python-2.7 - Python 子进程 wait() 在 mavericks 和 Yosemite 上表现不同

Question

我最近升级到了优胜美地。还有一些以前在 Mavericks 上运行的 Python 脚本挂了。我的版本是2.7.8。我创建了一个测试用例:

import subprocess
cat = subprocess.Popen(['top', '-l', '1'],
                            stdout=subprocess.PIPE,
                            )
cat.wait()

在 Maverics 上运行但在 Yosemite 上挂起。当我中断优胜美地时，我看到了以下回溯。

Traceback (most recent call last):
    File "test.py", line 5, in <module>
      cat.wait()
    File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/subprocess.py", line 1376, in wait
      pid, sts = _eintr_retry_call(os.waitpid, self.pid, 0)
    File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/subprocess.py", line 476, in _eintr_retry_call
      return func(*args)
    KeyboardInterrupt

关于我做错了什么的任何提示？

Answer 1

看来您需要调用communicate()。来自Python documentation :

Popen.wait()

Wait for child process to terminate. Set and return returncode attribute.

Warning: This will deadlock when using stdout=PIPE and/or stderr=PIPE and the child process generates enough output to a pipe such that it blocks waiting for the OS pipe buffer to accept more data. Use communicate() to avoid that.