Bash Yes/Now prompt implementation with default answer

prompt_yn.sh

prompt_yn() {
  def=$2

  # Normalize default answer and prompt
  case $def in
    [yY]) def="y"; read -r -p "${1} [Y/n] " input;;
    [nN]) def="n"; read -r -p "${1} [y/N] " input;;
  esac

  # Echo 1 if yes else 0
  case $input in
    "")
      if [ $def = "y" ]; then
	echo 1
      else
	echo 0
      fi
    ;;
    [yY][eE][sS]|[yY]) echo 1;;
    [nN][oO]|[nN]|*) echo 0;;
  esac
}