gpio-parse

#!/bin/bash

set -e
shopt -s extglob

fail() {
	local line
	for line in "$@"; do
		echo "$line" >&2
	done
	exit 1
}

usage() {
	fail "Usage: gpio-parse [OPT] [--] GPIOS..." \
		"where OPT is one of:" \
		"  -k | --kernel        kernel gpio number (default)" \
		"  -p | --path          sysfs path" \
		"  -h | --human         formatted identifier"
}

output=kernel
case "$1" in
	--kernel | -k )	output=kernel	; shift ;;
	--path | -p )	output=path	; shift ;;
	--human | -h )	output=human	; shift ;;
esac

if [[ $1 == -- ]]; then
	shift
fi

for arg in "$@"; do
	arg="${arg##@(?(*/)gpio|GPIO)?([ _-])}"
	if [[ "$arg" == [0-9][_.]@(?([0-2])[0-9]|3[01]) ]]; then
		arg=$(( ${arg##*[_.]*(0)} + 32 * ${arg%%[_.]*} ))
	elif [[ "$arg" == +([0-9]) ]]; then
		arg=$(( ${arg##*(0)} + 0 ))
	else
		fail "Can't parse as gpio: '$arg'"
	fi
	case $output in
		kernel	) echo $arg ;;
		path	) echo "/sys/class/gpio/gpio$arg" ;;
		human	) printf '%d.%02d\n' $(( arg / 32 )) $(( arg % 32 )) ;;
	esac
done