Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!hplabs!hpfcso!stroyan
From: stroyan@hpfcso.HP.COM (Mike Stroyan)
Newsgroups: comp.sys.hp
Subject: Re: Why can't I detect when the child dies? help.
Message-ID: <7370084@hpfcso.HP.COM>
Date: 18 Feb 90 22:22:42 GMT
References: <240@cmic.UUCP>
Organization: Hewlett-Packard, Fort Collins, CO, USA
Lines: 15

> I'm having a devil of a time with the following scrap of code. It will fork
> the child correctly, do all the I/O fine. It's just that the wait from the
> parent is never statisfied. The child becomes a zombie process, and won't
> go away until the parent is killed. All suggestions greatly appreciated.

The parent in your example has opened the master side of pty, while the
child has opened the slave side of the same pty.  If you have asked for
TIOCTRAP on the pty, then a close on the slave side will block until the
master side handshakes it.  When the child tries to exit, it will attempt
to close the pty on the way out.  Until the parent handshakes the close
the child will not completely exit, and the wait() for the child will
not complete.  Perhaps you could watch for a close operation before doing
a wait() or waitpid() for the corresponding process.

Mike Stroyan, stroyan@hpfcla.hp.com