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:
You can't use read behind a chain of pipes because commands behind pipes will be in a seperate subshell.
When your pipe chain's wider than the screen it's time to rethink what you're doing, anyway. What's the exact output from last and what's the output you want from your program?
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