Detects HTTP code of a server and mail a warning message if none of the expected HTTP codes are found

mail-no-httpcode.sh

#!/usr/bin/env bash
# Placed in a different machine than production with a cron

# Server
URL="https://example.com"
HTTP=$(curl --silent --insecure -m 30 -I GET "${URL}"|perl -lane 'if ($_=~/HTTP/) {$_=~/HTTP\S+\s+(\d+)\s+/; print $1;} ')
# Normal situation codes
CODES=(200)

MSG="Something is wrong with ${URL}. CODE: ${HTTP}"
SUBJECT="Server seems down: ${URL}"
TO="mail@example.com"
FROM="mail@example.com"

if [[ ! " ${CODES[@]} " =~ " ${HTTP} " ]]; then
        echo "${MSG}" | mail -s "${SUBJECT}" ${TO} -aFrom:${FROM}\>
fi