[英]python - prevent IOError: [Errno 5] Input/output error when running without stdout
I have a script that runs automatically on server through cronjob and it import and run several other scripts. 我有一个脚本通过cronjob在服务器上自动运行,它导入并运行其他几个脚本。
Some of them use prints, which naturally creates IOError: [Errno 5] Input/output error
because the script runs without any SSH / terminal connected, so there's no proper stdout setup. 其中一些使用print,这自然会产生IOError: [Errno 5] Input/output error
因为脚本在没有连接任何SSH /终端的情况下运行,因此没有正确的stdout设置。
There are lots of questions about this subject but I couldn't find anyone that actually solve it, assuming I can't remove the print or change the executed scripts. 关于这个主题有很多问题,但我找不到任何实际解决它的人,假设我无法删除打印或更改执行的脚本。
I tried several things, including: 我尝试了几件事,包括:
class StdOut(object):
def __init__(self):
pass
def write(self, string):
pass
sys.stdout = StdOut()
sys.stderr = StdOut()
and 和
from __future__ import print_function
import __builtin__
def print(*args, **kwargs):
pass
__builtin__.print = print
But none of it works. 但它都不起作用。 I assume it only affect the module itself and not the modules I import / run later. 我认为它只会影响模块本身,而不会影响我以后导入/运行的模块。
So how can I create a stub stdout that will affect all modules in the process? 那么如何创建一个会影响流程中所有模块的存根标准输出? Like I said, I don't want to change the scripts that are executed from the main module, but I can change everything inside the importing module. 就像我说的,我不想更改从主模块执行的脚本,但我可以更改导入模块中的所有内容。 And just to clearify - everything is imported, no new processes are spawned etc. 只是为了清除 - 一切都是进口的,没有新的流程产生等。
Thanks, 谢谢,
Modifying the builtin or changing sys.stdout
should work (except for subprocesses—but you ruled those out) as long as you do it early enough. 修改内置或更改sys.stdout
应该有效(除了子进程 - 但你已经排除了这些),只要你尽早完成。 If not, though, there's a lower level trick that's much easier: 如果没有,那么更低级别的技巧会更容易:
run your python scripts with I/O redirection that discards output: 使用丢弃输出的I / O重定向运行python脚本:
python foo.py >/dev/null 2>&1
(assuming Unix-y scripts, as implied by "cron" in the question) (假设Unix-y脚本,如问题中“cron”所暗示的那样)
or, redirect file descriptors 1 and 2 (same idea as above, but done within your Python startup rather than as part of the cron-invoked command): 或者,重定向文件描述符1和2(与上面相同的想法,但在Python启动时完成,而不是作为cron调用命令的一部分):
import os fd = os.open(os.devnull, os.O_RDWR) # NB: even if stdin is closed, fd >= 0 os.dup2(fd, 1) os.dup2(fd, 2) if fd > 2: os.close(fd)
(this particular bit of code has the side effect of making /dev/null act as stdin, if all descriptors were closed). (如果所有描述符都已关闭,则此特定位代码具有使/ dev / null充当stdin的副作用)。 [ Edit : I started with with open(...)
and then switched to os.open
and did not test the final version. [ 编辑 :我从with open(...)
,然后切换到os.open
并没有测试最终版本。 Fixed now.] 现在修复。]
All that said, a good cron really should have stdout and stderr connected somewhere, and should email the output/error-output to you. 总而言之,一个好的cron确实应该将stdout和stderr连接到某个地方,并且应该将输出/错误输出通过电子邮件发送给您。 Not all cron versions are this nice though. 不是所有的cron版本都很好。
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