Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!apple!vsi1!daver!apt!brian
From: brian@apt.UUCP (Brian Litzinger)
Newsgroups: comp.unix.questions
Subject: Re: spawning a child by double forking
Message-ID: <1668@apt.UUCP>
Date: 5 Jul 89 08:21:42 GMT
References: <12376@bloom-beacon.MIT.EDU> <JEFFL.89Jul4084155@berick.uucp>
Organization: APT Technology, Inc., San Jose, CA
Lines: 32

From article <JEFFL.89Jul4084155@berick.uucp>, by jeffl@berick.uucp (Jeff Lawhorn):
> ]  Thus far, two people have suggested that one way to prevent zombie
> ]processes from building up is to fork twice instead of once when
> ]starting a child -- the child of the first fork forks again and then
> ]immediately exits.  The "grandchild" which results is inherited by
> ]init, which takes care of cleanup, and the parent therefore doesn't
> ]have to worry about cleaning up.
> 
> There is a better way to do this.  Have the parent ignore the
> signal SIGCLD.  My man page for signal states:
> 

It is interesting how these discussions can become circular. 8-)

I believe this discussion originated from my posting regarding
a problem I was having with the creation of zombie processes.

Ignoring SIGCLD is a wonderful solution for people running
System V.  Unfortunately, ignoring SIGCHLD in most BSD systems will
not produce the same result.

Note:  BSD SIGCHLD generally equals System V SIGCLD.

The reasoning behind the double forking is that it is a more portable
solution than ignoring SIGCLD.

The discussion then seemed to move to the effeciency of double forking
and maybe using vfork().

<>  Brian Litzinger @ APT Technology Inc., San Jose, CA
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