argument-parser.sh

#!/bin/bash

# Define the regex for matching the arguments
regexArgShort='^-([a-zA-Z0-9])$'
regexArgShortChained='^-([a-zA-Z0-9]{2,})$'
regexArgLong='^--([a-zA-Z0-9\-]{2,})$'
regexArgLongWithValue='^--([a-zA-Z0-9\-]{2,})=(.*)$'

argChunks=()

# Expand chained short form arguments, eg -aih => -a -i -h
for argChunk in "$@"; do

	# See if this argument is a chained short form argument
	[[ $argChunk =~ $regexArgShortChained ]]
	if [ "${BASH_REMATCH[1]}" != "" ]; then

		# Get the chunk or arguments
		chainedChunk="${BASH_REMATCH[1]}";

		[ $ARG_DEBUG == true ] && echo "Expanding chained argument chunk: $chainedChunk"

		i=0
		# Expand out the chunk into individual arguments
		while (( i++ < ${#chainedChunk} )); do

			# Get just the argument on its own
			argumentIsolated="${chainedChunk:$i-1:1}"

			# Add the isolated argument to the argument chunk array
			argChunks+=("-$argumentIsolated")
		done
		continue;
	fi

	# Add the argument to the argument array
	argChunks+=("$argChunk")
done

[ "$ARG_DEBUG" == true ] && echo "Expanded argument list: ${argChunks[@]}"

# Initialise some variables
declare -A argv
lastWasArgument=0
lastArgument=""

declare -A argExpected

argGetName() {
	for k in "${!argExpected[@]}"
	do
		regexArg="\|($1)\|"
		[[ "|$k|" =~ $regexArg ]]
		if [ "${BASH_REMATCH[1]}" != "" ]; then

			regexArgName="(.+) - "
			[[ "${argExpected[$k]}" =~ $regexArgName ]]

			echo "${BASH_REMATCH[1]}"
			exit 0
		fi
	done

	# Check if the argument must be defined
	if [ "$ARG_MUST_BE_DEFINED" != false ]; then
		argUnexpected "$argChunk"
		exit 2
	fi

	# Default to using the argument as the name
	echo "$1"

	exit 1
}

argUnexpected() {
	echo "UNEXPECTED ARGUMENT $1"
}

argExists() {
	if [ -z ${argv["$1"]+abc} ]; then
		return 1
	else
		return 0
	fi
}

argValue() {
	if argExists "$1"; then
		echo "${argv["$1"]}"
	fi
}

argParse() {
	# Loop over all the argument chunks and determine if the argument type and value
	for argChunk in "${argChunks[@]}"; do

		# Check if this chunk is a short form argument
		[[ $argChunk =~ $regexArgShort ]]
		if [ "${BASH_REMATCH[1]}" != "" ]; then
			argument="${BASH_REMATCH[1]}"
			lastWasArgument=1
			lastArgument="$argument"

			# Get the name of the argument
			argName="$(argGetName "$argument")"

			# Check we could get an argument, return code 2 means an error was returned
			if [ "$?" == "2" ]; then
				echo "$argName"
				exit 1
			fi

			# Add the argument to the arguments array
			argv["$argName"]=''

			[ "$ARG_DEBUG" == true ] && echo "Argument (short): ${BASH_REMATCH[1]}"

			continue;
		fi

		# Check if this chunk is a long form with value argument
		[[ $argChunk =~ $regexArgLongWithValue ]]
		if [ "${BASH_REMATCH[1]}" != "" ]; then
			argument="${BASH_REMATCH[1]}"
			lastArgument="$argument"

			# Get the name of the argument
			argName="$(argGetName "$argument")"

			# Check we could get an argument, return code 2 means an error was returned
			if [ "$?" == "2" ]; then
				echo "$argName"
				exit 1
			fi

			# Add the argument to the arguments array
			argv["$argName"]="${BASH_REMATCH[2]}"

			[ "$ARG_DEBUG" == true ] && echo "Argument (long with value): ${BASH_REMATCH[1]}=${BASH_REMATCH[2]}"

			continue;
		fi

		# Check if this chunk is a long form argument
		[[ $argChunk =~ $regexArgLong ]]
		if [ "${BASH_REMATCH[1]}" != "" ]; then
			argument="${BASH_REMATCH[1]}"
			lastWasArgument=1
			lastArgument="$argument"

			# Get the name of the argument
			argName="$(argGetName "$argument")"

			# Check we could get an argument, return code 2 means an error was returned
			if [ "$?" == "2" ]; then
				echo "$argName"
				exit 1
			fi

			# Add the argument to the arguments array
			argv["$argName"]=''

			[ "$ARG_DEBUG" == true ] && echo "Argument (long): ${BASH_REMATCH[1]}"

			continue;
		fi

		# If the last chunk was an argument and this wasn't assume its an argument value
		if [ $lastWasArgument == 1 ]; then

			# Get the name of the argument
			argName="$(argGetName "$lastArgument")"

			# Check we could get an argument, return code 2 means an error was returned
			if [ "$?" == "2" ]; then
				echo "$argName"
				exit 1
			fi

			# Add the arguments value to the arguments array
			argv["$argName"]="$argChunk"

			[ "$ARG_DEBUG" == true ] && echo "Argument Value: $argChunk"

			lastWasArgument=0
		fi
	done

	[ "$ARG_DEBUG" == true ] && echo "Argument array:"
	[ "$ARG_DEBUG" == true ] && for k in "${!argv[@]}"
	do
		echo "ARG: $k = ${argv[$k]}"
	done

	# Add the standard argc variable containing the number of arguments
	argc=${#argv[@]}

	[ "$ARG_DEBUG" == true ] && echo "Argument Count: $argc"
}

# If we are accessing this script directly run the argument parser, useful for testing
if [ "$0" == "$BASH_SOURCE" ]; then
	argParse
fi