Sample System Monitor Shell Script -Menu Based

#!/bin/bash
# sys_monitor.sh
# Sample system monitor script using menu
# Tested under Fedora 9
#
# Create the following menu and clear the screen each time it appears
#

clear
echo -e "\033[1m `uname -or` Monitor script\033[0m"
items="       1.Date
       2.Current Users
       3.Disk Statistics
       4.Memory Statistics
       5.Top 10 Memory consuming process
       6.Top 10 CPU consuming process
       7.Exit"

exit_function()
{
   clear
   exit
}

#function enter is used to go  back to menu and clear screen

enter()
{
   ans=
   echo ""
   echo -e  "Do you want to continue(y/n):\c"
   stty -icanon min 0 time 0
# When -icanon is set then one character has been received.
# min 0 means that read should read 0 characters.
# time 0 ensures that read is terminated the moment one character is hit.

while [ -z "$ans" ]
do
   read ans
done
#The while loop ensures that so long as at least one character is not received
# "read" continue to get executed

if [ "$ans" = "y" -o "$ans" = "Y" ]
then
   stty sane          # Restoring terminal settings
   clear
else
   stty sane
   exit_function
fi
}

choice=
h10="head -10"
while true
do
   echo -e "\n\t    PROGRAM MENU \n"
   echo -e "$items \n"
   echo -n "Enter your choice :"
read choice
case $choice in
   1) clear; echo -e "\n\n\t\t Today's Date \n"
   date +"       %d-%h-%Y        Time %T"; enter;;
   2) clear; echo -e "\n\n\t\t Currently Logged In Users\n"
   who; enter;;
   3) clear; echo -e "\n\n\t\t Disk Statistics\n"
   df -h | grep "%"
   enter;;
   4) clear; echo -e "\n\n\t\t Memory Statistics\n "
   free -m | awk 'BEGIN{printf "\t\tTotal\tUsed\tFree\n\n"; OFS="\t" }\
/Mem/||/Swap/{printf "\t"; print $1,$2,$3,$4}'
  enter;;
   5) clear
   k3sort="sort -nr -k 3"
   echo -e "\033[1m PID   PPID  MEM  CPU COMMAND \033[0m "
   ps -Ao pid= -o ppid= -o pmem= -o pcpu= -o comm=|$k3sort|$h10
   enter;;
   6) clear
   k4sort="sort -nr -k 4"
   echo -e "\033[1m PID   PPID  MEM  CPU COMMAND \033[0m"
   ps -Ao pid= -o ppid= -o pmem= -o pcpu= -o comm=|$k4sort|$h10
   enter;;
   7)exit_function  ;;
   *)echo -e "You entered wrong option \n Please enter 1,2,3,4,5,6 or 7\n"
   echo " Press enter to continue"
   read
   clear
esac
done

Output:

2.6.25-14.fc9.i686 GNU/Linux Monitor script
           PROGRAM MENU

      1.Date
      2.Current Users
      3.Disk Statistics
      4.Memory Statistics  
      5.Top 10 memory cosuming process
      6.Top 10 CPU consuming process
      7.Exit

Enter your choice :5
PID   PPID  MEM  CPU COMMAND 
3122  3102  9.2  2.6 firefox
2765  2540  1.9  0.0 nautilus
3849     1  1.7  1.0 ktorrent
2882     1  1.6  0.0 tomboy
2810     1  1.6  0.0 /usr/bin/sealer
4041     1  1.4  0.1 gnome-terminal
2394  2393  1.4  1.8 Xorg
2759  2540  1.2  0.0 gnome-panel
2876     1  0.9  0.0 clock-applet
2870     1  0.9  0.0 mixer_applet2

Do you want to continue(y/n):