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From: @tree.uucp (Chris Gonnerman)
Newsgroups: comp.unix.internals
Subject: Re: temporary redirection under a Bourne-shell using "exec"
Summary: use a different number
Message-ID: <1990Oct15.211809.9353@tree.uucp>
Date: 15 Oct 90 21:18:09 GMT
References: <977@ign.UUCP> <906@mwtech.UUCP> <3845@awdprime.UUCP>
Organization: TREE BBS (916)349-0385 Sacramento, Ca
Lines: 22

In article <3845@awdprime.UUCP>, jeffe@sandino.austin.ibm.com (Peter Jeffe 512.823.4091) writes:
> In article <906@mwtech.UUCP> martin@mwtech.UUCP (Martin Weitzel) writes:
> ->exec 3<&1 >&-	# open File Descriptor 3 (stdout), and close stdout
> ->echo invisible	# shell stdout is closed, local stdout is FD 3
> ->exec 1<&3 3>&-	# reopen stdout (and close FD 3)
> ->echo hello
> -I would rather change this as follows:
> ->exec 3>&1 >/dev/null

Some shells don't like you using fd 3... in particular, ash and some
implementations of csh (sorry, forget which ones) use fd 3 for reading
the shell script.  Redirecting it causes strange behavior.

I have an application where I do much the same thing, but I
(arbitrarily) chose to use fd 9 instead of 3 (after my program
repeatedly broke).

-- 
 +----------------------------------------------------------------------------+
 | Chris Gonnerman (Mad Programmer At Large)   csusac.ecs.csus.edu!tree!jcg   |
 | @ the Tree BBS, Sacramento, CA              ucbvax!ucdavis!csusac!tree!jcg |
 +----------  DISCLAIMER: These opinions are mine... MINE, I say!  -----------+