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.
Each of the subprocess-creating functions has a @var{buffer-or-name}
argument which specifies where the standard output from the program will
-go. It should be a buffer or a buffer name (which will create the
-buffer if it does not already exist). It can also be @code{nil}, which
-says to discard the output unless a filter function handles it.
-(@xref{Filter Functions}, and @ref{Read and Print}.) Normally, you
-should avoid having multiple processes send output to the same buffer
-because their output would be intermixed randomly.
+go. It should be a buffer or a buffer name; if it is a buffer name,
+that will create the buffer if it does not already exist. It can also
+be @code{nil}, which says to discard the output unless a filter function
+handles it. (@xref{Filter Functions}, and @ref{Read and Print}.)
+Normally, you should avoid having multiple processes send output to the
+same buffer because their output would be intermixed randomly.
@cindex program arguments
All three of the subprocess-creating functions have a @code{&rest}
@code{default-directory} (@pxref{File Name Expansion}).
@cindex environment variables, subprocesses
- The subprocess inherits its environment from Emacs; but you can
+ The subprocess inherits its environment from Emacs, but you can
specify overrides for it with @code{process-environment}. @xref{System
Environment}.
@defvar exec-directory
@pindex movemail
-The value of this variable is the name of a directory (a string) that
-contains programs that come with GNU Emacs, that are intended for Emacs
+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.
@end defvar
@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 systems.}
+(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.
-@item (@var{real-destination} @var{error-destination})
+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},
and dispose of the error output according to @var{error-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-@sc{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 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 subprocess 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{}
@section Creating an Asynchronous Process
@cindex asynchronous subprocess
- After an @dfn{asynchronous process} is created, Emacs and the Lisp
-program both continue running immediately. The process thereafter runs
+ 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
addition, the total number of @sc{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} is used 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}.
away. If you delete a terminated process explicitly before it is
deleted automatically, no harm results.
-@defvar delete-exited-processes
+@defopt delete-exited-processes
This variable controls automatic deletion of processes that have
terminated (due to calling @code{exit} or to a signal). If it is
@code{nil}, then they continue to exist until the user runs
@code{list-processes}. Otherwise, they are deleted immediately after
they exit.
-@end defvar
+@end defopt
@defun delete-process name
This function deletes the process associated with @var{name}, killing it
@end smallexample
@end defun
-@defun process-kill-without-query process
-This function declares that Emacs need not query the user if
-@var{process} is still running when Emacs is exited. The process will
-be deleted silently. The value is @code{t}.
+@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
@code{coding-system-for-write}, if that is non-@code{nil}; or else from
the defaulting mechanism (@pxref{Default Coding Systems}).
+ 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.
+
@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
@end smallexample
@end defun
-@deffn Command process-send-region process-name start end
+@defun process-send-region process-name 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
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
+@end defun
@defun process-send-eof &optional process-name
This function makes @var{process-name} see an end-of-file in its
@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
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. If the system doesn't support waiting
-fractions of a second, you get an error if you specify nonzero
-@var{millisec}.
+@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
HCoop / bpt / emacs.git / blobdiff