Arguments: &optional nowait pid
This function has been replaced with reap-os-subprocess, which has the same functionality. reap-os-subprocess uses keyword arguments and so gives more control over behavior. Except for the changed argument list, the description of this function and reap-os-subprocess are the same.
If a process is started by the
run-shell-command with
the wait keyword argument
nil, then the process
will remain in the system after it completes until either Lisp exits
or Lisp executes sys:os-wait (or equivalently
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:os-wait (or equivalently
reap-os-subprocess)
after each
process finishes.
Exactly what sys:os-wait does depends on the status of spawned processes and the optional arguments. The pid argument controls what processes might be considered on by sys:os-wait. 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:os-wait'. See the Unix documentation of the waitpid() system call.
If there are any processes started by
run-shell-command with
the argument :wait nil which have exited but for which
sys:os-wait 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:os-wait depends on the
nowait arguments. If it is
nil (the
default), sys:os-wait will wait (disabling
multiprocessing, if necessary) until one of the running processes
exits. Then that process's status and id are returned. If
nowait is true, sys:os-wait will
return two values: nil and the
pid
argument to sys:os-wait immediately. (0 as the single
returned value indicates that there are processes running but none to
clean up, in contrast to nil -- no processes running,
none to clean up, and multiple values -- a process was cleaned
up.)
If there are no running processes, sys:os-wait
returns immediately with the values nil,
nil.
This function simply calls the Unix 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.