Re: manually pipe processes

[Greg Wooledge]

On Thu, Mar 05, 2009 at 12:28:00PM -0500, Brian J. Murrell wrote:

> tar cf - /etc | tar xf - | tee /tmp/outfile

> I want (specifically) the second
> tar command to run in the background and I want to wait for it so that
> the "trap" in the parent shell can process signals.  Altogether I want:

> #!/bin/bash
> trap 'echo got HUP' HUP
> (tar cf - /etc | tar xf - | tee /tmp/outfile) &
> wait ${pid_of_second_tar}

Something like this, perhaps?

trap ...
fifo=/tmp/fifo.$$   # or mktemp(1) or tempfile(1) etc.
mkfifo $fifo
tee /tmp/outfile < $fifo & teepid=$!
{ tar cf - /etc | tar xf - >$fifo 2>&1 ; } & tarpid=$!
wait $tarpid

That might be a little more heavy-handed than you were looking for,
but since you're already hitting /tmp it shouldn't be terrible to add
a FIFO there.