Python os.system without the output

问题:

I'm running this:

os.system("/etc/init.d/apache2 restart")

It restarts the webserver, as it should, and like it would if I had run the command directly from the terminal, it outputs this:

* Restarting web server apache2 ... waiting [ OK ]

However, I don't want it to actually output it in my app. How can I disable it? Thanks!

回答1:

Avoid os.system() by all means, and use subprocess instead:

with open(os.devnull, 'wb') as devnull:
    subprocess.check_call(['/etc/init.d/apache2', 'restart'], stdout=devnull, stderr=subprocess.STDOUT)

This is the subprocess equivalent of the /etc/init.d/apache2 restart &> /dev/null.

There is subprocess.DEVNULL on Python 3.3+:

#!/usr/bin/env python3
from subprocess import DEVNULL, STDOUT, check_call

check_call(['/etc/init.d/apache2', 'restart'], stdout=DEVNULL, stderr=STDOUT)

回答2:

Depending on your OS (and that's why as Noufal said, you should use subprocess instead) you can try something like

 os.system("/etc/init.d/apache restart > /dev/null")

or (to mute also the error)

os.system("/etc/init.d/apache restart > /dev/null 2>&1")

回答3:

You should use the subprocess module using which you can control the stdout and stderr in a flexible fashion. os.system is deprecated.

The subprocess module allows you to create an object which represents a running external process. You can read it from it's stdout/stderr, write to it's stdin, send it signals, terminate it etc. The main object in the module is Popen. There are a bunch of other convenience methods like call etc. The docs are very comprehensive and include a section on replacing the older functions (including os.system).

回答4:

Here is a system call function I pieced together several years ago and have used in various projects. If you don't want any output from the command at all you can just say out = syscmd(command) and then do nothing with out.

Tested and works in Python 2.7.12 and 3.5.2.

def syscmd(cmd, encoding=''):
    """
    Runs a command on the system, waits for the command to finish, and then
    returns the text output of the command. If the command produces no text
    output, the command's return code will be returned instead.
    """
    p = Popen(cmd, shell=True, stdin=PIPE, stdout=PIPE, stderr=STDOUT,
        close_fds=True)
    p.wait()
    output = p.stdout.read()
    if len(output) > 1:
        if encoding: return output.decode(encoding)
        else: return output
    return p.returncode