I have this idea.
I have a variable for the start of someones log in time,
(start=`who am i | cut -c30-34`)
and a variable for the log out time or present time,
(end=`date | cut -c12-16`)
but how do I go about subtracting them to get the total log in time.
I've tried adding a another variable total.
total=$end-$start, but that's just prints out everything in a numeric fashion.(2:30-2:10)
and if I use expr I get an error message saying "expr: non-numeric argument"
Now this seems simple but why won't this work.