This command (not to be confused with unglom which you probably should be using instead), takes an event file that has been through the FRIB event builder and breaks it up into event files containing the fragments from each event. Each source Id in the input event file will produce an output file named sid-source-id with the fragments from that source id. These files will be written in the current working directory.
For example, suppose your events are built from sources with ids 1,3,5. In that case you will get files; sid-1, sid-3 and sid-5. Note the lack of an .evt file type/extension.