From owner-freebsd-hackers  Sat Aug 28  5:29:22 1999
Delivered-To: freebsd-hackers@freebsd.org
Received: from dorifer.heim3.tu-clausthal.de (dorifer.heim3.tu-clausthal.de [139.174.243.252])
	by hub.freebsd.org (Postfix) with ESMTP id 3BE8F14DB9
	for <freebsd-hackers@FreeBSD.ORG>; Sat, 28 Aug 1999 05:29:16 -0700 (PDT)
	(envelope-from olli@dorifer.heim3.tu-clausthal.de)
Received: (from olli@localhost)
	by dorifer.heim3.tu-clausthal.de (8.8.8/8.8.8) id OAA28773
	for freebsd-hackers@FreeBSD.ORG; Sat, 28 Aug 1999 14:25:51 +0200 (CEST)
	(envelope-from olli)
Date: Sat, 28 Aug 1999 14:25:51 +0200 (CEST)
From: Oliver Fromme <olli@dorifer.heim3.tu-clausthal.de>
Message-Id: <199908281225.OAA28773@dorifer.heim3.tu-clausthal.de>
To: freebsd-hackers@FreeBSD.ORG
Subject: Re: Help with exit status in shell script
Organization: Administration Heim 3
Reply-To: freebsd-hackers@FreeBSD.ORG
MIME-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 8bit
X-Newsreader: TIN [version 1.2 RZTUC(3) PL2]
Sender: owner-freebsd-hackers@FreeBSD.ORG
Precedence: bulk
X-Loop: FreeBSD.ORG

Roger Hardiman wrote in list.freebsd-hackers:
 > There is a bug in the PicoBSD build shell script in and I have no idea
 > how to fix it. As a result, build errors are not caught.
 > It is all to do with Exit Status of programs called from a shell script.
 > Please help.
 > 
 > The code fragment from /usr/src/release/picobsd/build/build is
 >    ./stage1 2>&1 | tee stage1.out
 >     if [ "X$?" != "X0" ] ; then 
 >         echo "^G"
 >         echo "-> ERROR in \"${i}\" script. Aborting the build process."
 >         exit 10
 >     fi
 > 
 > Build calls Stage1. Stage1 will return with an error code in some cases
 > and we want to trap this and halt the Build script.
 > 
 >    ./stage1 2>&1 | tee stage1.out
 >     if [ "X$?" != "X0" ] ; then 
 > 
 > Normally, $? will return the Exit Status of the last executed program.
 > However, due to the pipe through Tee, the Exit Status I get is the
 > exit status of Tee and not the exit status of the Stage1 script.
 > 
 > I still want to output the stage1 script to screen and a log file.
 > How can I do this and preserve the exit status for the Build script.

There are several solutions, but all of them are somewhat
ugly...

One approach would be to use a named pipe, run stage1 in the
background and then wait for it, grabbing its exit status:

   FIFO=/tmp/`basename $0`.$$.fifo
   trap "rm -f $FIFO" 1 2 15
   mkfifo $FIFO
   ./stage1 > $FIFO 2>&1 &
   STAGE1PID=$!
   tee < $FIFO stage1.out
   wait $STAGE1PID
   if [ $? != 0 ]; then
   ...
   rm -f $FIFO

Maybe it's possible to open a new shell descriptor (e.g. 3)
instead of a named pipe, but I haven't tried this.

Another way would be to put the exit code into a temporary
file, like this:

   trap "rm -f stage1.result" 1 2 15
   (
           ./stage1 2>&1
           echo $? > stage1.result
   ) | tee stage1.out
   if [ `cat stage1.result` != 0 ]; then
   ...
   rm -f stage1.result

Regards
   Oliver

-- 
Oliver Fromme, Leibnizstr. 18/61, 38678 Clausthal, Germany
(Info: finger userinfo:olli@dorifer.heim3.tu-clausthal.de)

"In jedem Stück Kohle wartet ein Diamant auf seine Geburt"
                                         (Terry Pratchett)


To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-hackers" in the body of the message