We're doing a lot of things that aren't necessarily just basic SQL statements or commands.
You can run SQL Developer in debug mode to see the SQL we are running.
But I think maybe what you want is to build something out in SQL*Plus, tons of examples out there.
Or, submit an Exchange request for adding Export action as something available in our Command Line Interface.
You are right Got some help to find the command line export using the cart feature in SQL Developer 4.0 Early Adopter 1.
Works just fine. Great feature