如何在Python中将标准输出重定向到任意文件?

When a long-running Python script (e.g, web application) is started from within the ssh session and backgounded, and the ssh session is closed, the application will raise IOError and fail the moment it tries to write to stdout. I needed to find a way to make the application and modules output to a file rather than stdout to prevent failure due to IOError. Currently, I employ nohup to redirect output to a file, and that gets the job done, but I was wondering if there was a way to do it without using nohup, out of curiosity.

我已经试过了。Stdout = open('somefile', 'w'),但这似乎并没有阻止一些外部模块仍然输出到终端(或者sys. exe)。Stdout =…Line根本没有开火)。我知道它应该在我测试过的更简单的脚本上工作,但我还没有时间在web应用程序上进行测试。


当前回答

其他答案不包括您希望分叉进程共享您的新标准输出的情况。

做那件事:

from os import open, close, dup, O_WRONLY

old = dup(1)
close(1)
open("file", O_WRONLY) # should open on 1

..... do stuff and then restore

close(1)
dup(old) # should dup to 1
close(old) # get rid of left overs

其他回答

如果您想在Python脚本中进行重定向,请设置sys. exe。对文件对象的Stdout是有用的:

# for python3
import sys
with open('file', 'w') as sys.stdout:
    print('test')

一个更常见的方法是在执行时使用shell重定向(在Windows和Linux上相同):

$ python3 foo.py > file
import sys
sys.stdout = open('stdout.txt', 'w')

还有其他使用上下文的版本,但没有这么简单。实际上,我只是在谷歌上仔细检查了一下,并惊讶地没有看到它,所以对于其他人来说,寻找一个快速的解决方案是安全的,只针对上下文块中的代码,这里是:

import sys
with open('test_file', 'w') as sys.stdout:
    print('Testing 1 2 3')

测试如下:

$ cat redirect_stdout.py 导入系统 将open('test_file', 'w')作为sys.stdout: 打印('测试1 2 3') $ python redirect_stdout.py $ cat test_file 测试1 2 3

您需要一个终端多路复用器,比如tmux或GNU屏幕

我很惊讶Ryan Amos对原始问题的一个小评论是唯一一个比其他所有问题都更可取的解决方案,不管蟒蛇的诡计有多聪明,他们得到了多少点赞。根据Ryan的评论,tmux是GNU屏幕的一个很好的替代品。

But the principle is the same: if you ever find yourself wanting to leave a terminal job running while you log-out, head to the cafe for a sandwich, pop to the bathroom, go home (etc) and then later, reconnect to your terminal session from anywhere or any computer as though you'd never been away, terminal multiplexers are the answer. Think of them as VNC or remote desktop for terminal sessions. Anything else is a workaround. As a bonus, when the boss and/or partner comes in and you inadvertently ctrl-w / cmd-w your terminal window instead of your browser window with its dodgy content, you won't have lost the last 18 hours-worth of processing!

我知道这个问题已经得到了回答(使用python abc.py > output.log 2>&1),但我仍然不得不说:

在编写程序时,不要写入标准输出。总是使用日志来输出您想要的任何东西。这在以后你想重定向,过滤,旋转输出文件的时候会给你很大的自由。