How do you get current Perforce changelist number from an Unreal Engine plugin?

I have a debugging tool that dumps information to a file from an UE plugin about the current application state. Is there a Perforce command-line command or API call that can be used to get the latest changelist number from Perforce. I know the command p4 changes -m1 -s submitted [stream] exists. But, I don’t know how to get the current stream.

Were you able to figure this out?