Check expiry of SSL certificates used in apache with nagios check_http

check_certificates.sh

#!/bin/bash

SSL_CERTIFICATE_WARN_DAYS=7

source /etc/(apache2|httpd)/envvars

for i in `apache2 -S 2>/dev/null | grep "port 443" | awk '{print $4}' | sort | uniq`
do 
  /usr/lib/nagios/plugins/check_http -H $i -C $SSL_CERTIFICATE_WARN_DAYS | xargs echo "$i" | grep -v 'OK -'
done