Like any good programmer, I try to automate the crap out of everything. If you have to do it more than once, I try to write a script for it.

This time I want to show you how you can easily send an e-mail from a BASH script. The idea is that you want the script to send out an email to notify a user that something has happened.

We're going to use the GNU Mail utility here. The basic syntax to send an email is like this:

/usr/bin/mail -s "Subject" someone@example.org 


The trick when using this in a shell script is creating and using the message.txt file correctly.

Let's setup the basis first:

#!/bin/bash
SUBJECT="Automated Security Alert"
TO="alarms@ariejan.net"
MESSAGE="/tmp/message.txt"

/usr/bin/mail -s "$SUBJECT" "$TO" 


All we need to do now is create the message. In this example we're going to notify the receiver that something happened at a certain time. We can use the append (>>) operator to add text to the message file. Afterwards, we must remove the temporary message file, of course. The complete script now becomes:

#!/bin/bash
SUBJECT="Automated Security Alert"
TO="alarms@ariejan.net"
MESSAGE="/tmp/message.txt"

echo "Security breached!" >> $MESSAGE
echo "Time: `date`" >> $MESSAGE

/usr/bin/mail -s "$SUBJECT" "$TO" 


The email will contain the a timestamp from when the mail was sent.

This method is great for letting an administrator now if something happened. Maybe you need to check if your webserver is up and running. This script can an administrator about the issue.

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