read_ini.sh

#!/usr/bin/env bash
#
# Copyright (c) 2009    Kevin Porter / Advanced Web Construction Ltd
#                       (http://coding.tinternet.info, http://webutils.co.uk)
# Copyright (c) 2010-2014     Ruediger Meier <sweet_f_a@gmx.de>
#                             (https://github.com/rudimeier/)
#
# License: BSD-3-Clause, see LICENSE file
#
# Simple INI file parser.
#
# See README for usage.
#

function read_ini() {
	# Be strict with the prefix, since it's going to be run through eval
	function check_prefix() {
		if ! [[ ${VARNAME_PREFIX} =~ ^[a-zA-Z_][a-zA-Z0-9_]*$ ]]; then
			echo "read_ini: invalid prefix '${VARNAME_PREFIX}'" >&2
			return 1
		fi
	}

	function check_ini_file() {
		if [ ! -r "$INI_FILE" ]; then
			echo "read_ini: '${INI_FILE}' doesn't exist or not" \
				"readable" >&2
			return 1
		fi
	}

	# enable some optional shell behavior (shopt)
	function pollute_bash() {
		if ! shopt -q extglob; then
			SWITCH_SHOPT="${SWITCH_SHOPT} extglob"
		fi
		if ! shopt -q nocasematch; then
			SWITCH_SHOPT="${SWITCH_SHOPT} nocasematch"
		fi
		# shellcheck disable=SC2086
		shopt -q -s ${SWITCH_SHOPT}
	}

	# unset all local functions and restore shopt settings before returning
	# from read_ini()
	function cleanup_bash() {
		# shellcheck disable=SC2086
		shopt -q -u ${SWITCH_SHOPT}
		unset -f check_prefix check_ini_file pollute_bash cleanup_bash
	}

	local INI_FILE=""
	local INI_SECTION=""

	# {{{ START Deal with command line args

	# Set defaults
	local BOOLEANS=1
	local VARNAME_PREFIX=INI
	local CLEAN_ENV=0

	# {{{ START Options

	# Available options:
	#	--boolean		Whether to recognise special boolean values: ie for 'yes', 'true'
	#					and 'on' return 1; for 'no', 'false' and 'off' return 0. Quoted
	#					values will be left as strings
	#					Default: on
	#
	#	--prefix=STRING	String to begin all returned variables with (followed by '__').
	#					Default: INI
	#
	#	First non-option arg is filename, second is section name

	while [ $# -gt 0 ]; do

		case $1 in

		--clean | -c)
			CLEAN_ENV=1
			;;

		--booleans | -b)
			shift
			BOOLEANS=$1
			;;

		--prefix | -p)
			shift
			VARNAME_PREFIX=$1
			;;

		*)
			if [ -z "$INI_FILE" ]; then
				INI_FILE=$1
			else
				if [ -z "$INI_SECTION" ]; then
					INI_SECTION=$1
				fi
			fi
			;;

		esac

		shift
	done

	if [ -z "$INI_FILE" ] && [ "${CLEAN_ENV}" = 0 ]; then
		echo -e "Usage: read_ini [-c] [-b 0| -b 1]] [-p PREFIX] FILE" \
			"[SECTION]\n  or   read_ini -c [-p PREFIX]" >&2
		cleanup_bash
		return 1
	fi

	if ! check_prefix; then
		cleanup_bash
		return 1
	fi

	local INI_ALL_VARNAME="${VARNAME_PREFIX}__ALL_VARS"
	local INI_ALL_SECTION="${VARNAME_PREFIX}__ALL_SECTIONS"
	local INI_NUMSECTIONS_VARNAME="${VARNAME_PREFIX}__NUMSECTIONS"
	if [ "${CLEAN_ENV}" = 1 ]; then
		eval unset "\$${INI_ALL_VARNAME}"
	fi
	unset "${INI_ALL_VARNAME}"
	unset "${INI_ALL_SECTION}"
	unset "${INI_NUMSECTIONS_VARNAME}"

	if [ -z "$INI_FILE" ]; then
		cleanup_bash
		return 0
	fi

	if ! check_ini_file; then
		cleanup_bash
		return 1
	fi

	# Sanitise BOOLEANS - interpret "0" as 0, anything else as 1
	if [ "$BOOLEANS" != "0" ]; then
		BOOLEANS=1
	fi

	# }}} END Options

	# }}} END Deal with command line args

	local LINE_NUM=0
	local SECTIONS_NUM=0
	local SECTION=""

	# IFS is used in "read" and we want to switch it within the loop
	local IFS=$' \t\n'
	local IFS_OLD="${IFS}"

	# we need some optional shell behavior (shopt) but want to restore
	# current settings before returning
	local SWITCH_SHOPT=""
	pollute_bash

	while read -r line || [ -n "$line" ]; do
		#echo line = "$line"

		((LINE_NUM++))

		# Skip blank lines and comments
		if [ -z "$line" ] || [ "${line:0:1}" = ";" ] || [ "${line:0:1}" = "#" ]; then
			continue
		fi

		# Section marker?
		if [[ ${line} =~ ^\[[a-zA-Z0-9_]{1,}\]$ ]]; then

			# Set SECTION var to name of section (strip [ and ] from section marker)
			SECTION="${line#[}"
			SECTION="${SECTION%]}"
			eval "${INI_ALL_SECTION}=\"\${${INI_ALL_SECTION}# } $SECTION\""
			((SECTIONS_NUM++))

			continue
		fi

		# Are we getting only a specific section? And are we currently in it?
		if [ -n "$INI_SECTION" ]; then
			if [ "$SECTION" != "$INI_SECTION" ]; then
				continue
			fi
		fi

		# Valid var/value line? (check for variable name and then '=')
		if ! [[ ${line} =~ ^[a-zA-Z0-9._]{1,}[[:space:]]*= ]]; then
			echo "Error: Invalid line:" >&2
			echo " ${LINE_NUM}: $line" >&2
			cleanup_bash
			return 1
		fi

		# split line at "=" sign
		IFS="="
		read -r VAR VAL <<<"${line}"
		IFS="${IFS_OLD}"

		# delete spaces around the equal sign (using extglob)
		VAR="${VAR%%+([[:space:]])}"
		VAL="${VAL##+([[:space:]])}"
		# shellcheck disable=SC2116
		VAR=$(echo "$VAR")

		# Construct variable name:
		# ${VARNAME_PREFIX}__$SECTION__$VAR
		# Or if not in a section:
		# ${VARNAME_PREFIX}__$VAR
		# In both cases, full stops ('.') are replaced with underscores ('_')
		if [ -z "$SECTION" ]; then
			VARNAME=${VARNAME_PREFIX}__${VAR//./_}
		else
			VARNAME=${VARNAME_PREFIX}__${SECTION}__${VAR//./_}
		fi
		eval "${INI_ALL_VARNAME}=\"\${${INI_ALL_VARNAME}# } ${VARNAME}\""

		if [[ ${VAL} =~ ^\".*\"$ ]]; then
			# remove existing double quotes
			VAL="${VAL##\"}"
			VAL="${VAL%%\"}"
		elif [[ ${VAL} =~ ^\'.*\'$ ]]; then
			# remove existing single quotes
			VAL="${VAL##\'}"
			VAL="${VAL%%\'}"
		elif [ "$BOOLEANS" = 1 ]; then
			# Value is not enclosed in quotes
			# Booleans processing is switched on, check for special boolean
			# values and convert

			# here we compare case insensitive because
			# "shopt nocasematch"
			case "$VAL" in
			yes | true | on)
				VAL=1
				;;
			no | false | off)
				VAL=0
				;;
			esac
		fi

		# enclose the value in single quotes and escape any
		# single quotes and backslashes that may be in the value
		VAL="${VAL//\\/\\\\}"
		VAL="\$'${VAL//\'/\'}'"

		eval "$VARNAME=$VAL"
	done <"${INI_FILE}"

	# return also the number of parsed sections
	eval "$INI_NUMSECTIONS_VARNAME=$SECTIONS_NUM"

	cleanup_bash
}