elapsed-english

#!/usr/bin/env bash
#
#  Synopsis:
#	Elapsed time since "now", written in english, suitable for scripts.
#  Usage:
#	START_EPOCH=$(date +%s)
#	leave() {
#		echo "good bye, cruel world: $(elapsed-english $START_EPOCH)"
#		exit
#	}
#	echo 'hello world'
#	trap leave EXIT
#	sleep 10
#	exit 0
#  Exit Status:
#	0	duration written
#	1	unexpected error
#

die()
{
	echo "ERROR: $(basename $0): $@" >&1
	exit 1
}
test $# = 1 || die "wrong number of arguments, got $#, expected 1"
EPOCH=$1

if [[ ! ( "$EPOCH" =~ ^[1-9][0-9]{0,9}$ ) ]];  then
	die "unknown epoch: $EPOCH"
fi

exec duration-english $(expr $(date +%s) - $EPOCH)