在并发环境中追加到文件末尾 [英] Appending to the end of a file in a concurrent environment
问题描述
如果同时运行以下多个(示例)程序,则需要采取哪些步骤来确保始终将完整"行正确地始终附加到文件末尾.
What steps need to be taken to ensure that "full" lines are always correctly appended to the end of a file if multiple of the following (example) program are running concurrently.
#!/usr/bin/env python
import random
passwd_text=open("passwd.txt","a+")
u=("jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/sh",
"jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/sh",
"xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/sh")
for i in range(random.randint(1,2)):
print >> passwd_text, random.choice(u)
passwd_text.close()
并且:即使磁盘已满或设置了"ulimit -f",也可以保证在Linux/unix上全部或全部"追加吗?
And: Can an "all or nothing" append be guaranteed (on linux/unix) even if the the disk becomes full, or "ulimit -f" has been set?
(请注意类似的问题:如何附加到文件?)
(Note similar question: How do you append to a file?)
推荐答案
我认为此错误"
I think the discussion of this "bug" in python's normal open
function suggests that you don't get the POSIX atomic guarantee, but you do if you use
with io.open('myfile', 'a') as f:
f.write('stuff')
http://docs.python.org/2/library/io.html#io.open
if 操作系统正确实现了其write sys调用...
if the operating system implements its write sys call correctly...
http://bugs.python.org/issue15723
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