From owner-freebsd-hackers  Mon Sep  1 20:52:33 1997
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To: "Jamil J. Weatherbee" <jamil@counterintelligence.ml.org>
cc: Greg Lehey <grog@lemis.com>, freebsd-hackers@FreeBSD.ORG
Subject: Re: SIGCLD 
In-reply-to: Your message of "Mon, 01 Sep 1997 20:41:37 PDT."
             <Pine.BSF.3.96.970901203511.3844A-100000@counterintelligence.ml.org> 
From: David Greenman <dg@root.com>
Reply-To: dg@root.com
Date: Mon, 01 Sep 1997 20:54:13 -0700
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>what I am asking is if there is any differnce between
>
>  wait3 (&status, 0, (struct rusage *) NULL);
>
>and 
>
>  while (wait3(&status, WNOHANG, (struct rusage *) 0)>0);
>
>which is what stevens uses in his book.

   Yes, there is a difference. SIGCHLD signal delivery isn't reliable, so if
a SIGCHLD is missed, it is possible that more than one process needs to be
reaped. The first form will only reap on child, while the second form reaps
all of them. You want to use the second form.

-DG

David Greenman
Core-team/Principal Architect, The FreeBSD Project