Need linux uid in pg-psql

Is there a way to get the linux idsid of a user, even for a remote network connection?

If not, is there a way to capture this somehow when the original connection is made and maybe stuff it in a temp table or something using whatever means (a trigger-like mechanism? ) ? Is there a script/function that gets run whenever a connection is made, something I might have access to, in which I could piggy-back something like this? What I'm talking about is basically grabbing and storing $USER for me to read later on with a stored proc.

I could write a pg-perlu to get this, but I suspect it won't give me the original user when there's a remote connect.

Thanks for any suggestions !