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Date: Sat, 20 Jul 2002 10:47:36 +0100
From: Stephen Shirley <diamond@skynet.ie>
To: Irish Linux Users Group <ilug@linux.ie>
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Subject: [ILUG] vanquishing the daemons of shell scripting
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Mornin' all,
	Last night, i was involved in an epic struggle to write a shell
script to do a certain task. The battle raged for hours, but, i'm glad
to inform you, i emerged victorious. The problem was as follows:
	It's very easy to get one program to act on the output of a second
program: cmd1 | cmd2. But, what if you want cmd1 to act on the output of
cmd2 as well? Hmm. Eventually, I came up with this solution:

	mkfifo io
	cmd1 <io | cmd2 > io
	
and bingo, all was well with the world. Now, I have (and had) a sneaking
suspcion that it might be possible to do this without using a fifo, and
can be done using something like:

	exec 3>&1
	cmd1 <&3 | cmd2 >&3
	exec 3>&-

but that doesn't work in that form, and i couldn't work out an
incantation that would. Anyone got any suggestions? Anyway, victory is
mine, and i is happy person once again. In case you were wondering, the
aim of all of this was to write a shell script that could check for new
mail on an imap server.

Steve
-- 
"Oh look, it's the Pigeon of Love."

-- 
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