Bunch of useful bash functions

answer.sh

# $1 - question
# $2 - possible answers (space separated)
# $3 - optional function to call with the answer
# $4-end - optional parameter to pass to the function
function answer(){
	QUESTION=$1
	POSSIBLE_ANSWERS=$2
	DEFAULT_ANSWER=$(echo $POSSIBLE_ANSWERS | tr ' ' '\n' | grep -oP '.*[A-Z].*' | tr '\n' ' ' | tr -d ' ') # default answer is the one what have capital letter
	FUNCTION=$3
	[[ $# -ge 4 ]] && shift 3 && PARAMETERS=$*
	DEBUG="" # Add value for prefixing debug messages and enable debug mode

	# to lower case and remove spaces from the possible answers
	_POSSIBLE_ANSWERS=$(echo $POSSIBLE_ANSWERS | tr '[:upper:]' '[:lower:]')

	[[ -n $DEBUG ]] && echo "${DEBUG}Question: $QUESTION"
	[[ -n $DEBUG ]] && echo "${DEBUG}Possible answers: $POSSIBLE_ANSWERS"
	[[ -n $DEBUG ]] && echo "${DEBUG}Default answer: $DEFAULT_ANSWER"
	[[ -n $DEBUG ]] && echo "${DEBUG}Function: $FUNCTION"
	[[ -n $DEBUG ]] && echo "${DEBUG}Parameters: $PARAMETERS"


	# Check if the answer is valid if not ask again
	while true; do
		# Ask the question
		printf "$QUESTION [$(echo $POSSIBLE_ANSWERS | tr ' ' '/')]: "
		read ANSWER

		# if empty break
		[[ -z $ANSWER ]] && break

		# to lower case and remove spaces from the answer
		ANSWER=$(echo $ANSWER | tr '[:upper:]' '[:lower:]' | tr -d ' ')
		[[ -n $DEBUG ]] && echo "${DEBUG}Answer: $ANSWER\n"

		# if the answer is in the list of possible answers break
		[[ $_POSSIBLE_ANSWERS =~ $ANSWER ]] && break

		echo -e "Invalid answer\n"
	done

	# If the answer is empty, use the default answer
	[[ -z $ANSWER ]] && ANSWER=$(echo $DEFAULT_ANSWER | tr '[:upper:]' '[:lower:]') && [[ -n $DEBUG ]] && echo "${DEBUG}Answer: $ANSWER"

	# Call the function with the answer as a parameter
	[[ -n $FUNCTION ]] && $FUNCTION $ANSWER $PARAMETERS

	# Return the answer
	if [[ $3 == "return" ]]; then
		echo $ANSWER
	fi

	[[ -n $DEBUG ]] && echo "${DEBUG}Answer: $ANSWER\n"
}