Pattern matching filebeat to logstash

I wanted to know if it is possible to pattern match the path of the files coming in from file beat in log stash? I am trying to extract the path but it did not work.

I tried something like this

input {
beats {
port => 5044
}
}

filter {
grok {
match => {
"path" => "%{GREEDYDATA}%{SYSTEM:system}_%{LOG:log}%{GREEDYDATA}"
}
}
}

SYSTEM is not a built-in pattern. What does the field look like and which parts of it do you want to extract?