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Full Discussion: Bourne Shell - Problem with while loop variable scope.
Top Forums Shell Programming and Scripting Bourne Shell - Problem with while loop variable scope. Post 302476428 by DaveRich on Wednesday 1st of December 2010 04:04:27 PM
Old 12-01-2010
Bourne Shell - Problem with while loop variable scope.
Hello

I am having issues with a script I'm working on developing on a Solaris machine.

The script is intended to find out how many times a particular user (by given userid) has logged into the local system for more than one hour today.

Here is my while loop:
Code:
last $user | grep -v 'sshd' | grep -v 'still logged in' | grep "`date | cut -d' ' -f2-4`" | cut -d\( -f2 | cut -d: -f1 | while read numHours
do
        if [ $numHours -gt 0 ]; then
                numLogins=$(( $numLogins + 1 ))
                echo "$user logged in once for more than an hour ($numHours hours)." #DEBUG
        fi
done

I have declared numLogins before the loop, and the problem is after the loop I try and "echo $numLogins" but numLogins always contains 0. Even when my debug line prints out showing that the user has logged in for at least an hour.

I have determined that I believe this is because the while loop (when used in a pipeline) has a seperate variable scope, but I have tried rewriting my loop like:

Code:
while loop=read $line
do
        numHours=`echo $line | grep -v 'sshd' | grep -v 'still logged in' | grep "\`date | cut -d' ' -f2-4`" | cut -d\( -f2 | cut -d: -f1
        if [ $numHours -gt 0 ]; then
                numLogins=$(( $numLogins + 1 ))
                echo "$user logged in once for more than an hour ($numHours hours)." #DEBUG
        fi
done < `last $user`

I also thought it may be with the way I was incrementing my numLogins variable,
I have tried to use:
Code:
(( numLogins++ ))
using expr,
numLogins=`echo $numLogins + 1 | bc`

and a few other methods I can't quite remember.

Any help on this would be extremely appreciated.
Thanks a lot!
Last edited by DaveRich; 12-01-2010 at 05:10 PM..
 

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ZGREP(1)                                                      General Commands Manual                                                     ZGREP(1)

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       Zgrep  invokes  grep  on  compressed  or  gzipped  files.   These  grep  options  will  cause  zgrep  to  terminate  with  an  error  code:
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