syslog-ng Open Source Edition 3.18 - Administration Guide

Example: Referencing values from an earlier message

The following action can be used to log the length of an SSH session (the time difference between a login and a logout message in the context):

<actions>
    <action>
        <message>
            <values>
                <value name="MESSAGE">An SSH session for ${SSH_USERNAME}@1 from ${SSH_CLIENT_ADDRESS}@2 closed. Session lasted from ${DATE}@2 to ${DATE} </value>
            </values>
        </message>
    </action>
</actions>