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From: madd@bucsb.bu.edu.UUCP (Jim "Jack" Frost)
Newsgroups: comp.unix.wizards
Subject: Re: Zombies ???
Message-ID: <648@bucsb.bu.edu.UUCP>
Date: Tue, 9-Dec-86 18:24:05 EST
Article-I.D.: bucsb.648
Posted: Tue Dec  9 18:24:05 1986
Date-Received: Wed, 10-Dec-86 04:45:34 EST
References: <1327@brl-adm.ARPA>
Reply-To: madd@bucsb.bu.edu.UUCP (Jim "Jack" Frost)
Organization: ODO (Organization for the Disorganization of Organization)
Lines: 41
Keywords: pipes
Mood: Wet and bedraggled.


In article <1327@brl-adm.ARPA> larry@MITRE.arpa (Larry Henry) writes:
>
>	Does anyone out there have a clear understanding of exactly what
>	situations create zombie processes ??

One of the ways you can do it is not to close pipes when opening them
from within a process with popen().  If you repeatedly open a pipe
using the same variable and either omit the pclose() or use a
fclose(), this should cause zombies.  Killing the parent kills all of
them, BTW.

Example:

-- cut here --
#include <stdio.h>

main()
{ FILE *p,*popen();

  for (;;) {
    if ((p=popen("ps","r"))!=NULL) {
      /* do something with the data */
      fclose(p); /* <- omit this statement for same effect */
    }
    sleep(5);
  }
}
-- cut here --

Anyway, this should cause a new zombie every 5 seconds or so until the
parent is killed.

I'm sure there are others, but this one can be pretty nasty.  I found
it while playing with a daemon I was writing.
-- 
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                   - Jim Frost * The Madd Hacker -
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