitrary user-specified arguments in the command, you should quote it
596 with @code{shell-quote-argument} first, so that any special shell
597 characters do @emph{not} have their special shell meanings. @xref{Shell
601 @defun start-file-process-shell-command name buffer-or-name command &rest command-args
602 This function is like @code{start-process-shell-command}, but uses
603 @code{start-file-process} internally. By this, @var{command} can be
604 executed also on remote hosts, depending on @code{default-directory}.
607 @defvar process-connection-type
609 @cindex @acronym{PTY}s
610 This variable controls the type of device used to communicate with
611 asynchronous subprocesses. If it is non-@code{nil}, then @acronym{PTY}s are
612 used, when available. Otherwise, pipes are used.
614 @acronym{PTY}s are usually preferable for processes visible to the user, as
615 in Shell mode, because they allow job control (@kbd{C-c}, @kbd{C-z},
616 etc.) to work between the process and its children, whereas pipes do
617 not. For subprocesses used for internal purposes by programs, it is
618 often better to use a pipe, because they are more efficient. In
619 addition, the total number of @acronym{PTY}s is limited on many systems and
620 it is good not to waste them.
622 The value of @code{process-connection-type} takes effect when
623 @code{start-process} is called. So you can specify how to communicate
624 with one subprocess by binding the variable around the call to
625 @code{start-process}.
629 (let ((process-connection-type nil)) ; @r{Use a pipe.}
630 (start-process @dots{}))
634 To determine whether a given subprocess actually got a pipe or a
635 @acronym{PTY}, use the function @code{process-tty-name} (@pxref{Process
639 @node Deleting Processes
640 @section Deleting Processes
641 @cindex deleting processes
643 @dfn{Deleting a process} disconnects Emacs immediately from the
644 subprocess. Processes are deleted automatically after they terminate,
645 but not necessarily right away. You can delete a process explicitly
646 at any time. If you delete a terminated process explicitly before it
647 is deleted automatically, no harm results. Deleting a running
648 process sends a signal to terminate it (and its child processes if
649 any), and calls the process sentinel if it has one. @xref{Sentinels}.
651 When a process is deleted, the process object itself continues to
652 exist as long as other Lisp objects point to it. All the Lisp
653 primitives that work on process objects accept deleted processes, but
654 those that do I/O or send signals will report an error. The process
655 mark continues to point to the same place as before, usually into a
656 buffer where output from the process was being inserted.
658 @defopt delete-exited-processes
659 This variable controls automatic deletion of processes that have
660 terminated (due to calling @code{exit} or to a signal). If it is
661 @code{nil}, then they continue to exist until the user runs
662 @code{list-processes}. Otherwise, they are deleted immediately after
666 @defun delete-process process
667 This function deletes a process, killing it with a @code{SIGKILL}
668 signal. The argument may be a process, the name of a process, a
669 buffer, or the name of a buffer. (A buffer or buffer-name stands for
670 the process that @code{get-buffer-process} returns.) Calling
671 @code{delete-process} on a running process terminates it, updates the
672 process status, and runs the sentinel (if any) immediately. If the
673 process has already terminated, calling @code{delete-process} has no
674 effect on its status, or on the running of its sentinel (which will
675 happen sooner or later).
679 (delete-process "*shell*")
685 @node Process Information
686 @section Process Information
688 Several functions return information about processes.
689 @code{list-processes} is provided for interactive use.
691 @deffn Command list-processes &optional query-only
692 This command displays a listing of all living processes. In addition,
693 it finally deletes any process whose status was @samp{Exited} or
694 @samp{Signaled}. It returns @code{nil}.
696 If @var{query-only} is non-@code{nil} then it lists only processes
697 whose query flag is non-@code{nil}. @xref{Query Before Exit}.
701 This function returns a list of all processes that have not been deleted.
706 @result{} (#<process display-time> #<process shell>)
711 @defun get-process name
712 This function returns the process named @var{name}, or @code{nil} if
713 there is none. An error is signaled if @var{name} is not a string.
717 (get-process "shell")
718 @result{} #<process shell>
723 @defun process-command process
724 This function returns the command that was executed to start
725 @var{process}. This is a list of strings, the first string being the
726 program executed and the rest of the strings being the arguments that
727 were given to the program.
731 (process-command (get-process "shell"))
732 @result{} ("/bin/csh" "-i")
737 @defun process-contact process &optional key
739 This function returns information about how a network or serial
740 process was set up. For a network process, when @var{key} is
741 @code{nil}, it returns @code{(@var{hostname} @var{service})} which
742 specifies what you connected to. For a serial process, when @var{key}
743 is @code{nil}, it returns @code{(@var{port} @var{speed})}. For an
744 ordinary child process, this function always returns @code{t}.
746 If @var{key} is @code{t}, the value is the complete status information
747 for the connection, server, or serial port; that is, the list of
748 keywords and values specified in @code{make-network-process} or
749 @code{make-serial-process}, except that some of the values represent
750 the current status instead of what you specified.
752 For a network process:
756 The associated value is the process buffer.
758 The associated value is the process filter function.
760 The associated value is the process sentinel function.
762 In a connection, the address in internal format of the remote peer.
764 The local address, in internal format.
766 In a server, if you specified @code{t} for @var{service},
767 this value is the actual port number.
770 @code{:local} and @code{:remote} are included even if they were not
771 specified explicitly in @code{make-network-process}.
773 For a serial process, see @code{make-serial-process} and
774 @code{serial-process-configure} for a list of keys.
776 If @var{key} is a keyword, the function returns the value corresponding
780 @defun process-id process
781 This function returns the @acronym{PID} of @var{process}. This is an
782 integer that distinguishes the process @var{process} from all other
783 processes running on the same computer at the current time. The
784 @acronym{PID} of a process is chosen by the operating system kernel when the
785 process is started and remains constant as long as the process exists.
788 @defun process-name process
789 This function returns the name of @var{process}.
792 @defun process-status process-name
793 This function returns the status of @var{process-name} as a symbol.
794 The argument @var{process-name} must be a process, a buffer, or a
795 process name (a string).
797 The possible values for an actual subprocess are:
801 for a process that is running.
803 for a process that is stopped but continuable.
805 for a process that has exited.
807 for a process that has received a fatal signal.
809 for a network connection that is open.
811 for a network connection that is closed. Once a connection
812 is closed, you cannot reopen it, though you might be able to open
813 a new connection to the same place.
815 for a non-blocking connection that is waiting to complete.
817 for a non-blocking connection that has failed to complete.
819 for a network server that is listening.
821 if @var{process-name} is not the name of an existing process.
826 (process-status (get-buffer "*shell*"))
831 @result{} #<process xx<1>>
837 For a network connection, @code{process-status} returns one of the symbols
838 @code{open} or @code{closed}. The latter means that the other side
839 closed the connection, or Emacs did @code{delete-process}.
842 @defun process-type process
843 This function returns the symbol @code{network} for a network
844 connection or server, @code{serial} for a serial port connection, or
845 @code{real} for a real subprocess.
848 @defun process-exit-status process
849 This function returns the exit status of @var{process} or the signal
850 number that killed it. (Use the result of @code{process-status} to
851 determine which of those it is.) If @var{process} has not yet
852 terminated, the value is 0.
855 @defun process-tty-name process
856 This function returns the terminal name that @var{process} is using for
857 its communication with Emacs---or @code{nil} if it is using pipes
858 instead of a terminal (see @code{process-connection-type} in
859 @ref{Asynchronous Processes}).
862 @defun process-coding-system process
863 @anchor{Coding systems for a subprocess}
864 This function returns a cons cell describing the coding systems in use
865 for decoding output from @var{process} and for encoding input to
866 @var{process} (@pxref{Coding Systems}). The value has this form:
869 (@var{coding-system-for-decoding} . @var{coding-system-for-encoding})
873 @defun set-process-coding-system process &optional decoding-system encoding-system
874 This function specifies the coding systems to use for subsequent output
875 from and input to @var{process}. It will use @var{decoding-system} to
876 decode subprocess output, and @var{encoding-system} to encode subprocess
880 Every process also has a property list that you can use to store
881 miscellaneous values associated with the process.
883 @defun process-get process propname
884 This function returns the value of the @var{propname} property
888 @defun process-put process propname value
889 This function sets the value of the @var{propname} property
890 of @var{process} to @var{value}.
893 @defun process-plist process
894 This function returns the process plist of @var{process}.
897 @defun set-process-plist process plist
898 This function sets the process plist of @var{process} to @var{plist}.
901 @node Input to Processes
902 @section Sending Input to Processes
903 @cindex process input
905 Asynchronous subprocesses receive input when it is sent to them by
906 Emacs, which is done with the functions in this section. You must
907 specify the process to send input to, and the input data to send. The
908 data appears on the ``standard input'' of the subprocess.
910 Some operating systems have limited space for buffered input in a
911 @acronym{PTY}. On these systems, Emacs sends an @acronym{EOF}
912 periodically amidst the other characters, to force them through. For
913 most programs, these @acronym{EOF}s do no harm.
915 Subprocess input is normally encoded using a coding system before the
916 subprocess receives it, much like text written into a file. You can use
917 @code{set-process-coding-system} to specify which coding system to use
918 (@pxref{Process Information}). Otherwise, the coding system comes from
919 @code{coding-system-for-write}, if that is non-@code{nil}; or else from
920 the defaulting mechanism (@pxref{Default Coding Systems}).
922 Sometimes the system is unable to accept input for that process,
923 because the input buffer is full. When this happens, the send functions
924 wait a short while, accepting output from subprocesses, and then try
925 again. This gives the subprocess a chance to read more of its pending
926 input and make space in the buffer. It also allows filters, sentinels
927 and timers to run---so take account of that in writing your code.
929 In these functions, the @var{process} argument can be a process or
930 the name of a process, or a buffer or buffer name (which stands
931 for a process via @code{get-buffer-process}). @code{nil} means
932 the current buffer's process.
934 @defun process-send-string process string
935 This function sends @var{process} the contents of @var{string} as
936 standard input. If it is @code{nil}, the current buffer's process is used.
938 The function returns @code{nil}.
942 (process-send-string "shell<1>" "ls\n")
948 ---------- Buffer: *shell* ----------
950 introduction.texi syntax-tables.texi~
951 introduction.texi~ text.texi
952 introduction.txt text.texi~
954 ---------- Buffer: *shell* ----------
959 @defun process-send-region process start end
960 This function sends the text in the region defined by @var{start} and
961 @var{end} as standard input to @var{process}.
963 An error is signaled unless both @var{start} and @var{end} are
964 integers or markers that indicate positions in the current buffer. (It
965 is unimportant which number is larger.)
968 @defun process-send-eof &optional process
969 This function makes @var{process} see an end-of-file in its
970 input. The @acronym{EOF} comes after any text already sent to it.
972 The function returns @var{process}.
976 (process-send-eof "shell")
982 @defun process-running-child-p &optional process
983 This function will tell you whether a @var{process} has given control of
984 its terminal to its own child process. The value is @code{t} if this is
985 true, or if Emacs cannot tell; it is @code{nil} if Emacs can be certain
989 @node Signals to Processes
990 @section Sending Signals to Processes
991 @cindex process signals
992 @cindex sending signals
995 @dfn{Sending a signal} to a subprocess is a way of interrupting its
996 activities. There are several different signals, each with its own
997 meaning. The set of signals and their names is defined by the operating
998 system. For example, the signal @code{SIGINT} means that the user has
999 typed @kbd{C-c}, or that some analogous thing has happened.
1001 Each signal has a standard effect on the subprocess. Most signals
1002 kill the subprocess, but some stop or resume execution instead. Most
1003 signals can optionally be handled by programs; if the program handles
1004 the signal, then we can say nothing in general about its effects.
1006 You can send signals explicitly by calling the functions in this
1007 section. Emacs also sends signals automatically at certain times:
1008 killing a buffer sends a @code{SIGHUP} signal to all its associated
1009 processes; killing Emacs sends a @code{SIGHUP} signal to all remaining
1010 processes. (@code{SIGHUP} is a signal that usually indicates that the
1011 user hung up the phone.)
1013 Each of the signal-sending functions takes two optional arguments:
1014 @var{process} and @var{current-group}.
1016 The argument @var{process} must be either a process, a process
1017 name, a buffer, a buffer name, or @code{nil}. A buffer or buffer name
1018 stands for a process through @code{get-buffer-process}. @code{nil}
1019 stands for the process associated with the current buffer. An error
1020 is signaled if @var{process} does not identify a process.
1022 The argument @var{current-group} is a flag that makes a difference
1023 when you are running a job-control shell as an Emacs subprocess. If it
1024 is non-@code{nil}, then the signal is sent to the current process-group
1025 of the terminal that Emacs uses to communicate with the subprocess. If
1026 the process is a job-control shell, this means the shell's current
1027 subjob. If it is @code{nil}, the signal is sent to the process group of
1028 the immediate subprocess of Emacs. If the subprocess is a job-control
1029 shell, this is the shell itself.
1031 The flag @var{current-group} has no effect when a pipe is used to
1032 communicate with the subprocess, because the operating system does not
1033 support the distinction in the case of pipes. For the same reason,
1034 job-control shells won't work when a pipe is used. See
1035 @code{process-connection-type} in @ref{Asynchronous Processes}.
1037 @defun interrupt-process &optional process current-group
1038 This function interrupts the process @var{process} by sending the
1039 signal @code{SIGINT}. Outside of Emacs, typing the ``interrupt
1040 character'' (normally @kbd{C-c} on some systems, and @code{DEL} on
1041 others) sends this signal. When the argument @var{current-group} is
1042 non-@code{nil}, you can think of this function as ``typing @kbd{C-c}''
1043 on the terminal by which Emacs talks to the subprocess.
1046 @defun kill-process &optional process current-group
1047 This function kills the process @var{process} by sending the
1048 signal @code{SIGKILL}. This signal kills the subprocess immediately,
1049 and cannot be handled by the subprocess.
1052 @defun quit-process &optional process current-group
1053 This function sends the signal @code{SIGQUIT} to the process
1054 @var{process}. This signal is the one sent by the ``quit
1055 character'' (usually @kbd{C-b} or @kbd{C-\}) when you are not inside
1059 @defun stop-process &optional process current-group
1060 This function stops the process @var{process} by sending the
1061 signal @code{SIGTSTP}. Use @code{continue-process} to resume its
1064 Outside of Emacs, on systems with job control, the ``stop character''
1065 (usually @kbd{C-z}) normally sends this signal. When
1066 @var{current-group} is non-@code{nil}, you can think of this function as
1067 ``typing @kbd{C-z}'' on the terminal Emacs uses to communicate with the
1071 @defun continue-process &optional process current-group
1072 This function resumes execution of the process @var{process} by sending
1073 it the signal @code{SIGCONT}. This presumes that @var{process} was
1077 @defun signal-process process signal
1078 This function sends a signal to process @var{process}. The argument
1079 @var{signal} specifies which signal to send; it should be an integer.
1081 The @var{process} argument can be a system process @acronym{ID}; that
1082 allows you to send signals to processes that are not children of
1083 Emacs. @xref{System Processes}.
1086 @node Output from Processes
1087 @section Receiving Output from Processes
1088 @cindex process output
1089 @cindex output from processes
1091 There are two ways to receive the output that a subprocess writes to
1092 its standard output stream. The output can be inserted in a buffer,
1093 which is called the associated buffer of the process, or a function
1094 called the @dfn{filter function} can be called to act on the output. If
1095 the process has no buffer and no filter function, its output is
1098 When a subprocess terminates, Emacs reads any pending output,
1099 then stops reading output from that subprocess. Therefore, if the
1100 subprocess has children that are still live and still producing
1101 output, Emacs won't receive that output.
1103 Output from a subprocess can arrive only while Emacs is waiting: when
1104 reading terminal input, in @code{sit-for} and @code{sleep-for}
1105 (@pxref{Waiting}), and in @code{accept-process-output} (@pxref{Accepting
1106 Output}). This minimizes the problem of timing errors that usually
1107 plague parallel programming. For example, you can safely create a
1108 process and only then specify its buffer or filter function; no output
1109 can arrive before you finish, if the code in between does not call any
1110 primitive that waits.
1112 @defvar process-adaptive-read-buffering
1113 On some systems, when Emacs reads the output from a subprocess, the
1114 output data is read in very small blocks, potentially resulting in
1115 very poor performance. This behavior can be remedied to some extent
1116 by setting the variable @var{process-adaptive-read-buffering} to a
1117 non-@code{nil} value (the default), as it will automatically delay reading
1118 from such processes, thus allowing them to produce more output before
1119 Emacs tries to read it.
1122 It is impossible to separate the standard output and standard error
1123 streams of the subprocess, because Emacs normally spawns the subprocess
1124 inside a pseudo-TTY, and a pseudo-TTY has only one output channel. If
1125 you want to keep the output to those streams separate, you should
1126 redirect one of them to a file---for example, by using an appropriate
1130 * Process Buffers:: If no filter, output is put in a buffer.
1131 * Filter Functions:: Filter functions accept output from the process.
1132 * Decoding Output:: Filters can get unibyte or multibyte strings.
1133 * Accepting Output:: How to wait until process output arrives.
1136 @node Process Buffers
1137 @subsection Process Buffers
1139 A process can (and usually does) have an @dfn{associated buffer},
1140 which is an ordinary Emacs buffer that is used for two purposes: storing
1141 the output from the process, and deciding when to kill the process. You
1142 can also use the buffer to identify a process to operate on, since in
1143 normal practice only one process is associated with any given buffer.
1144 Many applications of processes also use the buffer for editing input to
1145 be sent to the process, but this is not built into Emacs Lisp.
1147 Unless the process has a filter function (@pxref{Filter Functions}),
1148 its output is inserted in the associated buffer. The position to insert
1149 the output is determined by the @code{process-mark}, which is then
1150 updated to point to the end of the text just inserted. Usually, but not
1151 always, the @code{process-mark} is at the end of the buffer.
1153 @defun process-buffer process
1154 This function returns the associated buffer of the process
1159 (process-buffer (get-process "shell"))
1160 @result{} #<buffer *shell*>
1165 @defun process-mark process
1166 This function returns the process marker for @var{process}, which is the
1167 marker that says where to insert output from the process.
1169 If @var{process} does not have a buffer, @code{process-mark} returns a
1170 marker that points nowhere.
1172 Insertion of process output in a buffer uses this marker to decide where
1173 to insert, and updates it to point after the inserted text. That is why
1174 successive batches of output are inserted consecutively.
1176 Filter functions normally should use this marker in the same fashion
1177 as is done by direct insertion of output in the buffer. A good
1178 example of a filter function that uses @code{process-mark} is found at
1179 the end of the following section.
1181 When the user is expected to enter input in the process buffer for
1182 transmission to the process, the process marker separates the new input
1183 from previous output.
1186 @defun set-process-buffer process buffer
1187 This function sets the buffer associated with @var{process} to
1188 @var{buffer}. If @var{buffer} is @code{nil}, the process becomes
1189 associated with no buffer.
1192 @defun get-buffer-process buffer-or-name
1193 This function returns a nondeleted process associated with the buffer
1194 specified by @var{buffer-or-name}. If there are several processes
1195 associated with it, this function chooses one (currently, the one most
1196 recently created, but don't count on that). Deletion of a process
1197 (see @code{delete-process}) makes it ineligible for this function to
1200 It is usually a bad idea to have more than one process associated with
1205 (get-buffer-process "*shell*")
1206 @result{} #<process shell>
1210 Killing the process's buffer deletes the process, which kills the
1211 subprocess with a @code{SIGHUP} signal (@pxref{Signals to Processes}).
1214 @node Filter Functions
1215 @subsection Process Filter Functions
1216 @cindex filter function
1217 @cindex process filter
1219 A process @dfn{filter function} is a function that receives the
1220 standard output from the associated process. If a process has a filter,
1221 then @emph{all} output from that process is passed to the filter. The
1222 process buffer is used directly for output from the process only when
1225 The filter function can only be called when Emacs is waiting for
1226 something, because process output arrives only at such times. Emacs
1227 waits when reading terminal input, in @code{sit-for} and
1228 @code{sleep-for} (@pxref{Waiting}), and in @code{accept-process-output}
1229 (@pxref{Accepting Output}).
1231 A filter function must accept two arguments: the associated process
1232 and a string, which is output just received from it. The function is
1233 then free to do whatever it chooses with the output.
1235 Quitting is normally inhibited within a filter function---otherwise,
1236 the effect of typing @kbd{C-g} at command level or to quit a user
1237 command would be unpredictable. If you want to permit quitting inside
1238 a filter function, bind @code{inhibit-quit} to @code{nil}. In most
1239 cases, the right way to do this is with the macro
1240 @code{with-local-quit}. @xref{Quitting}.
1242 If an error happens during execution of a filter function, it is
1243 caught automatically, so that it doesn't stop the execution of whatever
1244 program was running when the filter function was started. However, if
1245 @code{debug-on-error} is non-@code{nil}, the error-catching is turned
1246 off. This makes it possible to use the Lisp debugger to debug the
1247 filter function. @xref{Debugger}.
1249 Many filter functions sometimes or always insert the text in the
1250 process's buffer, mimicking the actions of Emacs when there is no
1251 filter. Such filter functions need to use @code{set-buffer} in order to
1252 be sure to insert in that buffer. To avoid setting the current buffer
1253 semipermanently, these filter functions must save and restore the
1254 current buffer. They should also update the process marker, and in some
1255 cases update the value of point. Here is how to do these things:
1259 (defun ordinary-insertion-filter (proc string)
1260 (with-current-buffer (process-buffer proc)
1261 (let ((moving (= (point) (process-mark proc))))
1265 ;; @r{Insert the text, advancing the process marker.}
1266 (goto-char (process-mark proc))
1268 (set-marker (process-mark proc) (point)))
1269 (if moving (goto-char (process-mark proc))))))
1274 The reason to use @code{with-current-buffer}, rather than using
1275 @code{save-excursion} to save and restore the current buffer, is so as
1276 to preserve the change in point made by the second call to
1279 To make the filter force the process buffer to be visible whenever new
1280 text arrives, insert the following line just before the
1281 @code{with-current-buffer} construct:
1284 (display-buffer (process-buffer proc))
1287 To force point to the end of the new output, no matter where it was
1288 previously, eliminate the variable @code{moving} and call
1289 @code{goto-char} unconditionally.
1291 In earlier Emacs versions, every filter function that did regular
1292 expression searching or matching had to explicitly save and restore the
1293 match data. Now Emacs does this automatically for filter functions;
1294 they never need to do it explicitly. @xref{Match Data}.
1296 A filter function that writes the output into the buffer of the
1297 process should check whether the buffer is still alive. If it tries to
1298 insert into a dead buffer, it will get an error. The expression
1299 @code{(buffer-name (process-buffer @var{process}))} returns @code{nil}
1300 if the buffer is dead.
1302 The output to the function may come in chunks of any size. A program
1303 that produces the same output twice in a row may send it as one batch of
1304 200 characters one time, and five batches of 40 characters the next. If
1305 the filter looks for certain text strings in the subprocess output, make
1306 sure to handle the case where one of these strings is split across two
1307 or more batches of output; one way to do this is to insert the
1308 received text into a temporary buffer, which can then be searched.
1310 @defun set-process-filter process filter
1311 This function gives @var{process} the filter function @var{filter}. If
1312 @var{filter} is @code{nil}, it gives the process no filter.
1315 @defun process-filter process
1316 This function returns the filter function of @var{process}, or @code{nil}
1320 Here is an example of use of a filter function:
1324 (defun keep-output (process output)
1325 (setq kept (cons output kept)))
1326 @result{} keep-output
1333 (set-process-filter (get-process "shell") 'keep-output)
1334 @result{} keep-output
1337 (process-send-string "shell" "ls ~/other\n")
1340 @result{} ("lewis@@slug[8] % "
1343 "FINAL-W87-SHORT.MSS backup.otl kolstad.mss~
1344 address.txt backup.psf kolstad.psf
1345 backup.bib~ david.mss resume-Dec-86.mss~
1346 backup.err david.psf resume-Dec.psf
1347 backup.mss dland syllabus.mss
1349 "#backups.mss# backup.mss~ kolstad.mss
1354 @ignore @c The code in this example doesn't show the right way to do things.
1355 Here is another, more realistic example, which demonstrates how to use
1356 the process mark to do insertion in the same fashion as is done when
1357 there is no filter function:
1361 ;; @r{Insert input in the buffer specified by @code{my-shell-buffer}}
1362 ;; @r{and make sure that buffer is shown in some window.}
1363 (defun my-process-filter (proc str)
1364 (let ((cur (selected-window))
1366 (pop-to-buffer my-shell-buffer)
1369 (goto-char (point-max))
1371 (set-marker (process-mark proc) (point-max))
1372 (select-window cur)))
1377 @node Decoding Output
1378 @subsection Decoding Process Output
1379 @cindex decode process output
1381 When Emacs writes process output directly into a multibyte buffer,
1382 it decodes the output according to the process output coding system.
1383 If the coding system is @code{raw-text} or @code{no-conversion}, Emacs
1384 converts the unibyte output to multibyte using
1385 @code{string-to-multibyte}, and inserts the resulting multibyte text.
1387 You can use @code{set-process-coding-system} to specify which coding
1388 system to use (@pxref{Process Information}). Otherwise, the coding
1389 system comes from @code{coding-system-for-read}, if that is
1390 non-@code{nil}; or else from the defaulting mechanism (@pxref{Default
1391 Coding Systems}). If the text output by a process contains null
1392 bytes, Emacs by default uses @code{no-conversion} for it; see
1393 @ref{Lisp and Coding Systems, inhibit-null-byte-detection}, for how to
1394 control this behavior.
1396 @strong{Warning:} Coding systems such as @code{undecided} which
1397 determine the coding system from the data do not work entirely
1398 reliably with asynchronous subprocess output. This is because Emacs
1399 has to process asynchronous subprocess output in batches, as it
1400 arrives. Emacs must try to detect the proper coding system from one
1401 batch at a time, and this does not always work. Therefore, if at all
1402 possible, specify a coding system that determines both the character
1403 code conversion and the end of line conversion---that is, one like
1404 @code{latin-1-unix}, rather than @code{undecided} or @code{latin-1}.
1406 @c Let's keep the index entries that were there for
1407 @c set-process-filter-multibyte and process-filter-multibyte-p,
1408 @cindex filter multibyte flag, of process
1409 @cindex process filter multibyte flag
1410 When Emacs calls a process filter function, it provides the process
1411 output as a multibyte string or as a unibyte string according to the
1412 process's filter coding system. Emacs
1413 decodes the output according to the process output coding system,
1414 which usually produces a multibyte string, except for coding systems
1415 such as @code{binary} and @code{raw-text}
1417 @node Accepting Output
1418 @subsection Accepting Output from Processes
1419 @cindex accept input from processes
1421 Output from asynchronous subprocesses normally arrives only while
1422 Emacs is waiting for some sort of external event, such as elapsed time
1423 or terminal input. Occasionally it is useful in a Lisp program to
1424 explicitly permit output to arrive at a specific point, or even to wait
1425 until output arrives from a process.
1427 @defun accept-process-output &optional process seconds millisec just-this-one
1428 This function allows Emacs to read pending output from processes. The
1429 output is inserted in the associated buffers or given to their filter
1430 functions. If @var{process} is non-@code{nil} then this function does
1431 not return until some output has been received from @var{process}.
1434 The arguments @var{seconds} and @var{millisec} let you specify timeout
1435 periods. The former specifies a period measured in seconds and the
1436 latter specifies one measured in milliseconds. The two time periods
1437 thus specified are added together, and @code{accept-process-output}
1438 returns after that much time, whether or not there has been any
1441 The argument @var{millisec} is semi-obsolete nowadays because
1442 @var{seconds} can be a floating point number to specify waiting a
1443 fractional number of seconds. If @var{seconds} is 0, the function
1444 accepts whatever output is pending but does not wait.
1446 @c Emacs 22.1 feature
1447 If @var{process} is a process, and the argument @var{just-this-one} is
1448 non-@code{nil}, only output from that process is handled, suspending output
1449 from other processes until some output has been received from that
1450 process or the timeout expires. If @var{just-this-one} is an integer,
1451 also inhibit running timers. This feature is generally not
1452 recommended, but may be necessary for specific applications, such as
1455 The function @code{accept-process-output} returns non-@code{nil} if it
1456 did get some output, or @code{nil} if the timeout expired before output
1461 @section Sentinels: Detecting Process Status Changes
1462 @cindex process sentinel
1463 @cindex sentinel (of process)
1465 A @dfn{process sentinel} is a function that is called whenever the
1466 associated process changes status for any reason, including signals
1467 (whether sent by Emacs or caused by the process's own actions) that
1468 terminate, stop, or continue the process. The process sentinel is
1469 also called if the process exits. The sentinel receives two
1470 arguments: the process for which the event occurred, and a string
1471 describing the type of event.
1473 The string describing the event looks like one of the following:
1477 @code{"finished\n"}.
1480 @code{"exited abnormally with code @var{exitcode}\n"}.
1483 @code{"@var{name-of-signal}\n"}.
1486 @code{"@var{name-of-signal} (core dumped)\n"}.
1489 A sentinel runs only while Emacs is waiting (e.g., for terminal
1490 input, or for time to elapse, or for process output). This avoids the
1491 timing errors that could result from running them at random places in
1492 the middle of other Lisp programs. A program can wait, so that
1493 sentinels will run, by calling @code{sit-for} or @code{sleep-for}
1494 (@pxref{Waiting}), or @code{accept-process-output} (@pxref{Accepting
1495 Output}). Emacs also allows sentinels to run when the command loop is
1496 reading input. @code{delete-process} calls the sentinel when it
1497 terminates a running process.
1499 Emacs does not keep a queue of multiple reasons to call the sentinel
1500 of one process; it records just the current status and the fact that
1501 there has been a change. Therefore two changes in status, coming in
1502 quick succession, can call the sentinel just once. However, process
1503 termination will always run the sentinel exactly once. This is
1504 because the process status can't change again after termination.
1506 Emacs explicitly checks for output from the process before running
1507 the process sentinel. Once the sentinel runs due to process
1508 termination, no further output can arrive from the process.
1510 A sentinel that writes the output into the buffer of the process
1511 should check whether the buffer is still alive. If it tries to insert
1512 into a dead buffer, it will get an error. If the buffer is dead,
1513 @code{(buffer-name (process-buffer @var{process}))} returns @code{nil}.
1515 Quitting is normally inhibited within a sentinel---otherwise, the
1516 effect of typing @kbd{C-g} at command level or to quit a user command
1517 would be unpredictable. If you want to permit quitting inside a
1518 sentinel, bind @code{inhibit-quit} to @code{nil}. In most cases, the
1519 right way to do this is with the macro @code{with-local-quit}.
1522 If an error happens during execution of a sentinel, it is caught
1523 automatically, so that it doesn't stop the execution of whatever
1524 programs was running when the sentinel was started. However, if
1525 @code{debug-on-error} is non-@code{nil}, the error-catching is turned
1526 off. This makes it possible to use the Lisp debugger to debug the
1527 sentinel. @xref{Debugger}.
1529 While a sentinel is running, the process sentinel is temporarily
1530 set to @code{nil} so that the sentinel won't run recursively.
1531 For this reason it is not possible for a sentinel to specify
1534 In earlier Emacs versions, every sentinel that did regular expression
1535 searching or matching had to explicitly save and restore the match data.
1536 Now Emacs does this automatically for sentinels; they never need to do
1537 it explicitly. @xref{Match Data}.
1539 @defun set-process-sentinel process sentinel
1540 This function associates @var{sentinel} with @var{process}. If
1541 @var{sentinel} is @code{nil}, then the process will have no sentinel.
1542 The default behavior when there is no sentinel is to insert a message in
1543 the process's buffer when the process status changes.
1545 Changes in process sentinel take effect immediately---if the sentinel
1546 is slated to be run but has not been called yet, and you specify a new
1547 sentinel, the eventual call to the sentinel will use the new one.
1551 (defun msg-me (process event)
1553 (format "Process: %s had the event `%s'" process event)))
1554 (set-process-sentinel (get-process "shell") 'msg-me)
1558 (kill-process (get-process "shell"))
1559 @print{} Process: #<process shell> had the event `killed'
1560 @result{} #<process shell>
1565 @defun process-sentinel process
1566 This function returns the sentinel of @var{process}, or @code{nil} if it
1570 @defun waiting-for-user-input-p
1571 While a sentinel or filter function is running, this function returns
1572 non-@code{nil} if Emacs was waiting for keyboard input from the user at
1573 the time the sentinel or filter function was called, @code{nil} if it
1577 @node Query Before Exit
1578 @section Querying Before Exit
1580 When Emacs exits, it terminates all its subprocesses by sending them
1581 the @code{SIGHUP} signal. Because subprocesses may be doing
1582 valuable work, Emacs normally asks the user to confirm that it is ok
1583 to terminate them. Each process has a query flag which, if
1584 non-@code{nil}, says that Emacs should ask for confirmation before
1585 exiting and thus killing that process. The default for the query flag
1586 is @code{t}, meaning @emph{do} query.
1588 @defun process-query-on-exit-flag process
1589 This returns the query flag of @var{process}.
1592 @defun set-process-query-on-exit-flag process flag
1593 This function sets the query flag of @var{process} to @var{flag}. It
1598 ;; @r{Don't query about the shell process}
1599 (set-process-query-on-exit-flag (get-process "shell") nil)
1605 @defun process-kill-without-query process &optional do-query
1606 This function clears the query flag of @var{process}, so that
1607 Emacs will not query the user on account of that process.
1609 Actually, the function does more than that: it returns the old value of
1610 the process's query flag, and sets the query flag to @var{do-query}.
1611 Please don't use this function to do those things any more---please
1612 use the newer, cleaner functions @code{process-query-on-exit-flag} and
1613 @code{set-process-query-on-exit-flag} in all but the simplest cases.
1614 The only way you should use @code{process-kill-without-query} nowadays
1619 ;; @r{Don't query about the shell process}
1620 (process-kill-without-query (get-process "shell"))
1625 @node System Processes
1626 @section Accessing Other Processes
1627 @cindex system processes
1629 In addition to accessing and manipulating processes that are
1630 subprocesses of the current Emacs session, Emacs Lisp programs can
1631 also access other processes running on the same machine. We call
1632 these @dfn{system processes}, to distinguish between them and Emacs
1635 Emacs provides several primitives for accessing system processes.
1636 Not all platforms support these primitives; on those which don't,
1637 these primitives return @code{nil}.
1639 @defun list-system-processes
1640 This function returns a list of all the processes running on the
1641 system. Each process is identified by its @acronym{PID}, a numerical
1642 process ID that is assigned by the OS and distinguishes the process
1643 from all the other processes running on the same machine at the same
1647 @defun process-attributes pid
1648 This function returns an alist of attributes for the process specified
1649 by its process ID @var{pid}. Each association in the alist is of the
1650 form @code{(@var{key} . @var{value})}, where @var{key} designates the
1651 attribute and @var{value} is the value of that attribute. The various
1652 attribute @var{key}'s that this function can return are listed below.
1653 Not all platforms support all of these attributes; if an attribute is
1654 not supported, its association will not appear in the returned alist.
1655 Values that are numbers can be either integer or floating-point,
1656 depending on the magnitude of the value.
1660 The effective user ID of the user who invoked the process. The
1661 corresponding @var{value} is a number. If the process was invoked by
1662 the same user who runs the current Emacs session, the value is
1663 identical to what @code{user-uid} returns (@pxref{User
1667 User name corresponding to the process's effective user ID, a string.
1670 The group ID of the effective user ID, a number.
1673 Group name corresponding to the effective user's group ID, a string.
1676 The name of the command that runs in the process. This is a string
1677 that usually specifies the name of the executable file of the process,
1678 without the leading directories. However, some special system
1679 processes can report strings that do not correspond to an executable
1683 The state code of the process. This is a short string that encodes
1684 the scheduling state of the process. Here's a list of the most
1685 frequently seen codes:
1689 uninterruptible sleep (usually I/O)
1693 interruptible sleep (waiting for some event)
1695 stopped, e.g., by a job control signal
1697 ``zombie'': a process that terminated, but was not reaped by its parent
1701 For the full list of the possible states, see the manual page of the
1702 @command{ps} command.
1705 The process ID of the parent process, a number.
1708 The process group ID of the process, a number.
1711 The session ID of the process. This is a number that is the process
1712 ID of the process's @dfn{session leader}.
1715 A string that is the name of the process's controlling terminal. On
1716 Unix and GNU systems, this is normally the file name of the
1717 corresponding terminal device, such as @file{/dev/pts65}.
1720 The numerical process group ID of the foreground process group that
1721 uses the process's terminal.
1724 The number of minor page faults caused by the process since its
1725 beginning. (Minor page faults are those that don't involve reading
1729 The number of major page faults caused by the process since its
1730 beginning. (Major page faults require a disk to be read, and are thus
1731 more expensive than minor page faults.)
1735 Like @code{minflt} and @code{majflt}, but include the number of page
1736 faults for all the child processes of the given process.
1739 Time spent by the process in the user context, for running the
1740 application's code. The corresponding @var{value} is in the
1741 @w{@code{(@var{high} @var{low} @var{microsec})}} format, the same
1742 format used by functions @code{current-time} (@pxref{Time of Day,
1743 current-time}) and @code{file-attributes} (@pxref{File Attributes}).
1746 Time spent by the process in the system (kernel) context, for
1747 processing system calls. The corresponding @var{value} is in the same
1748 format as for @code{utime}.
1751 The sum of @code{utime} and @code{stime}. The corresponding
1752 @var{value} is in the same format as for @code{utime}.
1757 Like @code{utime}, @code{stime}, and @code{time}, but include the
1758 times of all the child processes of the given process.
1761 The numerical priority of the process.
1764 The @dfn{nice value} of the process, a number. (Processes with smaller
1765 nice values get scheduled more favorably.)
1768 The number of threads in the process.
1771 The time the process was started, in the @w{@code{(@var{high}
1772 @var{low} @var{microsec})}} format used by @code{current-time} and
1773 @code{file-attributes}.
1776 The time elapsed since the process started, in the @w{@code{(@var{high}
1777 @var{low} @var{microsec})}} format.
1780 The virtual memory size of the process, measured in kilobytes.
1783 The size of the process's @dfn{resident set}, the number of kilobytes
1784 occupied by the process in the machine's physical memory.
1787 The percentage of the CPU time used by the process since it started.
1788 The corresponding @var{value} is a floating-point number between 0 and
1792 The percentage of the total physical memory installed on the machine
1793 used by the process's resident set. The value is a floating-point
1794 number between 0 and 100.
1797 The command-line with which the process was invoked. This is a string
1798 in which individual command-line arguments are separated by blanks;
1799 whitespace characters that are embedded in the arguments are quoted as
1800 appropriate for the system's shell: escaped by backslash characters on
1801 GNU and Unix, and enclosed in double quote characters on Windows.
1802 Thus, this command-line string can be directly used in primitives such
1803 as @code{shell-command}.
1809 @node Transaction Queues
1810 @section Transaction Queues
1811 @cindex transaction queue
1813 You can use a @dfn{transaction queue} to communicate with a subprocess
1814 using transactions. First use @code{tq-create} to create a transaction
1815 queue communicating with a specified process. Then you can call
1816 @code{tq-enqueue} to send a transaction.
1818 @defun tq-create process
1819 This function creates and returns a transaction queue communicating with
1820 @var{process}. The argument @var{process} should be a subprocess
1821 capable of sending and receiving streams of bytes. It may be a child
1822 process, or it may be a TCP connection to a server, possibly on another
1826 @defun tq-enqueue queue question regexp closure fn &optional delay-question
1827 This function sends a transaction to queue @var{queue}. Specifying the
1828 queue has the effect of specifying the subprocess to talk to.
1830 The argument @var{question} is the outgoing message that starts the
1831 transaction. The argument @var{fn} is the function to call when the
1832 corresponding answer comes back; it is called with two arguments:
1833 @var{closure}, and the answer received.
1835 The argument @var{regexp} is a regular expression that should match
1836 text at the end of the entire answer, but nothing before; that's how
1837 @code{tq-enqueue} determines where the answer ends.
1839 If the argument @var{delay-question} is non-@code{nil}, delay sending
1840 this question until the process has finished replying to any previous
1841 questions. This produces more reliable results with some processes.
1843 The return value of @code{tq-enqueue} itself is not meaningful.
1846 @defun tq-close queue
1847 Shut down transaction queue @var{queue}, waiting for all pending transactions
1848 to complete, and then terminate the connection or child process.
1851 Transaction queues are implemented by means of a filter function.
1852 @xref{Filter Functions}.
1855 @section Network Connections
1856 @cindex network connection
1860 Emacs Lisp programs can open stream (TCP) and datagram (UDP) network
1861 connections to other processes on the same machine or other machines.
1862 A network connection is handled by Lisp much like a subprocess, and is
1863 represented by a process object. However, the process you are
1864 communicating with is not a child of the Emacs process, so it has no
1865 process @acronym{ID}, and you can't kill it or send it signals. All you
1866 can do is send and receive data. @code{delete-process} closes the
1867 connection, but does not kill the program at the other end; that
1868 program must decide what to do about closure of the connection.
1870 Lisp programs can listen for connections by creating network
1871 servers. A network server is also represented by a kind of process
1872 object, but unlike a network connection, the network server never
1873 transfers data itself. When it receives a connection request, it
1874 creates a new network connection to represent the connection just
1875 made. (The network connection inherits certain information, including
1876 the process plist, from the server.) The network server then goes
1877 back to listening for more connection requests.
1879 Network connections and servers are created by calling
1880 @code{make-network-process} with an argument list consisting of
1881 keyword/argument pairs, for example @code{:server t} to create a
1882 server process, or @code{:type 'datagram} to create a datagram
1883 connection. @xref{Low-Level Network}, for details. You can also use
1884 the @code{open-network-stream} function described below.
1886 To distinguish the different types of processes, the
1887 @code{process-type} function returns the symbol @code{network} for a
1888 network connection or server, @code{serial} for a serial port
1889 connection, or @code{real} for a real subprocess.
1891 The @code{process-status} function returns @code{open},
1892 @code{closed}, @code{connect}, and @code{failed} for network
1893 connections. For a network server, the status is always
1894 @code{listen}. None of those values is possible for a real
1895 subprocess. @xref{Process Information}.
1897 You can stop and resume operation of a network process by calling
1898 @code{stop-process} and @code{continue-process}. For a server
1899 process, being stopped means not accepting new connections. (Up to 5
1900 connection requests will be queued for when you resume the server; you
1901 can increase this limit, unless it is imposed by the operating
1902 system.) For a network stream connection, being stopped means not
1903 processing input (any arriving input waits until you resume the
1904 connection). For a datagram connection, some number of packets may be
1905 queued but input may be lost. You can use the function
1906 @code{process-command} to determine whether a network connection or
1907 server is stopped; a non-@code{nil} value means yes.
1909 @defun open-network-stream name buffer-or-name host service
1910 This function opens a TCP connection, and returns a process object
1911 that represents the connection.
1913 The @var{name} argument specifies the name for the process object. It
1914 is modified as necessary to make it unique.
1916 The @var{buffer-or-name} argument is the buffer to associate with the
1917 connection. Output from the connection is inserted in the buffer,
1918 unless you specify a filter function to handle the output. If
1919 @var{buffer-or-name} is @code{nil}, it means that the connection is not
1920 associated with any buffer.
1922 The arguments @var{host} and @var{service} specify where to connect to;
1923 @var{host} is the host name (a string), and @var{service} is the name of
1924 a defined network service (a string) or a port number (an integer).
1927 @node Network Servers
1928 @section Network Servers
1929 @cindex network servers
1931 You create a server by calling @code{make-network-process} with
1932 @code{:server t}. The server will listen for connection requests from
1933 clients. When it accepts a client connection request, that creates a
1934 new network connection, itself a process object, with the following
1939 The connection's process name is constructed by concatenating the
1940 server process' @var{name} with a client identification string. The
1941 client identification string for an IPv4 connection looks like
1942 @samp{<@var{a}.@var{b}.@var{c}.@var{d}:@var{p}>}. Otherwise, it is a
1943 unique number in brackets, as in @samp{<@var{nnn}>}. The number
1944 is unique for each connection in the Emacs session.
1947 If the server's filter is non-@code{nil}, the connection process does
1948 not get a separate process buffer; otherwise, Emacs creates a new
1949 buffer for the purpose. The buffer name is the server's buffer name
1950 or process name, concatenated with the client identification string.
1952 The server's process buffer value is never used directly by Emacs, but
1953 it is passed to the log function, which can log connections by
1954 inserting text there.
1957 The communication type and the process filter and sentinel are
1958 inherited from those of the server. The server never directly
1959 uses its filter and sentinel; their sole purpose is to initialize
1960 connections made to the server.
1963 The connection's process contact info is set according to the client's
1964 addressing information (typically an IP address and a port number).
1965 This information is associated with the @code{process-contact}
1966 keywords @code{:host}, @code{:service}, @code{:remote}.
1969 The connection's local address is set up according to the port
1970 number used for the connection.
1973 The client process' plist is initialized from the server's plist.
1980 A datagram connection communicates with individual packets rather
1981 than streams of data. Each call to @code{process-send} sends one
1982 datagram packet (@pxref{Input to Processes}), and each datagram
1983 received results in one call to the filter function.
1985 The datagram connection doesn't have to talk with the same remote
1986 peer all the time. It has a @dfn{remote peer address} which specifies
1987 where to send datagrams to. Each time an incoming datagram is passed
1988 to the filter function, the peer address is set to the address that
1989 datagram came from; that way, if the filter function sends a datagram,
1990 it will go back to that place. You can specify the remote peer
1991 address when you create the datagram connection using the
1992 @code{:remote} keyword. You can change it later on by calling
1993 @code{set-process-datagram-address}.
1995 @defun process-datagram-address process
1996 If @var{process} is a datagram connection or server, this function
1997 returns its remote peer address.
2000 @defun set-process-datagram-address process address
2001 If @var{process} is a datagram connection or server, this function
2002 sets its remote peer address to @var{address}.
2005 @node Low-Level Network
2006 @section Low-Level Network Access
2008 You can also create network connections by operating at a lower
2009 level than that of @code{open-network-stream}, using
2010 @code{make-network-process}.
2013 * Proc: Network Processes. Using @code{make-network-process}.
2014 * Options: Network Options. Further control over network connections.
2015 * Features: Network Feature Testing.
2016 Determining which network features work on
2017 the machine you are using.
2020 @node Network Processes
2021 @subsection @code{make-network-process}
2023 The basic function for creating network connections and network
2024 servers is @code{make-network-process}. It can do either of those
2025 jobs, depending on the arguments you give it.
2027 @defun make-network-process &rest args
2028 This function creates a network connection or server and returns the
2029 process object that represents it. The arguments @var{args} are a
2030 list of keyword/argument pairs. Omitting a keyword is always
2031 equivalent to specifying it with value @code{nil}, except for
2032 @code{:coding}, @code{:filter-multibyte}, and @code{:reuseaddr}. Here
2033 are the meaningful keywords:
2036 @item :name @var{name}
2037 Use the string @var{name} as the process name. It is modified if
2038 necessary to make it unique.
2040 @item :type @var{type}
2041 Specify the communication type. A value of @code{nil} specifies a
2042 stream connection (the default); @code{datagram} specifies a datagram
2043 connection. Both connections and servers can be of either type.
2045 @item :server @var{server-flag}
2046 If @var{server-flag} is non-@code{nil}, create a server. Otherwise,
2047 create a connection. For a stream type server, @var{server-flag} may
2048 be an integer which then specifies the length of the queue of pending
2049 connections to the server. The default queue length is 5.
2051 @item :host @var{host}
2052 Specify the host to connect to. @var{host} should be a host name or
2053 Internet address, as a string, or the symbol @code{local} to specify
2054 the local host. If you specify @var{host} for a server, it must
2055 specify a valid address for the local host, and only clients
2056 connecting to that address will be accepted.
2058 @item :service @var{service}
2059 @var{service} specifies a port number to connect to, or, for a server,
2060 the port number to listen on. It should be a service name that
2061 translates to a port number, or an integer specifying the port number
2062 directly. For a server, it can also be @code{t}, which means to let
2063 the system select an unused port number.
2065 @item :family @var{family}
2066 @var{family} specifies the address (and protocol) family for
2067 communication. @code{nil} means determine the proper address family
2068 automatically for the given @var{host} and @var{service}.
2069 @code{local} specifies a Unix socket, in which case @var{host} is
2070 ignored. @code{ipv4} and @code{ipv6} specify to use IPv4 and IPv6
2073 @item :local @var{local-address}
2074 For a server process, @var{local-address} is the address to listen on.
2075 It overrides @var{family}, @var{host} and @var{service}, and you
2076 may as well not specify them.
2078 @item :remote @var{remote-address}
2079 For a connection, @var{remote-address} is the address to connect to.
2080 It overrides @var{family}, @var{host} and @var{service}, and you
2081 may as well not specify them.
2083 For a datagram server, @var{remote-address} specifies the initial
2084 setting of the remote datagram address.
2086 The format of @var{local-address} or @var{remote-address} depends on
2091 An IPv4 address is represented as a five-element vector of four 8-bit
2092 integers and one 16-bit integer
2093 @code{[@var{a} @var{b} @var{c} @var{d} @var{p}]} corresponding to
2094 numeric IPv4 address @var{a}.@var{b}.@var{c}.@var{d} and port number
2098 An IPv6 address is represented as a nine-element vector of 16-bit
2099 integers @code{[@var{a} @var{b} @var{c} @var{d} @var{e} @var{f}
2100 @var{g} @var{h} @var{p}]} corresponding to numeric IPv6 address
2101 @var{a}:@var{b}:@var{c}:@var{d}:@var{e}:@var{f}:@var{g}:@var{h} and
2102 port number @var{p}.
2105 A local address is represented as a string which specifies the address
2106 in the local address space.
2109 An ``unsupported family'' address is represented by a cons
2110 @code{(@var{f} . @var{av})}, where @var{f} is the family number and
2111 @var{av} is a vector specifying the socket address using one element
2112 per address data byte. Do not rely on this format in portable code,
2113 as it may depend on implementation defined constants, data sizes, and
2114 data structure alignment.
2117 @item :nowait @var{bool}
2118 If @var{bool} is non-@code{nil} for a stream connection, return
2119 without waiting for the connection to complete. When the connection
2120 succeeds or fails, Emacs will call the sentinel function, with a
2121 second argument matching @code{"open"} (if successful) or
2122 @code{"failed"}. The default is to block, so that
2123 @code{make-network-process} does not return until the connection
2124 has succeeded or failed.
2126 @item :stop @var{stopped}
2127 Start the network connection or server in the `stopped' state if
2128 @var{stopped} is non-@code{nil}.
2130 @item :buffer @var{buffer}
2131 Use @var{buffer} as the process buffer.
2133 @item :coding @var{coding}
2134 Use @var{coding} as the coding system for this process. To specify
2135 different coding systems for decoding data from the connection and for
2136 encoding data sent to it, specify @code{(@var{decoding} .
2137 @var{encoding})} for @var{coding}.
2139 If you don't specify this keyword at all, the default
2140 is to determine the coding systems from the data.
2142 @item :noquery @var{query-flag}
2143 Initialize the process query flag to @var{query-flag}.
2144 @xref{Query Before Exit}.
2146 @item :filter @var{filter}
2147 Initialize the process filter to @var{filter}.
2149 @item :filter-multibyte @var{bool}
2150 If @var{bool} is non-@code{nil}, strings given to the process filter
2151 are multibyte, otherwise they are unibyte. If you don't specify this
2152 keyword at all, the default is that the strings are multibyte if
2153 @code{default-enable-multibyte-characters} is non-@code{nil}.
2155 @item :sentinel @var{sentinel}
2156 Initialize the process sentinel to @var{sentinel}.
2158 @item :log @var{log}
2159 Initialize the log function of a server process to @var{log}. The log
2160 function is called each time the server accepts a network connection
2161 from a client. The arguments passed to the log function are
2162 @var{server}, @var{connection}, and @var{message}, where @var{server}
2163 is the server process, @var{connection} is the new process for the
2164 connection, and @var{message} is a string describing what has
2167 @item :plist @var{plist}
2168 Initialize the process plist to @var{plist}.
2171 The original argument list, modified with the actual connection
2172 information, is available via the @code{process-contact} function.
2175 @node Network Options
2176 @subsection Network Options
2178 The following network options can be specified when you create a
2179 network process. Except for @code{:reuseaddr}, you can also set or
2180 modify these options later, using @code{set-network-process-option}.
2182 For a server process, the options specified with
2183 @code{make-network-process} are not inherited by the client
2184 connections, so you will need to set the necessary options for each
2185 child connection as it is created.
2188 @item :bindtodevice @var{device-name}
2189 If @var{device-name} is a non-empty string identifying a network
2190 interface name (see @code{network-interface-list}), only handle
2191 packets received on that interface. If @var{device-name} is @code{nil}
2192 (the default), handle packets received on any interface.
2194 Using this option may require special privileges on some systems.
2196 @item :broadcast @var{broadcast-flag}
2197 If @var{broadcast-flag} is non-@code{nil} for a datagram process, the
2198 process will receive datagram packet sent to a broadcast address, and
2199 be able to send packets to a broadcast address. Ignored for a stream
2202 @item :dontroute @var{dontroute-flag}
2203 If @var{dontroute-flag} is non-@code{nil}, the process can only send
2204 to hosts on the same network as the local host.
2206 @item :keepalive @var{keepalive-flag}
2207 If @var{keepalive-flag} is non-@code{nil} for a stream connection,
2208 enable exchange of low-level keep-alive messages.
2210 @item :linger @var{linger-arg}
2211 If @var{linger-arg} is non-@code{nil}, wait for successful
2212 transmission of all queued packets on the connection before it is
2213 deleted (see @code{delete-process}). If @var{linger-arg} is an
2214 integer, it specifies the maximum time in seconds to wait for queued
2215 packets to be sent before closing the connection. Default is
2216 @code{nil} which means to discard unsent queued packets when the
2219 @item :oobinline @var{oobinline-flag}
2220 If @var{oobinline-flag} is non-@code{nil} for a stream connection,
2221 receive out-of-band data in the normal data stream. Otherwise, ignore
2224 @item :priority @var{priority}
2225 Set the priority for packets sent on this connection to the integer
2226 @var{priority}. The interpretation of this number is protocol
2227 specific, such as setting the TOS (type of service) field on IP
2228 packets sent on this connection. It may also have system dependent
2229 effects, such as selecting a specific output queue on the network
2232 @item :reuseaddr @var{reuseaddr-flag}
2233 If @var{reuseaddr-flag} is non-@code{nil} (the default) for a stream
2234 server process, allow this server to reuse a specific port number (see
2235 @code{:service}) unless another process on this host is already
2236 listening on that port. If @var{reuseaddr-flag} is @code{nil}, there
2237 may be a period of time after the last use of that port (by any
2238 process on the host), where it is not possible to make a new server on
2242 @defun set-network-process-option process option value &optional no-error
2243 This function sets or modifies a network option for network process
2244 @var{process}. See @code{make-network-process} for details of options
2245 @var{option} and their corresponding values @var{value}. If
2246 @var{no-error} is non-@code{nil}, this function returns @code{nil}
2247 instead of signaling an error if @var{option} is not a supported
2248 option. If the function successfully completes, it returns @code{t}.
2250 The current setting of an option is available via the
2251 @code{process-contact} function.
2254 @node Network Feature Testing
2255 @subsection Testing Availability of Network Features
2257 To test for the availability of a given network feature, use
2258 @code{featurep} like this:
2261 (featurep 'make-network-process '(@var{keyword} @var{value}))
2265 The result of the first form is @code{t} if it works to specify
2266 @var{keyword} with value @var{value} in @code{make-network-process}.
2267 The result of the second form is @code{t} if @var{keyword} is
2268 supported by @code{make-network-process}. Here are some of the
2269 @var{keyword}---@var{value} pairs you can test in
2274 Non-@code{nil} if non-blocking connect is supported.
2275 @item (:type datagram)
2276 Non-@code{nil} if datagrams are supported.
2277 @item (:family local)
2278 Non-@code{nil} if local (a.k.a.@: ``UNIX domain'') sockets are supported.
2279 @item (:family ipv6)
2280 Non-@code{nil} if IPv6 is supported.
2282 Non-@code{nil} if the system can select the port for a server.
2285 To test for the availability of a given network option, use
2286 @code{featurep} like this:
2289 (featurep 'make-network-process '@var{keyword})
2293 Here are some of the options you can test in this way.
2304 That particular network option is supported by
2305 @code{make-network-process} and @code{set-network-process-option}.
2309 @section Misc Network Facilities
2311 These additional functions are useful for creating and operating
2312 on network connections. Note that they are supported only on some
2315 @defun network-interface-list
2316 This function returns a list describing the network interfaces
2317 of the machine you are using. The value is an alist whose
2318 elements have the form @code{(@var{name} . @var{address})}.
2319 @var{address} has the same form as the @var{local-address}
2320 and @var{remote-address} arguments to @code{make-network-process}.
2323 @defun network-interface-info ifname
2324 This function returns information about the network interface named
2325 @var{ifname}. The value is a list of the form
2326 @code{(@var{addr} @var{bcast} @var{netmask} @var{hwaddr} @var{flags})}.
2330 The Internet protocol address.
2332 The broadcast address.
2336 The layer 2 address (Ethernet MAC address, for instance).
2338 The current flags of the interface.
2342 @defun format-network-address address &optional omit-port
2343 This function converts the Lisp representation of a network address to
2346 A five-element vector @code{[@var{a} @var{b} @var{c} @var{d} @var{p}]}
2347 represents an IPv4 address @var{a}.@var{b}.@var{c}.@var{d} and port
2348 number @var{p}. @code{format-network-address} converts that to the
2349 string @code{"@var{a}.@var{b}.@var{c}.@var{d}:@var{p}"}.
2351 A nine-element vector @code{[@var{a} @var{b} @var{c} @var{d} @var{e}
2352 @var{f} @var{g} @var{h} @var{p}]} represents an IPv6 address along
2353 with a port number. @code{format-network-address} converts that to
2355 @code{"[@var{a}:@var{b}:@var{c}:@var{d}:@var{e}:@var{f}:@var{g}:@var{h}]:@var{p}"}.
2357 If the vector does not include the port number, @var{p}, or if
2358 @var{omit-port} is non-@code{nil}, the result does not include the
2359 @code{:@var{p}} suffix.
2363 @section Communicating with Serial Ports
2364 @cindex @file{/dev/tty}
2366 @cindex serial connections
2368 Emacs can communicate with serial ports. For interactive use,
2369 @kbd{M-x serial-term} opens a terminal window. In a Lisp program,
2370 @code{make-serial-process} creates a process object.
2372 The serial port can be configured at run-time, without having to
2373 close and re-open it. The function @code{serial-process-configure}
2374 lets you change the speed, bytesize, and other parameters. In a
2375 terminal window created by @code{serial-term}, you can click on the
2376 mode line for configuration.
2378 A serial connection is represented by a process object which can be
2379 used similar to a subprocess or network process. You can send and
2380 receive data and configure the serial port. A serial process object
2381 has no process ID, you can't send signals to it, and the status codes
2382 are different from other types of processes.
2383 @code{delete-process} on the process object or @code{kill-buffer} on
2384 the process buffer close the connection, but this does not affect the
2385 device connected to the serial port.
2387 The function @code{process-type} returns the symbol @code{serial}
2388 for a process object representing a serial port connection.
2390 Serial ports are available on GNU/Linux, Unix, and Windows systems.
2392 @deffn Command serial-term port speed
2393 Start a terminal-emulator for a serial port in a new buffer.
2394 @var{port} is the name of the serial port to which to connect. For
2395 example, this could be @file{/dev/ttyS0} on Unix. On Windows, this
2396 could be @file{COM1}, or @file{\\.\COM10} (double the backslashes in
2399 @var{speed} is the speed of the serial port in bits per second. 9600
2400 is a common value. The buffer is in Term mode; see @ref{Term Mode,,,
2401 emacs, The GNU Emacs Manual}, for the commands to use in that buffer.
2402 You can change the speed and the configuration in the mode line menu.
2405 @defun make-serial-process &rest args
2406 This function creates a process and a buffer. Arguments are specified
2407 as keyword/argument pairs. Here's the list of the meaningful keywords:
2410 @item :port @var{port}@r{ (mandatory)}
2411 This is the name of the serial port. On Unix and GNU systems, this is
2412 a file name such as @file{/dev/ttyS0}. On Windows, this could be
2413 @file{COM1}, or @file{\\.\COM10} for ports higher than @file{COM9}
2414 (double the backslashes in Lisp strings).
2416 @item :speed @var{speed}@r{ (mandatory)}
2417 The speed of the serial port in bits per second. This function calls
2418 @code{serial-process-configure} to handle the speed.
2420 @item :name @var{name}
2421 The name of the process. If @var{name} is not given, @var{port} will
2422 serve as the process name as well.
2424 @item :buffer @var{buffer}
2425 The buffer to associate with the process. The value could be either a
2426 buffer or a string that names a buffer. Process output goes at the
2427 end of that buffer, unless you specify an output stream or filter
2428 function to handle the output. If @var{buffer} is not given, the
2429 process buffer's name is taken from the value of the @code{:name}
2432 @item :coding @var{coding}
2433 If @var{coding} is a symbol, it specifies the coding system used for
2434 both reading and writing for this process. If @var{coding} is a cons
2435 @code{(decoding . encoding)}, @var{decoding} is used for reading, and
2436 @var{encoding} is used for writing. If not specified, the default is
2437 to determine the coding systems from data itself.
2439 @item :noquery @var{query-flag}
2440 Initialize the process query flag to @var{query-flag}. @xref{Query
2441 Before Exit}. The flags defaults to @code{nil} if unspecified.
2443 @item :stop @var{bool}
2444 Start process in the @code{stopped} state if @var{bool} is
2445 non-@code{nil}. In the stopped state, a serial process does not
2446 accept incoming data, but you can send outgoing data. The stopped
2447 state is cleared by @code{continue-process} and set by
2448 @code{stop-process}.
2450 @item :filter @var{filter}
2451 Install @var{filter} as the process filter.
2453 @item :sentinel @var{sentinel}
2454 Install @var{sentinel} as the process sentinel.
2456 @item :plist @var{plist}
2457 Install @var{plist} as the initial plist of the process.
2464 These arguments are handled by @code{serial-process-configure}, which
2465 is called by @code{make-serial-process}.
2468 The original argument list, possibly modified by later configuration,
2469 is available via the function @code{process-contact}.
2474 (make-serial-process :port "/dev/ttyS0" :speed 9600)
2476 (make-serial-process :port "COM1" :speed 115200 :stopbits 2)
2478 (make-serial-process :port "\\\\.\\COM13" :speed 1200
2479 :bytesize 7 :parity 'odd)
2481 (make-serial-process :port "/dev/tty.BlueConsole-SPP-1" :speed nil)
2485 @defun serial-process-configure &rest args
2486 @cindex baud, in serial connections
2487 @cindex bytesize, in serial connections
2488 @cindex parity, in serial connections
2489 @cindex stopbits, in serial connections
2490 @cindex flowcontrol, in serial connections
2492 This functions configures a serial port connection. Arguments are
2493 specified as keyword/argument pairs. Attributes that are not given
2494 are re-initialized from the process's current configuration (available
2495 via the function @code{process-contact}) or set to reasonable default
2496 values. The following arguments are defined:
2499 @item :process @var{process}
2500 @itemx :name @var{name}
2501 @itemx :buffer @var{buffer}
2502 @itemx :port @var{port}
2503 Any of these arguments can be given to identify the process that is to
2504 be configured. If none of these arguments is given, the current
2505 buffer's process is used.
2507 @item :speed @var{speed}
2508 The speed of the serial port in bits per second, a.k.a.@: @dfn{baud
2509 rate}. The value can be any number, but most serial ports work only
2510 at a few defined values between 1200 and 115200, with 9600 being the
2511 most common value. If @var{speed} is @code{nil}, the function ignores
2512 all other arguments and does not configure the port. This may be
2513 useful for special serial ports such as Bluetooth-to-serial converters
2514 which can only be configured through AT commands sent through the
2515 connection. The value of @code{nil} for @var{speed} is valid only for
2516 connections that were already opened by a previous call to
2517 @code{make-serial-process} or @code{serial-term}.
2519 @item :bytesize @var{bytesize}
2520 The number of bits per byte, which can be 7 or 8. If @var{bytesize}
2521 is not given or @code{nil}, it defaults to 8.
2523 @item :parity @var{parity}
2524 The value can be @code{nil} (don't use parity), the symbol
2525 @code{odd} (use odd parity), or the symbol @code{even} (use even
2526 parity). If @var{parity} is not given, it defaults to no parity.
2528 @item :stopbits @var{stopbits}
2529 The number of stopbits used to terminate a transmission
2530 of each byte. @var{stopbits} can be 1 or 2. If @var{stopbits} is not
2531 given or @code{nil}, it defaults to 1.
2533 @item :flowcontrol @var{flowcontrol}
2534 The type of flow control to use for this connection, which is either
2535 @code{nil} (don't use flow control), the symbol @code{hw} (use RTS/CTS
2536 hardware flow control), or the symbol @code{sw} (use XON/XOFF software
2537 flow control). If @var{flowcontrol} is not given, it defaults to no
2541 @code{serial-process-configure} is called by @code{make-serial-process} for the
2542 initial configuration of the serial port.
2547 (serial-process-configure :process "/dev/ttyS0" :speed 1200)
2549 (serial-process-configure :buffer "COM1" :stopbits 1 :parity 'odd :flowcontrol 'hw)
2551 (serial-process-configure :port "\\\\.\\COM13" :bytesize 7)
2556 @section Packing and Unpacking Byte Arrays
2557 @cindex byte packing and unpacking
2559 This section describes how to pack and unpack arrays of bytes,
2560 usually for binary network protocols. These functions convert byte arrays
2561 to alists, and vice versa. The byte array can be represented as a
2562 unibyte string or as a vector of integers, while the alist associates
2563 symbols either with fixed-size objects or with recursive sub-alists.
2566 @cindex deserializing
2569 Conversion from byte arrays to nested alists is also known as
2570 @dfn{deserializing} or @dfn{unpacking}, while going in the opposite
2571 direction is also known as @dfn{serializing} or @dfn{packing}.
2574 * Bindat Spec:: Describing data layout.
2575 * Bindat Functions:: Doing the unpacking and packing.
2576 * Bindat Examples:: Samples of what bindat.el can do for you!
2580 @subsection Describing Data Layout
2582 To control unpacking and packing, you write a @dfn{data layout
2583 specification}, a special nested list describing named and typed
2584 @dfn{fields}. This specification controls length of each field to be
2585 processed, and how to pack or unpack it. We normally keep bindat specs
2586 in variables whose names end in @samp{-bindat-spec}; that kind of name
2587 is automatically recognized as ``risky.''
2591 @cindex little endian
2592 @cindex network byte ordering
2593 A field's @dfn{type} describes the size (in bytes) of the object
2594 that the field represents and, in the case of multibyte fields, how
2595 the bytes are ordered within the field. The two possible orderings
2596 are ``big endian'' (also known as ``network byte ordering'') and
2597 ``little endian.'' For instance, the number @code{#x23cd} (decimal
2598 9165) in big endian would be the two bytes @code{#x23} @code{#xcd};
2599 and in little endian, @code{#xcd} @code{#x23}. Here are the possible
2605 Unsigned byte, with length 1.
2610 Unsigned integer in network byte order, with length 2.
2613 Unsigned integer in network byte order, with length 3.
2618 Unsigned integer in network byte order, with length 4.
2619 Note: These values may be limited by Emacs' integer implementation limits.
2624 Unsigned integer in little endian order, with length 2, 3 and 4, respectively.
2627 String of length @var{len}.
2629 @item strz @var{len}
2630 Zero-terminated string, in a fixed-size field with length @var{len}.
2632 @item vec @var{len} [@var{type}]
2633 Vector of @var{len} elements of type @var{type}, or bytes if not
2634 @var{type} is specified.
2635 The @var{type} is any of the simple types above, or another vector
2636 specified as a list @code{(vec @var{len} [@var{type}])}.
2639 Four-byte vector representing an Internet address. For example:
2640 @code{[127 0 0 1]} for localhost.
2642 @item bits @var{len}
2643 List of set bits in @var{len} bytes. The bytes are taken in big
2644 endian order and the bits are numbered starting with @code{8 *
2645 @var{len} @minus{} 1} and ending with zero. For example: @code{bits
2646 2} unpacks @code{#x28} @code{#x1c} to @code{(2 3 4 11 13)} and
2647 @code{#x1c} @code{#x28} to @code{(3 5 10 11 12)}.
2649 @item (eval @var{form})
2650 @var{form} is a Lisp expression evaluated at the moment the field is
2651 unpacked or packed. The result of the evaluation should be one of the
2652 above-listed type specifications.
2655 For a fixed-size field, the length @var{len} is given as an integer
2656 specifying the number of bytes in the field.
2658 When the length of a field is not fixed, it typically depends on the
2659 value of a preceding field. In this case, the length @var{len} can be
2660 given either as a list @code{(@var{name} ...)} identifying a
2661 @dfn{field name} in the format specified for @code{bindat-get-field}
2662 below, or by an expression @code{(eval @var{form})} where @var{form}
2663 should evaluate to an integer, specifying the field length.
2665 A field specification generally has the form @code{([@var{name}]
2666 @var{handler})}. The square braces indicate that @var{name} is
2667 optional. (Don't use names that are symbols meaningful as type
2668 specifications (above) or handler specifications (below), since that
2669 would be ambiguous.) @var{name} can be a symbol or the expression
2670 @code{(eval @var{form})}, in which case @var{form} should evaluate to
2673 @var{handler} describes how to unpack or pack the field and can be one
2678 Unpack/pack this field according to the type specification @var{type}.
2680 @item eval @var{form}
2681 Evaluate @var{form}, a Lisp expression, for side-effect only. If the
2682 field name is specified, the value is bound to that field name.
2684 @item fill @var{len}
2685 Skip @var{len} bytes. In packing, this leaves them unchanged,
2686 which normally means they remain zero. In unpacking, this means
2689 @item align @var{len}
2690 Skip to the next multiple of @var{len} bytes.
2692 @item struct @var{spec-name}
2693 Process @var{spec-name} as a sub-specification. This describes a
2694 structure nested within another structure.
2696 @item union @var{form} (@var{tag} @var{spec})@dots{}
2697 @c ??? I don't see how one would actually use this.
2698 @c ??? what kind of expression would be useful for @var{form}?
2699 Evaluate @var{form}, a Lisp expression, find the first @var{tag}
2700 that matches it, and process its associated data layout specification
2701 @var{spec}. Matching can occur in one of three ways:
2705 If a @var{tag} has the form @code{(eval @var{expr})}, evaluate
2706 @var{expr} with the variable @code{tag} dynamically bound to the value
2707 of @var{form}. A non-@code{nil} result indicates a match.
2710 @var{tag} matches if it is @code{equal} to the value of @var{form}.
2713 @var{tag} matches unconditionally if it is @code{t}.
2716 @item repeat @var{count} @var{field-specs}@dots{}
2717 Process the @var{field-specs} recursively, in order, then repeat
2718 starting from the first one, processing all the specs @var{count}
2719 times overall. The @var{count} is given using the same formats as a
2720 field length---if an @code{eval} form is used, it is evaluated just once.
2721 For correct operation, each spec in @var{field-specs} must include a name.
2724 For the @code{(eval @var{form})} forms used in a bindat specification,
2725 the @var{form} can access and update these dynamically bound variables
2730 Value of the last field processed.
2733 The data as a byte array.
2736 Current index (within @code{bindat-raw}) for unpacking or packing.
2739 The alist containing the structured data that have been unpacked so
2740 far, or the entire structure being packed. You can use
2741 @code{bindat-get-field} to access specific fields of this structure.
2745 Inside a @code{repeat} block, these contain the maximum number of
2746 repetitions (as specified by the @var{count} parameter), and the
2747 current repetition number (counting from 0). Setting @code{count} to
2748 zero will terminate the inner-most repeat block after the current
2749 repetition has completed.
2752 @node Bindat Functions
2753 @subsection Functions to Unpack and Pack Bytes
2755 In the following documentation, @var{spec} refers to a data layout
2756 specification, @code{bindat-raw} to a byte array, and @var{struct} to an
2757 alist representing unpacked field data.
2759 @defun bindat-unpack spec bindat-raw &optional bindat-idx
2760 This function unpacks data from the unibyte string or byte
2761 array @code{bindat-raw}
2762 according to @var{spec}. Normally this starts unpacking at the
2763 beginning of the byte array, but if @var{bindat-idx} is non-@code{nil}, it
2764 specifies a zero-based starting position to use instead.
2766 The value is an alist or nested alist in which each element describes
2770 @defun bindat-get-field struct &rest name
2771 This function selects a field's data from the nested alist
2772 @var{struct}. Usually @var{struct} was returned by
2773 @code{bindat-unpack}. If @var{name} corresponds to just one argument,
2774 that means to extract a top-level field value. Multiple @var{name}
2775 arguments specify repeated lookup of sub-structures. An integer name
2776 acts as an array index.
2778 For example, if @var{name} is @code{(a b 2 c)}, that means to find
2779 field @code{c} in the third element of subfield @code{b} of field
2780 @code{a}. (This corresponds to @code{struct.a.b[2].c} in C.)
2783 Although packing and unpacking operations change the organization of
2784 data (in memory), they preserve the data's @dfn{total length}, which is
2785 the sum of all the fields' lengths, in bytes. This value is not
2786 generally inherent in either the specification or alist alone; instead,
2787 both pieces of information contribute to its calculation. Likewise, the
2788 length of a string or array being unpacked may be longer than the data's
2789 total length as described by the specification.
2791 @defun bindat-length spec struct
2792 This function returns the total length of the data in @var{struct},
2793 according to @var{spec}.
2796 @defun bindat-pack spec struct &optional bindat-raw bindat-idx
2797 This function returns a byte array packed according to @var{spec} from
2798 the data in the alist @var{struct}. Normally it creates and fills a
2799 new byte array starting at the beginning. However, if @var{bindat-raw}
2800 is non-@code{nil}, it specifies a pre-allocated unibyte string or vector to
2801 pack into. If @var{bindat-idx} is non-@code{nil}, it specifies the starting
2802 offset for packing into @code{bindat-raw}.
2804 When pre-allocating, you should make sure @code{(length @var{bindat-raw})}
2805 meets or exceeds the total length to avoid an out-of-range error.
2808 @defun bindat-ip-to-string ip
2809 Convert the Internet address vector @var{ip} to a string in the usual
2813 (bindat-ip-to-string [127 0 0 1])
2814 @result{} "127.0.0.1"
2818 @node Bindat Examples
2819 @subsection Examples of Byte Unpacking and Packing
2821 Here is a complete example of byte unpacking and packing:
2824 (defvar fcookie-index-spec
2832 (:offset repeat (:count)
2834 "Description of a fortune cookie index file's contents.")
2836 (defun fcookie (cookies &optional index)
2837 "Display a random fortune cookie from file COOKIES.
2838 Optional second arg INDEX specifies the associated index
2839 filename, which is by default constructed by appending
2840 \".dat\" to COOKIES. Display cookie text in possibly
2841 new buffer \"*Fortune Cookie: BASENAME*\" where BASENAME
2842 is COOKIES without the directory part."
2843 (interactive "fCookies file: ")
2844 (let* ((info (with-temp-buffer
2845 (insert-file-contents-literally
2846 (or index (concat cookies ".dat")))
2847 (bindat-unpack fcookie-index-spec
2849 (sel (random (bindat-get-field info :count)))
2850 (beg (cdar (bindat-get-field info :offset sel)))
2851 (end (or (cdar (bindat-get-field info
2853 (nth 7 (file-attributes cookies)))))
2856 (format "*Fortune Cookie: %s*"
2857 (file-name-nondirectory cookies))))
2859 (insert-file-contents-literally
2860 cookies nil beg (- end 3))))
2862 (defun fcookie-create-index (cookies &optional index delim)
2863 "Scan file COOKIES, and write out its index file.
2864 Optional second arg INDEX specifies the index filename,
2865 which is by default constructed by appending \".dat\" to
2866 COOKIES. Optional third arg DELIM specifies the unibyte
2867 character which, when found on a line of its own in
2868 COOKIES, indicates the border between entries."
2869 (interactive "fCookies file: ")
2870 (setq delim (or delim ?%))
2871 (let ((delim-line (format "\n%c\n" delim))
2874 min p q len offsets)
2875 (unless (= 3 (string-bytes delim-line))
2876 (error "Delimiter cannot be represented in one byte"))
2878 (insert-file-contents-literally cookies)
2879 (while (and (setq p (point))
2880 (search-forward delim-line (point-max) t)
2881 (setq len (- (point) 3 p)))
2882 (setq count (1+ count)
2884 min (min (or min max) len)
2885 offsets (cons (1- p) offsets))))
2887 (set-buffer-multibyte nil)
2897 (:offset . ,(mapcar (lambda (o)
2898 (list (cons :foo o)))
2899 (nreverse offsets))))))
2900 (let ((coding-system-for-write 'raw-text-unix))
2901 (write-file (or index (concat cookies ".dat")))))))
2904 Following is an example of defining and unpacking a complex structure.
2905 Consider the following C structures:
2909 unsigned long dest_ip;
2910 unsigned long src_ip;
2911 unsigned short dest_port;
2912 unsigned short src_port;
2917 unsigned char opcode;
2918 unsigned short length; /* In network byte order */
2919 unsigned char id[8]; /* null-terminated string */
2920 unsigned char data[/* (length + 3) & ~3 */];
2924 struct header header;
2925 unsigned long counters[2]; /* In little endian order */
2926 unsigned char items;
2927 unsigned char filler[3];
2928 struct data item[/* items */];
2933 The corresponding data layout specification:
2945 (length u16) ;; network byte order
2951 '((header struct header-spec)
2952 (counters vec 2 u32r) ;; little endian order
2955 (item repeat (items)
2956 (struct data-spec))))
2959 A binary data representation:
2963 [ 192 168 1 100 192 168 1 101 01 28 21 32
2964 160 134 1 0 5 1 0 0 2 0 0 0
2965 2 3 0 5 ?A ?B ?C ?D ?E ?F 0 0 1 2 3 4 5 0 0 0
2966 1 4 0 7 ?B ?C ?D ?E ?F ?G 0 0 6 7 8 9 10 11 12 0 ])
2969 The corresponding decoded structure:
2972 (setq decoded (bindat-unpack packet-spec binary-data))
2975 (dest-ip . [192 168 1 100])
2976 (src-ip . [192 168 1 101])
2979 (counters . [100000 261])
2981 (item ((data . [1 2 3 4 5])
2986 ((data . [6 7 8 9 10 11 12])
2993 Fetching data from this structure:
2996 (bindat-get-field decoded 'item 1 'id)
3001 arch-tag: ba9da253-e65f-4e7f-b727-08fba0a1df7a