与子流程一起检查流程状态.Python中的Popen

Question

如果我在Python中使用subprocess.Popen调用进程，如下所示:

myproc = subprocess.Popen(...).communicate()

查看其状态的正确方法是什么?不是它向标准输出或标准错误的输出，而是它完成后的退出状态(例如，0表示成功，另一个表示失败)?

Answer 1

returncode确实是答案，但解决方案不需要复杂。

process = subprocess.Popen(...)
stdoutdata, stderrdata = process.communicate()
print process.returncode

Python subprocess文档中的更多信息

Answer 2

进程在完成执行之前没有返回码。因此，如果它还没有完成，你必须决定你想做什么:等待它，或者返回一些"我还没有完成"的指示符。

如果您想等待，请使用communicate，然后检查returncode属性。

如果检查返回码是否设置，如果没有返回None，则使用Popen.poll()。

Popen.poll ()

检查子进程是否终止。设置并返回returncode属性。

(如果进程未终止，poll()返回None)

Answer 3

您可能需要在子流程上调用wait，然后(一旦完成)检查子流程实例的returncode字段中的状态。

我有一个调用东西的小程序，也许它会有帮助…

def singleProcessExecuter(command, ** kwargs):
    assert isinstance(command, list), "Expected 'command' parameter to be a list containing the process/arguments to execute. Got %s of type %s instead" % (command, type(command))
    assert len(command) > 0, "Received empty list of parameters"
    retval = {
            "exitCode": -1,
            "stderr": u"",
            "stdout": u"",
            "execTime": datetime.timedelta(0),
            "command": None,
            "pid": None
            }
    retval["command"] = command
    log.info("::singleProcessExecuter > At %s, executing "%s"" % (datetime.datetime.now(), " ".join(command)))
    #print("::singleProcessExecuter > At %s, executing "%s"" % (datetime.datetime.now(), " ".join(parameter)))
    cwd = kwargs.get("cwd", os.getcwd())
    user = kwargs.get("user", getUid())
    sheel = kwargs.get("shell", False)
    startDatetime = datetime.datetime.now()
    myPopy = subprocess.Popen(command, cwd=cwd, preexec_fn=os.seteuid(getUid(user)), shell=sheel, stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=subprocess.PIPE)
    retval["pid"] = myPopy.pid
    log.debug("::singleProcessExecuter > Command "%s" got pid %s" % (" ".join(command), myPopy.pid))
    try:
        retval["stdout"], retval["stderr"] = myPopy.communicate()
        myPopy.wait()
    except OSError, osErr:
        log.debug("::singleProcessExecuter > Got %s %s in myPopy.communicate() when trying get output of command %s. It is probably a bug (more info: http://bugs.python.org/issue1731717)" % (osErr, type(osErr), command[0]))
    except Exception, e:
        log.warn("::singleProcessExecuter > Got %s %s when trying to get stdout/stderr outputs of %s" % (type(e), e, " ".join(command)))
        log.debug("::singleProcessExecuter > Got %s %s when trying to get stdout/stderr outputs of %s. Showing traceback:n%s" % (type(e), e, " ".join(command), traceback.format_exc()))
        raise
    retval["exitCode"] = myPopy.returncode
    retval["execTime"] = datetime.datetime.now() - startDatetime
    #print(":singleProcessExecuter > This is %s's retval:n%s" % (" ".join(parameter), retval)) 
    return retval

你可以试试:

print "This is the return: %s" % singleProcessExecuter(["ls", "-la"])