Remove DNS suffix from $USER

[pcheng]

Basically I would like $USER to return username instead of username@bla.bla.bla

Some of the macs in my work environment have it set up to do this but the person who did it long ago failed to document the method he used. I'm not sure if I should be changing something more system-wide to remove the suffix, or if there is a place where $USER is defined to return something.

Thanks for your help!