Howto: workaround of close_fds=True and redirect stdout/stderr on windows(Howto:close_fds=True 的解决方法并在 Windows 上重定向 stdout/stderr)
问题描述
我遇到了一个问题:使用 Python 2.7,无法使用创建子进程
subprocess.Popen([.......], close_fds=True, stdout=subprocess.PIPE, ...)
由于限制,在 Windows 上.在我的情况下需要使用 close_fds
,因为我不希望子进程从已经打开的文件文件描述符继承.这是在库中调用的,这意味着我无法控制已打开的文件描述符(N
标志).
这是一个已知错误,已在Python 3.4+
我的问题是:如何在不获取的情况下使用子流程
<块引用>如果重定向 stdin/stdout/stderr,Windows 平台不支持 close_fds
下面回答
Python 3.7+ 默认已修复此问题
这绝对是一个棘手的技巧:答案是在使用 subprocess
模块之前遍历已经打开的文件描述符.
def _hack_windows_subprocess():"""HACK:python 2.7 文件描述符.这个神奇的 hack 修复了 https://bugs.python.org/issue19575通过将 HANDLE_FLAG_INHERIT 添加到所有已打开的文件描述符."""# 见 https://github.com/secdev/scapy/issues/1136进口统计从 ctypes 导入windll,wintypes从 msvcrt 导入 get_osfhandleHANDLE_FLAG_INHERIT = 0x00000001对于范围内的 fd(100):尝试:s = os.fstat(fd)除了:继续如果 stat.S_ISREG(s.st_mode):句柄 = wintypes.HANDLE(get_osfhandle(fd))掩码 = wintypes.DWORD(HANDLE_FLAG_INHERIT)标志 = wintypes.DWORD(0)windll.kernel32.SetHandleInformation(句柄、掩码、标志)
这是一个没有它会崩溃的示例:
导入操作系统,子进程f = open("a.txt", "w")subprocess.Popen([cmd"],stdin=subprocess.PIPE,stdout=subprocess.PIPE,stderr=subprocess.STDOUT)f.close()os.remove(f.name)
<块引用>
Traceback(最近一次调用最后一次):
文件stdin",第 1 行,在模块中
WindowsError: [Error 32] Le processus ne peut pas accÚder aufichier car ce fichier est utilisÚ par un autre processus: 'a.txt'
现在修复:
导入操作系统,子进程f = open("a.txt", "w")_hack_windows_subprocess()subprocess.Popen([cmd"],stdin=subprocess.PIPE,stdout=subprocess.PIPE,stderr=subprocess.STDOUT)f.close()os.remove(f.name)
工作.
希望对我有所帮助
I had a problem: using Python 2.7, it was not possible to create a subprocess using
subprocess.Popen([.......], close_fds=True, stdout=subprocess.PIPE, ...)
On windows, because of limitations. The use of close_fds
was needed in my case, as I did not wanted the subprocess to inherit from already opened files file-descriptor. This was called in a library, which meant I had no control over already opened- file descriptors (N
flag).
This is a known bug, which was fixed on Python 3.4+
The question I had was: How do I use subprocess without getting
close_fds is not supported on Windows platforms if you redirect stdin/stdout/stderr
Answer below
This issue is fixed on Python 3.7+ by default
This is definatly a tricky hack: answer is to iterate through already opened file descriptors, just before using the subprocess
module.
def _hack_windows_subprocess():
"""HACK: python 2.7 file descriptors.
This magic hack fixes https://bugs.python.org/issue19575
by adding HANDLE_FLAG_INHERIT to all already opened file descriptors.
"""
# See https://github.com/secdev/scapy/issues/1136
import stat
from ctypes import windll, wintypes
from msvcrt import get_osfhandle
HANDLE_FLAG_INHERIT = 0x00000001
for fd in range(100):
try:
s = os.fstat(fd)
except:
continue
if stat.S_ISREG(s.st_mode):
handle = wintypes.HANDLE(get_osfhandle(fd))
mask = wintypes.DWORD(HANDLE_FLAG_INHERIT)
flags = wintypes.DWORD(0)
windll.kernel32.SetHandleInformation(handle, mask, flags)
Here is a sample that would crash without it:
import os, subprocess
f = open("a.txt", "w")
subprocess.Popen(["cmd"], stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
f.close()
os.remove(f.name)
Traceback (most recent call last):
File "stdin", line 1, in module
WindowsError: [Error 32] Le processus ne peut pas accÚder au fichier car ce fichier est utilisÚ par un autre processus: 'a.txt'
Now with the fix:
import os, subprocess
f = open("a.txt", "w")
_hack_windows_subprocess()
subprocess.Popen(["cmd"], stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
f.close()
os.remove(f.name)
Works.
Hope i helped
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