Check for security updates on an Ubuntu server and send email notifications via Sendgrid

check-security-updates.sh

#!/bin/bash

# Script to send an email notification via Sendgrid when there are security updates pending for an Ubuntu server.

# Sendgrid API reference 
#      https://sendgrid.com/docs/API_Reference/Web_API_v3/Mail/index.html

# Bash Guide on if-statements 
#      https://tldp.org/LDP/Bash-Beginners-Guide/html/sect_07_01.html

# Ask Ubuntu: How to get a list of security updates
#     https://askubuntu.com/questions/774805/how-to-get-a-list-of-all-pending-security-updates



##### Change the following lines

sendgrid_api_key="Your Sendgrid API key"
hostname=`hostname`
from="[email protected]"
to="[email protected]"
subject="Security updates available"

#####


updates=`apt-get upgrade -s | grep "Inst.*-security" | wc -l`
if [ $updates -ne "0" ]
  then
    mailmsg=`cat <<EOM
{
  "personalizations": [
    {
      "to": [
        {
          "email": "$to"
        }
      ],
      "subject": "$subject"
    }
  ],
  "from": {
    "email": "$from"
  },
  "content": [
    {
      "type": "text/plain",
      "value": "There are $updates pending security updates on $hostname."
    }
  ]
}
EOM`

curl -X "POST" "https://api.sendgrid.com/v3/mail/send" -H "Authorization: Bearer $sendgrid_api_key" \
-H "Content-Type: application/json" -d "$mailmsg"
fi