From mboxrd@z Thu Jan  1 00:00:00 1970
From: wkt@tuhs.org (Warren Toomey)
Date: Thu, 10 Jul 2014 14:52:23 +1000
Subject: [TUHS] Excise process from a pipe
In-Reply-To: <201407100249.s6A2nMh3017869@coolidge.cs.dartmouth.edu>
References: <201407100249.s6A2nMh3017869@coolidge.cs.dartmouth.edu>
Message-ID: <20140710045223.GA19076@www.oztivo.net>

On Wed, Jul 09, 2014 at 10:49:22PM -0400, Doug McIlroy wrote:
> It's easy for a process to insert a new process into a
> pipeline either upstream or downstream. Was there ever a 
> flavor of Unix in which a process could excise itself
> from a pipeline without breaking the pipeline?

If in the middle of a pipeline, all I can think of is:

	close fd 0 and fd 1
	dup() read end of pipe 1 to be stdin (fd 0)
	dup() write end of pipe 2 to be stdout (fd 1)
	exec("/bin/cat")

Cheers, Warren