Lists of possible string encodings are here:

http://developer.apple.com/documentation/CoreFoundation/Reference/CFStringRef/Reference/reference.html#//apple_ref/c/tdef/CFStringBuiltInEncodings

and

http://developer.apple.com/documentation/CoreFoundation/Reference/CFStringRef/Reference/reference.html#//apple_ref/doc/constant_group/External_String_Encodings

So it would be interesting to know what CFStringGetSystemEncoding
returns on your system. Notice the special value
kCFStringEncodingInvalidId, which it might also return.

I think

  printf("Encoding is %x\n", enc);

should do.

I think mac_getscript is fine as it stands: if name is NULL, it tries
CFStringConvertEncodingToIANACharSetName which should perform a lookup
in the Apple database.