clear
c="y"while [ $c = "y" ]
do
echo "Enter any file name: "
read f1
if [ -f $f1 ]
then
    echo "Enter old string"
    read o
    echo "Enter new string to be replace:"
    read n
    replace $o $n <$f1
    echo $o" is replace by "$n
    echo "Do u want to view file? "
    read c
    if [ $c !="y" ] 
    then
        exit
    else
        cat $f1
    fi 
else
    echo "File not exist"
fi
done