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<HTML><HEAD><TITLE>Library Procedures - Tcl_DetachPids manual page</TITLE></HEAD><BODY>
<H3><A NAME="M2">NAME</A></H3>
Tcl_DetachPids, Tcl_ReapDetachedProcs - manage child processes in background
<H3><A NAME="M3">SYNOPSIS</A></H3>
<B>#include &lt;tcl.h&gt;</B><BR>
<B>Tcl_DetachPids</B>(<I>numPids, pidPtr</I>)<BR>
<B>Tcl_ReapDetachedProcs</B>()<BR>
<H3><A NAME="M4">ARGUMENTS</A></H3>
<DL>
<P><DT>int <B>numPids</B> (in)<DD>
Number of process ids contained in the array pointed to by <I>pidPtr</I>.
<P><DT>int <B>*pidPtr</B> (in)<DD>
Address of array containing <I>numPids</I> process ids.
<P></DL>
<H3><A NAME="M5">DESCRIPTION</A></H3>
<B>Tcl_DetachPids</B> and <B>Tcl_ReapDetachedProcs</B> 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 <B>waitpid</B> 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.
<P>
<B>Tcl_DetachPids</B> may be called to ask Tcl to take responsibility
for one or more processes whose process ids are contained in the
<I>pidPtr</I> 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.
<P>
<B>Tcl_ReapDetachedProcs</B> invokes the <B>waitpid</B> 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,
<B>Tcl_ReapDetachedProcs</B> doesn't wait for it to exit;  it will check again
the next time it is invoked.
Tcl automatically calls <B>Tcl_ReapDetachedProcs</B> each time the
<B><A HREF="../TclCmd/exec.htm">exec</A></B> command is executed, so in most cases it isn't necessary
for any code outside of Tcl to invoke <B>Tcl_ReapDetachedProcs</B>.
However, if you call <B>Tcl_DetachPids</B> in situations where the
<B><A HREF="../TclCmd/exec.htm">exec</A></B> command may never get executed, you may wish to call
<B>Tcl_ReapDetachedProcs</B> from time to time so that background
processes can be cleaned up.

<H3><A NAME="M6">KEYWORDS</A></H3>
<A href="../Keywords/B.htm#background">background</A>, <A href="../Keywords/C.htm#child">child</A>, <A href="../Keywords/D.htm#detach">detach</A>, <A href="../Keywords/P.htm#process">process</A>, <A href="../Keywords/W.htm#wait">wait</A>
<HR><PRE>
<A HREF="../copyright.htm">Copyright</A> &#169; 1989-1993 The Regents of the University of California.
<A HREF="../copyright.htm">Copyright</A> &#169; 1994-1996 Sun Microsystems, Inc.
<A HREF="../copyright.htm">Copyright</A> &#169; 1995-1997 Roger E. Critchlow Jr.</PRE>
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