Bash script to generate an email when security updates are pending on Ubuntu

security-update-notifier.sh

#!/bin/bash

# Grab the pending updates like 4;2
updates=$(/usr/lib/update-notifier/apt-check 2>&1)

# If there are no pending updates, exit now
if [ $updates == "0;0" ]
then
        exit
fi

# Get the number of security updates (after the colon)
security=$(echo "$updates" | cut -d ";" -f 2)
regular=$(echo "$updates" | cut -d ";" -f 1)

if [ $security != "0" ]
then
        # Generate some output which will be piped to cron
        summary=$(/usr/lib/update-notifier/apt-check --human-readable)
        middle=$'\n\n'"Packages pending upgrade:"$'\n'
        details=$((/usr/lib/update-notifier/apt-check --package-names) 2>&1)
        message="$summary$middle$details"
        echo "$message" | mail -s "$(hostname -s) $security security updates ($regular updates)" $(whoami)
fi