duration.sh

#!/bin/bash
#
# duration - format a time interval
#
# usage: duration [flags] <seconds>
# or:    . duration ; format_duration [flags] <seconds>
#
# flags:
#        -l: long format ("5 days 1 second")
#        -s: short format ("5:00:00:01")
#        -a: approximate by only printing largest component ("5 days")
#
# dsandler@dsandler.org

# print unless zero
function pz() {
	n="$1"
	suff="$2"
	if [ "$n" -gt 0 ]; then
		echo "$n$suff"
	fi
}

# pluralize word unless zero
function plz() {
	n="$1"
	w="$2"
	suff="$3"
	if [ "$n" -gt 0 ]; then
		if [ "$n" -eq 1 ]; then
			echo "$n $w$suff"
		else
			echo "$n ${w}s$suff"
		fi
	fi
}

function format_duration() {
	while true; do
		if [ -z "$1" -o "$1" = "-h" ]; then
			echo "usage: duration [-l|-s] [-a] <seconds>"
			return -1
		elif [ "$1" = "-l" ]; then
			long=1
			shift
		elif [ "$1" = "-s" ]; then
			short=1
			shift
		elif [ "$1" = "-a" ]; then
			approx=1
			shift
		else
			break
		fi
	done
	d="$1"
	str=""
	#((ms=$d % 1000))
	#((d=$d / 1000))
	((s=$d % 60))
	((d=$d / 60))
	((m=$d % 60))
	if [ "$approx" = "1" -a "$m" -gt 0 ]; then s=0; fi
	((d=$d / 60))
	((h=$d % 24))
	if [ "$approx" = "1" -a "$h" -gt 0 ]; then m=0; fi
	((d=$d / 24))
	if [ "$approx" = "1" -a "$d" -gt 0 ]; then h=0; fi
	
	if [ "$long" = "1" ]; then
		echo "$(plz $d day ' ')$(plz $h hour ' ')$(plz $m minute ' ')$(plz $s second)"
	elif [ "$short" = "1" ]; then
		printf "%s%02d:%02d:%02d\n" "$(pz $d :)" $h $m $s
	else
		echo "$(pz $d d)$(pz $h h)$(pz $m m)$(pz $s s)"
	fi
}

# if running the file directly instead of sourcing, invoke function
if [ "$0" = "$BASH_SOURCE" ]; then
	format_duration "$@"
fi