recognizing a file by scanning it

[Stephen J. Turnbull]

Thien-Thi Nguyen writes:

 > But before continuing, i would like to discover if anyone else is
 > working on something similar, to avoid (more?) duplicate effort.

file(1) contains a rather complete set of such heuristics and has been
stable for a long time.  AFAIK libmagic is free and GPL-compatible.

Also, it might be nice if you could call this facility from coding
systems (after all, what else is a BOM but file magic?)  This kind of
thing really doesn't need to be in Lisp, and might benefit from being
in C.