Bash functions for prompting yes/no question

answerYesNo.sh

# Bash function to prompt terminal user for yes|no
# Author: Oscar Kramer
#
# If interactive shell, prompts user for confirmation considering optional default (Y|N) specified.
# The default is returned if <enter> is typed in lieu of a y|n character. The prompt is appended with
# " [Y|n]:" or " [y|N]:" depending on default provided.
#
# If not interactive, returns answerYes=1, answerNo=0
# Returns boolean
#
# Bash examples: 
# if answerYes "Want to do something dangerous?" N; then
#    doSomethingDangerous
# fi
# if answerNo "Continue running script?" Y; then
#    exit 0
# fi
# 
function answerYes {
   # Check for non-interactive shell?

   echo
   local prompt default
   prompt="[Y/n]"
   default=0
   if [ "$2" == "n" ] || [ "$2" == "N" ]; then
      prompt="[y/N]"
      default=1
   fi
   while true; do
      read -n 1 -p "$1 ${prompt}: " yn
      echo
      if [ -n "$yn" ]; then
         if [ "$yn" == "Y" ] || [ "$yn" == "y" ]; then
            return 0;
         elif [ "$yn" == "N" ] || [ "$yn" == "n" ]; then
            return 1;
         fi
      else
         return $default;
      fi
   done
}

function answerNo {
   if answerYes $1 $2 ; then
      return 1
   fi
   return 0
}

### Example usage ###
if answerYes "Can ya dig it?" Y; then
  echo "You're in the groove, Jackson!"
else
  echo "Don't be a square!"
fi