check_updates.php

#!/usr/bin/php
<?php

$statusfile = "/var/local/nagios-update-check";
$data = array();
$ret = 0;
$updates = exec("/usr/lib/update-notifier/apt-check 2>&1", $data, $ret);
$up = explode(";", $updates);

$maxupdates = 15;

if($ret != 0)
{
        echo "Apt UNKNOWN: apt-check gave return code $ret.\n";
        exit(3);
}

if( $up[0] == 0 )
{
  	if(is_file($statusfile)) unlink($statusfile);
        echo "Apt OK: Nothing to update.\n";
        exit(0);
}

if( $up[0] <= $maxupdates && $up[1] == 0 )
{
		if(is_file($statusfile)) unlink($statusfile);
        echo "Apt OK: $up[0] updates are available.\n";
        exit(0);
}

if( $up[0] > $maxupdates && $up[1] == 0)
{
		if(is_file($statusfile)) {
			if(date_diff(new DateTime("@" . filectime($statusfile)), new DateTime())->d >= 1) {
				echo "Apt WARNING: $up[0] updates are available.\n";
				exit(1);
			}
			else {
				echo "Apt OKish: $up[0] updates are available.\n";
				exit(0);
			}
		}
		else {
			touch($statusfile);
			echo "Apt OKish: $up[0] updates are available.\n";
			exit(0);
		}
}

if( $up[0] != 0 && $up[1] != 0)
{
		if(is_file($statusfile)) {
			if(date_diff(new DateTime("@" . filectime($statusfile)), new DateTime())->d >= 1) {
				echo "Apt CRITICAL: $up[1] security updates are available, $up[0] total.\n";
				exit(2);
			}
			else {
				echo "Apt OKish: $up[1] security updates are available, $up[0] total.\n";
				exit(0);
			}
		}
		else {
			touch($statusfile);
			echo "Apt OKish: $up[1] security updates are available, $up[0] total.\n";
			exit(0);
		}
}

echo "Apt UNKNOWN: unspecified error.\n";
exit(3);