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Date: Mon, 1 Sep 1997 20:41:37 -0700 (PDT)
From: "Jamil J. Weatherbee" <jamil@counterintelligence.ml.org>
To: David Greenman <dg@root.com>
cc: Greg Lehey <grog@lemis.com>, freebsd-hackers@FreeBSD.ORG
Subject: Re: SIGCLD 
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So I would be right to assume that the following would work under sysV
without the die routine and signal call in main, and would leave no
zombies, but that the die routine is necessary under BSD if we want to
ignore the children --- 1 question also, will this work correctly with an
arbitrary number of exiting children:

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.

-------------------------------------------------------------------------
#include <stdio.h>
#include <unistd.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/wait.h>

void die (int sig)
{
  int status;
  wait3 (&status, 0, (struct rusage *) NULL);
}

void main (void)
{
  signal (SIGCHLD, die);
  printf ("Parent.\n");
  if (fork())
   {
      printf ("Hanging Parent.\n");
      for (;;);
   }
  printf ("Child Dying.\n");
}
--------------------------------------------------------------------------