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[英]How to automatically get returncode from Popen after terminating child process?
[英]returncode of Popen object is None after the process is terminated
我正在使用Popen
运行一个进程。 我需要等待进程终止。 我正在检查进程是否已通过returncode
终止。 当returncode
与None
,进程必须终止。 问题是当print_output
为False
, returncode
始终为None
,即使进程已完成运行(终止)也是如此。 但是,当print_output
为True
时,情况并非如此。 我正在使用以下代码来运行该过程:
def run(command, print_output=True):
# code mostly from: http://sharats.me/the-ever-useful-and-neat-subprocess-module.html
from subprocess import Popen, PIPE
from threading import Thread
from queue import Queue, Empty
from time import sleep
io_q = Queue()
def stream_watcher(identifier, stream):
for line in stream:
io_q.put((identifier, line))
if not stream.closed:
stream.close()
with Popen(command, stdout=PIPE, stderr=PIPE, universal_newlines=True) as proc:
if print_output:
Thread(target=stream_watcher, name='stdout-watcher', args=('STDOUT', proc.stdout)).start()
Thread(target=stream_watcher, name='stderr-watcher', args=('STDERR', proc.stderr)).start()
def printer():
while True:
try:
# Block for 1 second.
item = io_q.get(True, 1)
except Empty:
# No output in either streams for a second. Are we done?
if proc.poll() is not None:
break
else:
identifier, line = item
print(identifier + ':', line, end='')
Thread(target=printer, name='printer').start()
while proc.returncode is None:
sleep(2)
proc.poll()
if not proc.returncode == 0:
raise RuntimeError(
'The process call "{}" returned with code {}. The return code is not 0, thus an error '
'occurred.'.format(list(command), proc.returncode))
return proc.stdout, proc.stderr
什么可能导致这个问题的线索?
编辑:发现了一些非常奇怪的东西。 我正在运行以下代码:
run(my_command, True)
print('--------done--------')
run(my_command, False)
print('--------done--------')
即使run(my_command, False)
也不会打印'--------done--------'
。
在popen.wait()
之后添加popen.wait()
subprocess.Popen()
Python过快,子进程结束但无法读取返回码
(我真的不知道它为什么这样做。欢迎解释)
shell命令的执行,并同时获得返回代码和输出(stdout)
def exec_cmd(cmd):
pop = subprocess.Popen(shlex.split(cmd), stderr=subprocess.STDOUT, stdout=subprocess.PIPE)
pop.wait()
return [pop.returncode, pop.communicate()[0]]
另外:请阅读popen页面上的.wait
警告
我不确定它为什么不起作用,但我认为它与不关闭流有关。 以下代码有效:
def run(command, print_output=True):
from subprocess import Popen, PIPE, STDOUT
from io import StringIO
popen = Popen(command, stdout=PIPE, stderr=STDOUT, universal_newlines=True)
out = StringIO()
for line in popen.stdout:
if print_output:
print(line, end='')
else:
out.write(line)
popen.stdout.close()
return_code = popen.wait()
if not return_code == 0:
raise RuntimeError(
'The process call "{}" returned with code {}. The return code is not 0, thus an error '
'occurred.'.format(list(command), return_code))
stdout_string = out.getvalue()
out.close()
return stdout_string
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