#!/bin/bash

echo '___________________________________________'
echo 'Script to convert Uppercase to Lowercase'
echo '___________________________________________'
echo "1.Uppercase to Lowercase"
echo "2.Exit"
echo '___________________________________________'
echo -e "Enter Your Choice \c"
read ch
case "$ch" in
1) echo -e "Enter The Filename \c"
read f1
if [ -f $f1 ]
then
echo "Converting Uppercase to Lowercase"
tr '[A-Z]' '[a-z]' <$f1
else
echo "$f1 File Does't Exists"
fi ;;
2)
exit;;
esac

godarda@gd:~$ bash gd.sh
___________________________________________
Script to convert Uppercase to Lowercase 
___________________________________________
1.Uppercase to Lowercase
2.Exit
___________________________________________
Enter Your Choice 1
Enter The Filename gd.txt
Converting Uppercase to Lowercase
shell scripting is very easy
godarda@gd:~$