Check ssl certificate expiration

check-ssl-cert-expiry.sh

#!/bin/bash
gracedays=90

# get domain names from a file
# a domain at each line
domain_file="domains.txt"

cat $domain_file | while read -a domains;
do
    server=${domains[0]}

    data=`echo | openssl s_client -connect "${server}:443" -servername "${server}" 2>/dev/null | openssl x509 -noout -enddate | sed -e 's#notAfter=##'`

    ssldate=`date -d "${data}" '+%s'`
    nowdate=`date '+%s'`
    diff="$((${ssldate}-${nowdate}))"

    if test "${diff}" -lt "$((${gracedays}*24*3600))";
    then
        if test "${diff}" -lt "0";
        then
            echo "The certificate for ${server} has already expired."
        else
            echo "The certificate for ${server} will expire in $((${diff}/3600/24)) days."
        fi
    fi
done