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From: maart@cs.vu.nl (Maarten Litmaath)
Newsgroups: comp.unix.questions
Subject: Re: redirecting standard i/o from an exec'ed programme
Message-ID: <7324@star.cs.vu.nl>
Date: 16 Aug 90 18:53:10 GMT
References: <377@fe2o3.UUCP> <410@sun13.scri.fsu.edu>
Sender: news@cs.vu.nl
Reply-To: maart@cs.vu.nl (Maarten Litmaath)
Organization: VU Dept. of Computer Science, Amsterdam, The Netherlands
Lines: 29

In article <410@sun13.scri.fsu.edu>,
	mayne@VSSERV.SCRI.FSU.EDU (William (Bill) Mayne) writes:
)...
)    /* Close unused pipes */
)    close (TOCHILD);
)    close (FROMCHILD);
)    /* Change stdin and stdout to pipe */
)    close(0);
)    dup(FROMPARENT);

     close(FROMPARENT);		/* !!! */

)    close(1);
)    dup(TOPARENT);

     close(TOPARENT);		/* !!! */

I've deleted the rest of the code, but there were still a few other places
where calls to close() should be added.
Always close every unused file descriptor (esp. when dealing with pipes),
else you will get bitten one day; example scenario:

	- the child exits
	- the parent reads from the pipe to the child
	- the parent still has the write side of the pipe open
	- the read hangs...
--
   "UNIX was never designed to keep people from doing stupid things, because
    that policy would also keep them from doing clever things."  (Doug Gwyn)