子进程popen实时输出，带超时

Question

经过一些研究，我一直在使用 subprocess.check_output() ，它接受超时参数，并在达到命令超时时引发 TimeoutExpired 。没关系，但限制是我没有得到实时输出，所以我被迫直接使用 Popen，基本上：

def execute_cmd(cmd, timeout=2):
    p = subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
    for line in iter(p.stdout.readline, b''):
        print(line.rstrip().decode("utf-8"))
    p.stdout.close()
    retcode = p.wait()

如何在这段代码中添加超时？

Answer 1

我终于用定时器想出了一个解决方案。不确定这是最好的方法，但它有效。

import os
import signal
import subprocess
import time
from threading import Timer

def execute_bash_cmd(cmd, timeout=5):
    print("cmd: " + cmd)
    def timerout(p):
        print("Command timed out")
        timer.cancel()
        os.killpg(os.getpgid(p.pid), signal.SIGTERM)
        # or use p.kill() if shell==False

    p = subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
    timer = Timer(timeout, timerout, args=[p])
    timer.start()
    for line in iter(p.stdout.readline,b''):
        line = line.rstrip().decode("utf-8")
        print(line)
    p.stdout.close()
    retcode = p.wait()
    timer.cancel()

例子：

execute_bash_cmd('ls -l /')
execute_bash_cmd('sleep 2', 3)
execute_bash_cmd('sleep 4', 3)

输出：

cmd: ls -l /
total 92
drwxr-xr-x   2 root root  4096 Feb 18 15:28 bin
drwxr-xr-x   3 root root  4096 Feb 18 15:16 boot
drwxr-xr-x  20 root root  4020 Feb 18 15:43 dev
drwxr-xr-x 134 root root 12288 Feb 19 22:42 etc
drwxr-xr-x   3 root root  4096 Jun  7  2018 home
drwxr-xr-x   7 root root  4096 Feb 18 15:28 lib
drwxr-xr-x   5 root root  4096 Feb 18 15:28 lib64
drwx------   2 root root 16384 Feb 18 13:12 lost+found
drwxr-xr-x   2 root root  4096 Jun  7  2018 mnt
drwxr-xr-x   3 root root  4096 Feb 18 15:26 opt
dr-xr-xr-x 247 root root     0 Feb 18 15:43 proc
drwx------  10 root root  4096 Feb 19 22:42 root
drwxr-xr-x  37 root root  1060 Feb 19 20:21 run
drwxr-xr-x   2 root root 12288 Feb 18 15:20 sbin
drwxr-xr-x   2 root root  4096 Jun  7  2018 selinux
drwxr-xr-x   5 root root  4096 Feb 18 15:18 srv
dr-xr-xr-x  13 root root     0 Feb 19 22:42 sys
drwxrwxrwt  23 root root  4096 Feb 19 22:37 tmp
drwxr-xr-x  11 root root  4096 Jun  7  2018 usr
drwxr-xr-x  11 root root  4096 Feb 18 14:15 var

cmd: sleep 2

cmd: sleep 4
Command timed out
Terminated