Shell programming using filters (including grep, egrep, fgrep)

 echo "Main Menu"

echo "Press 1 for using Grep Command"

echo "Press 2 for using Egrep Command"

echo "Press 3 for using Fgrep Command"

read a

case $a in

                1) echo "For single pattern search, Enter Pattern below :"

                   read b

                   grep "$b" City_names.txt

                   ;;

                2) echo "For double Pattern search, Enter b,c pattern :"

                   read b

                   read c

                   egrep "$b" City_names.txt

                   grep -E "$c" City_names.txt

                   ;;

                3) echo "For Pattern From a File, Enter Pattern :"

                   read b

                   grep -F "$b" City_names.txt

                   ;;

esac