Is there a method to generate a standard 128bit GUID (UUID) on the Mac?

Question

UUIDs are handled in Core Foundation, by the CFUUID library. The function you are looking for is CFUUIDCreate.

FYI for further searches: these are most commonly known as UUIDs, the term GUID isn't used very often outside of the Microsoft world. You might have more luck with that search term.

At least on MacOSX 10.5.x you might use the command line tool "uuidgen" to get your string e.g.

$ uuidgen

054209C4-3873-4679-8104-3C18AE780512

there's also an option -hdr with this comand that conveniently generates it in header style

See man-page for further infos.

Some code:

For a string UUID, the following class method should do the trick:

+(NSString*)UUIDString {
    CFUUIDRef theUUID = CFUUIDCreate(NULL);
    CFStringRef string = CFUUIDCreateString(NULL, theUUID);
    CFRelease(theUUID);
    return [(NSString *)string autorelease];
}

if you really want the bytes (not the string):

+(CFUUIDBytes)UUIDBytes {
    CFUUIDRef theUUID = CFUUIDCreate(NULL);
    CFUUIDBytes bytes = CFUUIDGetUUIDBytes(theUUID);
    CFRelease(theUUID);
    return bytes;
}

where CFUUIDBytes is a struct of the UUID bytes.

or there's the uuidgen command line tool.