exit status of command in a pipe line - UNIX for Dummies Questions & Answers

topcat8 · #1 (**permalink**) 02-12-2004

Hi,

I am trying to test the exit status of the cleartool lsvtree statement below, but it doesn't seem to be working due to the tail pipe, which it is testing instead. Is there a way around this without adding a tonne of new code?

Code:

   cleartool lsvtree $testlocation/$exe_name | tail -15
   #exit out if not file not in dir
   if [ $? -ne 0 ]; then
          echo "Error: File not in test or application area"
          exit 1
   fi

Thanks
Cath

added code tags for readability --oombera

Optimus_P · #2 (**permalink**) 02-12-2004

unfortunetly not that i have found.

i also hit that wall when i do certin stuff.

Perderabo · #3 (**permalink**) 02-12-2004

This depends on the shell. ksh can smash through that wall by moving the "tail -15" to a co-process. I don't know that cleartool command so I'll use "cat /etc/passwd" for my example:

Code:

#! /usr/bin/ksh
exec 4>&1
tail -5 >&4 |&
exec >&p
cat /etc/passwd
exitcode=$?
exec >&- >&4
wait
echo exitcode = $exitcode
exit 0

Optimus_P · #4 (**permalink**) 02-12-2004

something says i shouldnt have skipped that section on file handles.

here2learn · #5 (**permalink**) 02-04-2006

As usual, very ingenious solution Perderabo.

Would there be any way possible to utilize xargs to facilitate this same requirement?

tmarikle · #6 (**permalink**) 02-04-2006

Quote:

Originally Posted by Perderabo

This depends on the shell. ksh can smash through that wall by moving the "tail -15" to a co-process. I don't know that cleartool command so I'll use "cat /etc/passwd" for my example:

Code:

#! /usr/bin/ksh
exec 4>&1
tail -5 >&4 |&
exec >&p
cat /etc/passwd
exitcode=$?
exec >&- >&4
wait
echo exitcode = $exitcode
exit 0

I use this technique as well however, on occassion, I'll use the following, if I know that I'll be parsing the output anyway:

Code:

set -A ARRAY $(
    somecommand
    print RC=$?
)

for i in ${ARRAY[@]}
do
     case $i in
        RC*) ... ;;
        whateverelse) ... ;;
     esac
done

reborg · #7 (**permalink**) 02-04-2006

Ok, I'm on a PC with no shell access at them moment, and it's not very elegant but this should also work.

Code:

(cat /etc/passwd 2> /dev/null || \
        echo "Error: File not in test or application area" ; \
        exit 1 )| tail -15;

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