blkid: blkid_probe_lookup_value() - strange partition types

I need to check filesystem type on a thumb drive in my C++ application. It must be done before mounting a new partition. I also prefer not to call system() function. I tried to use the following test code: #include #include int main() { blkid_probe pr; const char *ptname; const char* devname = "/dev/sdb1"; pr = blkid_new_probe_from_filename(devname); if (!pr) printf("faild to open device\n"); else { blkid_probe_enable_partitions(pr, true); blkid_do_fullprobe(pr); blkid_probe_lookup_value(pr, "PTTYPE", &ptname, NULL); printf("%s partition type detected\n", ptname); blkid_free_probe(pr); } } When I plug in thumb drive with ntfs this piece of code shows that my partions is dos. When I plug in thumb drive with fat or ext4 the code returns strange string but the same for these two filesystems: AWAVI��AUATL�%� . What causes these strange outputs? Maybe there is a better way to check a filesystem? Thank you in advance for any help.