Event Handler

Event handler allows you to execute scripts when a string that matches a regex appears in a text stream (e.g. log file).

It uses “feeds” (output of commands, or a named pipes) and “policies” that define what to execute if a regex is matched.

    feed <name>
    description <feed description>
    policy <policy name>
        syslog # Use the syslog logs for feed
        command <command to execute> # E.g. "tail -f /var/log/somelogfile"
        named-pipe <path to a names pipe>
    policy <policy name>
    description <policy description>
    event <event name>
        description <event description>
        pattern <regex>
        run <command to run>

In this small example a script runs every time a login failed and an interface goes down

vyos@vyos# show system event-handler
feed Syslog {
    policy MyPolicy
    source {
        preset syslog
policy MyPolicy {
    description "Test policy"
    event BadThingsHappened {
        pattern "authentication failure"
        pattern "interface \.* index \d+ .* DOWN.*"
        run /config/scripts/email-to-admin