Autoprocessing the Inbox
When processing from the command line with the EDI Exchange module enabled, the argument you need is "Auto". The directory used to look for new files and the processing options are defined in the setup screens for EDI Exchange. No further arguments are needed.
To setup autoprocess options, go to EDI Exchange 
Autoprocess Setup:
Autoprocess Setup option in EDI Exchange menu
Any options selected for autoprocessing will carry over to the command line.
EDI Exchange Automatic Processing options
Autoprocessing a Single File
To run a single file through the autoprocessor, add the full filename as second argument to your command.
Command to autoprocess a single file.