yes or no dialog in bash

.sh .bash

read -p "Are you sure (y/n)? " -r
# $REPLY is where 'read' store user input by default
if [[ ! $REPLY =~ ^[Yy](es)*$ ]]; then
    echo "Bye!"; exit 1;
fi

## loop-based variant:
while true; do
    read -p "Do you want to start y/n? " yn
    case $yn in
        [Yy]* ) break;;
        [Nn]* ) exit;;
        * ) echo "Please answer yes or no.";;
    esac
done