Question

I m: 从事基本工作:

def startProcess(name, path):
    """
    Starts a process in the background and writes a PID file

    returns integer: pid
    """

    # Check if the process is already running
    status, pid = processStatus(name)

    if status == RUNNING:
        raise AlreadyStartedError(pid)

    # Start process
    process = subprocess.Popen(path +   > /dev/null 2> /dev/null & , shell=True)

    # Write PID file
    pidfilename = os.path.join(PIDPATH, name +  .pid )
    pidfile = open(pidfilename,  w )
    pidfile.write(str(process.pid))
    pidfile.close()

    return process.pid

问题是<代码>处理.pid 是正确的项目设计书。这似乎总是比正确的购买力平价低1。例如,它说,这一过程始于31729年,但ps称其运行时间为31730。每当我打着一把。 I m guessing the PID is the PID of the Current process, not thestart one, and the new process have the next pid which is 1 greater. 如果是这样的话,我只能依靠返回<代码>。段次页次我没有保证它永远是正确的。

为什么登t <代码>process.pid 回到新程序项目数据库,以及我如何能够在一米之后实现行为。

Answer 1

From the documentation at http://docs.python.org/library/subprocess.html:

P open.pid 儿童进程情况。

Note that if you set the shell argument to True, this is the process ID of the spawned shell.

如果shell是假的,那么,正如你所期望的那样,我会这样做。

If you were relying on shell being True for resolving executable paths using the PATH environment variable, you can accomplish the same thing using shutil.which instead, then pass the absolute path to Popen instead. (As an aside, if you are using Python 3.5 or newer, you should be using subprocess.run rather than Popen.

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