无法在python中按名称获取进程的PID

Question

我有一段非常简单的代码

import subprocess
print(subprocess.check_output(["pidof","ffmpeg"]))

应该打印名为ffmpeg的进程的PID（参见here）。但是，我总是收到以下错误：

subprocess.CalledProcessError: Command '['pidof', 'ffmpeg']' returned non-zero exit status 1

对于python2和python3。我究竟做错了什么？

Answer 1

来自man pidof：

EXIT STATUS
       0      At least one program was found with the requested name.

       1      No program was found with the requested name.

你没有任何名为ffmpeg的进程。

Answer 2

你可以使用try除了避免阻塞执行

用这个

import subprocess

try:

    print(subprocess.check_output(["pidof","ffmpeg"]))
except subprocess.CalledProcessError:
    print("no process named ffmpeg")

你得到错误，因为如果pidof ffmpeg没有输出并使用print(subprocess.check_output(["pidof","ffmpeg"]))我们期望从该命令输出。

你也可以用

print(subprocess.getoutput("pidof ffmpeg"))

即使该命令的输出是none，也不会出错

如果你检查库方法check_output你可以找到这个

def check_output(*popenargs, timeout=None, **kwargs):
    r"""Run command with arguments and return its output.

    If the exit code was non-zero it raises a CalledProcessError.  The
    CalledProcessError object will have the return code in the returncode
    attribute and output in the output attribute.

    The arguments are the same as for the Popen constructor.... """