Bash script to check if user logged on

[oblong]

As part of an assignment on iteration I need to create a script that will "check every 60 seconds whether a particular user has logged on to the system. The user name is passed into the script as a command line argument".

So far I've got ...

# get username
echo "Enter username"
read username

# see if user is logged on
who | grep $username

# while exit status is false continue to check
while [ $? != 0 ]
do
        sleep 60
done

echo "$username has logged on"

The problem is that if I enter a username that's isn't logged in it still gets past the while statement. I think this is because the sleep command returns a true exit status?

[kaka189]

you are right..... while checks for $? which returns the exit status of the previous command executed...so in second iteration sleep returns 0 and $? becomes 0.
a better solution would be
while [ $(who | grep $username) != 0 ]
do
sleep 60
done
echo "$username logged in"