acquire an exclusive lock on an given fd with non-blocking

file_lock_with_nonblocking

import errno
import fcntl

'''
just run this script twice to see different output
'''

'''
`doc string in fcntl.lockf`
When operation is LOCK_SH or LOCK_EX, it can also be bitwise ORed with
    LOCK_NB to avoid blocking on lock acquisition. 
'''

f = open('test.lock','w')
try:
    fcntl.lockf(f,fcntl.LOCK_EX | fcntl.LOCK_NB)
except IOError as e:
    if e.errno in(errno.EACCES, errno.EAGAIN):
        print 'locked by other user'
except Exception as e2:
    print 'get lock failed'
else:
    print 'get lock success'

raw_input()