@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
-@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998 Free Software Foundation, Inc.
+@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2002, 2003,
+@c 2004, 2005, 2006 Free Software Foundation, Inc.
@c See the file elisp.texi for copying conditions.
@setfilename ../info/processes
@node Processes, Display, Abbrevs, Top
an asynchronous subprocess.
* Output from Processes:: Collecting output from an asynchronous subprocess.
* Sentinels:: Sentinels run when process run-status changes.
+* Query Before Exit:: Whether to query if exiting will kill a process.
* Transaction Queues:: Transaction-based communication with subprocesses.
* Network:: Opening network connections.
+* Network Servers:: Network servers let Emacs accept net connections.
+* Datagrams:: UDP network connections.
+* Low-Level Network:: Lower-level but more general function
+ to create connections and servers.
+* Misc Network:: Additional relevant functions for network connections.
+* Byte Packing:: Using bindat to pack and unpack binary data.
@end menu
@node Subprocess Creation
create a synchronous process and do not return a process object
(@pxref{Synchronous Processes}).
- Synchronous and asynchronous processes are explained in following
+ Synchronous and asynchronous processes are explained in the following
sections. Since the three functions are all called in a similar
fashion, their common arguments are described here.
@code{exec-path} contains a list of directories to search. Emacs
initializes @code{exec-path} when it starts up, based on the value of
the environment variable @code{PATH}. The standard file name
-constructs, @samp{~}, @samp{.}, and @samp{..}, are interpreted as usual
-in @code{exec-path}, but environment variable substitutions
+constructs, @samp{~}, @samp{.}, and @samp{..}, are interpreted as
+usual in @code{exec-path}, but environment variable substitutions
(@samp{$HOME}, etc.) are not recognized; use
@code{substitute-in-file-name} to perform them (@pxref{File Name
-Expansion}).
+Expansion}). @code{nil} in this list refers to
+@code{default-directory}.
+
+ Executing a program can also try adding suffixes to the specified
+name:
+
+@defvar exec-suffixes
+This variable is a list of suffixes (strings) to try adding to the
+specified program file name. The list should include @code{""} if you
+want the name to be tried exactly as specified. The default value is
+system-dependent.
+@end defvar
+
+ @strong{Please note:} The argument @var{program} contains only the
+name of the program; it may not contain any command-line arguments. You
+must use @var{args} to provide those.
Each of the subprocess-creating functions has a @var{buffer-or-name}
argument which specifies where the standard output from the program will
argument, @var{args}. The @var{args} must all be strings, and they are
supplied to @var{program} as separate command line arguments. Wildcard
characters and other shell constructs have no special meanings in these
-strings, since the whole strings are passed directly to the specified
-program.
-
- @strong{Please note:} The argument @var{program} contains only the
-name of the program; it may not contain any command-line arguments. You
-must use @var{args} to provide those.
+strings, since the strings are passed directly to the specified program.
The subprocess gets its current directory from the value of
@code{default-directory} (@pxref{File Name Expansion}).
specify overrides for it with @code{process-environment}. @xref{System
Environment}.
-@defvar exec-directory
+@defvar exec-directory
@pindex movemail
-The value of this variable is the name of a directory (a string) that
+The value of this variable is a string, the name of a directory that
contains programs that come with GNU Emacs, programs intended for Emacs
to invoke. The program @code{movemail} is an example of such a program;
Rmail uses it to fetch new mail from an inbox.
@section Shell Arguments
Lisp programs sometimes need to run a shell and give it a command
-which contains file names that were specified by the user. These
+that contains file names that were specified by the user. These
programs ought to be able to support any valid file name. But the shell
gives special treatment to certain characters, and if these characters
occur in the file name, they will confuse the shell. To handle these
and then pass it to a shell for execution.
Precisely what this function does depends on your operating system. The
-function is designed to work with the usual shell syntax; if you use an
-unusual shell, you will need to redefine this function. On MS-DOS, the
-function returns @var{argument} unchanged; while this is not really
-correct, it is the best one can do, since the MS-DOS shell has no
-quoting features.
+function is designed to work with the syntax of your system's standard
+shell; if you use an unusual shell, you will need to redefine this
+function.
@example
;; @r{This example shows the behavior on GNU and Unix systems.}
(shell-quote-argument "foo > bar")
@result{} "foo\\ \\>\\ bar"
+
+;; @r{This example shows the behavior on MS-DOS and MS-Windows.}
+(shell-quote-argument "foo > bar")
+ @result{} "\"foo > bar\""
@end example
Here's an example of using @code{shell-quote-argument} to construct
@cindex synchronous subprocess
After a @dfn{synchronous process} is created, Emacs waits for the
-process to terminate before continuing. Starting Dired is an example of
-this: it runs @code{ls} in a synchronous process, then modifies the
-output slightly. Because the process is synchronous, the entire
-directory listing arrives in the buffer before Emacs tries to do
-anything with it.
+process to terminate before continuing. Starting Dired on GNU or
+Unix@footnote{On other systems, Emacs uses a Lisp emulation of
+@code{ls}; see @ref{Contents of Directories}.} is an example of this: it
+runs @code{ls} in a synchronous process, then modifies the output
+slightly. Because the process is synchronous, the entire directory
+listing arrives in the buffer before Emacs tries to do anything with it.
While Emacs waits for the synchronous subprocess to terminate, the
user can quit by typing @kbd{C-g}. The first @kbd{C-g} tries to kill
the subprocess with a @code{SIGINT} signal; but it waits until the
subprocess actually terminates before quitting. If during that time the
user types another @kbd{C-g}, that kills the subprocess instantly with
-@code{SIGKILL} and quits immediately. @xref{Quitting}.
+@code{SIGKILL} and quits immediately (except on MS-DOS, where killing
+other processes doesn't work). @xref{Quitting}.
The synchronous subprocess functions return an indication of how the
process terminated.
it to finish.
The standard input for the process comes from file @var{infile} if
-@var{infile} is not @code{nil}, and from @file{/dev/null} otherwise.
+@var{infile} is not @code{nil}, and from the null device otherwise.
The argument @var{destination} says where to put the process output.
Here are the possibilities:
Discard the output.
@item 0
-Discard the output, and return immediately without waiting
+Discard the output, and return @code{nil} immediately without waiting
for the subprocess to finish.
In this case, the process is not truly synchronous, since it can run in
Emacs is essentially finished with the subprocess as soon as this
function returns.
+MS-DOS doesn't support asynchronous subprocesses, so this option doesn't
+work there.
+
@item @code{(@var{real-destination} @var{error-destination})}
Keep the standard output stream separate from the standard error stream;
deal with the ordinary output as specified by @var{real-destination},
the buffer as output is inserted. (However, if the coding system chosen
for decoding output is @code{undecided}, meaning deduce the encoding
from the actual data, then redisplay sometimes cannot continue once
-non-@sc{ASCII} characters are encountered. There are fundamental
-reasons why it is hard to fix this.) Otherwise the function
-@code{call-process} does no redisplay, and the results become visible on
-the screen only when Emacs redisplays that buffer in the normal course
-of events.
+non-@acronym{ASCII} characters are encountered. There are fundamental
+reasons why it is hard to fix this; see @ref{Output from Processes}.)
+
+Otherwise the function @code{call-process} does no redisplay, and the
+results become visible on the screen only when Emacs redisplays that
+buffer in the normal course of events.
The remaining arguments, @var{args}, are strings that specify command
line arguments for the program.
@smallexample
@group
(call-process "pwd" nil t)
- @result{} nil
+ @result{} 0
---------- Buffer: foo ----------
/usr/user/lewis/manual
@group
(call-process "grep" nil "bar" nil "lewis" "/etc/passwd")
- @result{} nil
+ @result{} 0
---------- Buffer: bar ----------
lewis:5LTsHm66CSWKg:398:21:Bil Lewis:/user/lewis:/bin/csh
@end smallexample
@end defun
+@defun process-file program &optional infile buffer display &rest args
+This function processes files synchronously in a separate process. It
+is similar to @code{call-process} but may invoke a file handler based
+on the value of the variable @code{default-directory}. The current
+working directory of the subprocess is @code{default-directory}.
+
+The arguments are handled in almost the same way as for
+@code{call-process}, with the following differences:
+
+Some file handlers may not support all combinations and forms of the
+arguments @var{infile}, @var{buffer}, and @var{display}. For example,
+some file handlers might behave as if @var{display} were @code{nil},
+regardless of the value actually passed. As another example, some
+file handlers might not support separating standard output and error
+output by way of the @var{buffer} argument.
+
+If a file handler is invoked, it determines the program to run based
+on the first argument @var{program}. For instance, consider that a
+handler for remote files is invoked. Then the path that is used for
+searching the program might be different than @code{exec-path}.
+
+The second argument @var{infile} may invoke a file handler. The file
+handler could be different from the handler chosen for the
+@code{process-file} function itself. (For example,
+@code{default-directory} could be on a remote host, whereas
+@var{infile} is on another remote host. Or @code{default-directory}
+could be non-special, whereas @var{infile} is on a remote host.)
+
+If @var{buffer} has the form @code{(@var{real-destination}
+@var{error-destination})}, and @var{error-destination} names a file,
+then the same remarks as for @var{infile} apply.
+
+The remaining arguments (@var{args}) will be passed to the process
+verbatim. Emacs is not involved in processing file names that are
+present in @var{args}. To avoid confusion, it may be best to avoid
+absolute file names in @var{args}, but rather to specify all file
+names as relative to @code{default-directory}. The function
+@code{file-relative-name} is useful for constructing such relative
+file names.
+@end defun
+
@defun call-process-region start end program &optional delete destination display &rest args
-This function sends the text between @var{start} to @var{end} as
+This function sends the text from @var{start} to @var{end} as
standard input to a process running @var{program}. It deletes the text
sent if @var{delete} is non-@code{nil}; this is useful when
@var{destination} is @code{t}, to insert the output in the current
as it comes in. For details, see the description of
@code{call-process}, above. If @var{destination} is the integer 0,
@code{call-process-region} discards the output and returns @code{nil}
-immediately, without waiting for the subprocess to finish.
+immediately, without waiting for the subprocess to finish (this only
+works if asynchronous subprocesses are supported).
The remaining arguments, @var{args}, are strings that specify command
line arguments for the program.
@group
(call-process-region 1 6 "cat" nil t)
- @result{} nil
+ @result{} 0
---------- Buffer: foo ----------
inputinput@point{}
@smallexample
@group
-(call-process-region
- start end
+(call-process-region
+ start end
shell-file-name ; @r{Name of program.}
nil ; @r{Do not delete region.}
buffer ; @r{Send output to @code{buffer}.}
@end smallexample
@end defun
+@defun call-process-shell-command command &optional infile destination display &rest args
+This function executes the shell command @var{command} synchronously
+in a separate process. The final arguments @var{args} are additional
+arguments to add at the end of @var{command}. The other arguments
+are handled as in @code{call-process}.
+@end defun
+
@defun shell-command-to-string command
-@tindex shell-command-to-string
This function executes @var{command} (a string) as a shell command,
then returns the command's output as a string.
@end defun
After an @dfn{asynchronous process} is created, Emacs and the subprocess
both continue running immediately. The process thereafter runs
in parallel with Emacs, and the two can communicate with each other
-using the functions described in following sections. However,
+using the functions described in the following sections. However,
communication is only partially asynchronous: Emacs sends data to the
process only when certain functions are called, and Emacs accepts data
from the process only when Emacs is waiting for input or for a time
The point of running a program through the shell, rather than directly
with @code{start-process}, is so that you can employ shell features such
as wildcards in the arguments. It follows that if you include an
-arbitrary user-specified filename in the command, you should quote it
+arbitrary user-specified arguments in the command, you should quote it
with @code{shell-quote-argument} first, so that any special shell
-characters in the file name do @emph{not} have their special shell
-meanings. @xref{Shell Arguments}.
+characters do @emph{not} have their special shell meanings. @xref{Shell
+Arguments}.
@end defun
@defvar process-connection-type
@cindex pipes
-@cindex @sc{pty}s
+@cindex @acronym{PTY}s
This variable controls the type of device used to communicate with
-asynchronous subprocesses. If it is non-@code{nil}, then @sc{pty}s are
+asynchronous subprocesses. If it is non-@code{nil}, then @acronym{PTY}s are
used, when available. Otherwise, pipes are used.
-@sc{pty}s are usually preferable for processes visible to the user, as
+@acronym{PTY}s are usually preferable for processes visible to the user, as
in Shell mode, because they allow job control (@kbd{C-c}, @kbd{C-z},
etc.) to work between the process and its children, whereas pipes do
not. For subprocesses used for internal purposes by programs, it is
often better to use a pipe, because they are more efficient. In
-addition, the total number of @sc{pty}s is limited on many systems and
+addition, the total number of @acronym{PTY}s is limited on many systems and
it is good not to waste them.
-The value @code{process-connection-type} is used when
+The value of @code{process-connection-type} takes effect when
@code{start-process} is called. So you can specify how to communicate
with one subprocess by binding the variable around the call to
@code{start-process}.
@end smallexample
To determine whether a given subprocess actually got a pipe or a
-@sc{pty}, use the function @code{process-tty-name} (@pxref{Process
+@acronym{PTY}, use the function @code{process-tty-name} (@pxref{Process
Information}).
@end defvar
@cindex deleting processes
@dfn{Deleting a process} disconnects Emacs immediately from the
-subprocess, and removes it from the list of active processes. It sends
-a signal to the subprocess to make the subprocess terminate, but this is
-not guaranteed to happen immediately. The process object itself
-continues to exist as long as other Lisp objects point to it. The
-process mark continues to point to the same place as before (usually
-into a buffer where output from the process was being inserted).
-
- You can delete a process explicitly at any time. Processes are
-deleted automatically after they terminate, but not necessarily right
-away. If you delete a terminated process explicitly before it is
-deleted automatically, no harm results.
+subprocess. Processes are deleted automatically after they terminate,
+but not necessarily right away. You can delete a process explicitly
+at any time. If you delete a terminated process explicitly before it
+is deleted automatically, no harm results. Deleting a running
+process sends a signal to terminate it (and its child processes if
+any), and calls the process sentinel if it has one. @xref{Sentinels}.
+
+ When a process is deleted, the process object itself continues to
+exist as long as other Lisp objects point to it. All the Lisp
+primitives that work on process objects accept deleted processes, but
+those that do I/O or send signals will report an error. The process
+mark continues to point to the same place as before, usually into a
+buffer where output from the process was being inserted.
@defopt delete-exited-processes
This variable controls automatic deletion of processes that have
they exit.
@end defopt
-@defun delete-process name
-This function deletes the process associated with @var{name}, killing it
-with a @code{SIGHUP} signal. The argument @var{name} may be a process,
-the name of a process, a buffer, or the name of a buffer.
+@defun delete-process process
+This function deletes a process, killing it with a @code{SIGKILL}
+signal. The argument may be a process, the name of a process, a
+buffer, or the name of a buffer. (A buffer or buffer-name stands for
+the process that @code{get-buffer-process} returns.) Calling
+@code{delete-process} on a running process terminates it, updates the
+process status, and runs the sentinel (if any) immediately. If the
+process has already terminated, calling @code{delete-process} has no
+effect on its status, or on the running of its sentinel (which will
+happen sooner or later).
@smallexample
@group
@end smallexample
@end defun
-@defun process-kill-without-query process &optional do-query
-This function specifies whether Emacs should query the user if
-@var{process} is still running when Emacs is exited. If @var{do-query}
-is @code{nil}, the process will be deleted silently.
-Otherwise, Emacs will query about killing it.
-
-The value is @code{t} if the process was formerly set up to require
-query, @code{nil} otherwise. A newly-created process always requires
-query.
-
-@smallexample
-@group
-(process-kill-without-query (get-process "shell"))
- @result{} t
-@end group
-@end smallexample
-@end defun
-
@node Process Information
@section Process Information
Several functions return information about processes.
@code{list-processes} is provided for interactive use.
-@deffn Command list-processes
+@deffn Command list-processes &optional query-only
This command displays a listing of all living processes. In addition,
it finally deletes any process whose status was @samp{Exited} or
@samp{Signaled}. It returns @code{nil}.
+
+If @var{query-only} is non-@code{nil} then it lists only processes
+whose query flag is non-@code{nil}. @xref{Query Before Exit}.
@end deffn
@defun process-list
@end defun
@defun process-id process
-This function returns the @sc{pid} of @var{process}. This is an
+This function returns the @acronym{PID} of @var{process}. This is an
integer that distinguishes the process @var{process} from all other
processes running on the same computer at the current time. The
-@sc{pid} of a process is chosen by the operating system kernel when the
+@acronym{PID} of a process is chosen by the operating system kernel when the
process is started and remains constant as long as the process exists.
@end defun
This function returns the name of @var{process}.
@end defun
-@defun process-contact process
-@tindex process-contact
-This function returns @code{t} for an ordinary child process, and
-@code{(@var{hostname} @var{service})} for a net connection
-(@pxref{Network}).
-@end defun
-
@defun process-status process-name
This function returns the status of @var{process-name} as a symbol.
The argument @var{process-name} must be a process, a buffer, a
for a network connection that is closed. Once a connection
is closed, you cannot reopen it, though you might be able to open
a new connection to the same place.
+@item connect
+for a non-blocking connection that is waiting to complete.
+@item failed
+for a non-blocking connection that has failed to complete.
+@item listen
+for a network server that is listening.
@item nil
if @var{process-name} is not the name of an existing process.
@end table
@end defun
@defun process-coding-system process
-@tindex process-coding-system
+@anchor{Coding systems for a subprocess}
This function returns a cons cell describing the coding systems in use
for decoding output from @var{process} and for encoding input to
@var{process} (@pxref{Coding Systems}). The value has this form:
@end example
@end defun
-@defun set-process-coding-system process decoding-system encoding-system
-@tindex set-process-coding-system
+@defun set-process-coding-system process &optional decoding-system encoding-system
This function specifies the coding systems to use for subsequent output
from and input to @var{process}. It will use @var{decoding-system} to
decode subprocess output, and @var{encoding-system} to encode subprocess
input.
+@end defun
+
+ Every process also has a property list that you can use to store
+miscellaneous values associated with the process.
+
+@defun process-get process propname
+This function returns the value of the @var{propname} property
+of @var{process}.
+@end defun
+
+@defun process-put process propname value
+This function sets the value of the @var{propname} property
+of @var{process} to @var{value}.
+@end defun
+
+@defun process-plist process
+This function returns the process plist of @var{process}.
+@end defun
+
+@defun set-process-plist process plist
+This function sets the process plist of @var{process} to @var{plist}.
@end defun
@node Input to Processes
data appears on the ``standard input'' of the subprocess.
Some operating systems have limited space for buffered input in a
-@sc{pty}. On these systems, Emacs sends an @sc{eof} periodically amidst
-the other characters, to force them through. For most programs,
-these @sc{eof}s do no harm.
+@acronym{PTY}. On these systems, Emacs sends an @acronym{EOF}
+periodically amidst the other characters, to force them through. For
+most programs, these @acronym{EOF}s do no harm.
Subprocess input is normally encoded using a coding system before the
subprocess receives it, much like text written into a file. You can use
@code{coding-system-for-write}, if that is non-@code{nil}; or else from
the defaulting mechanism (@pxref{Default Coding Systems}).
-@defun process-send-string process-name string
-This function sends @var{process-name} the contents of @var{string} as
-standard input. The argument @var{process-name} must be a process or
-the name of a process. If it is @code{nil}, the current buffer's
-process is used.
+ Sometimes the system is unable to accept input for that process,
+because the input buffer is full. When this happens, the send functions
+wait a short while, accepting output from subprocesses, and then try
+again. This gives the subprocess a chance to read more of its pending
+input and make space in the buffer. It also allows filters, sentinels
+and timers to run---so take account of that in writing your code.
+
+ In these functions, the @var{process} argument can be a process or
+the name of a process, or a buffer or buffer name (which stands
+for a process via @code{get-buffer-process}). @code{nil} means
+the current buffer's process.
+
+@defun process-send-string process string
+This function sends @var{process} the contents of @var{string} as
+standard input. If it is @code{nil}, the current buffer's process is used.
The function returns @code{nil}.
@end smallexample
@end defun
-@deffn Command process-send-region process-name start end
+@defun process-send-region process start end
This function sends the text in the region defined by @var{start} and
-@var{end} as standard input to @var{process-name}, which is a process or
-a process name. (If it is @code{nil}, the current buffer's process is
-used.)
+@var{end} as standard input to @var{process}.
An error is signaled unless both @var{start} and @var{end} are
integers or markers that indicate positions in the current buffer. (It
is unimportant which number is larger.)
-@end deffn
-
-@defun process-send-eof &optional process-name
- This function makes @var{process-name} see an end-of-file in its
-input. The @sc{eof} comes after any text already sent to it.
+@end defun
- If @var{process-name} is not supplied, or if it is @code{nil}, then
-this function sends the @sc{eof} to the current buffer's process. An
-error is signaled if the current buffer has no process.
+@defun process-send-eof &optional process
+This function makes @var{process} see an end-of-file in its
+input. The @acronym{EOF} comes after any text already sent to it.
- The function returns @var{process-name}.
+The function returns @var{process}.
@smallexample
@group
@end smallexample
@end defun
+@defun process-running-child-p process
+@tindex process-running-child-p process
+This function will tell you whether a subprocess has given control of
+its terminal to its own child process. The value is @code{t} if this is
+true, or if Emacs cannot tell; it is @code{nil} if Emacs can be certain
+that this is not so.
+@end defun
+
@node Signals to Processes
@section Sending Signals to Processes
@cindex process signals
user hung up the phone.)
Each of the signal-sending functions takes two optional arguments:
-@var{process-name} and @var{current-group}.
+@var{process} and @var{current-group}.
- The argument @var{process-name} must be either a process, the name of
-one, or @code{nil}. If it is @code{nil}, the process defaults to the
-process associated with the current buffer. An error is signaled if
-@var{process-name} does not identify a process.
+ The argument @var{process} must be either a process, a process
+name, a buffer, a buffer name, or @code{nil}. A buffer or buffer name
+stands for a process through @code{get-buffer-process}. @code{nil}
+stands for the process associated with the current buffer. An error
+is signaled if @var{process} does not identify a process.
The argument @var{current-group} is a flag that makes a difference
when you are running a job-control shell as an Emacs subprocess. If it
job-control shells won't work when a pipe is used. See
@code{process-connection-type} in @ref{Asynchronous Processes}.
-@defun interrupt-process &optional process-name current-group
-This function interrupts the process @var{process-name} by sending the
+@defun interrupt-process &optional process current-group
+This function interrupts the process @var{process} by sending the
signal @code{SIGINT}. Outside of Emacs, typing the ``interrupt
character'' (normally @kbd{C-c} on some systems, and @code{DEL} on
others) sends this signal. When the argument @var{current-group} is
on the terminal by which Emacs talks to the subprocess.
@end defun
-@defun kill-process &optional process-name current-group
-This function kills the process @var{process-name} by sending the
+@defun kill-process &optional process current-group
+This function kills the process @var{process} by sending the
signal @code{SIGKILL}. This signal kills the subprocess immediately,
and cannot be handled by the subprocess.
@end defun
-@defun quit-process &optional process-name current-group
+@defun quit-process &optional process current-group
This function sends the signal @code{SIGQUIT} to the process
-@var{process-name}. This signal is the one sent by the ``quit
+@var{process}. This signal is the one sent by the ``quit
character'' (usually @kbd{C-b} or @kbd{C-\}) when you are not inside
Emacs.
@end defun
-@defun stop-process &optional process-name current-group
-This function stops the process @var{process-name} by sending the
+@defun stop-process &optional process current-group
+This function stops the process @var{process} by sending the
signal @code{SIGTSTP}. Use @code{continue-process} to resume its
execution.
subprocess.
@end defun
-@defun continue-process &optional process-name current-group
+@defun continue-process &optional process current-group
This function resumes execution of the process @var{process} by sending
-it the signal @code{SIGCONT}. This presumes that @var{process-name} was
+it the signal @code{SIGCONT}. This presumes that @var{process} was
stopped previously.
@end defun
@c Emacs 19 feature
-@defun signal-process pid signal
-This function sends a signal to process @var{pid}, which need not be
-a child of Emacs. The argument @var{signal} specifies which signal
-to send; it should be an integer.
+@defun signal-process process signal
+This function sends a signal to process @var{process}. The argument
+@var{signal} specifies which signal to send; it should be an integer.
+
+The @var{process} argument can be a system process @acronym{ID}; that
+allows you to send signals to processes that are not children of
+Emacs.
@end defun
@node Output from Processes
the process has no buffer and no filter function, its output is
discarded.
+ When a subprocess terminates, Emacs reads any pending output,
+then stops reading output from that subprocess. Therefore, if the
+subprocess has children that are still live and still producing
+output, Emacs won't receive that output.
+
Output from a subprocess can arrive only while Emacs is waiting: when
reading terminal input, in @code{sit-for} and @code{sleep-for}
(@pxref{Waiting}), and in @code{accept-process-output} (@pxref{Accepting
can arrive before you finish, if the code in between does not call any
primitive that waits.
- Subprocess output is normally decoded using a coding system before the
-buffer or filter function receives it, much like text read from a file.
-You can use @code{set-process-coding-system} to specify which coding
-system to use (@pxref{Process Information}). Otherwise, the coding
-system comes from @code{coding-system-for-read}, if that is
-non-@code{nil}; or else from the defaulting mechanism (@pxref{Default
-Coding Systems}).
+@defvar process-adaptive-read-buffering
+On some systems, when Emacs reads the output from a subprocess, the
+output data is read in very small blocks, potentially resulting in
+very poor performance. This behavior can be remedied to some extent
+by setting the variable @var{process-adaptive-read-buffering} to a
+non-@code{nil} value (the default), as it will automatically delay reading
+from such processes, thus allowing them to produce more output before
+Emacs tries to read it.
+@end defvar
- @strong{Warning:} Coding systems such as @code{undecided} which
-determine the coding system from the data do not work entirely reliably
-with asynchronous subprocess output. This is because Emacs has to
-process asynchronous subprocess output in batches, as it arrives. Emacs
-must try to detect the proper coding system from one batch at a time,
-and this does not always work. Therefore, if at all possible, use a
-coding system which determines both the character code conversion and
-the end of line conversion---that is, one like @code{latin-1-unix},
-rather than @code{undecided} or @code{latin-1}.
+ It is impossible to separate the standard output and standard error
+streams of the subprocess, because Emacs normally spawns the subprocess
+inside a pseudo-TTY, and a pseudo-TTY has only one output channel. If
+you want to keep the output to those streams separate, you should
+redirect one of them to a file---for example, by using an appropriate
+shell command.
@menu
-* Process Buffers:: If no filter, output is put in a buffer.
-* Filter Functions:: Filter functions accept output from the process.
-* Accepting Output:: Explicitly permitting subprocess output.
- Waiting for subprocess output.
+* Process Buffers:: If no filter, output is put in a buffer.
+* Filter Functions:: Filter functions accept output from the process.
+* Decoding Output:: Filters can get unibyte or multibyte strings.
+* Accepting Output:: How to wait until process output arrives.
@end menu
@node Process Buffers
@end defun
@defun get-buffer-process buffer-or-name
-This function returns the process associated with @var{buffer-or-name}.
-If there are several processes associated with it, then one is chosen.
-(Currently, the one chosen is the one most recently created.) It is
-usually a bad idea to have more than one process associated with the
-same buffer.
+This function returns a nondeleted process associated with the buffer
+specified by @var{buffer-or-name}. If there are several processes
+associated with it, this function chooses one (currently, the one most
+recently created, but don't count on that). Deletion of a process
+(see @code{delete-process}) makes it ineligible for this function to
+return.
+
+It is usually a bad idea to have more than one process associated with
+the same buffer.
@smallexample
@group
Quitting is normally inhibited within a filter function---otherwise,
the effect of typing @kbd{C-g} at command level or to quit a user
-command would be unpredictable. If you want to permit quitting inside a
-filter function, bind @code{inhibit-quit} to @code{nil}.
-@xref{Quitting}.
+command would be unpredictable. If you want to permit quitting inside
+a filter function, bind @code{inhibit-quit} to @code{nil}. In most
+cases, the right way to do this is with the macro
+@code{with-local-quit}. @xref{Quitting}.
If an error happens during execution of a filter function, it is
caught automatically, so that it doesn't stop the execution of whatever
@end smallexample
@end ignore
+@node Decoding Output
+@subsection Decoding Process Output
+
+ When Emacs writes process output directly into a multibyte buffer,
+it decodes the output according to the process output coding system.
+If the coding system is @code{raw-text} or @code{no-conversion}, Emacs
+converts the unibyte output to multibyte using
+@code{string-to-multibyte}, and inserts the resulting multibyte text.
+
+ You can use @code{set-process-coding-system} to specify which coding
+system to use (@pxref{Process Information}). Otherwise, the coding
+system comes from @code{coding-system-for-read}, if that is
+non-@code{nil}; or else from the defaulting mechanism (@pxref{Default
+Coding Systems}).
+
+ @strong{Warning:} Coding systems such as @code{undecided} which
+determine the coding system from the data do not work entirely
+reliably with asynchronous subprocess output. This is because Emacs
+has to process asynchronous subprocess output in batches, as it
+arrives. Emacs must try to detect the proper coding system from one
+batch at a time, and this does not always work. Therefore, if at all
+possible, specify a coding system that determines both the character
+code conversion and the end of line conversion---that is, one like
+@code{latin-1-unix}, rather than @code{undecided} or @code{latin-1}.
+
+@cindex filter multibyte flag, of process
+@cindex process filter multibyte flag
+ When Emacs calls a process filter function, it provides the process
+output as a multibyte string or as a unibyte string according to the
+process's filter multibyte flag. If the flag is non-@code{nil}, Emacs
+decodes the output according to the process output coding system to
+produce a multibyte string, and passes that to the process. If the
+flag is @code{nil}, Emacs puts the output into a unibyte string, with
+no decoding, and passes that.
+
+ When you create a process, the filter multibyte flag takes its
+initial value from @code{default-enable-multibyte-characters}. If you
+want to change the flag later on, use
+@code{set-process-filter-multibyte}.
+
+@defun set-process-filter-multibyte process multibyte
+This function sets the filter multibyte flag of @var{process}
+to @var{multibyte}.
+@end defun
+
+@defun process-filter-multibyte-p process
+This function returns the filter multibyte flag of @var{process}.
+@end defun
+
@node Accepting Output
@subsection Accepting Output from Processes
explicitly permit output to arrive at a specific point, or even to wait
until output arrives from a process.
-@defun accept-process-output &optional process seconds millisec
+@defun accept-process-output &optional process seconds millisec just-this-one
This function allows Emacs to read pending output from processes. The
output is inserted in the associated buffers or given to their filter
functions. If @var{process} is non-@code{nil} then this function does
The argument @var{seconds} need not be an integer. If it is a floating
point number, this function waits for a fractional number of seconds.
-Some systems support only a whole number of seconds; on these systems,
-@var{seconds} is rounded down.
-Not all operating systems support waiting periods other than multiples
-of a second; on those that do not, you get an error if you specify
-nonzero @var{millisec}.
+@c Emacs 22.1 feature
+If @var{process} is a process, and the argument @var{just-this-one} is
+non-@code{nil}, only output from that process is handled, suspending output
+from other processes until some output has been received from that
+process or the timeout expires. If @var{just-this-one} is an integer,
+also inhibit running timers. This feature is generally not
+recommended, but may be necessary for specific applications, such as
+speech synthesis.
The function @code{accept-process-output} returns non-@code{nil} if it
did get some output, or @code{nil} if the timeout expired before output
A @dfn{process sentinel} is a function that is called whenever the
associated process changes status for any reason, including signals
(whether sent by Emacs or caused by the process's own actions) that
-terminate, stop, or continue the process. The process sentinel is also
-called if the process exits. The sentinel receives two arguments: the
-process for which the event occurred, and a string describing the type
-of event.
+terminate, stop, or continue the process. The process sentinel is
+also called if the process exits. The sentinel receives two
+arguments: the process for which the event occurred, and a string
+describing the type of event.
The string describing the event looks like one of the following:
@itemize @bullet
-@item
+@item
@code{"finished\n"}.
@item
@code{"@var{name-of-signal} (core dumped)\n"}.
@end itemize
- A sentinel runs only while Emacs is waiting (e.g., for terminal input,
-or for time to elapse, or for process output). This avoids the timing
-errors that could result from running them at random places in the
-middle of other Lisp programs. A program can wait, so that sentinels
-will run, by calling @code{sit-for} or @code{sleep-for}
+ A sentinel runs only while Emacs is waiting (e.g., for terminal
+input, or for time to elapse, or for process output). This avoids the
+timing errors that could result from running them at random places in
+the middle of other Lisp programs. A program can wait, so that
+sentinels will run, by calling @code{sit-for} or @code{sleep-for}
(@pxref{Waiting}), or @code{accept-process-output} (@pxref{Accepting
Output}). Emacs also allows sentinels to run when the command loop is
-reading input.
+reading input. @code{delete-process} calls the sentinel when it
+terminates a running process.
- Quitting is normally inhibited within a sentinel---otherwise, the
-effect of typing @kbd{C-g} at command level or to quit a user command
-would be unpredictable. If you want to permit quitting inside a
-sentinel, bind @code{inhibit-quit} to @code{nil}. @xref{Quitting}.
+ Emacs does not keep a queue of multiple reasons to call the sentinel
+of one process; it records just the current status and the fact that
+there has been a change. Therefore two changes in status, coming in
+quick succession, can call the sentinel just once. However, process
+termination will always run the sentinel exactly once. This is
+because the process status can't change again after termination.
+
+ Emacs explicitly checks for output from the process before running
+the process sentinel. Once the sentinel runs due to process
+termination, no further output can arrive from the process.
A sentinel that writes the output into the buffer of the process
should check whether the buffer is still alive. If it tries to insert
into a dead buffer, it will get an error. If the buffer is dead,
@code{(buffer-name (process-buffer @var{process}))} returns @code{nil}.
+ Quitting is normally inhibited within a sentinel---otherwise, the
+effect of typing @kbd{C-g} at command level or to quit a user command
+would be unpredictable. If you want to permit quitting inside a
+sentinel, bind @code{inhibit-quit} to @code{nil}. In most cases, the
+right way to do this is with the macro @code{with-local-quit}.
+@xref{Quitting}.
+
If an error happens during execution of a sentinel, it is caught
automatically, so that it doesn't stop the execution of whatever
programs was running when the sentinel was started. However, if
off. This makes it possible to use the Lisp debugger to debug the
sentinel. @xref{Debugger}.
+ While a sentinel is running, the process sentinel is temporarily
+set to @code{nil} so that the sentinel won't run recursively.
+For this reason it is not possible for a sentinel to specify
+a new sentinel.
+
In earlier Emacs versions, every sentinel that did regular expression
searching or matching had to explicitly save and restore the match data.
Now Emacs does this automatically for sentinels; they never need to do
The default behavior when there is no sentinel is to insert a message in
the process's buffer when the process status changes.
+Changes in process sentinel take effect immediately---if the sentinel
+is slated to be run but has not been called yet, and you specify a new
+sentinel, the eventual call to the sentinel will use the new one.
+
@smallexample
@group
(defun msg-me (process event)
was not.
@end defun
+@node Query Before Exit
+@section Querying Before Exit
+
+ When Emacs exits, it terminates all its subprocesses by sending them
+the @code{SIGHUP} signal. Because subprocesses may be doing
+valuable work, Emacs normally asks the user to confirm that it is ok
+to terminate them. Each process has a query flag which, if
+non-@code{nil}, says that Emacs should ask for confirmation before
+exiting and thus killing that process. The default for the query flag
+is @code{t}, meaning @emph{do} query.
+
+@tindex process-query-on-exit-flag
+@defun process-query-on-exit-flag process
+This returns the query flag of @var{process}.
+@end defun
+
+@tindex set-process-query-on-exit-flag
+@defun set-process-query-on-exit-flag process flag
+This function sets the query flag of @var{process} to @var{flag}. It
+returns @var{flag}.
+
+@smallexample
+@group
+;; @r{Don't query about the shell process}
+(set-process-query-on-exit-flag (get-process "shell") nil)
+ @result{} t
+@end group
+@end smallexample
+@end defun
+
+@defun process-kill-without-query process &optional do-query
+This function clears the query flag of @var{process}, so that
+Emacs will not query the user on account of that process.
+
+Actually, the function does more than that: it returns the old value of
+the process's query flag, and sets the query flag to @var{do-query}.
+Please don't use this function to do those things any more---please
+use the newer, cleaner functions @code{process-query-on-exit-flag} and
+@code{set-process-query-on-exit-flag} in all but the simplest cases.
+The only way you should use @code{process-kill-without-query} nowadays
+is like this:
+
+@smallexample
+@group
+;; @r{Don't query about the shell process}
+(process-kill-without-query (get-process "shell"))
+@end group
+@end smallexample
+@end defun
+
@node Transaction Queues
@section Transaction Queues
@cindex transaction queue
machine.
@end defun
-@defun tq-enqueue queue question regexp closure fn
+@defun tq-enqueue queue question regexp closure fn &optional delay-question
This function sends a transaction to queue @var{queue}. Specifying the
queue has the effect of specifying the subprocess to talk to.
corresponding answer comes back; it is called with two arguments:
@var{closure}, and the answer received.
-The argument @var{regexp} is a regular expression that should match the
-entire answer, but nothing less; that's how @code{tq-enqueue} determines
-where the answer ends.
+The argument @var{regexp} is a regular expression that should match
+text at the end of the entire answer, but nothing before; that's how
+@code{tq-enqueue} determines where the answer ends.
+
+If the argument @var{delay-question} is non-nil, delay sending this
+question until the process has finished replying to any previous
+questions. This produces more reliable results with some processes."
The return value of @code{tq-enqueue} itself is not meaningful.
@end defun
@section Network Connections
@cindex network connection
@cindex TCP
-
- Emacs Lisp programs can open TCP network connections to other processes on
-the same machine or other machines. A network connection is handled by Lisp
-much like a subprocess, and is represented by a process object.
-However, the process you are communicating with is not a child of the
-Emacs process, so you can't kill it or send it signals. All you can do
-is send and receive data. @code{delete-process} closes the connection,
-but does not kill the process at the other end; that process must decide
-what to do about closure of the connection.
+@cindex UDP
+
+ Emacs Lisp programs can open stream (TCP) and datagram (UDP) network
+connections to other processes on the same machine or other machines.
+A network connection is handled by Lisp much like a subprocess, and is
+represented by a process object. However, the process you are
+communicating with is not a child of the Emacs process, so it has no
+process @acronym{ID}, and you can't kill it or send it signals. All you
+can do is send and receive data. @code{delete-process} closes the
+connection, but does not kill the program at the other end; that
+program must decide what to do about closure of the connection.
+
+ Lisp programs can listen for connections by creating network
+servers. A network server is also represented by a kind of process
+object, but unlike a network connection, the network server never
+transfers data itself. When it receives a connection request, it
+creates a new network connection to represent the connection just
+made. (The network connection inherits certain information, including
+the process plist, from the server.) The network server then goes
+back to listening for more connection requests.
+
+ Network connections and servers are created by calling
+@code{make-network-process} with an argument list consisting of
+keyword/argument pairs, for example @code{:server t} to create a
+server process, or @code{:type 'datagram} to create a datagram
+connection. @xref{Low-Level Network}, for details. You can also use
+the @code{open-network-stream} function described below.
You can distinguish process objects representing network connections
-from those representing subprocesses with the @code{process-status}
-function. It always returns either @code{open} or @code{closed} for a
-network connection, and it never returns either of those values for a
-real subprocess. @xref{Process Information}.
+and servers from those representing subprocesses with the
+@code{process-status} function. The possible status values for
+network connections are @code{open}, @code{closed}, @code{connect},
+and @code{failed}. For a network server, the status is always
+@code{listen}. None of those values is possible for a real
+subprocess. @xref{Process Information}.
+
+ You can stop and resume operation of a network process by calling
+@code{stop-process} and @code{continue-process}. For a server
+process, being stopped means not accepting new connections. (Up to 5
+connection requests will be queued for when you resume the server; you
+can increase this limit, unless it is imposed by the operating
+system.) For a network stream connection, being stopped means not
+processing input (any arriving input waits until you resume the
+connection). For a datagram connection, some number of packets may be
+queued but input may be lost. You can use the function
+@code{process-command} to determine whether a network connection or
+server is stopped; a non-@code{nil} value means yes.
@defun open-network-stream name buffer-or-name host service
-This function opens a TCP connection for a service to a host. It
-returns a process object to represent the connection.
+This function opens a TCP connection, and returns a process object
+that represents the connection.
The @var{name} argument specifies the name for the process object. It
is modified as necessary to make it unique.
@var{host} is the host name (a string), and @var{service} is the name of
a defined network service (a string) or a port number (an integer).
@end defun
+
+@defun process-contact process &optional key
+This function returns information about how a network process was set
+up. For a connection, when @var{key} is @code{nil}, it returns
+@code{(@var{hostname} @var{service})} which specifies what you
+connected to.
+
+If @var{key} is @code{t}, the value is the complete status information
+for the connection or server; that is, the list of keywords and values
+specified in @code{make-network-process}, except that some of the
+values represent the current status instead of what you specified:
+
+@table @code
+@item :buffer
+The associated value is the process buffer.
+@item :filter
+The associated value is the process filter function.
+@item :sentinel
+The associated value is the process sentinel function.
+@item :remote
+In a connection, this is the address in internal format of the remote peer.
+@item :local
+The local address, in internal format.
+@item :service
+In a server, if you specified @code{t} for @var{service},
+this value is the actual port number.
+@end table
+
+@code{:local} and @code{:remote} are included even if they were not
+specified explicitly in @code{make-network-process}.
+
+If @var{key} is a keyword, the function returns the value corresponding
+to that keyword.
+
+For an ordinary child process, this function always returns @code{t}.
+@end defun
+
+@node Network Servers
+@section Network Servers
+
+ You create a server by calling @code{make-network-process} with
+@code{:server t}. The server will listen for connection requests from
+clients. When it accepts a client connection request, that creates a
+new network connection, itself a process object, with the following
+parameters:
+
+@itemize @bullet
+@item
+The connection's process name is constructed by concatenating the
+server process' @var{name} with a client identification string. The
+client identification string for an IPv4 connection looks like
+@samp{<@var{a}.@var{b}.@var{c}.@var{d}:@var{p}>}. Otherwise, it is a
+unique number in brackets, as in @samp{<@var{nnn}>}. The number
+is unique for each connection in the Emacs session.
+
+@item
+If the server's filter is non-@code{nil}, the connection process does
+not get a separate process buffer; otherwise, Emacs creates a new
+buffer for the purpose. The buffer name is the server's buffer name
+or process name, concatenated with the client identification string.
+
+The server's process buffer value is never used directly by Emacs, but
+it is passed to the log function, which can log connections by
+inserting text there.
+
+@item
+The communication type and the process filter and sentinel are
+inherited from those of the server. The server never directly
+uses its filter and sentinel; their sole purpose is to initialize
+connections made to the server.
+
+@item
+The connection's process contact info is set according to the client's
+addressing information (typically an IP address and a port number).
+This information is associated with the @code{process-contact}
+keywords @code{:host}, @code{:service}, @code{:remote}.
+
+@item
+The connection's local address is set up according to the port
+number used for the connection.
+
+@item
+The client process' plist is initialized from the server's plist.
+@end itemize
+
+@node Datagrams
+@section Datagrams
+@cindex datagrams
+
+ A datagram connection communicates with individual packets rather
+than streams of data. Each call to @code{process-send} sends one
+datagram packet (@pxref{Input to Processes}), and each datagram
+received results in one call to the filter function.
+
+ The datagram connection doesn't have to talk with the same remote
+peer all the time. It has a @dfn{remote peer address} which specifies
+where to send datagrams to. Each time an incoming datagram is passed
+to the filter function, the peer address is set to the address that
+datagram came from; that way, if the filter function sends a datagram,
+it will go back to that place. You can specify the remote peer
+address when you create the datagram connection using the
+@code{:remote} keyword. You can change it later on by calling
+@code{set-process-datagram-address}.
+
+@defun process-datagram-address process
+If @var{process} is a datagram connection or server, this function
+returns its remote peer address.
+@end defun
+
+@defun set-process-datagram-address process address
+If @var{process} is a datagram connection or server, this function
+sets its remote peer address to @var{address}.
+@end defun
+
+@node Low-Level Network
+@section Low-Level Network Access
+
+ You can also create network connections by operating at a lower
+level that that of @code{open-network-stream}, using
+@code{make-network-process}.
+
+@menu
+* Make Network:: Using @code{make-network-process}.
+* Network Options:: Further control over network connections.
+* Network Feature Testing:: Determining which network features work on
+ the machine you are using.
+@end menu
+
+@node Make Network
+@subsection @code{make-network-process}
+
+ The basic function for creating network connections and network
+servers is @code{make-network-process}. It can do either of those
+jobs, depending on the arguments you give it.
+
+@defun make-network-process &rest args
+This function creates a network connection or server and returns the
+process object that represents it. The arguments @var{args} are a
+list of keyword/argument pairs. Omitting a keyword is always
+equivalent to specifying it with value @code{nil}, except for
+@code{:coding}, @code{:filter-multibyte}, and @code{:reuseaddr}. Here
+are the meaningful keywords:
+
+@table @asis
+@item :name @var{name}
+Use the string @var{name} as the process name. It is modified if
+necessary to make it unique.
+
+@item :type @var{type}
+Specify the communication type. A value of @code{nil} specifies a
+stream connection (the default); @code{datagram} specifies a datagram
+connection. Both connections and servers can be of either type.
+
+@item :server @var{server-flag}
+If @var{server-flag} is non-@code{nil}, create a server. Otherwise,
+create a connection. For a stream type server, @var{server-flag} may
+be an integer which then specifies the length of the queue of pending
+connections to the server. The default queue length is 5.
+
+@item :host @var{host}
+Specify the host to connect to. @var{host} should be a host name or
+internet address, as a string, or the symbol @code{local} to specify
+the local host. If you specify @var{host} for a server, it must
+specify a valid address for the local host, and only clients
+connecting to that address will be accepted.
+
+@item :service @var{service}
+@var{service} specifies a port number to connect to, or, for a server,
+the port number to listen on. It should be a service name that
+translates to a port number, or an integer specifying the port number
+directly. For a server, it can also be @code{t}, which means to let
+the system select an unused port number.
+
+@item :family @var{family}
+@var{family} specifies the address (and protocol) family for
+communication. @code{nil} means determine the proper address family
+automatically for the given @var{host} and @var{service}.
+@code{local} specifies a Unix socket, in which case @var{host} is
+ignored. @code{ipv4} and @code{ipv6} specify to use IPv4 and IPv6
+respectively.
+
+@item :local @var{local-address}
+For a server process, @var{local-address} is the address to listen on.
+It overrides @var{family}, @var{host} and @var{service}, and you
+may as well not specify them.
+
+@item :remote @var{remote-address}
+For a connection, @var{remote-address} is the address to connect to.
+It overrides @var{family}, @var{host} and @var{service}, and you
+may as well not specify them.
+
+For a datagram server, @var{remote-address} specifies the initial
+setting of the remote datagram address.
+
+The format of @var{local-address} or @var{remote-address} depends on
+the address family:
+
+@itemize -
+@item
+An IPv4 address is represented as a five-element vector of four 8-bit
+integers and one 16-bit integer
+@code{[@var{a} @var{b} @var{c} @var{d} @var{p}]} corresponding to
+numeric IPv4 address @var{a}.@var{b}.@var{c}.@var{d} and port number
+@var{p}.
+
+@item
+An IPv6 address is represented as a nine-element vector of 16-bit
+integers @code{[@var{a} @var{b} @var{c} @var{d} @var{e} @var{f}
+@var{g} @var{h} @var{p}]} corresponding to numeric IPv6 address
+@var{a}:@var{b}:@var{c}:@var{d}:@var{e}:@var{f}:@var{g}:@var{h} and
+port number @var{p}.
+
+@item
+A local address is represented as a string which specifies the address
+in the local address space.
+
+@item
+An ``unsupported family'' address is represented by a cons
+@code{(@var{f} . @var{av})}, where @var{f} is the family number and
+@var{av} is a vector specifying the socket address using one element
+per address data byte. Do not rely on this format in portable code,
+as it may depend on implementation defined constants, data sizes, and
+data structure alignment.
+@end itemize
+
+@item :nowait @var{bool}
+If @var{bool} is non-@code{nil} for a stream connection, return
+without waiting for the connection to complete. When the connection
+succeeds or fails, Emacs will call the sentinel function, with a
+second argument matching @code{"open"} (if successful) or
+@code{"failed"}. The default is to block, so that
+@code{make-network-process} does not return until the connection
+has succeeded or failed.
+
+@item :stop @var{stopped}
+Start the network connection or server in the `stopped' state if
+@var{stopped} is non-@code{nil}.
+
+@item :buffer @var{buffer}
+Use @var{buffer} as the process buffer.
+
+@item :coding @var{coding}
+Use @var{coding} as the coding system for this process. To specify
+different coding systems for decoding data from the connection and for
+encoding data sent to it, specify @code{(@var{decoding} .
+@var{encoding})} for @var{coding}.
+
+If you don't specify this keyword at all, the default
+is to determine the coding systems from the data.
+
+@item :noquery @var{query-flag}
+Initialize the process query flag to @var{query-flag}.
+@xref{Query Before Exit}.
+
+@item :filter @var{filter}
+Initialize the process filter to @var{filter}.
+
+@item :filter-multibyte @var{bool}
+If @var{bool} is non-@code{nil}, strings given to the process filter
+are multibyte, otherwise they are unibyte. If you don't specify this
+keyword at all, the default is that the strings are multibyte if
+@code{default-enable-multibyte-characters} is non-@code{nil}.
+
+@item :sentinel @var{sentinel}
+Initialize the process sentinel to @var{sentinel}.
+
+@item :log @var{log}
+Initialize the log function of a server process to @var{log}. The log
+function is called each time the server accepts a network connection
+from a client. The arguments passed to the log function are
+@var{server}, @var{connection}, and @var{message}, where @var{server}
+is the server process, @var{connection} is the new process for the
+connection, and @var{message} is a string describing what has
+happened.
+
+@item :plist @var{plist}
+Initialize the process plist to @var{plist}.
+@end table
+
+The original argument list, modified with the actual connection
+information, is available via the @code{process-contact} function.
+@end defun
+
+@node Network Options
+@subsection Network Options
+
+ The following network options can be specified when you create a
+network process. Except for @code{:reuseaddr}, you can also set or
+modify these options later, using @code{set-network-process-option}.
+
+ For a server process, the options specified with
+@code{make-network-process} are not inherited by the client
+connections, so you will need to set the necessary options for each
+child connection as it is created.
+
+@table @asis
+@item :bindtodevice @var{device-name}
+If @var{device-name} is a non-empty string identifying a network
+interface name (see @code{network-interface-list}), only handle
+packets received on that interface. If @var{device-name} is @code{nil}
+(the default), handle packets received on any interface.
+
+Using this option may require special privileges on some systems.
+
+@item :broadcast @var{broadcast-flag}
+If @var{broadcast-flag} is non-@code{nil} for a datagram process, the
+process will receive datagram packet sent to a broadcast address, and
+be able to send packets to a broadcast address. Ignored for a stream
+connection.
+
+@item :dontroute @var{dontroute-flag}
+If @var{dontroute-flag} is non-@code{nil}, the process can only send
+to hosts on the same network as the local host.
+
+@item :keepalive @var{keepalive-flag}
+If @var{keepalive-flag} is non-@code{nil} for a stream connection,
+enable exchange of low-level keep-alive messages.
+
+@item :linger @var{linger-arg}
+If @var{linger-arg} is non-@code{nil}, wait for successful
+transmission of all queued packets on the connection before it is
+deleted (see @code{delete-process}). If @var{linger-arg} is an
+integer, it specifies the maximum time in seconds to wait for queued
+packets to be sent before closing the connection. Default is
+@code{nil} which means to discard unsent queued packets when the
+process is deleted.
+
+@item :oobinline @var{oobinline-flag}
+If @var{oobinline-flag} is non-@code{nil} for a stream connection,
+receive out-of-band data in the normal data stream. Otherwise, ignore
+out-of-band data.
+
+@item :priority @var{priority}
+Set the priority for packets sent on this connection to the integer
+@var{priority}. The interpretation of this number is protocol
+specific, such as setting the TOS (type of service) field on IP
+packets sent on this connection. It may also have system dependent
+effects, such as selecting a specific output queue on the network
+interface.
+
+@item :reuseaddr @var{reuseaddr-flag}
+If @var{reuseaddr-flag} is non-@code{nil} (the default) for a stream
+server process, allow this server to reuse a specific port number (see
+@code{:service}) unless another process on this host is already
+listening on that port. If @var{reuseaddr-flag} is @code{nil}, there
+may be a period of time after the last use of that port (by any
+process on the host), where it is not possible to make a new server on
+that port.
+@end table
+
+@defun set-network-process-option process option value
+This function sets or modifies a network option for network process
+@var{process}. See @code{make-network-process} for details of options
+@var{option} and their corresponding values @var{value}.
+
+The current setting of an option is available via the
+@code{process-contact} function.
+@end defun
+
+@node Network Feature Testing
+@subsection Testing Availability of Network Features
+
+ To test for the availability of a given network feature, use
+@code{featurep} like this:
+
+@example
+(featurep 'make-network-process '(@var{keyword} @var{value}))
+@end example
+
+@noindent
+The result of the first form is @code{t} if it works to specify
+@var{keyword} with value @var{value} in @code{make-network-process}.
+The result of the second form is @code{t} if @var{keyword} is
+supported by @code{make-network-process}. Here are some of the
+@var{keyword}---@var{value} pairs you can test in
+this way.
+
+@table @code
+@item (:nowait t)
+Non-@code{nil} if non-blocking connect is supported.
+@item (:type datagram)
+Non-@code{nil} if datagrams are supported.
+@item (:family local)
+Non-@code{nil} if local (aka ``UNIX domain'') sockets are supported.
+@item (:family ipv6)
+Non-@code{nil} if IPv6 is supported.
+@item (:service t)
+Non-@code{nil} if the system can select the port for a server.
+@end table
+
+ To test for the availability of a given network option, use
+@code{featurep} like this:
+
+@example
+(featurep 'make-network-process '@var{keyword})
+@end example
+
+@noindent
+Here are some of the options you can test in this way.
+
+@table @code
+@item :bindtodevice
+@itemx :broadcast
+@itemx :dontroute
+@itemx :keepalive
+@itemx :linger
+@itemx :oobinline
+@itemx :priority
+@itemx :reuseaddr
+That particular network option is supported by
+@code{make-network-process} and @code{set-network-process-option}.
+@end table
+
+@node Misc Network
+@section Misc Network Facilities
+
+ These additional functions are useful for creating and operating
+on network connections.
+
+@defun network-interface-list
+This function returns a list describing the network interfaces
+of the machine you are using. The value is an alist whose
+elements have the form @code{(@var{name} . @var{address})}.
+@var{address} has the same form as the @var{local-address}
+and @var{remote-address} arguments to @code{make-network-process}.
+@end defun
+
+@defun network-interface-info ifname
+This function returns information about the network interface named
+@var{ifname}. The value is a list of the form
+@code{(@var{addr} @var{bcast} @var{netmask} @var{hwaddr} @var{flags})}.
+
+@table @var
+@item addr
+The internet protocol address.
+@item bcast
+The broadcast address.
+@item netmask
+The network mask.
+@item hwaddr
+The layer 2 address (Ethernet MAC address, for instance).
+@item flags
+The current flags of the interface.
+@end table
+@end defun
+
+@defun format-network-address address &optional omit-port
+This function converts the Lisp representation of a network address to
+a string.
+
+A five-element vector @code{[@var{a} @var{b} @var{c} @var{d} @var{p}]}
+represents an IPv4 address @var{a}.@var{b}.@var{c}.@var{d} and port
+number @var{p}. @code{format-network-address} converts that to the
+string @code{"@var{a}.@var{b}.@var{c}.@var{d}:@var{p}"}.
+
+A nine-element vector @code{[@var{a} @var{b} @var{c} @var{d} @var{e}
+@var{f} @var{g} @var{h} @var{p}]} represents an IPv6 address and port
+number. @code{format-network-address} converts that to the string
+@code{"[@var{a}:@var{b}:@var{c}:@var{d}:@var{e}:@var{f}:@var{g}:@var{h}]:@var{p}"}.
+
+If the vector does not include the port number, @var{p}, or if
+@var{omit-port} is non-@code{nil}, the result does not include the
+@code{:@var{p}} suffix.
+@end defun
+
+@node Byte Packing
+@section Packing and Unpacking Byte Arrays
+
+ This section describes how to pack and unpack arrays of bytes,
+usually for binary network protocols. These functions convert byte arrays
+to alists, and vice versa. The byte array can be represented as a
+unibyte string or as a vector of integers, while the alist associates
+symbols either with fixed-size objects or with recursive sub-alists.
+
+@cindex serializing
+@cindex deserializing
+@cindex packing
+@cindex unpacking
+ Conversion from byte arrays to nested alists is also known as
+@dfn{deserializing} or @dfn{unpacking}, while going in the opposite
+direction is also known as @dfn{serializing} or @dfn{packing}.
+
+@menu
+* Bindat Spec:: Describing data layout.
+* Bindat Functions:: Doing the unpacking and packing.
+* Bindat Examples:: Samples of what bindat.el can do for you!
+@end menu
+
+@node Bindat Spec
+@subsection Describing Data Layout
+
+ To control unpacking and packing, you write a @dfn{data layout
+specification}, a special nested list describing named and typed
+@dfn{fields}. This specification controls length of each field to be
+processed, and how to pack or unpack it.
+
+@cindex endianness
+@cindex big endian
+@cindex little endian
+@cindex network byte ordering
+ A field's @dfn{type} describes the size (in bytes) of the object
+that the field represents and, in the case of multibyte fields, how
+the bytes are ordered within the field. The two possible orderings
+are ``big endian'' (also known as ``network byte ordering'') and
+``little endian''. For instance, the number @code{#x23cd} (decimal
+9165) in big endian would be the two bytes @code{#x23} @code{#xcd};
+and in little endian, @code{#xcd} @code{#x23}. Here are the possible
+type values:
+
+@table @code
+@item u8
+@itemx byte
+Unsigned byte, with length 1.
+
+@item u16
+@itemx word
+@itemx short
+Unsigned integer in network byte order, with length 2.
+
+@item u24
+Unsigned integer in network byte order, with length 3.
+
+@item u32
+@itemx dword
+@itemx long
+Unsigned integer in network byte order, with length 4.
+Note: These values may be limited by Emacs' integer implementation limits.
+
+@item u16r
+@itemx u24r
+@itemx u32r
+Unsigned integer in little endian order, with length 2, 3 and 4, respectively.
+
+@item str @var{len}
+String of length @var{len}.
+
+@item strz @var{len}
+Zero-terminated string of length @var{len}.
+
+@item vec @var{len}
+Vector of @var{len} bytes.
+
+@item ip
+Four-byte vector representing an Internet address. For example:
+@code{[127 0 0 1]} for localhost.
+
+@item bits @var{len}
+List of set bits in @var{len} bytes. The bytes are taken in big
+endian order and the bits are numbered starting with @code{8 *
+@var{len} @minus{} 1} and ending with zero. For example: @code{bits
+2} unpacks @code{#x28} @code{#x1c} to @code{(2 3 4 11 13)} and
+@code{#x1c} @code{#x28} to @code{(3 5 10 11 12)}.
+
+@item (eval @var{form})
+@var{form} is a Lisp expression evaluated at the moment the field is
+unpacked or packed. The result of the evaluation should be one of the
+above-listed type specifications.
+@end table
+
+A field specification generally has the form @code{([@var{name}]
+@var{handler})}. The square braces indicate that @var{name} is
+optional. (Don't use names that are symbols meaningful as type
+specifications (above) or handler specifications (below), since that
+would be ambiguous.) @var{name} can be a symbol or the expression
+@code{(eval @var{form})}, in which case @var{form} should evaluate to
+a symbol.
+
+@var{handler} describes how to unpack or pack the field and can be one
+of the following:
+
+@table @code
+@item @var{type}
+Unpack/pack this field according to the type specification @var{type}.
+
+@item eval @var{form}
+Evaluate @var{form}, a Lisp expression, for side-effect only. If the
+field name is specified, the value is bound to that field name.
+@var{form} can access and update these dynamically bound variables:
+
+@table @code
+@item raw-data
+The data as a byte array.
+
+@item pos
+Current position of the unpacking or packing operation.
+
+@item struct
+Alist.
+
+@item last
+Value of the last field processed.
+@end table
+
+@item fill @var{len}
+Skip @var{len} bytes. In packing, this leaves them unchanged,
+which normally means they remain zero. In unpacking, this means
+they are ignored.
+
+@item align @var{len}
+Skip to the next multiple of @var{len} bytes.
+
+@item struct @var{spec-name}
+Process @var{spec-name} as a sub-specification. This describes a
+structure nested within another structure.
+
+@item union @var{form} (@var{tag} @var{spec})@dots{}
+@c ??? I don't see how one would actually use this.
+@c ??? what kind of expression would be useful for @var{form}?
+Evaluate @var{form}, a Lisp expression, find the first @var{tag}
+that matches it, and process its associated data layout specification
+@var{spec}. Matching can occur in one of three ways:
+
+@itemize
+@item
+If a @var{tag} has the form @code{(eval @var{expr})}, evaluate
+@var{expr} with the variable @code{tag} dynamically bound to the value
+of @var{form}. A non-@code{nil} result indicates a match.
+
+@item
+@var{tag} matches if it is @code{equal} to the value of @var{form}.
+
+@item
+@var{tag} matches unconditionally if it is @code{t}.
+@end itemize
+
+@item repeat @var{count} @var{field-spec}@dots{}
+@var{count} may be an integer, or a list of one element naming a
+previous field. For correct operation, each @var{field-spec} must
+include a name.
+@c ??? What does it MEAN?
+@end table
+
+@node Bindat Functions
+@subsection Functions to Unpack and Pack Bytes
+
+ In the following documentation, @var{spec} refers to a data layout
+specification, @code{raw-data} to a byte array, and @var{struct} to an
+alist representing unpacked field data.
+
+@defun bindat-unpack spec raw-data &optional pos
+This function unpacks data from the byte array @code{raw-data}
+according to @var{spec}. Normally this starts unpacking at the
+beginning of the byte array, but if @var{pos} is non-@code{nil}, it
+specifies a zero-based starting position to use instead.
+
+The value is an alist or nested alist in which each element describes
+one unpacked field.
+@end defun
+
+@defun bindat-get-field struct &rest name
+This function selects a field's data from the nested alist
+@var{struct}. Usually @var{struct} was returned by
+@code{bindat-unpack}. If @var{name} corresponds to just one argument,
+that means to extract a top-level field value. Multiple @var{name}
+arguments specify repeated lookup of sub-structures. An integer name
+acts as an array index.
+
+For example, if @var{name} is @code{(a b 2 c)}, that means to find
+field @code{c} in the third element of subfield @code{b} of field
+@code{a}. (This corresponds to @code{struct.a.b[2].c} in C.)
+@end defun
+
+@defun bindat-length spec struct
+@c ??? I don't understand this at all -- rms
+This function returns the length in bytes of @var{struct}, according
+to @var{spec}.
+@end defun
+
+@defun bindat-pack spec struct &optional raw-data pos
+This function returns a byte array packed according to @var{spec} from
+the data in the alist @var{struct}. Normally it creates and fills a
+new byte array starting at the beginning. However, if @var{raw-data}
+is non-@code{nil}, it specifies a pre-allocated string or vector to
+pack into. If @var{pos} is non-@code{nil}, it specifies the starting
+offset for packing into @code{raw-data}.
+
+@c ??? Isn't this a bug? Shouldn't it always be unibyte?
+Note: The result is a multibyte string; use @code{string-make-unibyte}
+on it to make it unibyte if necessary.
+@end defun
+
+@defun bindat-ip-to-string ip
+Convert the Internet address vector @var{ip} to a string in the usual
+dotted notation.
+
+@example
+(bindat-ip-to-string [127 0 0 1])
+ @result{} "127.0.0.1"
+@end example
+@end defun
+
+@node Bindat Examples
+@subsection Examples of Byte Unpacking and Packing
+
+ Here is a complete example of byte unpacking and packing:
+
+@lisp
+(defvar fcookie-index-spec
+ '((:version u32)
+ (:count u32)
+ (:longest u32)
+ (:shortest u32)
+ (:flags u32)
+ (:delim u8)
+ (:ignored fill 3)
+ (:offset repeat (:count)
+ (:foo u32)))
+ "Description of a fortune cookie index file's contents.")
+
+(defun fcookie (cookies &optional index)
+ "Display a random fortune cookie from file COOKIES.
+Optional second arg INDEX specifies the associated index
+filename, which is by default constructed by appending
+\".dat\" to COOKIES. Display cookie text in possibly
+new buffer \"*Fortune Cookie: BASENAME*\" where BASENAME
+is COOKIES without the directory part."
+ (interactive "fCookies file: ")
+ (let* ((info (with-temp-buffer
+ (insert-file-contents-literally
+ (or index (concat cookies ".dat")))
+ (bindat-unpack fcookie-index-spec
+ (buffer-string))))
+ (sel (random (bindat-get-field info :count)))
+ (beg (cdar (bindat-get-field info :offset sel)))
+ (end (or (cdar (bindat-get-field info
+ :offset (1+ sel)))
+ (nth 7 (file-attributes cookies)))))
+ (switch-to-buffer
+ (get-buffer-create
+ (format "*Fortune Cookie: %s*"
+ (file-name-nondirectory cookies))))
+ (erase-buffer)
+ (insert-file-contents-literally
+ cookies nil beg (- end 3))))
+
+(defun fcookie-create-index (cookies &optional index delim)
+ "Scan file COOKIES, and write out its index file.
+Optional second arg INDEX specifies the index filename,
+which is by default constructed by appending \".dat\" to
+COOKIES. Optional third arg DELIM specifies the unibyte
+character which, when found on a line of its own in
+COOKIES, indicates the border between entries."
+ (interactive "fCookies file: ")
+ (setq delim (or delim ?%))
+ (let ((delim-line (format "\n%c\n" delim))
+ (count 0)
+ (max 0)
+ min p q len offsets)
+ (unless (= 3 (string-bytes delim-line))
+ (error "Delimiter cannot be represented in one byte"))
+ (with-temp-buffer
+ (insert-file-contents-literally cookies)
+ (while (and (setq p (point))
+ (search-forward delim-line (point-max) t)
+ (setq len (- (point) 3 p)))
+ (setq count (1+ count)
+ max (max max len)
+ min (min (or min max) len)
+ offsets (cons (1- p) offsets))))
+ (with-temp-buffer
+ (set-buffer-multibyte nil)
+ (insert
+ (string-make-unibyte
+ (bindat-pack
+ fcookie-index-spec
+ `((:version . 2)
+ (:count . ,count)
+ (:longest . ,max)
+ (:shortest . ,min)
+ (:flags . 0)
+ (:delim . ,delim)
+ (:offset . ,(mapcar (lambda (o)
+ (list (cons :foo o)))
+ (nreverse offsets)))))))
+ (let ((coding-system-for-write 'raw-text-unix))
+ (write-file (or index (concat cookies ".dat")))))))
+@end lisp
+
+Following is an example of defining and unpacking a complex structure.
+Consider the following C structures:
+
+@example
+struct header @{
+ unsigned long dest_ip;
+ unsigned long src_ip;
+ unsigned short dest_port;
+ unsigned short src_port;
+@};
+
+struct data @{
+ unsigned char type;
+ unsigned char opcode;
+ unsigned long length; /* In little endian order */
+ unsigned char id[8]; /* null-terminated string */
+ unsigned char data[/* (length + 3) & ~3 */];
+@};
+
+struct packet @{
+ struct header header;
+ unsigned char items;
+ unsigned char filler[3];
+ struct data item[/* items */];
+
+@};
+@end example
+
+The corresponding data layout specification:
+
+@lisp
+(setq header-spec
+ '((dest-ip ip)
+ (src-ip ip)
+ (dest-port u16)
+ (src-port u16)))
+
+(setq data-spec
+ '((type u8)
+ (opcode u8)
+ (length u16r) ;; little endian order
+ (id strz 8)
+ (data vec (length))
+ (align 4)))
+
+(setq packet-spec
+ '((header struct header-spec)
+ (items u8)
+ (fill 3)
+ (item repeat (items)
+ (struct data-spec))))
+@end lisp
+
+A binary data representation:
+
+@lisp
+(setq binary-data
+ [ 192 168 1 100 192 168 1 101 01 28 21 32 2 0 0 0
+ 2 3 5 0 ?A ?B ?C ?D ?E ?F 0 0 1 2 3 4 5 0 0 0
+ 1 4 7 0 ?B ?C ?D ?E ?F ?G 0 0 6 7 8 9 10 11 12 0 ])
+@end lisp
+
+The corresponding decoded structure:
+
+@lisp
+(setq decoded (bindat-unpack packet-spec binary-data))
+ @result{}
+((header
+ (dest-ip . [192 168 1 100])
+ (src-ip . [192 168 1 101])
+ (dest-port . 284)
+ (src-port . 5408))
+ (items . 2)
+ (item ((data . [1 2 3 4 5])
+ (id . "ABCDEF")
+ (length . 5)
+ (opcode . 3)
+ (type . 2))
+ ((data . [6 7 8 9 10 11 12])
+ (id . "BCDEFG")
+ (length . 7)
+ (opcode . 4)
+ (type . 1))))
+@end lisp
+
+Fetching data from this structure:
+
+@lisp
+(bindat-get-field decoded 'item 1 'id)
+ @result{} "BCDEFG"
+@end lisp
+
+@ignore
+ arch-tag: ba9da253-e65f-4e7f-b727-08fba0a1df7a
+@end ignore