fcntl-example-1.py

# coding=UTF-8
import fcntl
import os, time
FILE = "counter.txt"
if not os.path.exists(FILE):
    # create the counter file if it doesn't exist
# 创建 counter 文件
    file = open(FILE, "w")
    file.write("0")
    file.close()
for i in range(20):
    # increment the counter
    file = open(FILE, "r+")

    fcntl.flock(file.fileno(), fcntl.LOCK_EX)
    counter = int(file.readline()) + 1
    file.seek(0)
    file.write(str(counter))
    file.close() # unlocks the file
    print os.getpid(), "=>", counter
    time.sleep(0.1)