2 @c This is part of the GNU Emacs Lisp Reference Manual.
3 @c Copyright (C) 1990-1995, 1998-1999, 2001-2011
4 @c Free Software Foundation, Inc.
5 @c See the file elisp.texi for copying conditions.
6 @setfilename ../../info/processes
7 @node Processes, Display, Abbrevs, Top
10 @cindex parent process
14 In the terminology of operating systems, a @dfn{process} is a space in
15 which a program can execute. Emacs runs in a process. Emacs Lisp
16 programs can invoke other programs in processes of their own. These are
17 called @dfn{subprocesses} or @dfn{child processes} of the Emacs process,
18 which is their @dfn{parent process}.
20 A subprocess of Emacs may be @dfn{synchronous} or @dfn{asynchronous},
21 depending on how it is created. When you create a synchronous
22 subprocess, the Lisp program waits for the subprocess to terminate
23 before continuing execution. When you create an asynchronous
24 subprocess, it can run in parallel with the Lisp program. This kind of
25 subprocess is represented within Emacs by a Lisp object which is also
26 called a ``process.'' Lisp programs can use this object to communicate
27 with the subprocess or to control it. For example, you can send
28 signals, obtain status information, receive output from the process, or
31 @defun processp object
32 This function returns @code{t} if @var{object} represents an Emacs
33 subprocess, @code{nil} otherwise.
36 In addition to subprocesses of the current Emacs session, you can
37 also access other processes running on your machine. @xref{System
41 * Subprocess Creation:: Functions that start subprocesses.
42 * Shell Arguments:: Quoting an argument to pass it to a shell.
43 * Synchronous Processes:: Details of using synchronous subprocesses.
44 * Asynchronous Processes:: Starting up an asynchronous subprocess.
45 * Deleting Processes:: Eliminating an asynchronous subprocess.
46 * Process Information:: Accessing run-status and other attributes.
47 * Input to Processes:: Sending input to an asynchronous subprocess.
48 * Signals to Processes:: Stopping, continuing or interrupting
49 an asynchronous subprocess.
50 * Output from Processes:: Collecting output from an asynchronous subprocess.
51 * Sentinels:: Sentinels run when process run-status changes.
52 * Query Before Exit:: Whether to query if exiting will kill a process.
53 * System Processes:: Accessing other processes running on your system.
54 * Transaction Queues:: Transaction-based communication with subprocesses.
55 * Network:: Opening network connections.
56 * Network Servers:: Network servers let Emacs accept net connections.
57 * Datagrams:: UDP network connections.
58 * Low-Level Network:: Lower-level but more general function
59 to create connections and servers.
60 * Misc Network:: Additional relevant functions for net connections.
61 * Serial Ports:: Communicating with serial ports.
62 * Byte Packing:: Using bindat to pack and unpack binary data.
65 @node Subprocess Creation
66 @section Functions that Create Subprocesses
68 There are three primitives that create a new subprocess in which to run
69 a program. One of them, @code{start-process}, creates an asynchronous
70 process and returns a process object (@pxref{Asynchronous Processes}).
71 The other two, @code{call-process} and @code{call-process-region},
72 create a synchronous process and do not return a process object
73 (@pxref{Synchronous Processes}).
75 Synchronous and asynchronous processes are explained in the following
76 sections. Since the three functions are all called in a similar
77 fashion, their common arguments are described here.
79 @cindex execute program
80 @cindex @code{PATH} environment variable
81 @cindex @code{HOME} environment variable
82 In all cases, the function's @var{program} argument specifies the
83 program to be run. An error is signaled if the file is not found or
84 cannot be executed. If the file name is relative, the variable
85 @code{exec-path} contains a list of directories to search. Emacs
86 initializes @code{exec-path} when it starts up, based on the value of
87 the environment variable @code{PATH}. The standard file name
88 constructs, @samp{~}, @samp{.}, and @samp{..}, are interpreted as
89 usual in @code{exec-path}, but environment variable substitutions
90 (@samp{$HOME}, etc.) are not recognized; use
91 @code{substitute-in-file-name} to perform them (@pxref{File Name
92 Expansion}). @code{nil} in this list refers to
93 @code{default-directory}.
95 Executing a program can also try adding suffixes to the specified
99 This variable is a list of suffixes (strings) to try adding to the
100 specified program file name. The list should include @code{""} if you
101 want the name to be tried exactly as specified. The default value is
105 @strong{Please note:} The argument @var{program} contains only the
106 name of the program; it may not contain any command-line arguments. You
107 must use @var{args} to provide those.
109 Each of the subprocess-creating functions has a @var{buffer-or-name}
110 argument which specifies where the standard output from the program will
111 go. It should be a buffer or a buffer name; if it is a buffer name,
112 that will create the buffer if it does not already exist. It can also
113 be @code{nil}, which says to discard the output unless a filter function
114 handles it. (@xref{Filter Functions}, and @ref{Read and Print}.)
115 Normally, you should avoid having multiple processes send output to the
116 same buffer because their output would be intermixed randomly.
118 @cindex program arguments
119 All three of the subprocess-creating functions have a @code{&rest}
120 argument, @var{args}. The @var{args} must all be strings, and they are
121 supplied to @var{program} as separate command line arguments. Wildcard
122 characters and other shell constructs have no special meanings in these
123 strings, since the strings are passed directly to the specified program.
125 The subprocess gets its current directory from the value of
126 @code{default-directory} (@pxref{File Name Expansion}).
128 @cindex environment variables, subprocesses
129 The subprocess inherits its environment from Emacs, but you can
130 specify overrides for it with @code{process-environment}. @xref{System
133 @defvar exec-directory
135 The value of this variable is a string, the name of a directory that
136 contains programs that come with GNU Emacs, programs intended for Emacs
137 to invoke. The program @code{movemail} is an example of such a program;
138 Rmail uses it to fetch new mail from an inbox.
142 The value of this variable is a list of directories to search for
143 programs to run in subprocesses. Each element is either the name of a
144 directory (i.e., a string), or @code{nil}, which stands for the default
145 directory (which is the value of @code{default-directory}).
146 @cindex program directories
148 The value of @code{exec-path} is used by @code{call-process} and
149 @code{start-process} when the @var{program} argument is not an absolute
153 @node Shell Arguments
154 @section Shell Arguments
155 @cindex arguments for shell commands
156 @cindex shell command arguments
158 Lisp programs sometimes need to run a shell and give it a command
159 that contains file names that were specified by the user. These
160 programs ought to be able to support any valid file name. But the shell
161 gives special treatment to certain characters, and if these characters
162 occur in the file name, they will confuse the shell. To handle these
163 characters, use the function @code{shell-quote-argument}:
165 @defun shell-quote-argument argument
166 This function returns a string which represents, in shell syntax,
167 an argument whose actual contents are @var{argument}. It should
168 work reliably to concatenate the return value into a shell command
169 and then pass it to a shell for execution.
171 Precisely what this function does depends on your operating system. The
172 function is designed to work with the syntax of your system's standard
173 shell; if you use an unusual shell, you will need to redefine this
177 ;; @r{This example shows the behavior on GNU and Unix systems.}
178 (shell-quote-argument "foo > bar")
179 @result{} "foo\\ \\>\\ bar"
181 ;; @r{This example shows the behavior on MS-DOS and MS-Windows.}
182 (shell-quote-argument "foo > bar")
183 @result{} "\"foo > bar\""
186 Here's an example of using @code{shell-quote-argument} to construct
191 (shell-quote-argument oldfile)
193 (shell-quote-argument newfile))
197 @cindex quoting and unquoting command-line arguments
198 @cindex minibuffer input, and command-line arguments
199 @cindex @code{call-process}, command-line arguments from minibuffer
200 @cindex @code{start-process}, command-line arguments from minibuffer
201 The following two functions are useful for combining a list of
202 individual command-line argument strings into a single string, and
203 taking a string apart into a list of individual command-line
204 arguments. These functions are mainly intended to be used for
205 converting user input in the minibuffer, a Lisp string, into a list of
206 string arguments to be passed to @code{call-process} or
207 @code{start-process}, or for the converting such lists of arguments in
208 a single Lisp string to be presented in the minibuffer or echo area.
210 @defun split-string-and-unquote string &optional separators
211 This function splits @var{string} into substrings at matches for the
212 regular expression @var{separators}, like @code{split-string} does
213 (@pxref{Creating Strings}); in addition, it removes quoting from the
214 substrings. It then makes a list of the substrings and returns it.
216 If @var{separators} is omitted or @code{nil}, it defaults to
217 @code{"\\s-+"}, which is a regular expression that matches one or more
218 characters with whitespace syntax (@pxref{Syntax Class Table}).
220 This function supports two types of quoting: enclosing a whole string
221 in double quotes @code{"@dots{}"}, and quoting individual characters
222 with a backslash escape @samp{\}. The latter is also used in Lisp
223 strings, so this function can handle those as well.
226 @defun combine-and-quote-strings list-of-strings &optional separator
227 This function concatenates @var{list-of-strings} into a single string,
228 quoting each string as necessary. It also sticks the @var{separator}
229 string between each pair of strings; if @var{separator} is omitted or
230 @code{nil}, it defaults to @code{" "}. The return value is the
233 The strings in @var{list-of-strings} that need quoting are those that
234 include @var{separator} as their substring. Quoting a string encloses
235 it in double quotes @code{"@dots{}"}. In the simplest case, if you
236 are consing a command from the individual command-line arguments,
237 every argument that includes embedded blanks will be quoted.
240 @node Synchronous Processes
241 @section Creating a Synchronous Process
242 @cindex synchronous subprocess
244 After a @dfn{synchronous process} is created, Emacs waits for the
245 process to terminate before continuing. Starting Dired on GNU or
246 Unix@footnote{On other systems, Emacs uses a Lisp emulation of
247 @code{ls}; see @ref{Contents of Directories}.} is an example of this: it
248 runs @code{ls} in a synchronous process, then modifies the output
249 slightly. Because the process is synchronous, the entire directory
250 listing arrives in the buffer before Emacs tries to do anything with it.
252 While Emacs waits for the synchronous subprocess to terminate, the
253 user can quit by typing @kbd{C-g}. The first @kbd{C-g} tries to kill
254 the subprocess with a @code{SIGINT} signal; but it waits until the
255 subprocess actually terminates before quitting. If during that time the
256 user types another @kbd{C-g}, that kills the subprocess instantly with
257 @code{SIGKILL} and quits immediately (except on MS-DOS, where killing
258 other processes doesn't work). @xref{Quitting}.
260 The synchronous subprocess functions return an indication of how the
263 The output from a synchronous subprocess is generally decoded using a
264 coding system, much like text read from a file. The input sent to a
265 subprocess by @code{call-process-region} is encoded using a coding
266 system, much like text written into a file. @xref{Coding Systems}.
268 @defun call-process program &optional infile destination display &rest args
269 This function calls @var{program} and waits for it to finish.
271 The standard input for the new process comes from file @var{infile} if
272 @var{infile} is not @code{nil}, and from the null device otherwise.
273 The argument @var{destination} says where to put the process output.
274 Here are the possibilities:
278 Insert the output in that buffer, before point. This includes both the
279 standard output stream and the standard error stream of the process.
282 Insert the output in a buffer with that name, before point.
285 Insert the output in the current buffer, before point.
291 Discard the output, and return @code{nil} immediately without waiting
292 for the subprocess to finish.
294 In this case, the process is not truly synchronous, since it can run in
295 parallel with Emacs; but you can think of it as synchronous in that
296 Emacs is essentially finished with the subprocess as soon as this
299 MS-DOS doesn't support asynchronous subprocesses, so this option doesn't
302 @item @code{(:file @var{file-name})}
303 Send the output to the file name specified.
305 @item @code{(@var{real-destination} @var{error-destination})}
306 Keep the standard output stream separate from the standard error stream;
307 deal with the ordinary output as specified by @var{real-destination},
308 and dispose of the error output according to @var{error-destination}.
309 If @var{error-destination} is @code{nil}, that means to discard the
310 error output, @code{t} means mix it with the ordinary output, and a
311 string specifies a file name to redirect error output into.
313 You can't directly specify a buffer to put the error output in; that is
314 too difficult to implement. But you can achieve this result by sending
315 the error output to a temporary file and then inserting the file into a
319 If @var{display} is non-@code{nil}, then @code{call-process} redisplays
320 the buffer as output is inserted. (However, if the coding system chosen
321 for decoding output is @code{undecided}, meaning deduce the encoding
322 from the actual data, then redisplay sometimes cannot continue once
323 non-@acronym{ASCII} characters are encountered. There are fundamental
324 reasons why it is hard to fix this; see @ref{Output from Processes}.)
326 Otherwise the function @code{call-process} does no redisplay, and the
327 results become visible on the screen only when Emacs redisplays that
328 buffer in the normal course of events.
330 The remaining arguments, @var{args}, are strings that specify command
331 line arguments for the program.
333 The value returned by @code{call-process} (unless you told it not to
334 wait) indicates the reason for process termination. A number gives the
335 exit status of the subprocess; 0 means success, and any other value
336 means failure. If the process terminated with a signal,
337 @code{call-process} returns a string describing the signal.
339 In the examples below, the buffer @samp{foo} is current.
343 (call-process "pwd" nil t)
346 ---------- Buffer: foo ----------
347 /usr/user/lewis/manual
348 ---------- Buffer: foo ----------
352 (call-process "grep" nil "bar" nil "lewis" "/etc/passwd")
355 ---------- Buffer: bar ----------
356 lewis:5LTsHm66CSWKg:398:21:Bil Lewis:/user/lewis:/bin/csh
358 ---------- Buffer: bar ----------
362 Here is a good example of the use of @code{call-process}, which used to
363 be found in the definition of @code{insert-directory}:
367 (call-process insert-directory-program nil t nil @var{switches}
369 (concat (file-name-as-directory file) ".")
375 @defun process-file program &optional infile buffer display &rest args
376 This function processes files synchronously in a separate process. It
377 is similar to @code{call-process} but may invoke a file handler based
378 on the value of the variable @code{default-directory}. The current
379 working directory of the subprocess is @code{default-directory}.
381 The arguments are handled in almost the same way as for
382 @code{call-process}, with the following differences:
384 Some file handlers may not support all combinations and forms of the
385 arguments @var{infile}, @var{buffer}, and @var{display}. For example,
386 some file handlers might behave as if @var{display} were @code{nil},
387 regardless of the value actually passed. As another example, some
388 file handlers might not support separating standard output and error
389 output by way of the @var{buffer} argument.
391 If a file handler is invoked, it determines the program to run based
392 on the first argument @var{program}. For instance, consider that a
393 handler for remote files is invoked. Then the path that is used for
394 searching the program might be different than @code{exec-path}.
396 The second argument @var{infile} may invoke a file handler. The file
397 handler could be different from the handler chosen for the
398 @code{process-file} function itself. (For example,
399 @code{default-directory} could be on a remote host, whereas
400 @var{infile} is on another remote host. Or @code{default-directory}
401 could be non-special, whereas @var{infile} is on a remote host.)
403 If @var{buffer} is a list of the form @code{(@var{real-destination}
404 @var{error-destination})}, and @var{error-destination} names a file,
405 then the same remarks as for @var{infile} apply.
407 The remaining arguments (@var{args}) will be passed to the process
408 verbatim. Emacs is not involved in processing file names that are
409 present in @var{args}. To avoid confusion, it may be best to avoid
410 absolute file names in @var{args}, but rather to specify all file
411 names as relative to @code{default-directory}. The function
412 @code{file-relative-name} is useful for constructing such relative
416 @defvar process-file-side-effects
417 This variable indicates, whether a call of @code{process-file} changes
420 Per default, this variable is always set to @code{t}, meaning that a
421 call of @code{process-file} could potentially change any file on a
422 remote host. When set to @code{nil}, a file handler could optimize
423 its behaviour with respect to remote file attributes caching.
425 This variable should never be changed by @code{setq}. Instead of, it
426 shall be set only by let-binding.
429 @defun call-process-region start end program &optional delete destination display &rest args
430 This function sends the text from @var{start} to @var{end} as
431 standard input to a process running @var{program}. It deletes the text
432 sent if @var{delete} is non-@code{nil}; this is useful when
433 @var{destination} is @code{t}, to insert the output in the current
434 buffer in place of the input.
436 The arguments @var{destination} and @var{display} control what to do
437 with the output from the subprocess, and whether to update the display
438 as it comes in. For details, see the description of
439 @code{call-process}, above. If @var{destination} is the integer 0,
440 @code{call-process-region} discards the output and returns @code{nil}
441 immediately, without waiting for the subprocess to finish (this only
442 works if asynchronous subprocesses are supported).
444 The remaining arguments, @var{args}, are strings that specify command
445 line arguments for the program.
447 The return value of @code{call-process-region} is just like that of
448 @code{call-process}: @code{nil} if you told it to return without
449 waiting; otherwise, a number or string which indicates how the
450 subprocess terminated.
452 In the following example, we use @code{call-process-region} to run the
453 @code{cat} utility, with standard input being the first five characters
454 in buffer @samp{foo} (the word @samp{input}). @code{cat} copies its
455 standard input into its standard output. Since the argument
456 @var{destination} is @code{t}, this output is inserted in the current
461 ---------- Buffer: foo ----------
463 ---------- Buffer: foo ----------
467 (call-process-region 1 6 "cat" nil t)
470 ---------- Buffer: foo ----------
472 ---------- Buffer: foo ----------
476 The @code{shell-command-on-region} command uses
477 @code{call-process-region} like this:
483 shell-file-name ; @r{Name of program.}
484 nil ; @r{Do not delete region.}
485 buffer ; @r{Send output to @code{buffer}.}
486 nil ; @r{No redisplay during output.}
487 "-c" command) ; @r{Arguments for the shell.}
492 @defun call-process-shell-command command &optional infile destination display &rest args
493 This function executes the shell command @var{command} synchronously.
494 The final arguments @var{args} are additional arguments to add at the
495 end of @var{command}. The other arguments are handled as in
499 @defun process-file-shell-command command &optional infile destination display &rest args
500 This function is like @code{call-process-shell-command}, but uses
501 @code{process-file} internally. Depending on @code{default-directory},
502 @var{command} can be executed also on remote hosts.
505 @defun shell-command-to-string command
506 This function executes @var{command} (a string) as a shell command,
507 then returns the command's output as a string.
510 @defun process-lines program &rest args
511 This function runs @var{program}, waits for it to finish, and returns
512 its output as a list of strings. Each string in the list holds a
513 single line of text output by the program; the end-of-line characters
514 are stripped from each line. The arguments beyond @var{program},
515 @var{args}, are strings that specify command-line arguments with which
518 If @var{program} exits with a non-zero exit status, this function
521 This function works by calling @code{call-process}, so program output
522 is decoded in the same way as for @code{call-process}.
525 @node Asynchronous Processes
526 @section Creating an Asynchronous Process
527 @cindex asynchronous subprocess
529 After an @dfn{asynchronous process} is created, Emacs and the subprocess
530 both continue running immediately. The process thereafter runs
531 in parallel with Emacs, and the two can communicate with each other
532 using the functions described in the following sections. However,
533 communication is only partially asynchronous: Emacs sends data to the
534 process only when certain functions are called, and Emacs accepts data
535 from the process only when Emacs is waiting for input or for a time
538 Here we describe how to create an asynchronous process.
540 @defun start-process name buffer-or-name program &rest args
541 This function creates a new asynchronous subprocess and starts the
542 program @var{program} running in it. It returns a process object that
543 stands for the new subprocess in Lisp. The argument @var{name}
544 specifies the name for the process object; if a process with this name
545 already exists, then @var{name} is modified (by appending @samp{<1>},
546 etc.) to be unique. The buffer @var{buffer-or-name} is the buffer to
547 associate with the process.
549 The remaining arguments, @var{args}, are strings that specify command
550 line arguments for the program.
552 In the example below, the first process is started and runs (rather,
553 sleeps) for 100 seconds. Meanwhile, the second process is started, and
554 given the name @samp{my-process<1>} for the sake of uniqueness. It
555 inserts the directory listing at the end of the buffer @samp{foo},
556 before the first process finishes. Then it finishes, and a message to
557 that effect is inserted in the buffer. Much later, the first process
558 finishes, and another message is inserted in the buffer for it.
562 (start-process "my-process" "foo" "sleep" "100")
563 @result{} #<process my-process>
567 (start-process "my-process" "foo" "ls" "-l" "/user/lewis/bin")
568 @result{} #<process my-process<1>>
570 ---------- Buffer: foo ----------
572 lrwxrwxrwx 1 lewis 14 Jul 22 10:12 gnuemacs --> /emacs
573 -rwxrwxrwx 1 lewis 19 Jul 30 21:02 lemon
575 Process my-process<1> finished
577 Process my-process finished
578 ---------- Buffer: foo ----------
583 @defun start-file-process name buffer-or-name program &rest args
584 Like @code{start-process}, this function starts a new asynchronous
585 subprocess running @var{program} in it, and returns its process
586 object---when @code{default-directory} is not a magic file name.
588 If @code{default-directory} is magic, the function invokes its file
589 handler instead. This handler ought to run @var{program}, perhaps on
590 the local host, perhaps on a remote host that corresponds to
591 @code{default-directory}. In the latter case, the local part of
592 @code{default-directory} becomes the working directory of the process.
594 This function does not try to invoke file name handlers for
595 @var{program} or for the @var{program-args}.
597 Depending on the implementation of the file handler, it might not be
598 possible to apply @code{process-filter} or @code{process-sentinel} to
599 the resulting process object (@pxref{Filter Functions}, @pxref{Sentinels}).
601 Some file handlers may not support @code{start-file-process} (for
602 example @code{ange-ftp-hook-function}). In such cases, the function
603 does nothing and returns @code{nil}.
606 @defun start-process-shell-command name buffer-or-name command
607 This function is like @code{start-process} except that it uses a shell
608 to execute the specified command. The argument @var{command} is a shell
609 command name. The variable @code{shell-file-name} specifies which shell to
612 The point of running a program through the shell, rather than directly
613 with @code{start-process}, is so that you can employ shell features such
614 as wildcards in the arguments. It follows that if you include an
615 arbitrary user-specified arguments in the command, you should quote it
616 with @code{shell-quote-argument} first, so that any special shell
617 characters do @emph{not} have their special shell meanings. @xref{Shell
621 @defun start-file-process-shell-command name buffer-or-name command
622 This function is like @code{start-process-shell-command}, but uses
623 @code{start-file-process} internally. By this, @var{command} can be
624 executed also on remote hosts, depending on @code{default-directory}.
627 @defvar process-connection-type
629 @cindex @acronym{PTY}s
630 This variable controls the type of device used to communicate with
631 asynchronous subprocesses. If it is non-@code{nil}, then @acronym{PTY}s are
632 used, when available. Otherwise, pipes are used.
634 @acronym{PTY}s are usually preferable for processes visible to the user, as
635 in Shell mode, because they allow job control (@kbd{C-c}, @kbd{C-z},
636 etc.) to work between the process and its children, whereas pipes do
637 not. For subprocesses used for internal purposes by programs, it is
638 often better to use a pipe, because they are more efficient. In
639 addition, the total number of @acronym{PTY}s is limited on many systems and
640 it is good not to waste them.
642 The value of @code{process-connection-type} takes effect when
643 @code{start-process} is called. So you can specify how to communicate
644 with one subprocess by binding the variable around the call to
645 @code{start-process}.
649 (let ((process-connection-type nil)) ; @r{Use a pipe.}
650 (start-process @dots{}))
654 To determine whether a given subprocess actually got a pipe or a
655 @acronym{PTY}, use the function @code{process-tty-name} (@pxref{Process
659 @node Deleting Processes
660 @section Deleting Processes
661 @cindex deleting processes
663 @dfn{Deleting a process} disconnects Emacs immediately from the
664 subprocess. Processes are deleted automatically after they terminate,
665 but not necessarily right away. You can delete a process explicitly
666 at any time. If you delete a terminated process explicitly before it
667 is deleted automatically, no harm results. Deleting a running
668 process sends a signal to terminate it (and its child processes if
669 any), and calls the process sentinel if it has one. @xref{Sentinels}.
671 When a process is deleted, the process object itself continues to
672 exist as long as other Lisp objects point to it. All the Lisp
673 primitives that work on process objects accept deleted processes, but
674 those that do I/O or send signals will report an error. The process
675 mark continues to point to the same place as before, usually into a
676 buffer where output from the process was being inserted.
678 @defopt delete-exited-processes
679 This variable controls automatic deletion of processes that have
680 terminated (due to calling @code{exit} or to a signal). If it is
681 @code{nil}, then they continue to exist until the user runs
682 @code{list-processes}. Otherwise, they are deleted immediately after
686 @defun delete-process process
687 This function deletes a process, killing it with a @code{SIGKILL}
688 signal. The argument may be a process, the name of a process, a
689 buffer, or the name of a buffer. (A buffer or buffer-name stands for
690 the process that @code{get-buffer-process} returns.) Calling
691 @code{delete-process} on a running process terminates it, updates the
692 process status, and runs the sentinel (if any) immediately. If the
693 process has already terminated, calling @code{delete-process} has no
694 effect on its status, or on the running of its sentinel (which will
695 happen sooner or later).
699 (delete-process "*shell*")
705 @node Process Information
706 @section Process Information
708 Several functions return information about processes.
709 @code{list-processes} is provided for interactive use.
711 @deffn Command list-processes &optional query-only
712 This command displays a listing of all living processes. In addition,
713 it finally deletes any process whose status was @samp{Exited} or
714 @samp{Signaled}. It returns @code{nil}.
716 If @var{query-only} is non-@code{nil} then it lists only processes
717 whose query flag is non-@code{nil}. @xref{Query Before Exit}.
721 This function returns a list of all processes that have not been deleted.
726 @result{} (#<process display-time> #<process shell>)
731 @defun get-process name
732 This function returns the process named @var{name}, or @code{nil} if
733 there is none. An error is signaled if @var{name} is not a string.
737 (get-process "shell")
738 @result{} #<process shell>
743 @defun process-command process
744 This function returns the command that was executed to start
745 @var{process}. This is a list of strings, the first string being the
746 program executed and the rest of the strings being the arguments that
747 were given to the program.
751 (process-command (get-process "shell"))
752 @result{} ("/bin/csh" "-i")
757 @defun process-contact process &optional key
759 This function returns information about how a network or serial
760 process was set up. For a network process, when @var{key} is
761 @code{nil}, it returns @code{(@var{hostname} @var{service})} which
762 specifies what you connected to. For a serial process, when @var{key}
763 is @code{nil}, it returns @code{(@var{port} @var{speed})}. For an
764 ordinary child process, this function always returns @code{t}.
766 If @var{key} is @code{t}, the value is the complete status information
767 for the connection, server, or serial port; that is, the list of
768 keywords and values specified in @code{make-network-process} or
769 @code{make-serial-process}, except that some of the values represent
770 the current status instead of what you specified.
772 For a network process:
776 The associated value is the process buffer.
778 The associated value is the process filter function.
780 The associated value is the process sentinel function.
782 In a connection, the address in internal format of the remote peer.
784 The local address, in internal format.
786 In a server, if you specified @code{t} for @var{service},
787 this value is the actual port number.
790 @code{:local} and @code{:remote} are included even if they were not
791 specified explicitly in @code{make-network-process}.
793 For a serial process, see @code{make-serial-process} and
794 @code{serial-process-configure} for a list of keys.
796 If @var{key} is a keyword, the function returns the value corresponding
800 @defun process-id process
801 This function returns the @acronym{PID} of @var{process}. This is an
802 integer that distinguishes the process @var{process} from all other
803 processes running on the same computer at the current time. The
804 @acronym{PID} of a process is chosen by the operating system kernel when the
805 process is started and remains constant as long as the process exists.
808 @defun process-name process
809 This function returns the name of @var{process}.
812 @defun process-status process-name
813 This function returns the status of @var{process-name} as a symbol.
814 The argument @var{process-name} must be a process, a buffer, or a
815 process name (a string).
817 The possible values for an actual subprocess are:
821 for a process that is running.
823 for a process that is stopped but continuable.
825 for a process that has exited.
827 for a process that has received a fatal signal.
829 for a network connection that is open.
831 for a network connection that is closed. Once a connection
832 is closed, you cannot reopen it, though you might be able to open
833 a new connection to the same place.
835 for a non-blocking connection that is waiting to complete.
837 for a non-blocking connection that has failed to complete.
839 for a network server that is listening.
841 if @var{process-name} is not the name of an existing process.
846 (process-status (get-buffer "*shell*"))
851 @result{} #<process xx<1>>
857 For a network connection, @code{process-status} returns one of the symbols
858 @code{open} or @code{closed}. The latter means that the other side
859 closed the connection, or Emacs did @code{delete-process}.
862 @defun process-type process
863 This function returns the symbol @code{network} for a network
864 connection or server, @code{serial} for a serial port connection, or
865 @code{real} for a real subprocess.
868 @defun process-exit-status process
869 This function returns the exit status of @var{process} or the signal
870 number that killed it. (Use the result of @code{process-status} to
871 determine which of those it is.) If @var{process} has not yet
872 terminated, the value is 0.
875 @defun process-tty-name process
876 This function returns the terminal name that @var{process} is using for
877 its communication with Emacs---or @code{nil} if it is using pipes
878 instead of a terminal (see @code{process-connection-type} in
879 @ref{Asynchronous Processes}). If @var{process} represents a program
880 running on a remote host, the terminal name used by that program on
881 the remote host is provided as process property @code{remote-tty}.
884 @defun process-coding-system process
885 @anchor{Coding systems for a subprocess}
886 This function returns a cons cell describing the coding systems in use
887 for decoding output from @var{process} and for encoding input to
888 @var{process} (@pxref{Coding Systems}). The value has this form:
891 (@var{coding-system-for-decoding} . @var{coding-system-for-encoding})
895 @defun set-process-coding-system process &optional decoding-system encoding-system
896 This function specifies the coding systems to use for subsequent output
897 from and input to @var{process}. It will use @var{decoding-system} to
898 decode subprocess output, and @var{encoding-system} to encode subprocess
902 Every process also has a property list that you can use to store
903 miscellaneous values associated with the process.
905 @defun process-get process propname
906 This function returns the value of the @var{propname} property
910 @defun process-put process propname value
911 This function sets the value of the @var{propname} property
912 of @var{process} to @var{value}.
915 @defun process-plist process
916 This function returns the process plist of @var{process}.
919 @defun set-process-plist process plist
920 This function sets the process plist of @var{process} to @var{plist}.
923 @node Input to Processes
924 @section Sending Input to Processes
925 @cindex process input
927 Asynchronous subprocesses receive input when it is sent to them by
928 Emacs, which is done with the functions in this section. You must
929 specify the process to send input to, and the input data to send. The
930 data appears on the ``standard input'' of the subprocess.
932 Some operating systems have limited space for buffered input in a
933 @acronym{PTY}. On these systems, Emacs sends an @acronym{EOF}
934 periodically amidst the other characters, to force them through. For
935 most programs, these @acronym{EOF}s do no harm.
937 Subprocess input is normally encoded using a coding system before the
938 subprocess receives it, much like text written into a file. You can use
939 @code{set-process-coding-system} to specify which coding system to use
940 (@pxref{Process Information}). Otherwise, the coding system comes from
941 @code{coding-system-for-write}, if that is non-@code{nil}; or else from
942 the defaulting mechanism (@pxref{Default Coding Systems}).
944 Sometimes the system is unable to accept input for that process,
945 because the input buffer is full. When this happens, the send functions
946 wait a short while, accepting output from subprocesses, and then try
947 again. This gives the subprocess a chance to read more of its pending
948 input and make space in the buffer. It also allows filters, sentinels
949 and timers to run---so take account of that in writing your code.
951 In these functions, the @var{process} argument can be a process or
952 the name of a process, or a buffer or buffer name (which stands
953 for a process via @code{get-buffer-process}). @code{nil} means
954 the current buffer's process.
956 @defun process-send-string process string
957 This function sends @var{process} the contents of @var{string} as
958 standard input. If it is @code{nil}, the current buffer's process is used.
960 The function returns @code{nil}.
964 (process-send-string "shell<1>" "ls\n")
970 ---------- Buffer: *shell* ----------
972 introduction.texi syntax-tables.texi~
973 introduction.texi~ text.texi
974 introduction.txt text.texi~
976 ---------- Buffer: *shell* ----------
981 @defun process-send-region process start end
982 This function sends the text in the region defined by @var{start} and
983 @var{end} as standard input to @var{process}.
985 An error is signaled unless both @var{start} and @var{end} are
986 integers or markers that indicate positions in the current buffer. (It
987 is unimportant which number is larger.)
990 @defun process-send-eof &optional process
991 This function makes @var{process} see an end-of-file in its
992 input. The @acronym{EOF} comes after any text already sent to it.
994 The function returns @var{process}.
998 (process-send-eof "shell")
1004 @defun process-running-child-p &optional process
1005 This function will tell you whether a @var{process} has given control of
1006 its terminal to its own child process. The value is @code{t} if this is
1007 true, or if Emacs cannot tell; it is @code{nil} if Emacs can be certain
1008 that this is not so.
1011 @node Signals to Processes
1012 @section Sending Signals to Processes
1013 @cindex process signals
1014 @cindex sending signals
1017 @dfn{Sending a signal} to a subprocess is a way of interrupting its
1018 activities. There are several different signals, each with its own
1019 meaning. The set of signals and their names is defined by the operating
1020 system. For example, the signal @code{SIGINT} means that the user has
1021 typed @kbd{C-c}, or that some analogous thing has happened.
1023 Each signal has a standard effect on the subprocess. Most signals
1024 kill the subprocess, but some stop or resume execution instead. Most
1025 signals can optionally be handled by programs; if the program handles
1026 the signal, then we can say nothing in general about its effects.
1028 You can send signals explicitly by calling the functions in this
1029 section. Emacs also sends signals automatically at certain times:
1030 killing a buffer sends a @code{SIGHUP} signal to all its associated
1031 processes; killing Emacs sends a @code{SIGHUP} signal to all remaining
1032 processes. (@code{SIGHUP} is a signal that usually indicates that the
1033 user hung up the phone.)
1035 Each of the signal-sending functions takes two optional arguments:
1036 @var{process} and @var{current-group}.
1038 The argument @var{process} must be either a process, a process
1039 name, a buffer, a buffer name, or @code{nil}. A buffer or buffer name
1040 stands for a process through @code{get-buffer-process}. @code{nil}
1041 stands for the process associated with the current buffer. An error
1042 is signaled if @var{process} does not identify a process.
1044 The argument @var{current-group} is a flag that makes a difference
1045 when you are running a job-control shell as an Emacs subprocess. If it
1046 is non-@code{nil}, then the signal is sent to the current process-group
1047 of the terminal that Emacs uses to communicate with the subprocess. If
1048 the process is a job-control shell, this means the shell's current
1049 subjob. If it is @code{nil}, the signal is sent to the process group of
1050 the immediate subprocess of Emacs. If the subprocess is a job-control
1051 shell, this is the shell itself.
1053 The flag @var{current-group} has no effect when a pipe is used to
1054 communicate with the subprocess, because the operating system does not
1055 support the distinction in the case of pipes. For the same reason,
1056 job-control shells won't work when a pipe is used. See
1057 @code{process-connection-type} in @ref{Asynchronous Processes}.
1059 @defun interrupt-process &optional process current-group
1060 This function interrupts the process @var{process} by sending the
1061 signal @code{SIGINT}. Outside of Emacs, typing the ``interrupt
1062 character'' (normally @kbd{C-c} on some systems, and @code{DEL} on
1063 others) sends this signal. When the argument @var{current-group} is
1064 non-@code{nil}, you can think of this function as ``typing @kbd{C-c}''
1065 on the terminal by which Emacs talks to the subprocess.
1068 @defun kill-process &optional process current-group
1069 This function kills the process @var{process} by sending the
1070 signal @code{SIGKILL}. This signal kills the subprocess immediately,
1071 and cannot be handled by the subprocess.
1074 @defun quit-process &optional process current-group
1075 This function sends the signal @code{SIGQUIT} to the process
1076 @var{process}. This signal is the one sent by the ``quit
1077 character'' (usually @kbd{C-b} or @kbd{C-\}) when you are not inside
1081 @defun stop-process &optional process current-group
1082 This function stops the process @var{process} by sending the
1083 signal @code{SIGTSTP}. Use @code{continue-process} to resume its
1086 Outside of Emacs, on systems with job control, the ``stop character''
1087 (usually @kbd{C-z}) normally sends this signal. When
1088 @var{current-group} is non-@code{nil}, you can think of this function as
1089 ``typing @kbd{C-z}'' on the terminal Emacs uses to communicate with the
1093 @defun continue-process &optional process current-group
1094 This function resumes execution of the process @var{process} by sending
1095 it the signal @code{SIGCONT}. This presumes that @var{process} was
1099 @defun signal-process process signal
1100 This function sends a signal to process @var{process}. The argument
1101 @var{signal} specifies which signal to send; it should be an integer.
1103 The @var{process} argument can be a system process @acronym{ID}; that
1104 allows you to send signals to processes that are not children of
1105 Emacs. @xref{System Processes}.
1108 @node Output from Processes
1109 @section Receiving Output from Processes
1110 @cindex process output
1111 @cindex output from processes
1113 There are two ways to receive the output that a subprocess writes to
1114 its standard output stream. The output can be inserted in a buffer,
1115 which is called the associated buffer of the process, or a function
1116 called the @dfn{filter function} can be called to act on the output. If
1117 the process has no buffer and no filter function, its output is
1120 When a subprocess terminates, Emacs reads any pending output,
1121 then stops reading output from that subprocess. Therefore, if the
1122 subprocess has children that are still live and still producing
1123 output, Emacs won't receive that output.
1125 Output from a subprocess can arrive only while Emacs is waiting: when
1126 reading terminal input, in @code{sit-for} and @code{sleep-for}
1127 (@pxref{Waiting}), and in @code{accept-process-output} (@pxref{Accepting
1128 Output}). This minimizes the problem of timing errors that usually
1129 plague parallel programming. For example, you can safely create a
1130 process and only then specify its buffer or filter function; no output
1131 can arrive before you finish, if the code in between does not call any
1132 primitive that waits.
1134 @defvar process-adaptive-read-buffering
1135 On some systems, when Emacs reads the output from a subprocess, the
1136 output data is read in very small blocks, potentially resulting in
1137 very poor performance. This behavior can be remedied to some extent
1138 by setting the variable @var{process-adaptive-read-buffering} to a
1139 non-@code{nil} value (the default), as it will automatically delay reading
1140 from such processes, thus allowing them to produce more output before
1141 Emacs tries to read it.
1144 It is impossible to separate the standard output and standard error
1145 streams of the subprocess, because Emacs normally spawns the subprocess
1146 inside a pseudo-TTY, and a pseudo-TTY has only one output channel. If
1147 you want to keep the output to those streams separate, you should
1148 redirect one of them to a file---for example, by using an appropriate
1152 * Process Buffers:: If no filter, output is put in a buffer.
1153 * Filter Functions:: Filter functions accept output from the process.
1154 * Decoding Output:: Filters can get unibyte or multibyte strings.
1155 * Accepting Output:: How to wait until process output arrives.
1158 @node Process Buffers
1159 @subsection Process Buffers
1161 A process can (and usually does) have an @dfn{associated buffer},
1162 which is an ordinary Emacs buffer that is used for two purposes: storing
1163 the output from the process, and deciding when to kill the process. You
1164 can also use the buffer to identify a process to operate on, since in
1165 normal practice only one process is associated with any given buffer.
1166 Many applications of processes also use the buffer for editing input to
1167 be sent to the process, but this is not built into Emacs Lisp.
1169 Unless the process has a filter function (@pxref{Filter Functions}),
1170 its output is inserted in the associated buffer. The position to insert
1171 the output is determined by the @code{process-mark}, which is then
1172 updated to point to the end of the text just inserted. Usually, but not
1173 always, the @code{process-mark} is at the end of the buffer.
1175 @findex process-kill-buffer-query-function
1176 Killing the associated buffer of a process also kills the process.
1177 Emacs asks for confirmation first, if the process's
1178 @code{process-query-on-exit-flag} is non-@code{nil} (@pxref{Query
1179 Before Exit}). This confirmation is done by the function
1180 @code{process-kill-buffer-query-function}, which is run from
1181 @code{kill-buffer-query-functions} (@pxref{Killing Buffers}).
1183 @defun process-buffer process
1184 This function returns the associated buffer of the process
1189 (process-buffer (get-process "shell"))
1190 @result{} #<buffer *shell*>
1195 @defun process-mark process
1196 This function returns the process marker for @var{process}, which is the
1197 marker that says where to insert output from the process.
1199 If @var{process} does not have a buffer, @code{process-mark} returns a
1200 marker that points nowhere.
1202 Insertion of process output in a buffer uses this marker to decide where
1203 to insert, and updates it to point after the inserted text. That is why
1204 successive batches of output are inserted consecutively.
1206 Filter functions normally should use this marker in the same fashion
1207 as is done by direct insertion of output in the buffer. A good
1208 example of a filter function that uses @code{process-mark} is found at
1209 the end of the following section.
1211 When the user is expected to enter input in the process buffer for
1212 transmission to the process, the process marker separates the new input
1213 from previous output.
1216 @defun set-process-buffer process buffer
1217 This function sets the buffer associated with @var{process} to
1218 @var{buffer}. If @var{buffer} is @code{nil}, the process becomes
1219 associated with no buffer.
1222 @defun get-buffer-process buffer-or-name
1223 This function returns a nondeleted process associated with the buffer
1224 specified by @var{buffer-or-name}. If there are several processes
1225 associated with it, this function chooses one (currently, the one most
1226 recently created, but don't count on that). Deletion of a process
1227 (see @code{delete-process}) makes it ineligible for this function to
1230 It is usually a bad idea to have more than one process associated with
1235 (get-buffer-process "*shell*")
1236 @result{} #<process shell>
1240 Killing the process's buffer deletes the process, which kills the
1241 subprocess with a @code{SIGHUP} signal (@pxref{Signals to Processes}).
1244 @node Filter Functions
1245 @subsection Process Filter Functions
1246 @cindex filter function
1247 @cindex process filter
1249 A process @dfn{filter function} is a function that receives the
1250 standard output from the associated process. If a process has a filter,
1251 then @emph{all} output from that process is passed to the filter. The
1252 process buffer is used directly for output from the process only when
1255 The filter function can only be called when Emacs is waiting for
1256 something, because process output arrives only at such times. Emacs
1257 waits when reading terminal input, in @code{sit-for} and
1258 @code{sleep-for} (@pxref{Waiting}), and in @code{accept-process-output}
1259 (@pxref{Accepting Output}).
1261 A filter function must accept two arguments: the associated process
1262 and a string, which is output just received from it. The function is
1263 then free to do whatever it chooses with the output.
1265 Quitting is normally inhibited within a filter function---otherwise,
1266 the effect of typing @kbd{C-g} at command level or to quit a user
1267 command would be unpredictable. If you want to permit quitting inside
1268 a filter function, bind @code{inhibit-quit} to @code{nil}. In most
1269 cases, the right way to do this is with the macro
1270 @code{with-local-quit}. @xref{Quitting}.
1272 If an error happens during execution of a filter function, it is
1273 caught automatically, so that it doesn't stop the execution of whatever
1274 program was running when the filter function was started. However, if
1275 @code{debug-on-error} is non-@code{nil}, the error-catching is turned
1276 off. This makes it possible to use the Lisp debugger to debug the
1277 filter function. @xref{Debugger}.
1279 Many filter functions sometimes or always insert the text in the
1280 process's buffer, mimicking the actions of Emacs when there is no
1281 filter. Such filter functions need to use @code{set-buffer} in order to
1282 be sure to insert in that buffer. To avoid setting the current buffer
1283 semipermanently, these filter functions must save and restore the
1284 current buffer. They should also check whether the buffer is still
1285 alive, update the process marker, and in some cases update the value
1286 of point. Here is how to do these things:
1290 (defun ordinary-insertion-filter (proc string)
1291 (when (buffer-live-p (process-buffer proc))
1292 (with-current-buffer (process-buffer proc)
1293 (let ((moving (= (point) (process-mark proc))))
1297 ;; @r{Insert the text, advancing the process marker.}
1298 (goto-char (process-mark proc))
1300 (set-marker (process-mark proc) (point)))
1301 (if moving (goto-char (process-mark proc)))))))
1306 The reason to use @code{with-current-buffer}, rather than using
1307 @code{save-excursion} to save and restore the current buffer, is so as
1308 to preserve the change in point made by the second call to
1311 To make the filter force the process buffer to be visible whenever new
1312 text arrives, insert the following line just before the
1313 @code{with-current-buffer} construct:
1316 (display-buffer (process-buffer proc))
1319 To force point to the end of the new output, no matter where it was
1320 previously, eliminate the variable @code{moving} and call
1321 @code{goto-char} unconditionally.
1323 In earlier Emacs versions, every filter function that did regular
1324 expression searching or matching had to explicitly save and restore the
1325 match data. Now Emacs does this automatically for filter functions;
1326 they never need to do it explicitly. @xref{Match Data}.
1328 The output to the function may come in chunks of any size. A program
1329 that produces the same output twice in a row may send it as one batch of
1330 200 characters one time, and five batches of 40 characters the next. If
1331 the filter looks for certain text strings in the subprocess output, make
1332 sure to handle the case where one of these strings is split across two
1333 or more batches of output; one way to do this is to insert the
1334 received text into a temporary buffer, which can then be searched.
1336 @defun set-process-filter process filter
1337 This function gives @var{process} the filter function @var{filter}. If
1338 @var{filter} is @code{nil}, it gives the process no filter.
1341 @defun process-filter process
1342 This function returns the filter function of @var{process}, or @code{nil}
1346 Here is an example of use of a filter function:
1350 (defun keep-output (process output)
1351 (setq kept (cons output kept)))
1352 @result{} keep-output
1359 (set-process-filter (get-process "shell") 'keep-output)
1360 @result{} keep-output
1363 (process-send-string "shell" "ls ~/other\n")
1366 @result{} ("lewis@@slug[8] % "
1369 "FINAL-W87-SHORT.MSS backup.otl kolstad.mss~
1370 address.txt backup.psf kolstad.psf
1371 backup.bib~ david.mss resume-Dec-86.mss~
1372 backup.err david.psf resume-Dec.psf
1373 backup.mss dland syllabus.mss
1375 "#backups.mss# backup.mss~ kolstad.mss
1380 @ignore @c The code in this example doesn't show the right way to do things.
1381 Here is another, more realistic example, which demonstrates how to use
1382 the process mark to do insertion in the same fashion as is done when
1383 there is no filter function:
1387 ;; @r{Insert input in the buffer specified by @code{my-shell-buffer}}
1388 ;; @r{and make sure that buffer is shown in some window.}
1389 (defun my-process-filter (proc str)
1390 (let ((cur (selected-window))
1392 (pop-to-buffer my-shell-buffer)
1395 (goto-char (point-max))
1397 (set-marker (process-mark proc) (point-max))
1398 (select-window cur)))
1403 @node Decoding Output
1404 @subsection Decoding Process Output
1405 @cindex decode process output
1407 When Emacs writes process output directly into a multibyte buffer,
1408 it decodes the output according to the process output coding system.
1409 If the coding system is @code{raw-text} or @code{no-conversion}, Emacs
1410 converts the unibyte output to multibyte using
1411 @code{string-to-multibyte}, and inserts the resulting multibyte text.
1413 You can use @code{set-process-coding-system} to specify which coding
1414 system to use (@pxref{Process Information}). Otherwise, the coding
1415 system comes from @code{coding-system-for-read}, if that is
1416 non-@code{nil}; or else from the defaulting mechanism (@pxref{Default
1417 Coding Systems}). If the text output by a process contains null
1418 bytes, Emacs by default uses @code{no-conversion} for it; see
1419 @ref{Lisp and Coding Systems, inhibit-null-byte-detection}, for how to
1420 control this behavior.
1422 @strong{Warning:} Coding systems such as @code{undecided} which
1423 determine the coding system from the data do not work entirely
1424 reliably with asynchronous subprocess output. This is because Emacs
1425 has to process asynchronous subprocess output in batches, as it
1426 arrives. Emacs must try to detect the proper coding system from one
1427 batch at a time, and this does not always work. Therefore, if at all
1428 possible, specify a coding system that determines both the character
1429 code conversion and the end of line conversion---that is, one like
1430 @code{latin-1-unix}, rather than @code{undecided} or @code{latin-1}.
1432 @c Let's keep the index entries that were there for
1433 @c set-process-filter-multibyte and process-filter-multibyte-p,
1434 @cindex filter multibyte flag, of process
1435 @cindex process filter multibyte flag
1436 When Emacs calls a process filter function, it provides the process
1437 output as a multibyte string or as a unibyte string according to the
1438 process's filter coding system. Emacs
1439 decodes the output according to the process output coding system,
1440 which usually produces a multibyte string, except for coding systems
1441 such as @code{binary} and @code{raw-text}
1443 @node Accepting Output
1444 @subsection Accepting Output from Processes
1445 @cindex accept input from processes
1447 Output from asynchronous subprocesses normally arrives only while
1448 Emacs is waiting for some sort of external event, such as elapsed time
1449 or terminal input. Occasionally it is useful in a Lisp program to
1450 explicitly permit output to arrive at a specific point, or even to wait
1451 until output arrives from a process.
1453 @defun accept-process-output &optional process seconds millisec just-this-one
1454 This function allows Emacs to read pending output from processes. The
1455 output is inserted in the associated buffers or given to their filter
1456 functions. If @var{process} is non-@code{nil} then this function does
1457 not return until some output has been received from @var{process}.
1460 The arguments @var{seconds} and @var{millisec} let you specify timeout
1461 periods. The former specifies a period measured in seconds and the
1462 latter specifies one measured in milliseconds. The two time periods
1463 thus specified are added together, and @code{accept-process-output}
1464 returns after that much time, whether or not there has been any
1467 The argument @var{millisec} is semi-obsolete nowadays because
1468 @var{seconds} can be a floating point number to specify waiting a
1469 fractional number of seconds. If @var{seconds} is 0, the function
1470 accepts whatever output is pending but does not wait.
1472 @c Emacs 22.1 feature
1473 If @var{process} is a process, and the argument @var{just-this-one} is
1474 non-@code{nil}, only output from that process is handled, suspending output
1475 from other processes until some output has been received from that
1476 process or the timeout expires. If @var{just-this-one} is an integer,
1477 also inhibit running timers. This feature is generally not
1478 recommended, but may be necessary for specific applications, such as
1481 The function @code{accept-process-output} returns non-@code{nil} if it
1482 did get some output, or @code{nil} if the timeout expired before output
1487 @section Sentinels: Detecting Process Status Changes
1488 @cindex process sentinel
1489 @cindex sentinel (of process)
1491 A @dfn{process sentinel} is a function that is called whenever the
1492 associated process changes status for any reason, including signals
1493 (whether sent by Emacs or caused by the process's own actions) that
1494 terminate, stop, or continue the process. The process sentinel is
1495 also called if the process exits. The sentinel receives two
1496 arguments: the process for which the event occurred, and a string
1497 describing the type of event.
1499 The string describing the event looks like one of the following:
1503 @code{"finished\n"}.
1506 @code{"exited abnormally with code @var{exitcode}\n"}.
1509 @code{"@var{name-of-signal}\n"}.
1512 @code{"@var{name-of-signal} (core dumped)\n"}.
1515 A sentinel runs only while Emacs is waiting (e.g., for terminal
1516 input, or for time to elapse, or for process output). This avoids the
1517 timing errors that could result from running them at random places in
1518 the middle of other Lisp programs. A program can wait, so that
1519 sentinels will run, by calling @code{sit-for} or @code{sleep-for}
1520 (@pxref{Waiting}), or @code{accept-process-output} (@pxref{Accepting
1521 Output}). Emacs also allows sentinels to run when the command loop is
1522 reading input. @code{delete-process} calls the sentinel when it
1523 terminates a running process.
1525 Emacs does not keep a queue of multiple reasons to call the sentinel
1526 of one process; it records just the current status and the fact that
1527 there has been a change. Therefore two changes in status, coming in
1528 quick succession, can call the sentinel just once. However, process
1529 termination will always run the sentinel exactly once. This is
1530 because the process status can't change again after termination.
1532 Emacs explicitly checks for output from the process before running
1533 the process sentinel. Once the sentinel runs due to process
1534 termination, no further output can arrive from the process.
1536 A sentinel that writes the output into the buffer of the process
1537 should check whether the buffer is still alive. If it tries to insert
1538 into a dead buffer, it will get an error. If the buffer is dead,
1539 @code{(buffer-name (process-buffer @var{process}))} returns @code{nil}.
1541 Quitting is normally inhibited within a sentinel---otherwise, the
1542 effect of typing @kbd{C-g} at command level or to quit a user command
1543 would be unpredictable. If you want to permit quitting inside a
1544 sentinel, bind @code{inhibit-quit} to @code{nil}. In most cases, the
1545 right way to do this is with the macro @code{with-local-quit}.
1548 If an error happens during execution of a sentinel, it is caught
1549 automatically, so that it doesn't stop the execution of whatever
1550 programs was running when the sentinel was started. However, if
1551 @code{debug-on-error} is non-@code{nil}, the error-catching is turned
1552 off. This makes it possible to use the Lisp debugger to debug the
1553 sentinel. @xref{Debugger}.
1555 While a sentinel is running, the process sentinel is temporarily
1556 set to @code{nil} so that the sentinel won't run recursively.
1557 For this reason it is not possible for a sentinel to specify
1560 In earlier Emacs versions, every sentinel that did regular expression
1561 searching or matching had to explicitly save and restore the match data.
1562 Now Emacs does this automatically for sentinels; they never need to do
1563 it explicitly. @xref{Match Data}.
1565 @defun set-process-sentinel process sentinel
1566 This function associates @var{sentinel} with @var{process}. If
1567 @var{sentinel} is @code{nil}, then the process will have no sentinel.
1568 The default behavior when there is no sentinel is to insert a message in
1569 the process's buffer when the process status changes.
1571 Changes in process sentinel take effect immediately---if the sentinel
1572 is slated to be run but has not been called yet, and you specify a new
1573 sentinel, the eventual call to the sentinel will use the new one.
1577 (defun msg-me (process event)
1579 (format "Process: %s had the event `%s'" process event)))
1580 (set-process-sentinel (get-process "shell") 'msg-me)
1584 (kill-process (get-process "shell"))
1585 @print{} Process: #<process shell> had the event `killed'
1586 @result{} #<process shell>
1591 @defun process-sentinel process
1592 This function returns the sentinel of @var{process}, or @code{nil} if it
1596 @defun waiting-for-user-input-p
1597 While a sentinel or filter function is running, this function returns
1598 non-@code{nil} if Emacs was waiting for keyboard input from the user at
1599 the time the sentinel or filter function was called, @code{nil} if it
1603 @node Query Before Exit
1604 @section Querying Before Exit
1606 When Emacs exits, it terminates all its subprocesses by sending them
1607 the @code{SIGHUP} signal. Because subprocesses may be doing
1608 valuable work, Emacs normally asks the user to confirm that it is ok
1609 to terminate them. Each process has a query flag which, if
1610 non-@code{nil}, says that Emacs should ask for confirmation before
1611 exiting and thus killing that process. The default for the query flag
1612 is @code{t}, meaning @emph{do} query.
1614 @defun process-query-on-exit-flag process
1615 This returns the query flag of @var{process}.
1618 @defun set-process-query-on-exit-flag process flag
1619 This function sets the query flag of @var{process} to @var{flag}. It
1624 ;; @r{Don't query about the shell process}
1625 (set-process-query-on-exit-flag (get-process "shell") nil)
1631 @defun process-kill-without-query process &optional do-query
1632 This function clears the query flag of @var{process}, so that
1633 Emacs will not query the user on account of that process.
1635 Actually, the function does more than that: it returns the old value of
1636 the process's query flag, and sets the query flag to @var{do-query}.
1637 Please don't use this function to do those things any more---please
1638 use the newer, cleaner functions @code{process-query-on-exit-flag} and
1639 @code{set-process-query-on-exit-flag} in all but the simplest cases.
1640 The only way you should use @code{process-kill-without-query} nowadays
1645 ;; @r{Don't query about the shell process}
1646 (process-kill-without-query (get-process "shell"))
1651 @node System Processes
1652 @section Accessing Other Processes
1653 @cindex system processes
1655 In addition to accessing and manipulating processes that are
1656 subprocesses of the current Emacs session, Emacs Lisp programs can
1657 also access other processes running on the same machine. We call
1658 these @dfn{system processes}, to distinguish between them and Emacs
1661 Emacs provides several primitives for accessing system processes.
1662 Not all platforms support these primitives; on those which don't,
1663 these primitives return @code{nil}.
1665 @defun list-system-processes
1666 This function returns a list of all the processes running on the
1667 system. Each process is identified by its @acronym{PID}, a numerical
1668 process ID that is assigned by the OS and distinguishes the process
1669 from all the other processes running on the same machine at the same
1673 @defun process-attributes pid
1674 This function returns an alist of attributes for the process specified
1675 by its process ID @var{pid}. Each association in the alist is of the
1676 form @code{(@var{key} . @var{value})}, where @var{key} designates the
1677 attribute and @var{value} is the value of that attribute. The various
1678 attribute @var{key}'s that this function can return are listed below.
1679 Not all platforms support all of these attributes; if an attribute is
1680 not supported, its association will not appear in the returned alist.
1681 Values that are numbers can be either integer or floating-point,
1682 depending on the magnitude of the value.
1686 The effective user ID of the user who invoked the process. The
1687 corresponding @var{value} is a number. If the process was invoked by
1688 the same user who runs the current Emacs session, the value is
1689 identical to what @code{user-uid} returns (@pxref{User
1693 User name corresponding to the process's effective user ID, a string.
1696 The group ID of the effective user ID, a number.
1699 Group name corresponding to the effective user's group ID, a string.
1702 The name of the command that runs in the process. This is a string
1703 that usually specifies the name of the executable file of the process,
1704 without the leading directories. However, some special system
1705 processes can report strings that do not correspond to an executable
1709 The state code of the process. This is a short string that encodes
1710 the scheduling state of the process. Here's a list of the most
1711 frequently seen codes:
1715 uninterruptible sleep (usually I/O)
1719 interruptible sleep (waiting for some event)
1721 stopped, e.g., by a job control signal
1723 ``zombie'': a process that terminated, but was not reaped by its parent
1727 For the full list of the possible states, see the manual page of the
1728 @command{ps} command.
1731 The process ID of the parent process, a number.
1734 The process group ID of the process, a number.
1737 The session ID of the process. This is a number that is the process
1738 ID of the process's @dfn{session leader}.
1741 A string that is the name of the process's controlling terminal. On
1742 Unix and GNU systems, this is normally the file name of the
1743 corresponding terminal device, such as @file{/dev/pts65}.
1746 The numerical process group ID of the foreground process group that
1747 uses the process's terminal.
1750 The number of minor page faults caused by the process since its
1751 beginning. (Minor page faults are those that don't involve reading
1755 The number of major page faults caused by the process since its
1756 beginning. (Major page faults require a disk to be read, and are thus
1757 more expensive than minor page faults.)
1761 Like @code{minflt} and @code{majflt}, but include the number of page
1762 faults for all the child processes of the given process.
1765 Time spent by the process in the user context, for running the
1766 application's code. The corresponding @var{value} is in the
1767 @w{@code{(@var{high} @var{low} @var{microsec})}} format, the same
1768 format used by functions @code{current-time} (@pxref{Time of Day,
1769 current-time}) and @code{file-attributes} (@pxref{File Attributes}).
1772 Time spent by the process in the system (kernel) context, for
1773 processing system calls. The corresponding @var{value} is in the same
1774 format as for @code{utime}.
1777 The sum of @code{utime} and @code{stime}. The corresponding
1778 @var{value} is in the same format as for @code{utime}.
1783 Like @code{utime}, @code{stime}, and @code{time}, but include the
1784 times of all the child processes of the given process.
1787 The numerical priority of the process.
1790 The @dfn{nice value} of the process, a number. (Processes with smaller
1791 nice values get scheduled more favorably.)
1794 The number of threads in the process.
1797 The time the process was started, in the @w{@code{(@var{high}
1798 @var{low} @var{microsec})}} format used by @code{current-time} and
1799 @code{file-attributes}.
1802 The time elapsed since the process started, in the @w{@code{(@var{high}
1803 @var{low} @var{microsec})}} format.
1806 The virtual memory size of the process, measured in kilobytes.
1809 The size of the process's @dfn{resident set}, the number of kilobytes
1810 occupied by the process in the machine's physical memory.
1813 The percentage of the CPU time used by the process since it started.
1814 The corresponding @var{value} is a floating-point number between 0 and
1818 The percentage of the total physical memory installed on the machine
1819 used by the process's resident set. The value is a floating-point
1820 number between 0 and 100.
1823 The command-line with which the process was invoked. This is a string
1824 in which individual command-line arguments are separated by blanks;
1825 whitespace characters that are embedded in the arguments are quoted as
1826 appropriate for the system's shell: escaped by backslash characters on
1827 GNU and Unix, and enclosed in double quote characters on Windows.
1828 Thus, this command-line string can be directly used in primitives such
1829 as @code{shell-command}.
1835 @node Transaction Queues
1836 @section Transaction Queues
1837 @cindex transaction queue
1839 You can use a @dfn{transaction queue} to communicate with a subprocess
1840 using transactions. First use @code{tq-create} to create a transaction
1841 queue communicating with a specified process. Then you can call
1842 @code{tq-enqueue} to send a transaction.
1844 @defun tq-create process
1845 This function creates and returns a transaction queue communicating with
1846 @var{process}. The argument @var{process} should be a subprocess
1847 capable of sending and receiving streams of bytes. It may be a child
1848 process, or it may be a TCP connection to a server, possibly on another
1852 @defun tq-enqueue queue question regexp closure fn &optional delay-question
1853 This function sends a transaction to queue @var{queue}. Specifying the
1854 queue has the effect of specifying the subprocess to talk to.
1856 The argument @var{question} is the outgoing message that starts the
1857 transaction. The argument @var{fn} is the function to call when the
1858 corresponding answer comes back; it is called with two arguments:
1859 @var{closure}, and the answer received.
1861 The argument @var{regexp} is a regular expression that should match
1862 text at the end of the entire answer, but nothing before; that's how
1863 @code{tq-enqueue} determines where the answer ends.
1865 If the argument @var{delay-question} is non-@code{nil}, delay sending
1866 this question until the process has finished replying to any previous
1867 questions. This produces more reliable results with some processes.
1869 The return value of @code{tq-enqueue} itself is not meaningful.
1872 @defun tq-close queue
1873 Shut down transaction queue @var{queue}, waiting for all pending transactions
1874 to complete, and then terminate the connection or child process.
1877 Transaction queues are implemented by means of a filter function.
1878 @xref{Filter Functions}.
1881 @section Network Connections
1882 @cindex network connection
1886 Emacs Lisp programs can open stream (TCP) and datagram (UDP) network
1887 connections to other processes on the same machine or other machines.
1888 A network connection is handled by Lisp much like a subprocess, and is
1889 represented by a process object. However, the process you are
1890 communicating with is not a child of the Emacs process, so it has no
1891 process @acronym{ID}, and you can't kill it or send it signals. All you
1892 can do is send and receive data. @code{delete-process} closes the
1893 connection, but does not kill the program at the other end; that
1894 program must decide what to do about closure of the connection.
1896 Lisp programs can listen for connections by creating network
1897 servers. A network server is also represented by a kind of process
1898 object, but unlike a network connection, the network server never
1899 transfers data itself. When it receives a connection request, it
1900 creates a new network connection to represent the connection just
1901 made. (The network connection inherits certain information, including
1902 the process plist, from the server.) The network server then goes
1903 back to listening for more connection requests.
1905 Network connections and servers are created by calling
1906 @code{make-network-process} with an argument list consisting of
1907 keyword/argument pairs, for example @code{:server t} to create a
1908 server process, or @code{:type 'datagram} to create a datagram
1909 connection. @xref{Low-Level Network}, for details. You can also use
1910 the @code{open-network-stream} function described below.
1912 To distinguish the different types of processes, the
1913 @code{process-type} function returns the symbol @code{network} for a
1914 network connection or server, @code{serial} for a serial port
1915 connection, or @code{real} for a real subprocess.
1917 The @code{process-status} function returns @code{open},
1918 @code{closed}, @code{connect}, and @code{failed} for network
1919 connections. For a network server, the status is always
1920 @code{listen}. None of those values is possible for a real
1921 subprocess. @xref{Process Information}.
1923 You can stop and resume operation of a network process by calling
1924 @code{stop-process} and @code{continue-process}. For a server
1925 process, being stopped means not accepting new connections. (Up to 5
1926 connection requests will be queued for when you resume the server; you
1927 can increase this limit, unless it is imposed by the operating
1928 system.) For a network stream connection, being stopped means not
1929 processing input (any arriving input waits until you resume the
1930 connection). For a datagram connection, some number of packets may be
1931 queued but input may be lost. You can use the function
1932 @code{process-command} to determine whether a network connection or
1933 server is stopped; a non-@code{nil} value means yes.
1935 @defun open-network-stream name buffer-or-name host service
1936 This function opens a TCP connection, and returns a process object
1937 that represents the connection.
1939 The @var{name} argument specifies the name for the process object. It
1940 is modified as necessary to make it unique.
1942 The @var{buffer-or-name} argument is the buffer to associate with the
1943 connection. Output from the connection is inserted in the buffer,
1944 unless you specify a filter function to handle the output. If
1945 @var{buffer-or-name} is @code{nil}, it means that the connection is not
1946 associated with any buffer.
1948 The arguments @var{host} and @var{service} specify where to connect to;
1949 @var{host} is the host name (a string), and @var{service} is the name of
1950 a defined network service (a string) or a port number (an integer).
1953 @node Network Servers
1954 @section Network Servers
1955 @cindex network servers
1957 You create a server by calling @code{make-network-process} with
1958 @code{:server t}. The server will listen for connection requests from
1959 clients. When it accepts a client connection request, that creates a
1960 new network connection, itself a process object, with the following
1965 The connection's process name is constructed by concatenating the
1966 server process' @var{name} with a client identification string. The
1967 client identification string for an IPv4 connection looks like
1968 @samp{<@var{a}.@var{b}.@var{c}.@var{d}:@var{p}>}. Otherwise, it is a
1969 unique number in brackets, as in @samp{<@var{nnn}>}. The number
1970 is unique for each connection in the Emacs session.
1973 If the server's filter is non-@code{nil}, the connection process does
1974 not get a separate process buffer; otherwise, Emacs creates a new
1975 buffer for the purpose. The buffer name is the server's buffer name
1976 or process name, concatenated with the client identification string.
1978 The server's process buffer value is never used directly by Emacs, but
1979 it is passed to the log function, which can log connections by
1980 inserting text there.
1983 The communication type and the process filter and sentinel are
1984 inherited from those of the server. The server never directly
1985 uses its filter and sentinel; their sole purpose is to initialize
1986 connections made to the server.
1989 The connection's process contact info is set according to the client's
1990 addressing information (typically an IP address and a port number).
1991 This information is associated with the @code{process-contact}
1992 keywords @code{:host}, @code{:service}, @code{:remote}.
1995 The connection's local address is set up according to the port
1996 number used for the connection.
1999 The client process' plist is initialized from the server's plist.
2006 A datagram connection communicates with individual packets rather
2007 than streams of data. Each call to @code{process-send} sends one
2008 datagram packet (@pxref{Input to Processes}), and each datagram
2009 received results in one call to the filter function.
2011 The datagram connection doesn't have to talk with the same remote
2012 peer all the time. It has a @dfn{remote peer address} which specifies
2013 where to send datagrams to. Each time an incoming datagram is passed
2014 to the filter function, the peer address is set to the address that
2015 datagram came from; that way, if the filter function sends a datagram,
2016 it will go back to that place. You can specify the remote peer
2017 address when you create the datagram connection using the
2018 @code{:remote} keyword. You can change it later on by calling
2019 @code{set-process-datagram-address}.
2021 @defun process-datagram-address process
2022 If @var{process} is a datagram connection or server, this function
2023 returns its remote peer address.
2026 @defun set-process-datagram-address process address
2027 If @var{process} is a datagram connection or server, this function
2028 sets its remote peer address to @var{address}.
2031 @node Low-Level Network
2032 @section Low-Level Network Access
2034 You can also create network connections by operating at a lower
2035 level than that of @code{open-network-stream}, using
2036 @code{make-network-process}.
2039 * Proc: Network Processes. Using @code{make-network-process}.
2040 * Options: Network Options. Further control over network connections.
2041 * Features: Network Feature Testing.
2042 Determining which network features work on
2043 the machine you are using.
2046 @node Network Processes
2047 @subsection @code{make-network-process}
2049 The basic function for creating network connections and network
2050 servers is @code{make-network-process}. It can do either of those
2051 jobs, depending on the arguments you give it.
2053 @defun make-network-process &rest args
2054 This function creates a network connection or server and returns the
2055 process object that represents it. The arguments @var{args} are a
2056 list of keyword/argument pairs. Omitting a keyword is always
2057 equivalent to specifying it with value @code{nil}, except for
2058 @code{:coding}, @code{:filter-multibyte}, and @code{:reuseaddr}. Here
2059 are the meaningful keywords:
2062 @item :name @var{name}
2063 Use the string @var{name} as the process name. It is modified if
2064 necessary to make it unique.
2066 @item :type @var{type}
2067 Specify the communication type. A value of @code{nil} specifies a
2068 stream connection (the default); @code{datagram} specifies a datagram
2069 connection; @code{seqpacket} specifies a ``sequenced packet stream''
2070 connection. Both connections and servers can be of these types.
2072 @item :server @var{server-flag}
2073 If @var{server-flag} is non-@code{nil}, create a server. Otherwise,
2074 create a connection. For a stream type server, @var{server-flag} may
2075 be an integer which then specifies the length of the queue of pending
2076 connections to the server. The default queue length is 5.
2078 @item :host @var{host}
2079 Specify the host to connect to. @var{host} should be a host name or
2080 Internet address, as a string, or the symbol @code{local} to specify
2081 the local host. If you specify @var{host} for a server, it must
2082 specify a valid address for the local host, and only clients
2083 connecting to that address will be accepted.
2085 @item :service @var{service}
2086 @var{service} specifies a port number to connect to, or, for a server,
2087 the port number to listen on. It should be a service name that
2088 translates to a port number, or an integer specifying the port number
2089 directly. For a server, it can also be @code{t}, which means to let
2090 the system select an unused port number.
2092 @item :family @var{family}
2093 @var{family} specifies the address (and protocol) family for
2094 communication. @code{nil} means determine the proper address family
2095 automatically for the given @var{host} and @var{service}.
2096 @code{local} specifies a Unix socket, in which case @var{host} is
2097 ignored. @code{ipv4} and @code{ipv6} specify to use IPv4 and IPv6
2100 @item :local @var{local-address}
2101 For a server process, @var{local-address} is the address to listen on.
2102 It overrides @var{family}, @var{host} and @var{service}, and you
2103 may as well not specify them.
2105 @item :remote @var{remote-address}
2106 For a connection, @var{remote-address} is the address to connect to.
2107 It overrides @var{family}, @var{host} and @var{service}, and you
2108 may as well not specify them.
2110 For a datagram server, @var{remote-address} specifies the initial
2111 setting of the remote datagram address.
2113 The format of @var{local-address} or @var{remote-address} depends on
2118 An IPv4 address is represented as a five-element vector of four 8-bit
2119 integers and one 16-bit integer
2120 @code{[@var{a} @var{b} @var{c} @var{d} @var{p}]} corresponding to
2121 numeric IPv4 address @var{a}.@var{b}.@var{c}.@var{d} and port number
2125 An IPv6 address is represented as a nine-element vector of 16-bit
2126 integers @code{[@var{a} @var{b} @var{c} @var{d} @var{e} @var{f}
2127 @var{g} @var{h} @var{p}]} corresponding to numeric IPv6 address
2128 @var{a}:@var{b}:@var{c}:@var{d}:@var{e}:@var{f}:@var{g}:@var{h} and
2129 port number @var{p}.
2132 A local address is represented as a string which specifies the address
2133 in the local address space.
2136 An ``unsupported family'' address is represented by a cons
2137 @code{(@var{f} . @var{av})}, where @var{f} is the family number and
2138 @var{av} is a vector specifying the socket address using one element
2139 per address data byte. Do not rely on this format in portable code,
2140 as it may depend on implementation defined constants, data sizes, and
2141 data structure alignment.
2144 @item :nowait @var{bool}
2145 If @var{bool} is non-@code{nil} for a stream connection, return
2146 without waiting for the connection to complete. When the connection
2147 succeeds or fails, Emacs will call the sentinel function, with a
2148 second argument matching @code{"open"} (if successful) or
2149 @code{"failed"}. The default is to block, so that
2150 @code{make-network-process} does not return until the connection
2151 has succeeded or failed.
2153 @item :stop @var{stopped}
2154 Start the network connection or server in the `stopped' state if
2155 @var{stopped} is non-@code{nil}.
2157 @item :buffer @var{buffer}
2158 Use @var{buffer} as the process buffer.
2160 @item :coding @var{coding}
2161 Use @var{coding} as the coding system for this process. To specify
2162 different coding systems for decoding data from the connection and for
2163 encoding data sent to it, specify @code{(@var{decoding} .
2164 @var{encoding})} for @var{coding}.
2166 If you don't specify this keyword at all, the default
2167 is to determine the coding systems from the data.
2169 @item :noquery @var{query-flag}
2170 Initialize the process query flag to @var{query-flag}.
2171 @xref{Query Before Exit}.
2173 @item :filter @var{filter}
2174 Initialize the process filter to @var{filter}.
2176 @item :sentinel @var{sentinel}
2177 Initialize the process sentinel to @var{sentinel}.
2179 @item :log @var{log}
2180 Initialize the log function of a server process to @var{log}. The log
2181 function is called each time the server accepts a network connection
2182 from a client. The arguments passed to the log function are
2183 @var{server}, @var{connection}, and @var{message}, where @var{server}
2184 is the server process, @var{connection} is the new process for the
2185 connection, and @var{message} is a string describing what has
2188 @item :plist @var{plist}
2189 Initialize the process plist to @var{plist}.
2192 The original argument list, modified with the actual connection
2193 information, is available via the @code{process-contact} function.
2196 @node Network Options
2197 @subsection Network Options
2199 The following network options can be specified when you create a
2200 network process. Except for @code{:reuseaddr}, you can also set or
2201 modify these options later, using @code{set-network-process-option}.
2203 For a server process, the options specified with
2204 @code{make-network-process} are not inherited by the client
2205 connections, so you will need to set the necessary options for each
2206 child connection as it is created.
2209 @item :bindtodevice @var{device-name}
2210 If @var{device-name} is a non-empty string identifying a network
2211 interface name (see @code{network-interface-list}), only handle
2212 packets received on that interface. If @var{device-name} is @code{nil}
2213 (the default), handle packets received on any interface.
2215 Using this option may require special privileges on some systems.
2217 @item :broadcast @var{broadcast-flag}
2218 If @var{broadcast-flag} is non-@code{nil} for a datagram process, the
2219 process will receive datagram packet sent to a broadcast address, and
2220 be able to send packets to a broadcast address. Ignored for a stream
2223 @item :dontroute @var{dontroute-flag}
2224 If @var{dontroute-flag} is non-@code{nil}, the process can only send
2225 to hosts on the same network as the local host.
2227 @item :keepalive @var{keepalive-flag}
2228 If @var{keepalive-flag} is non-@code{nil} for a stream connection,
2229 enable exchange of low-level keep-alive messages.
2231 @item :linger @var{linger-arg}
2232 If @var{linger-arg} is non-@code{nil}, wait for successful
2233 transmission of all queued packets on the connection before it is
2234 deleted (see @code{delete-process}). If @var{linger-arg} is an
2235 integer, it specifies the maximum time in seconds to wait for queued
2236 packets to be sent before closing the connection. Default is
2237 @code{nil} which means to discard unsent queued packets when the
2240 @item :oobinline @var{oobinline-flag}
2241 If @var{oobinline-flag} is non-@code{nil} for a stream connection,
2242 receive out-of-band data in the normal data stream. Otherwise, ignore
2245 @item :priority @var{priority}
2246 Set the priority for packets sent on this connection to the integer
2247 @var{priority}. The interpretation of this number is protocol
2248 specific, such as setting the TOS (type of service) field on IP
2249 packets sent on this connection. It may also have system dependent
2250 effects, such as selecting a specific output queue on the network
2253 @item :reuseaddr @var{reuseaddr-flag}
2254 If @var{reuseaddr-flag} is non-@code{nil} (the default) for a stream
2255 server process, allow this server to reuse a specific port number (see
2256 @code{:service}) unless another process on this host is already
2257 listening on that port. If @var{reuseaddr-flag} is @code{nil}, there
2258 may be a period of time after the last use of that port (by any
2259 process on the host), where it is not possible to make a new server on
2263 @defun set-network-process-option process option value &optional no-error
2264 This function sets or modifies a network option for network process
2265 @var{process}. See @code{make-network-process} for details of options
2266 @var{option} and their corresponding values @var{value}. If
2267 @var{no-error} is non-@code{nil}, this function returns @code{nil}
2268 instead of signaling an error if @var{option} is not a supported
2269 option. If the function successfully completes, it returns @code{t}.
2271 The current setting of an option is available via the
2272 @code{process-contact} function.
2275 @node Network Feature Testing
2276 @subsection Testing Availability of Network Features
2278 To test for the availability of a given network feature, use
2279 @code{featurep} like this:
2282 (featurep 'make-network-process '(@var{keyword} @var{value}))
2286 The result of the first form is @code{t} if it works to specify
2287 @var{keyword} with value @var{value} in @code{make-network-process}.
2288 The result of the second form is @code{t} if @var{keyword} is
2289 supported by @code{make-network-process}. Here are some of the
2290 @var{keyword}---@var{value} pairs you can test in
2295 Non-@code{nil} if non-blocking connect is supported.
2296 @item (:type datagram)
2297 Non-@code{nil} if datagrams are supported.
2298 @item (:family local)
2299 Non-@code{nil} if local (a.k.a.@: ``UNIX domain'') sockets are supported.
2300 @item (:family ipv6)
2301 Non-@code{nil} if IPv6 is supported.
2303 Non-@code{nil} if the system can select the port for a server.
2306 To test for the availability of a given network option, use
2307 @code{featurep} like this:
2310 (featurep 'make-network-process '@var{keyword})
2314 Here are some of the options you can test in this way.
2325 That particular network option is supported by
2326 @code{make-network-process} and @code{set-network-process-option}.
2330 @section Misc Network Facilities
2332 These additional functions are useful for creating and operating
2333 on network connections. Note that they are supported only on some
2336 @defun network-interface-list
2337 This function returns a list describing the network interfaces
2338 of the machine you are using. The value is an alist whose
2339 elements have the form @code{(@var{name} . @var{address})}.
2340 @var{address} has the same form as the @var{local-address}
2341 and @var{remote-address} arguments to @code{make-network-process}.
2344 @defun network-interface-info ifname
2345 This function returns information about the network interface named
2346 @var{ifname}. The value is a list of the form
2347 @code{(@var{addr} @var{bcast} @var{netmask} @var{hwaddr} @var{flags})}.
2351 The Internet protocol address.
2353 The broadcast address.
2357 The layer 2 address (Ethernet MAC address, for instance).
2359 The current flags of the interface.
2363 @defun format-network-address address &optional omit-port
2364 This function converts the Lisp representation of a network address to
2367 A five-element vector @code{[@var{a} @var{b} @var{c} @var{d} @var{p}]}
2368 represents an IPv4 address @var{a}.@var{b}.@var{c}.@var{d} and port
2369 number @var{p}. @code{format-network-address} converts that to the
2370 string @code{"@var{a}.@var{b}.@var{c}.@var{d}:@var{p}"}.
2372 A nine-element vector @code{[@var{a} @var{b} @var{c} @var{d} @var{e}
2373 @var{f} @var{g} @var{h} @var{p}]} represents an IPv6 address along
2374 with a port number. @code{format-network-address} converts that to
2376 @code{"[@var{a}:@var{b}:@var{c}:@var{d}:@var{e}:@var{f}:@var{g}:@var{h}]:@var{p}"}.
2378 If the vector does not include the port number, @var{p}, or if
2379 @var{omit-port} is non-@code{nil}, the result does not include the
2380 @code{:@var{p}} suffix.
2384 @section Communicating with Serial Ports
2385 @cindex @file{/dev/tty}
2387 @cindex serial connections
2389 Emacs can communicate with serial ports. For interactive use,
2390 @kbd{M-x serial-term} opens a terminal window. In a Lisp program,
2391 @code{make-serial-process} creates a process object.
2393 The serial port can be configured at run-time, without having to
2394 close and re-open it. The function @code{serial-process-configure}
2395 lets you change the speed, bytesize, and other parameters. In a
2396 terminal window created by @code{serial-term}, you can click on the
2397 mode line for configuration.
2399 A serial connection is represented by a process object which can be
2400 used similar to a subprocess or network process. You can send and
2401 receive data and configure the serial port. A serial process object
2402 has no process ID, you can't send signals to it, and the status codes
2403 are different from other types of processes.
2404 @code{delete-process} on the process object or @code{kill-buffer} on
2405 the process buffer close the connection, but this does not affect the
2406 device connected to the serial port.
2408 The function @code{process-type} returns the symbol @code{serial}
2409 for a process object representing a serial port connection.
2411 Serial ports are available on GNU/Linux, Unix, and Windows systems.
2413 @deffn Command serial-term port speed
2414 Start a terminal-emulator for a serial port in a new buffer.
2415 @var{port} is the name of the serial port to which to connect. For
2416 example, this could be @file{/dev/ttyS0} on Unix. On Windows, this
2417 could be @file{COM1}, or @file{\\.\COM10} (double the backslashes in
2420 @var{speed} is the speed of the serial port in bits per second. 9600
2421 is a common value. The buffer is in Term mode; see @ref{Term Mode,,,
2422 emacs, The GNU Emacs Manual}, for the commands to use in that buffer.
2423 You can change the speed and the configuration in the mode line menu.
2426 @defun make-serial-process &rest args
2427 This function creates a process and a buffer. Arguments are specified
2428 as keyword/argument pairs. Here's the list of the meaningful keywords:
2431 @item :port @var{port}@r{ (mandatory)}
2432 This is the name of the serial port. On Unix and GNU systems, this is
2433 a file name such as @file{/dev/ttyS0}. On Windows, this could be
2434 @file{COM1}, or @file{\\.\COM10} for ports higher than @file{COM9}
2435 (double the backslashes in Lisp strings).
2437 @item :speed @var{speed}@r{ (mandatory)}
2438 The speed of the serial port in bits per second. This function calls
2439 @code{serial-process-configure} to handle the speed.
2441 @item :name @var{name}
2442 The name of the process. If @var{name} is not given, @var{port} will
2443 serve as the process name as well.
2445 @item :buffer @var{buffer}
2446 The buffer to associate with the process. The value could be either a
2447 buffer or a string that names a buffer. Process output goes at the
2448 end of that buffer, unless you specify an output stream or filter
2449 function to handle the output. If @var{buffer} is not given, the
2450 process buffer's name is taken from the value of the @code{:name}
2453 @item :coding @var{coding}
2454 If @var{coding} is a symbol, it specifies the coding system used for
2455 both reading and writing for this process. If @var{coding} is a cons
2456 @code{(decoding . encoding)}, @var{decoding} is used for reading, and
2457 @var{encoding} is used for writing. If not specified, the default is
2458 to determine the coding systems from data itself.
2460 @item :noquery @var{query-flag}
2461 Initialize the process query flag to @var{query-flag}. @xref{Query
2462 Before Exit}. The flags defaults to @code{nil} if unspecified.
2464 @item :stop @var{bool}
2465 Start process in the @code{stopped} state if @var{bool} is
2466 non-@code{nil}. In the stopped state, a serial process does not
2467 accept incoming data, but you can send outgoing data. The stopped
2468 state is cleared by @code{continue-process} and set by
2469 @code{stop-process}.
2471 @item :filter @var{filter}
2472 Install @var{filter} as the process filter.
2474 @item :sentinel @var{sentinel}
2475 Install @var{sentinel} as the process sentinel.
2477 @item :plist @var{plist}
2478 Install @var{plist} as the initial plist of the process.
2485 These arguments are handled by @code{serial-process-configure}, which
2486 is called by @code{make-serial-process}.
2489 The original argument list, possibly modified by later configuration,
2490 is available via the function @code{process-contact}.
2495 (make-serial-process :port "/dev/ttyS0" :speed 9600)
2497 (make-serial-process :port "COM1" :speed 115200 :stopbits 2)
2499 (make-serial-process :port "\\\\.\\COM13" :speed 1200
2500 :bytesize 7 :parity 'odd)
2502 (make-serial-process :port "/dev/tty.BlueConsole-SPP-1"
2507 @defun serial-process-configure &rest args
2508 @cindex baud, in serial connections
2509 @cindex bytesize, in serial connections
2510 @cindex parity, in serial connections
2511 @cindex stopbits, in serial connections
2512 @cindex flowcontrol, in serial connections
2514 This functions configures a serial port connection. Arguments are
2515 specified as keyword/argument pairs. Attributes that are not given
2516 are re-initialized from the process's current configuration (available
2517 via the function @code{process-contact}) or set to reasonable default
2518 values. The following arguments are defined:
2521 @item :process @var{process}
2522 @itemx :name @var{name}
2523 @itemx :buffer @var{buffer}
2524 @itemx :port @var{port}
2525 Any of these arguments can be given to identify the process that is to
2526 be configured. If none of these arguments is given, the current
2527 buffer's process is used.
2529 @item :speed @var{speed}
2530 The speed of the serial port in bits per second, a.k.a.@: @dfn{baud
2531 rate}. The value can be any number, but most serial ports work only
2532 at a few defined values between 1200 and 115200, with 9600 being the
2533 most common value. If @var{speed} is @code{nil}, the function ignores
2534 all other arguments and does not configure the port. This may be
2535 useful for special serial ports such as Bluetooth-to-serial converters
2536 which can only be configured through AT commands sent through the
2537 connection. The value of @code{nil} for @var{speed} is valid only for
2538 connections that were already opened by a previous call to
2539 @code{make-serial-process} or @code{serial-term}.
2541 @item :bytesize @var{bytesize}
2542 The number of bits per byte, which can be 7 or 8. If @var{bytesize}
2543 is not given or @code{nil}, it defaults to 8.
2545 @item :parity @var{parity}
2546 The value can be @code{nil} (don't use parity), the symbol
2547 @code{odd} (use odd parity), or the symbol @code{even} (use even
2548 parity). If @var{parity} is not given, it defaults to no parity.
2550 @item :stopbits @var{stopbits}
2551 The number of stopbits used to terminate a transmission
2552 of each byte. @var{stopbits} can be 1 or 2. If @var{stopbits} is not
2553 given or @code{nil}, it defaults to 1.
2555 @item :flowcontrol @var{flowcontrol}
2556 The type of flow control to use for this connection, which is either
2557 @code{nil} (don't use flow control), the symbol @code{hw} (use RTS/CTS
2558 hardware flow control), or the symbol @code{sw} (use XON/XOFF software
2559 flow control). If @var{flowcontrol} is not given, it defaults to no
2563 @code{serial-process-configure} is called by @code{make-serial-process} for the
2564 initial configuration of the serial port.
2569 (serial-process-configure :process "/dev/ttyS0" :speed 1200)
2571 (serial-process-configure :buffer "COM1" :stopbits 1
2572 :parity 'odd :flowcontrol 'hw)
2574 (serial-process-configure :port "\\\\.\\COM13" :bytesize 7)
2579 @section Packing and Unpacking Byte Arrays
2580 @cindex byte packing and unpacking
2582 This section describes how to pack and unpack arrays of bytes,
2583 usually for binary network protocols. These functions convert byte arrays
2584 to alists, and vice versa. The byte array can be represented as a
2585 unibyte string or as a vector of integers, while the alist associates
2586 symbols either with fixed-size objects or with recursive sub-alists.
2589 @cindex deserializing
2592 Conversion from byte arrays to nested alists is also known as
2593 @dfn{deserializing} or @dfn{unpacking}, while going in the opposite
2594 direction is also known as @dfn{serializing} or @dfn{packing}.
2597 * Bindat Spec:: Describing data layout.
2598 * Bindat Functions:: Doing the unpacking and packing.
2599 * Bindat Examples:: Samples of what bindat.el can do for you!
2603 @subsection Describing Data Layout
2605 To control unpacking and packing, you write a @dfn{data layout
2606 specification}, a special nested list describing named and typed
2607 @dfn{fields}. This specification controls length of each field to be
2608 processed, and how to pack or unpack it. We normally keep bindat specs
2609 in variables whose names end in @samp{-bindat-spec}; that kind of name
2610 is automatically recognized as ``risky.''
2614 @cindex little endian
2615 @cindex network byte ordering
2616 A field's @dfn{type} describes the size (in bytes) of the object
2617 that the field represents and, in the case of multibyte fields, how
2618 the bytes are ordered within the field. The two possible orderings
2619 are ``big endian'' (also known as ``network byte ordering'') and
2620 ``little endian.'' For instance, the number @code{#x23cd} (decimal
2621 9165) in big endian would be the two bytes @code{#x23} @code{#xcd};
2622 and in little endian, @code{#xcd} @code{#x23}. Here are the possible
2628 Unsigned byte, with length 1.
2633 Unsigned integer in network byte order, with length 2.
2636 Unsigned integer in network byte order, with length 3.
2641 Unsigned integer in network byte order, with length 4.
2642 Note: These values may be limited by Emacs' integer implementation limits.
2647 Unsigned integer in little endian order, with length 2, 3 and 4, respectively.
2650 String of length @var{len}.
2652 @item strz @var{len}
2653 Zero-terminated string, in a fixed-size field with length @var{len}.
2655 @item vec @var{len} [@var{type}]
2656 Vector of @var{len} elements of type @var{type}, or bytes if not
2657 @var{type} is specified.
2658 The @var{type} is any of the simple types above, or another vector
2659 specified as a list @code{(vec @var{len} [@var{type}])}.
2662 Four-byte vector representing an Internet address. For example:
2663 @code{[127 0 0 1]} for localhost.
2665 @item bits @var{len}
2666 List of set bits in @var{len} bytes. The bytes are taken in big
2667 endian order and the bits are numbered starting with @code{8 *
2668 @var{len} @minus{} 1} and ending with zero. For example: @code{bits
2669 2} unpacks @code{#x28} @code{#x1c} to @code{(2 3 4 11 13)} and
2670 @code{#x1c} @code{#x28} to @code{(3 5 10 11 12)}.
2672 @item (eval @var{form})
2673 @var{form} is a Lisp expression evaluated at the moment the field is
2674 unpacked or packed. The result of the evaluation should be one of the
2675 above-listed type specifications.
2678 For a fixed-size field, the length @var{len} is given as an integer
2679 specifying the number of bytes in the field.
2681 When the length of a field is not fixed, it typically depends on the
2682 value of a preceding field. In this case, the length @var{len} can be
2683 given either as a list @code{(@var{name} ...)} identifying a
2684 @dfn{field name} in the format specified for @code{bindat-get-field}
2685 below, or by an expression @code{(eval @var{form})} where @var{form}
2686 should evaluate to an integer, specifying the field length.
2688 A field specification generally has the form @code{([@var{name}]
2689 @var{handler})}. The square braces indicate that @var{name} is
2690 optional. (Don't use names that are symbols meaningful as type
2691 specifications (above) or handler specifications (below), since that
2692 would be ambiguous.) @var{name} can be a symbol or the expression
2693 @code{(eval @var{form})}, in which case @var{form} should evaluate to
2696 @var{handler} describes how to unpack or pack the field and can be one
2701 Unpack/pack this field according to the type specification @var{type}.
2703 @item eval @var{form}
2704 Evaluate @var{form}, a Lisp expression, for side-effect only. If the
2705 field name is specified, the value is bound to that field name.
2707 @item fill @var{len}
2708 Skip @var{len} bytes. In packing, this leaves them unchanged,
2709 which normally means they remain zero. In unpacking, this means
2712 @item align @var{len}
2713 Skip to the next multiple of @var{len} bytes.
2715 @item struct @var{spec-name}
2716 Process @var{spec-name} as a sub-specification. This describes a
2717 structure nested within another structure.
2719 @item union @var{form} (@var{tag} @var{spec})@dots{}
2720 @c ??? I don't see how one would actually use this.
2721 @c ??? what kind of expression would be useful for @var{form}?
2722 Evaluate @var{form}, a Lisp expression, find the first @var{tag}
2723 that matches it, and process its associated data layout specification
2724 @var{spec}. Matching can occur in one of three ways:
2728 If a @var{tag} has the form @code{(eval @var{expr})}, evaluate
2729 @var{expr} with the variable @code{tag} dynamically bound to the value
2730 of @var{form}. A non-@code{nil} result indicates a match.
2733 @var{tag} matches if it is @code{equal} to the value of @var{form}.
2736 @var{tag} matches unconditionally if it is @code{t}.
2739 @item repeat @var{count} @var{field-specs}@dots{}
2740 Process the @var{field-specs} recursively, in order, then repeat
2741 starting from the first one, processing all the specs @var{count}
2742 times overall. The @var{count} is given using the same formats as a
2743 field length---if an @code{eval} form is used, it is evaluated just once.
2744 For correct operation, each spec in @var{field-specs} must include a name.
2747 For the @code{(eval @var{form})} forms used in a bindat specification,
2748 the @var{form} can access and update these dynamically bound variables
2753 Value of the last field processed.
2756 The data as a byte array.
2759 Current index (within @code{bindat-raw}) for unpacking or packing.
2762 The alist containing the structured data that have been unpacked so
2763 far, or the entire structure being packed. You can use
2764 @code{bindat-get-field} to access specific fields of this structure.
2768 Inside a @code{repeat} block, these contain the maximum number of
2769 repetitions (as specified by the @var{count} parameter), and the
2770 current repetition number (counting from 0). Setting @code{count} to
2771 zero will terminate the inner-most repeat block after the current
2772 repetition has completed.
2775 @node Bindat Functions
2776 @subsection Functions to Unpack and Pack Bytes
2778 In the following documentation, @var{spec} refers to a data layout
2779 specification, @code{bindat-raw} to a byte array, and @var{struct} to an
2780 alist representing unpacked field data.
2782 @defun bindat-unpack spec bindat-raw &optional bindat-idx
2783 This function unpacks data from the unibyte string or byte
2784 array @code{bindat-raw}
2785 according to @var{spec}. Normally this starts unpacking at the
2786 beginning of the byte array, but if @var{bindat-idx} is non-@code{nil}, it
2787 specifies a zero-based starting position to use instead.
2789 The value is an alist or nested alist in which each element describes
2793 @defun bindat-get-field struct &rest name
2794 This function selects a field's data from the nested alist
2795 @var{struct}. Usually @var{struct} was returned by
2796 @code{bindat-unpack}. If @var{name} corresponds to just one argument,
2797 that means to extract a top-level field value. Multiple @var{name}
2798 arguments specify repeated lookup of sub-structures. An integer name
2799 acts as an array index.
2801 For example, if @var{name} is @code{(a b 2 c)}, that means to find
2802 field @code{c} in the third element of subfield @code{b} of field
2803 @code{a}. (This corresponds to @code{struct.a.b[2].c} in C.)
2806 Although packing and unpacking operations change the organization of
2807 data (in memory), they preserve the data's @dfn{total length}, which is
2808 the sum of all the fields' lengths, in bytes. This value is not
2809 generally inherent in either the specification or alist alone; instead,
2810 both pieces of information contribute to its calculation. Likewise, the
2811 length of a string or array being unpacked may be longer than the data's
2812 total length as described by the specification.
2814 @defun bindat-length spec struct
2815 This function returns the total length of the data in @var{struct},
2816 according to @var{spec}.
2819 @defun bindat-pack spec struct &optional bindat-raw bindat-idx
2820 This function returns a byte array packed according to @var{spec} from
2821 the data in the alist @var{struct}. Normally it creates and fills a
2822 new byte array starting at the beginning. However, if @var{bindat-raw}
2823 is non-@code{nil}, it specifies a pre-allocated unibyte string or vector to
2824 pack into. If @var{bindat-idx} is non-@code{nil}, it specifies the starting
2825 offset for packing into @code{bindat-raw}.
2827 When pre-allocating, you should make sure @code{(length @var{bindat-raw})}
2828 meets or exceeds the total length to avoid an out-of-range error.
2831 @defun bindat-ip-to-string ip
2832 Convert the Internet address vector @var{ip} to a string in the usual
2836 (bindat-ip-to-string [127 0 0 1])
2837 @result{} "127.0.0.1"
2841 @node Bindat Examples
2842 @subsection Examples of Byte Unpacking and Packing
2844 Here is a complete example of byte unpacking and packing:
2847 (defvar fcookie-index-spec
2855 (:offset repeat (:count)
2857 "Description of a fortune cookie index file's contents.")
2859 (defun fcookie (cookies &optional index)
2860 "Display a random fortune cookie from file COOKIES.
2861 Optional second arg INDEX specifies the associated index
2862 filename, which is by default constructed by appending
2863 \".dat\" to COOKIES. Display cookie text in possibly
2864 new buffer \"*Fortune Cookie: BASENAME*\" where BASENAME
2865 is COOKIES without the directory part."
2866 (interactive "fCookies file: ")
2867 (let* ((info (with-temp-buffer
2868 (insert-file-contents-literally
2869 (or index (concat cookies ".dat")))
2870 (bindat-unpack fcookie-index-spec
2872 (sel (random (bindat-get-field info :count)))
2873 (beg (cdar (bindat-get-field info :offset sel)))
2874 (end (or (cdar (bindat-get-field info
2876 (nth 7 (file-attributes cookies)))))
2879 (format "*Fortune Cookie: %s*"
2880 (file-name-nondirectory cookies))))
2882 (insert-file-contents-literally
2883 cookies nil beg (- end 3))))
2885 (defun fcookie-create-index (cookies &optional index delim)
2886 "Scan file COOKIES, and write out its index file.
2887 Optional second arg INDEX specifies the index filename,
2888 which is by default constructed by appending \".dat\" to
2889 COOKIES. Optional third arg DELIM specifies the unibyte
2890 character which, when found on a line of its own in
2891 COOKIES, indicates the border between entries."
2892 (interactive "fCookies file: ")
2893 (setq delim (or delim ?%))
2894 (let ((delim-line (format "\n%c\n" delim))
2897 min p q len offsets)
2898 (unless (= 3 (string-bytes delim-line))
2899 (error "Delimiter cannot be represented in one byte"))
2901 (insert-file-contents-literally cookies)
2902 (while (and (setq p (point))
2903 (search-forward delim-line (point-max) t)
2904 (setq len (- (point) 3 p)))
2905 (setq count (1+ count)
2907 min (min (or min max) len)
2908 offsets (cons (1- p) offsets))))
2910 (set-buffer-multibyte nil)
2920 (:offset . ,(mapcar (lambda (o)
2921 (list (cons :foo o)))
2922 (nreverse offsets))))))
2923 (let ((coding-system-for-write 'raw-text-unix))
2924 (write-file (or index (concat cookies ".dat")))))))
2927 Following is an example of defining and unpacking a complex structure.
2928 Consider the following C structures:
2932 unsigned long dest_ip;
2933 unsigned long src_ip;
2934 unsigned short dest_port;
2935 unsigned short src_port;
2940 unsigned char opcode;
2941 unsigned short length; /* In network byte order */
2942 unsigned char id[8]; /* null-terminated string */
2943 unsigned char data[/* (length + 3) & ~3 */];
2947 struct header header;
2948 unsigned long counters[2]; /* In little endian order */
2949 unsigned char items;
2950 unsigned char filler[3];
2951 struct data item[/* items */];
2956 The corresponding data layout specification:
2968 (length u16) ;; network byte order
2974 '((header struct header-spec)
2975 (counters vec 2 u32r) ;; little endian order
2978 (item repeat (items)
2979 (struct data-spec))))
2982 A binary data representation:
2986 [ 192 168 1 100 192 168 1 101 01 28 21 32
2987 160 134 1 0 5 1 0 0 2 0 0 0
2988 2 3 0 5 ?A ?B ?C ?D ?E ?F 0 0 1 2 3 4 5 0 0 0
2989 1 4 0 7 ?B ?C ?D ?E ?F ?G 0 0 6 7 8 9 10 11 12 0 ])
2992 The corresponding decoded structure:
2995 (setq decoded (bindat-unpack packet-spec binary-data))
2998 (dest-ip . [192 168 1 100])
2999 (src-ip . [192 168 1 101])
3002 (counters . [100000 261])
3004 (item ((data . [1 2 3 4 5])
3009 ((data . [6 7 8 9 10 11 12])
3016 Fetching data from this structure:
3019 (bindat-get-field decoded 'item 1 'id)