如何判断通过subprocess.Popen打开的文件是否已经关闭？

Question

我在Python中用以下命令打开文件：

file = os.path.normpath(file_path)
phandler = subprocess.Popen(['open', '-W', file])

我在轮询

is_opened = phandler.poll() == None

来检查这个进程是否已经结束。如果我用cmd+Q来关闭进程，这个方法是有效的。但是，如果我用cmd+w来关闭文件，这个方法就不管用了。有没有什么可靠的方法可以确保文件不再打开？

另外，从phandler那里，我也可以通过phandler.pid获取进程的ID，如果需要的话。

如果没有其他方法可以做到这一点，我可能需要使用像watchdog这样的库，它是iNotify的一个封装。不过，如果能用像psutils这样的库来实现，那就更好了。

Answer 1

你在找的东西是不是像这样：

from __future__ import print_function  # If in Python 2.x, import print function from Python 3.x

import os
import subprocess
import time

import psutil

def get_proc_status(pid):
    """Get the status of the process which has the specified process id."""

    proc_status = None
    try:
        proc_status = psutil.Process(pid).status()
    except psutil.NoSuchProcess as no_proc_exc:
        print(no_proc_exc)
    except psutil.ZombieProcess as zombie_proc_exc:  
        # For Python 3.0+ in Linux (and MacOS?).
        print(zombie_proc_exc)
    return proc_status

def open_file(app, file_path):
    """Open the specified file with the specified app, and wait for the file to be closed. """

    my_file = os.path.normpath(file_path)
    # phandler = subprocess.Popen(['open', '-W', my_file])
    # Must be for Macs. Doesn't work in Windows or Linux.
    phandler = subprocess.Popen([app, my_file])
    pid = phandler.pid

    pstatus = get_proc_status(pid)
    while pstatus is not None and pstatus != "zombie":
        # The allowed set of statuses might differ on your system.
        print("subprocess %s, current process status: %s." % (pid, pstatus))
        time.sleep(1)  # Wait 1 second.
        pstatus = get_proc_status(pid)
        # Get process status to check in 'while' clause at start of next loop iteration.

    if os.name == 'posix' and pstatus == "zombie":   # Handle zombie processes in Linux (and MacOS?).
        print("subprocess %s, near-final process status: %s." % (pid, pstatus))
        phandler.communicate()

    pstatus = get_proc_status(pid)
    print("subprocess %s, final process status: %s.\n" % (pid, pstatus))

open_file(r"Evince\bin\Evince.exe", "fuzzed_file.pdf")
open_file(r"Evince\bin\Evince.exe", "unfuzzed_file.pdf")

根据Python的资料，非阻塞和非僵尸进程以及如何杀死（或避免）使用子进程模块的僵尸进程，看起来在Linux中，调用communicate()是处理“僵尸”进程所需要的（我觉得在MacOS中也是如此）。

（查看StackOverflow的僵尸进程标签信息。）

这会生成类似于以下的输出：

subprocess 6844, current process status: running.
subprocess 6844, current process status: running.
subprocess 6844, current process status: running.
subprocess 6844, current process status: running.
psutil.NoSuchProcess no process found with pid 6844
psutil.NoSuchProcess no process found with pid 6844
subprocess 6844, final process status: None.

subprocess 5460, current process status: running.
subprocess 5460, current process status: running.
subprocess 5460, current process status: running.
subprocess 5460, current process status: running.
subprocess 5460, current process status: running.
subprocess 5460, current process status: running.
psutil.NoSuchProcess no process found with pid 5460
psutil.NoSuchProcess no process found with pid 5460
subprocess 5460, final process status: None.