在后台启动另一个进程并用Python捕获输出

Question

在python中，我想启动另一个python脚本作为后台进程，几秒钟后，我需要终止这个派生的进程，并将stdout放入一个变量中。在

我尝试使用subprocess.Popen，我可以作为后台进程生成并在几秒钟后终止。但至少在将stdout重定向到一个变量时，它会被阻塞。在

有人能建议我修一下吗？或者除了subprocess.Popen之外，还有其他模块可以执行此操作吗？在

g_flag = 0
class StartChecking(Thread):
    def __init__(self):
        Thread.__init__(self)
    def run(self):
        global g_flag
        print 'Starting thread'
        proc = subprocess.Popen(["./cmd.py"], stdout=subprocess.PIPE, shell=True)
        pid = proc.pid
        print 'Sniff started ' + str(pid)
        if (pid != 0) and (pid != 1):
            while g_flag == 0:
                sleep(0.1)
            os.kill(pid, signal.SIGTERM)
            print 'Killed ' + str(pid)
        (out, err) = proc.communicate() # Currently its blocking here
        print out


th = StartChecking()
th.start()
#Do something else
sleep(5)
g_flag = 1
th.join()
print 'thread joined'

输出是

^{pr2}$

注意：在ubuntu 16.04中使用Python 2.7.12。在

Answer 1

Here is a good explaination of shell=True

将shell参数设置为true值会导致子进程生成一个中间shell进程，并告诉它运行命令

总是使用=shell=False，但是您的代码在我的linux环境中运行如下，为了简单起见，我使用shell文件作为命令来运行]：

import os,signal
import time
import subprocess
from threading import Thread

g_flag = 0
class StartChecking(Thread):
    def __init__(self):
        Thread.__init__(self)
    def run(self):
        global g_flag
        print 'Starting thread'
        proc = subprocess.Popen(["./a.sh"], stdout=subprocess.PIPE, shell=True)
        pid = proc.pid
        print 'Sniff started ' + str(pid)
        if (pid != 0) and (pid != 1):
            while g_flag == 0:
                time.sleep(0.1)
            os.kill(pid, signal.SIGTERM)
            print 'Killed ' + str(pid)
        (out, err) = proc.communicate() # Currently its blocking here
        print out


th = StartChecking()
th.start()
#Do something else
time.sleep(5)
g_flag = 1
th.join()
print 'thread joined'