Question

I have a simple example:

#!/usr/bin/python
import time
import fcntl
file = open("e", "w")
fcntl.lockf(file.fileno(),fcntl.LOCK_EX)
file.write("foo")
file.close()

How to know locked file or not ? ( Not waiting until file is unlocked )

Answer 1

That’s what fcntl.LOCK_NB is for. For example:

import warnings
try:
    fcntl.flock(myfile, fcntl.LOCK_EX|fcntl.LOCK_NB)
except IOError:
    warnings.warn("can't immediately write-lock the file ($!), blocking ...")
    fcntl.flock(myfile, fcntl.LOCK_EX)

From file access.