Tcl_DetachPids(3) Tcl Tcl_DetachPids(3)
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NAME
Tcl_DetachPids, Tcl_ReapDetachedProcs - manage child
processes in background
SYNOPSIS
#include <tcl.h>
Tcl_DetachPids(numPids, pidPtr)
Tcl_ReapDetachedProcs()
ARGUMENTS
int numPids (in) Number of process ids contained
in the array pointed to by
pidPtr.
int *pidPtr (in) Address of array containing
numPids process ids.
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DESCRIPTION
Tcl_DetachPids and Tcl_ReapDetachedProcs provide a mechanism
for managing subprocesses that are running in background.
These procedures are needed because the parent of a process
must eventually invoke the waitpid kernel call (or one of a
few other similar kernel calls) to wait for the child to
exit. Until the parent waits for the child, the child's
state cannot be completely reclaimed by the system. If a
parent continually creates children and doesn't wait on
them, the system's process table will eventually overflow,
even if all the children have exited.
Tcl_DetachPids may be called to ask Tcl to take
responsibility for one or more processes whose process ids
are contained in the pidPtr array passed as argument. The
caller presumably has started these processes running in
background and doesn't want to have to deal with them again.
Tcl_ReapDetachedProcs invokes the waitpid kernel call on
each of the background processes so that its state can be
cleaned up if it has exited. If the process hasn't exited
yet, Tcl_ReapDetachedProcs doesn't wait for it to exit; it
will check again the next time it is invoked. Tcl
automatically calls Tcl_ReapDetachedProcs each time the exec
command is executed, so in most cases it isn't necessary for
any code outside of Tcl to invoke Tcl_ReapDetachedProcs.
However, if you call Tcl_DetachPids in situations where the
exec command may never get executed, you may wish to call
Tcl_ReapDetachedProcs from time to time so that background
Page 1 (printed 2/19/99)
Tcl_DetachPids(3) Tcl Tcl_DetachPids(3)
processes can be cleaned up.
KEYWORDS
background, child, detach, process, wait
Page 2 (printed 2/19/99)
