Arguments: &key pid wait
This function replaced os-wait, which has the same functionality. This function has a better interface (using keyword rather than optional arguments).
If a process is started by the
run-shell-command
with
the wait keyword
argument to that function nil,
then the process will remain in the system after it completes until
either Lisp exits or Lisp executes
sys:reap-os-subprocess
to inquire about the exit
status. To prevent the system becoming clogged with processes, a
program that spawns a number of processes with :wait nil
must be sure to call
sys:reap-os-subprocess
after
each process finishes.
Exactly what sys:reap-os-subprocess does depends on the status of spawned processes and the keyword arguments. The pid argument controls what processes might be considered on by sys:reap-os-subprocess. If pid is -1 (the default), all processes are considered. If pid is 0, only processes in the same process group (as the executing Lisp image) are considered. If pid is a positive integer, only the process with that process id is considered. In the rest of this description, processes means `processes considered by sys:reap-os-subprocess'. See the Unix system documentation of the waitpid() system call (you can usually see this by typing "man waitpid" at a Unix prompt).
If there are any processes started by
run-shell-command
with
the argument :wait nil which have exited but for which
sys:reap-os-subprocess
has not been run, one of them
is selected by the operating system and its status and process id are
returned in that order as multiple values.
If there are no such processes which have exited but there are
processes which are still running, then the behavior of
sys:reap-os-subprocess
depends on the
wait keyword argument.
If it is t
(the default),
sys:reap-os-subprocess
will wait
(disabling multiprocessing, if necessary) until one of the running
processes exits. Then that process's status and id are returned. If
wait is nil,
sys:reap-os-subprocess
will immediately return two
values: nil and nil if there are no processes to clean up; a status
and a pid if the process with number pid is cleaned up,
nil and the pid argument to
sys:reap-os-subprocess
if processes are still running
and none has yet exited.
If there are no running processes,
sys:reap-os-subprocess
returns immediately with the
values nil, nil.
This function simply calls the Unix system function waitpid with the pid and nohang flags. Its behavior is determined by the behavior of that function.
See os-interface.htm for information on running shell programs.
The documentation is described in introduction.htm and the index is in index.htm.
Copyright (c) 1998-2000, Franz Inc. Berkeley, CA., USA. All rights reserved.
Created 2000.10.5.