Shell Programming and Scripting

        if [ $file = "temp1" ]; then
            echo "User "$user" has logged out."
        fi
            
        
        if [ $file = "temp2" ]; then
            echo "User "$user" has logged in." 
        fi

#! /bin/sh 

echo "The current users are:" 

who | awk '{print $1}' | sort > temp1 
cp temp1 temp2 
more temp1 

while true 
do 
    who | awk '{print $1}' | sort > temp2 
    cmp -s temp1 temp2 

    case "$?" in 
     
    0) 
        echo "No user has logged in/out in the last 5 seconds." 
        ;; 
     
    1) 
        user=`comm -23 temp1 temp2` 
        file=`grep $user temp1 temp2 | cut -c 1-5` 

        [ $file = "temp1" ] && echo "User "$user" has logged out." 
             
         
        [ $file = "temp2" ] && echo "User "$user" has logged in." 
        ;; 
         
    esac 
    rm temp1 
    mv temp2 temp1 
    sleep 5 

done