🚀 go-pugleaf

This method is better yet: it does not require write access to the
device in order to work.  (It does require read access: I haven't
found any way around that!)  Just be sure that you mark the EXE header
of the program that uses this test to be "longfilename-aware":

    int IsFAT (char chDriveName)
    {
        char szFileSpec[] = "*:123456789";
        HDIR hdir = HDIR_CREATE;
        USHORT usAttribute = FILE_NORMAL;
        USHORT usSearchCount = 1;
        FILEFINDBUF findbuf;
        USHORT cbBuf;
        USHORT usCode;

        szFileSpec[0] = chDriveName;
        usCode = DosFindFirst (szFileSpec, 
            &hdir, usAttribute, &findbuf, (USHORT)sizeof(findbuf),
            &usSearchCount, 0L
            );
        if  (usCode == 0)
            DosFindClose (hdir);

        return usCode == ERROR_FILENAME_EXCED_RANGE;
    }