I am trying to implement a login screen to the following code how would i go about doing so. I have try to place the password in a variable using if statements which would usually work but as i have the system in a while loop i think i need to find another method.

#!/bin/bash
#Filename: Assigntest Author: Luke Francis
quit=n
while [ "$quit" = "n" ]
do
  clear
  echo "OPERATOR ADMINISTRATIVE TOOL"
  echo
  echo "1. User Information"
  echo "2. Network Connectivity"
  echo "3. Processes"
  echo "4. System Information"
  echo "5. Hardware Utilization"
  echo "Q. Quit"
  echo
  echo "Which option do you require?"
  read menunumber
case $menunumber in
       1)clear
         echo "USER INFORMATION"
         echo
         echo "1. Registered Users"
         echo "2. Disk Usage"
         echo "3. Last Logins"
         echo "4. Users Currently Logged In"
         echo "5. Total number of users"
         echo "B. Back to Main Menu"
         echo "Q. Quit"
         echo
         echo "Which option do you require?"
         read menunumber2
         case $menunumber2 in
              1)clear
                echo "The users registered on the system are:"
                echo
                awk -F: '{print $1}' /etc/passwd
                echo
                echo "Hit the Enter Key to continue"
                 read junk;;
              2)clear
                echo "Disk Usage is as follows:"
                echo
                du
                echo
                echo "Hit Enter Key to continue"
                read junk;;
              3)clear
                echo "Information on last noted login can be found next to      each username."
                echo
                last
                echo
                echo "Hit Enter Key to continue"
                read junk;;
              4)clear
                echo "Users currently logged in are:"
                echo
                w
                echo
                echo "Hit Enter Key to continue"
                read junk;;
              5)clear
                echo "The total number of users are:"
                echo
                who -q
                echo
                echo "Hit Enter Key to continue"
                read junk;;
              Q|q)clear
                  echo "Are you sure you want to quit? Y/N"
                  read choice1
                  case $choice1 in
                       N|n)clear
                           echo "Hit Enter Key to continue"
                           read junk;;
                       Y|y)quit=y;;
                         *)clear
sleep 1;;
                  esac
                  ;;
         esac
         ;;
       2)clear
         echo "NETWORK CONNECTIVITY"
         echo
         echo "1. NIC Status"
         echo "2. Machine Availability"
         echo "B. Back to Main Menu"
         echo "Q. Quit"
         echo
         echo "Which option do you require?"
         read menunumber4
         case $menunumber4 in
              1)clear
                echo "Information reagrding NIC status can be found below:"
                echo
                /sbin/ifconfig
                echo
                echo "Hit the Enter Key to continue"
                read junk;;
              2)clear
                echo "Available hosts and addresses are shown below:"
                echo
                cat /etc/hosts
                echo
                echo "Hit Enter Key to continue"
                read junk;;
       Q|q)clear
           echo "Are you sure you want to quit? Y/N"
           read choice2
           case $choice2 in
                N|n)clear
                    echo "Hit Enter key to continue"
                    read junk;;
                Y|y)quit=y;;
 *)clear
                sleep 2;;
           esac
           ;;
         esac
          ;;
        3)clear
          echo "PROCESSES"
          echo
          echo "1. Running Processes"
          echo "2. Installed Software"
          echo "B. Back to Main Menu"
          echo "Q. Quit"
          echo
          echo "Which option do you require?"
          read menunumber5
          case $menunumber5 in
               1)clear
                 echo "Current running processes are displayed below"
                 echo
                 ps aux
                 echo
                 echo "Hit Enter key to continue"
                 read junk;;
               2)clear
                 echo "The software currently installed on this host is:"
                 echo
                 rpm -qa
                 echo
                 echo "Hit Enter key to continue"
                 read junk;;
        Q|q)clear
           echo "Are you sure you want to quit? Y/N"
           read choice3
           case $choice3 in
                N|n)clear
                    echo "Hit Enter key to continue"
                    read junk;;
 Y|y)quit=y;;
                  *)clear
                sleep 3;;
           esac
            ;;
         esac
          ;;
        4)clear
          echo "SYSTEM INFORMATION"
          echo
          echo "1. Machine Name"
          echo "2. System Date & Time"
          echo "3. Licensing Information"
          echo "4. Last System Reboot"
          echo "B. Back to Main Menu"
          echo "Q. Quit"
          echo
          echo "Which option do you require?"
          read menunumber6
          case $menunumber6 in
               1)clear
                 echo "The name of the machine is:"
                 uname -m
                 echo
                 echo "Hit Enter key to continue"
                 read junk;;
               2)clear
                 echo "The current date and time is:"
                 echo
                 date
                 echo
                 echo "Hit Enter key to continue"
                 read junk;;
               4)clear
                 echo "The last scheduled system reboot was:"
                 echo
                 who -b
                 echo
echo "Hit Enter Key to continue"
                 read junk;;
               B)read junk;;
               Q|q)clear
                   echo "Are you sure you want to quit? Y/N"
                   read choice4
                   case $choice4 in
                   N|n)clear
                       echo "Hit Enter key to continue"
                       read junk;;
                   Y|y)quit=y;;
                     *)clear
                   sleep 4;;
               esac
             ;;
         esac
         ;;
       5)clear
         echo "HARDWARE UTILISATION"
         echo
         echo "1. Unix Filesystem Usage"
         echo "2. RAM Availability"
         echo "3. Swap Space"
         echo "4. CPU Utility"
         echo "Q. Quit"
         echo
         echo "Which option do you require?"
         read menunumber6
         case $menunumber6 in
              1)clear
                echo "Information regarding usage of the Unix filesystem as requested can be found below:"
                echo
                df -h
                echo
                echo "Hit Enter Key to continue"
                read junk;;
              2)clear
                echo "RAM usage information can be found below:"
echo
                cat /proc/meminfo
                echo
                echo "Hit Enter Key to continue"
                read junk;;
              3)clear
                echo "The amount of free and used Swap space is:"
                echo
                cat /proc/meminfo
                echo
                echo "Hit Enter Key to continue"
                read junk;;
              4)clear
                echo "The first column indicates size of CPU run queue"
                echo
                vmstat
                echo
                echo "Hit Enter Key to continue"
                read junk;;
        esac
        ;;
       Q|q)clear
            echo "Are you sure you want to quit? Y/N"
                   read choice5
                   case $choice5 in
                   N|n)clear
                       echo "Hit Enter key to continue"
                       read junk;;
                   Y|y)quit=y;;
                     *)clear
                   sleep 5;;
              esac
              ;;
  esac
done
clear
echo "Thank you for using the Operator Administrative Tool"