getDeltaTime

#!/usr/bin/env bash

if [ "$1" = '--help' ]; then
	exit 1
elif [ "$1" = '--version' ]; then
	exit 1
fi

declare from=
declare result=''
declare format='%-s'
declare fTruncate='false'
while (($# > 0)); do
	case "$1" in
		-f | --from)
			shift
			declare -r from="$1"
			;;
		-t | --to)
			shift
			[ -n "$1" ] && declare -r result="$1"
			;;
		-s | --seconds)
			declare -r format='%-s'
			declare -r fTruncate='false'
			;;
		-m | --milliseconds)
			declare -r format='%-s%0N'
			declare -r fTruncate='true'
			;;
		-n | --nanoseconds)
			declare -r format='%-s%0N'
			declare -r fTruncate='false'
			;;
		# *) ;;
	esac
	shift
done
((eCode=0))
# set -e
if [ -z "$result" ]; then
	result="$(date -u +"$format")"
	((eCode=$?))
	if eval "$fTruncate"; then result="${result:0:-6}"; fi
	# declare -r result
fi
# if [ -n "$from" ]; then result="$(bc -l <<< "$result - $from")"; ((eCode=$?)); fi
if [ -n "$from" ]; then bc -l <<< "$result - $from"; exit; fi
echo -E "$result"
exit $eCode