#!/bin/bash

parse_dates () {
	while read url file junk; do
		url=$(echo $url | sed -e "s/'//g")
		url_time=$(date -d "$(curl -sqI ${url} | grep Last-Modified: | sed -e 's/Last-Modified: //')" +%s)
		if [ ! -f "/var/lib/apt/lists/${file}" ]; then
			return 0
		fi
		file_time=$(stat -c %Y /var/lib/apt/lists/${file})
		if [ $url_time -gt $file_time ]; then
			return 0
		fi
	done
	return 1
}

su nobody -c 'apt-get update -s --print-uris' | grep 'Release ' | parse_dates
exit $?