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From: smb@ulysses.att.com (Steven Bellovin)
Newsgroups: comp.unix.wizards
Subject: Re: How can a parent find out if one of its children is still alive
Message-ID: <13071@ulysses.att.com>
Date: 6 Jun 90 19:22:28 GMT
References: <30408@cup.portal.com> <6334@ozdaltx.UUCP> <1046@gargoyle.uchicago.edu>
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In article <1046@gargoyle.uchicago.edu>, matt@group-w.uchicago.edu (Matt Crawford) writes:
} ) DeadHead@cup.portal.com (Bruce M Ong) writes:
} ) > 	How can a parent find out if one of its children is still alive
} ) > or not without
} 
} Tom Armistead, wizard-wannabe, answers:
} ) i.e.:   if( kill( child_pid, 0 ) == -1 )
} )             puts( "The child is dead" );
} 
} overlooking the possibility that the child exited many minutes ago and
} the pid is now being used by some unrelated process.

You can look at errno to determine if the kill() failed because of
a uid mismatch.  That will yield a lot of info if root isn't doing
the checking.