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From: vrm@babcock.cerc.wvu.wvnet.edu (Vasile R. Montan)
Newsgroups: comp.lang.c
Subject: Re: Catching termination of child process and system() call
Message-ID: <1232@babcock.cerc.wvu.wvnet.edu>
Date: 24 Jan 91 19:13:51 GMT
References: <1991Jan24.084230.12153@cai.uucp>
Sender: news@cerc.wvu.wvnet.edu
Distribution: comp.lang.c
Lines: 34

From article <1991Jan24.084230.12153@cai.uucp>, by davel@cai.uucp (David W. Lauderback):
> However, if you are just trying to get rid of left-over child processes
> "zombie processes",
> just use:
> 	signal(SIGCHLD,SIG_IGN);
> instead of:
> 	signal(SIGCHLD, dowait);
> and you need no wait. (see signal(2) or signal(3c) in BSD)
> 
> FYI: The zombie process is storing the child process' exit status, so must
> remain until its parent process has read this information.  SIG_IGN to SIGCHLD
> states this process' child's return value should be discarded.

   I have seen this solution proposed many times, but it doesn't work
for me. I am using a Sun4 SunOS4.1.  I have created the following test
routine.  Maybe someone could tell me if I am doing something wrong or
if it is the operating system.

#include <signal.h>

main()
{
  int i;
  signal(SIGCHLD, SIG_IGN);

  for (i=0; i< 10; i++) {
    if (! fork()) exit (0);
  }
  while (1) {}
}

It generates 10 children, which immediately exit then it waits in an
infinite loop.  When I do a "ps", I see all 10 <defunct> processes
hanging around.