使用os.system（）抑制输出

Question

Why does the below MWE not redirect output to /dev/null.

#!/usr/bin/env python
import os

if __name__ == "__main__":
   os.system ( 'echo hello &>/dev/null' )

Answer 1

Not sure, but another (better) way to do it is:

from os import devnull
from subprocess import call

if __name__ == "__main__":
    with open(devnull, 'w') as dn:
        call(['echo', 'hello'], stdout=dn, stderr=dn)

This opens /dev/null for writing, and redirects output of the spawned process to there.

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UPDATE based on comments from @abarnert

In the specific case of echo , to get identically the same behavior you will want to use shell=True because otherwise it will call /bin/echo , not the shell builtin:

call('echo hello', shell=True, stdout=dn, stderr=dn)

Also, on Python 3.3+, you can do

from subprocess import call, DEVNULL

if __name__ == "__main__":
    call('echo hello', shell=True, stdout=DEVNULL, stderr=DEVNULL)