Invalid argument with fcntl.fcntl

[Mitko Haralanov]

I am trying to use the advisory locking with fcntl over NFS (thus, me
choosing fcntl instead of flock and friends).

I have the following code:
lockdata = struct.pack ("hhllhh", fcntl.F_RDLCK, 0, 0, 0, 0, 0)
print self.fd, type (self.fd), len (lockdata), type (lockdata)
ret = fcntl.fcntl (self.fd, fcntl.F_GETLK, lockdata)

when this code executes, I always get the following:

<open file 'test.py', mode 'a' at 0xb7e99458> <type 'file'> 16 <type
'str'> Traceback (most recent call last):
  File "<stdin>", line 1, in ?
  File "filelock.py", line 154, in _get_lock_state_nfs
    ret = fcntl.fcntl (self.fd, fcntl.F_GETLK, lockdata)
IOError: [Errno 22] Invalid argument


If I execute the same code in the Python interpreter (replacing self.fd
with an open file object), it work.

Can anyone shed some light on why this code would produce that error?
Thanks

-- 
Mitko Haralanov					 mitko at qlogic.com
Senior Software Engineer			     650.934.8064
System Interconnect Group		    http://www.qlogic.com

==========================================
FORTRAN is a good example of a language which is easier to parse
using ad hoc techniques.
		-- D. Gries
		[What's good about it?  Ed.]