Documentation error

[gborg (Gudrun Olafsdottir)]

In the logstash mutete filter documentation there seems to be an error, or at least it seems like an error to me

      mutate {
        split => ["hostname", "."]
        add_field => { "shortHostname" => "%{hostname[0]}" }
    }

does not work, however this works

      mutate {
        split => ["hostname", "."]
        add_field => { "shortHostname" => "%{hostname][0]}" }
    }

Both the field name and the indexing number need to be in square brackets

Mutate filter plugin | Logstash Reference [7.9] | Elastic

[Badger]

@gborg

it seems like an error to me

Indeed. "%{hostname[0]}" worked up until the 7.0 release, at which point it started to result in an error.