blkid.py

from _ctypes import POINTER, byref
import ctypes
import os

def get_block_uuid(block_dev):
    """
    This queries blkid to get the uuid for a block device.
    :param block_dev: Name of the block device to query.
    :return: The UUID of the device or None on Error.
    """
    try:
        blkid = ctypes.cdll.LoadLibrary("libblkid.so")
        # extern int blkid_probe_lookup_value(blkid_probe pr, const char *name,
        #                                     const char **data, size_t *len);
        blkid.blkid_new_probe_from_filename.argtypes = [ctypes.c_char_p]
        blkid.blkid_probe_lookup_value.argtypes = [ctypes.c_void_p,
                                                   ctypes.c_char_p,
                                                   POINTER(ctypes.c_char_p),
                                                   POINTER(ctypes.c_ulong)]
    except OSError as err:
        print('get_block_uuid loading libblkid.so failed with error: {}'.format(os.strerror(err.errno)))
        raise err
    if not os.path.exists(block_dev):
        return None
    probe = blkid.blkid_new_probe_from_filename(ctypes.c_char_p(block_dev))
    blkid.blkid_do_probe(probe)
    if probe < 0:
        print('get_block_uuid new_probe_from_filename failed: {}'.format(os.strerror(probe)))
        raise OSError(probe, os.strerror(probe))
    result = blkid.blkid_do_safeprobe(probe)
    print("do_probe: {}".format(result))
    if result != 0:
        print('get_block_uuid do_probe failed with error: {}'.format(os.strerror(result)))
        raise OSError(result, os.strerror(result))
    uuid = ctypes.c_char_p()
    result = blkid.blkid_probe_lookup_value(probe,
                                            ctypes.c_char_p('UUID'.encode('ascii')),
                                            byref(uuid), None)
    if result < 0:
        print('get_block_uuid lookup_value failed with error: {}'.format(os.strerror(result)))
        raise OSError(probe, os.strerror(probe))
    blkid.blkid_free_probe(probe)
    return ctypes.string_at(uuid).decode('ascii')