当子进程不退出时，Python 的 subprocess.Popen 对象挂起收集子输出 [英] Python's subprocess.Popen object hangs gathering child output when child process does not exit

问题描述

当进程异常退出或根本不退出时，我仍然希望能够收集到该点之前它可能生成的输出.

When a process exits abnormally or not at all, I still want to be able to gather what output it may have generated up until that point.

此示例代码的明显解决方案是使用 os.kill 杀死子进程，但在我的实际代码中，子进程挂起等待 NFS 并且不响应 SIGKILL.

The obvious solution to this example code is to kill the child process with an os.kill, but in my real code, the child is hung waiting for NFS and does not respond to a SIGKILL.

#!/usr/bin/python
import subprocess
import os
import time
import signal
import sys
child_script = """
#!/bin/bash
i=0
while [ 1 ]; do
    echo "output line $i"
    i=$(expr $i + 1)
    sleep 1
done
"""
childFile = open("/tmp/childProc.sh", 'w')
childFile.write(child_script)
childFile.close()

cmd = ["bash", "/tmp/childProc.sh"]
finish = time.time() + 3
p = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=subprocess.PIPE)
while p.poll() is None:
    time.sleep(0.05)
    if finish < time.time():
        print "timed out and killed child, collecting what output exists so far"
        out, err = p.communicate()
        print "got it"
        sys.exit(0)

在这种情况下，出现有关超时的打印语句，python 脚本永远不会退出或继续.有谁知道我可以如何以不同的方式做到这一点，并且仍然从我的子进程中获得输出

In this case, the print statement about timing out appears and the python script never exits or progresses. Does anybody know how I can do this differently and still get output from my child processe

推荐答案

问题是 bash 在未连接终端时不响应 CTRL-C.切换到 SIGHUP 或 SIGTERM 似乎可以解决问题:

Problem is that bash doesn't answer to CTRL-C when not connected with a terminal. Switching to SIGHUP or SIGTERM seems to do the trick:

cmd = ["bash", 'childProc.sh']
p = subprocess.Popen(cmd, stdout=subprocess.PIPE, 
                          stderr=subprocess.STDOUT, 
                          close_fds=True)
time.sleep(3)
print 'killing pid', p.pid
os.kill(p.pid, signal.SIGTERM)
print "timed out and killed child, collecting what output exists so far"
out  = p.communicate()[0]
print "got it", out

输出:

killing pid 5844
timed out and killed child, collecting what output exists so far
got it output line 0
output line 1
output line 2

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