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# portalocker.py - Cross-platform (posix/nt) API for flock-style file locking.
# Requires python 1.5.2 or better.
# See http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/65203/index_txt
# Except where otherwise noted, recipes in the Python Cookbook are
# published under the Python license.
"""Cross-platform (posix/nt) API for flock-style file locking.
Synopsis:
import portalocker
file = open("somefile", "r+")
portalocker.lock(file, portalocker.LOCK_EX)
file.seek(12)
file.write("foo")
file.close()
If you know what you're doing, you may choose to
portalocker.unlock(file)
before closing the file, but why?
Methods:
lock( file, flags )
unlock( file )
Constants:
LOCK_EX
LOCK_SH
LOCK_NB
I learned the win32 technique for locking files from sample code
provided by John Nielsen <nielsenjf@my-deja.com> in the documentation
that accompanies the win32 modules.
Author: Jonathan Feinberg <jdf@pobox.com>
Version: $Id: portalocker.py,v 1.3 2001/05/29 18:47:55 Administrator Exp $
"""
import os
if os.name == 'nt':
import win32con
import win32file
import pywintypes
LOCK_EX = win32con.LOCKFILE_EXCLUSIVE_LOCK
LOCK_SH = 0 # the default
LOCK_NB = win32con.LOCKFILE_FAIL_IMMEDIATELY
# is there any reason not to reuse the following structure?
__overlapped = pywintypes.OVERLAPPED()
elif os.name == 'posix':
import fcntl
LOCK_EX = fcntl.LOCK_EX
LOCK_SH = fcntl.LOCK_SH
LOCK_NB = fcntl.LOCK_NB
else:
raise RuntimeError("PortaLocker only defined for nt and posix platforms")
if os.name == 'nt':
def lock(file, flags):
hfile = win32file._get_osfhandle(file.fileno())
win32file.LockFileEx(hfile, flags, 0, -0x10000, __overlapped)
def unlock(file):
hfile = win32file._get_osfhandle(file.fileno())
win32file.UnlockFileEx(hfile, 0, -0x10000, __overlapped)
elif os.name =='posix':
def lock(file, flags):
fcntl.flock(file.fileno(), flags)
def unlock(file):
fcntl.flock(file.fileno(), fcntl.LOCK_UN)
if __name__ == '__main__':
from time import time, strftime, localtime
import sys
import portalocker
log = open('log.txt', "a+")
portalocker.lock(log, portalocker.LOCK_EX)
timestamp = strftime("%m/%d/%Y %H:%M:%S\n", localtime(time()))
log.write( timestamp )
print "Wrote lines. Hit enter to release lock."
dummy = sys.stdin.readline()
log.close()