Create interactive shell script. Prompt for Yes / No input

Prompt for Yes/No/Cancel input in a Linux shell / bash script

Example:

#!/bin/bash

echo "This script will ask a question.";

while true; do

    read -p "Do you want to continue ?" yn

    case $yn in

        [Yy]* ) break;;

        [Nn]* ) exit;;

        * ) echo "Please answer yes or no.";;

    esac

done

echo "Your answer is 'YES'";