myfirstscript.sh

# You can follow the steps below (not the only way):
#[x] 1. Using the commands who and cut, extract the list of usernames currently 
#    logged in the system
#[x] 2. To check after a minute, the sleep command can be used: sleep 60
#[x] 3. Get the new list of users logged in after a minute
#[x] 4. For each user in the list;
#[x]     1. check if he is in the second list using if and grep. You can dump the 
#        output of grep to /dev/null when using it in the as a test for the if 
#        statement
#[x]     2. If the user is not in the second list, print that the user has logged out
#[x] 5. For each user in the second list,
#[x]     1. If he is in the first list, print that the user has logged in
#[x] 6. Rename the second list as the first list
#[x] 7. Repeat the process from step 2

# Example: 
#  jcantre5 logged in
#  ramdisk  logged in
#  dugger   logged in
#  ngfinch  logged in
#  yucanyu  logged in
#  ebrody   logged out
#  ybudiya  logged in
#  cdchapm2 logged in

mapfile -t first_list < <(who | cut -d" " -f1)
while true; do
        sleep 60
        mapfile -t secon_list < <(who | cut -d" " -f1)

        for user in ${first_list[*]}; do
                valid=$(echo -e "${secon_list[*]}" | grep -Ec "${user}")
                if [ "$valid" == 1 ]; then
                        echo "${user} logged in"
                else
                        echo "${user} logged out"
                fi
        done

        for user in ${secon_list[*]}; do
                valid=$(echo -e "${first_list[*]}" | grep -Ec "${user}")
                if [ "$valid" == 1 ]; then
                        echo "${user} logged in"
                else
                        echo "${user} logged out"
                fi
        done
        first_list=${secon_list[*]}
done