Suppress output in Python calls to executables

user_84861 0
Viewed 43173

I have a binary named A that generates output when called. If I call it from a Bash shell, most of the output is suppressed by A > /dev/null. All of the output is suppressed by A &> /dev/null

I have a python script named B that needs to call A. I want to be able to generate output from B, while suppressing all the output from A.

From within B, I've tried os.system('A'), os.system('A > /dev/null'), and os.system('A &> /dev/null'), os.execvp('...'), etc. but none of those suppress all the output from A.

I could run B &> /dev/null, but that suppresses all of B's output too and I don't want that.

Anyone have suggestions?

redirect python
9 Answers
import os
import subprocess

command = ["executable", "argument_1", "argument_2"]

with open(os.devnull, "w") as fnull:
    result = subprocess.call(command, stdout = fnull, stderr = fnull)

If the command doesn't have any arguments, you can just provide it as a simple string.

If your command relies on shell features like wildcards, pipes, or environment variables, you'll need to provide the whole command as a string, and also specify shell = True. This should be avoided, though, since it represents a security hazard if the contents of the string aren't carefully validated.

user_510250

If you have Python 2.4, you can use the subprocess module:

>>> import subprocess
>>> s = subprocess.Popen(['cowsay', 'hello'], \
      stderr=subprocess.STDOUT, stdout=subprocess.PIPE).communicate()[0]
>>> print s
 _______ 
< hello >
 ------- 
        \   ^__^
         \  (oo)\_______
            (__)\       )\/\
                ||----w |
                ||     ||
user_843490

As the os.system() docs mention, use the subprocess module, and, if you like, set stdout=open(os.devnull, 'w') (and perhaps the same for stderr) when you open the subprocess.

Devin_Jeanpierre_185150

I know it's late to the game, but why not simply redirect output to /dev/null from within os.system? E.g.:

tgt_file = "./bogus.txt"
os.sytem("d2u '%s' &> /dev/null" % tgt_file)

This seems to work for those occasions when you don't want to deal with subprocess.STDOUT.

user_990630
Related