file 4.09-1 (i386 binary) in ubuntu warty

Determines file type using "magic" numbers
 File tests each argument in an attempt to classify it. There are three
 sets of tests, performed in this order: filesystem tests, magic number
 tests, and language tests. The first test that succeeds causes the
 file type to be printed.
 .
 Starting with version 4, the file command is not much more than a wrapper
 around the "magic" library.