Check if file is newer than X minutes

newerthan.sh

#!/bin/sh -eu
usage () { printf "%s file [time-in-minutes]\n" ${0##*/} >&2 ; }
test $# -eq 0 && { usage ; exit 2 ; }
WHAT=$1
test -e $WHAT || { echo "$WHAT not found" >&2 ; exit 2 ; }
MINUTES=${2:-30}

case ${0##*/} in
older*)
	test $(($(date +%s)-$(stat --printf "%Y\n" "$WHAT"))) -gt $(($MINUTES*60))
	;;
newer*)
	test $(($(date +%s)-$(stat --printf "%Y\n" "$WHAT"))) -lt $(($MINUTES*60))
	;;
*)
	usage
	exit 2
	;;
esac