shell confirmation/yes-no prompt

confirm.sh

# From http://stackoverflow.com/a/3232082
confirm () {
    # call with a prompt string or use a default
    read -r -p "${1:-Are you sure? [y/N]} " response
    case $response in
        [yY][eE][sS]|[yY])
            true;;
        *)
            false;;
    esac
}