# !/usr/bin/env python"""Guess which db package to use to open a db file.""" import osimport structimport sys try:    import dbm    _dbmerror = dbm.errorexcept ImportError:    dbm = None    # just some sort of valid exception which might be raised in the    # dbm test    _dbmerror = IOError def whichdb(filename):    """Guess which db package to use to open a db file.     Return values:     - None if the database file can't be read;    - empty string if the file can be read but can't be recognized    - the module name (e.g. "dbm" or "gdbm") if recognized.     Importing the given module may still fail, and opening the    database using that module may still fail.    """     # Check for dbm first -- this has a .pag and a .dir file    try:        f = open(filename + os.extsep + "pag", "rb")        f.close()        # dbm linked with gdbm on OS/2 doesn't have .dir file        if not (dbm.library == "GNU gdbm" and sys.platform == "os2emx"):            f = open(filename + os.extsep + "dir", "rb")            f.close()        return "dbm"    except IOError:        # some dbm emulations based on Berkeley DB generate a .db file        # some do not, but they should be caught by the dbhash checks        try:            f = open(filename + os.extsep + "db", "rb")            f.close()            # guarantee we can actually open the file using dbm            # kind of overkill, but since we are dealing with emulations            # it seems like a prudent step            if dbm is not None:                d = dbm.open(filename)                d.close()                return "dbm"        except (IOError, _dbmerror):            pass     # Check for dumbdbm next -- this has a .dir and a .dat file    try:        # First check for presence of files        os.stat(filename + os.extsep + "dat")        size = os.stat(filename + os.extsep + "dir").st_size        # dumbdbm files with no keys are empty        if size == 0:            return "dumbdbm"        f = open(filename + os.extsep + "dir", "rb")        try:            if f.read(1) in ("'", '"'):                return "dumbdbm"        finally:            f.close()    except (OSError, IOError):        pass     # See if the file exists, return None if not    try:        f = open(filename, "rb")    except IOError:        return None     # Read the start of the file -- the magic number    s16 = f.read(16)    f.close()    s = s16[0:4]     # Return "" if not at least 4 bytes    if len(s) != 4:        return ""     # Convert to 4-byte int in native byte order -- return "" if impossible    try:        (magic,) = struct.unpack("=l", s)    except struct.error:        return ""     # Check for GNU dbm    if magic == 0x13579ace:        return "gdbm"     # Check for old Berkeley db hash file format v2    if magic in (0x00061561, 0x61150600):        return "bsddb185"     # Later versions of Berkeley db hash file have a 12-byte pad in    # front of the file type    try:        (magic,) = struct.unpack("=l", s16[-4:])    except struct.error:        return ""     # Check for BSD hash    if magic in (0x00061561, 0x61150600):        return "dbhash"     # Unknown    return "" if __name__ == "__main__":    for filename in sys.argv[1:]:        print whichdb(filename) or "UNKNOWN", filename