Determines the type of a file using "magic numbers" and various other
heuristics.

 PERMSSN    UID  GID    PACKED    SIZE  RATIO     CRC       STAMP          NAME
---------- ----------- ------- ------- ------ ---------- ------------ -------------
-rw-rw-r-- 20025/200     87504  348160  25.1% -lh5- 0f16 Mar 30  1998 file-3.20-src.tar
---------- ----------- ------- ------- ------ ---------- ------------ -------------
 Total         1 file    87504  348160  25.1%            Mar 16  1998