How to run “ ps cax | grep something ” in Python?

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Question :

How to run “ ps cax | grep something ” in Python?

How do I run a command with a pipe | in it?

The subprocess module seems complex…

Is there something like

output,error = `ps cax | grep something`

as in shell script?

Asked By: eugene

||

Answer #1:

See Replacing shell pipeline:

import subprocess

proc1 = subprocess.Popen(['ps', 'cax'], stdout=subprocess.PIPE)
proc2 = subprocess.Popen(['grep', 'python'], stdin=proc1.stdout,
                         stdout=subprocess.PIPE, stderr=subprocess.PIPE)

proc1.stdout.close() # Allow proc1 to receive a SIGPIPE if proc2 exits.
out, err = proc2.communicate()
print('out: {0}'.format(out))
print('err: {0}'.format(err))

PS. Using shell=True can be dangerous. See for example the warning in the docs.


There is also the sh module which can make subprocess scripting in Python a lot more pleasant:

import sh
print(sh.grep(sh.ps("cax"), 'something'))
Answered By: unutbu

Answer #2:

You’ve already accepted an answer, but:

Do you really need to use grep? I’d write something like:

import subprocess
ps = subprocess.Popen(('ps', 'cax'), stdout=subprocess.PIPE)
output = ps.communicate()[0]
for line in output.split('n'):
    if 'something' in line:
        ...

This has the advantages of not involving shell=True and its riskiness, doesn’t fork off a separate grep process, and looks an awful lot like the kind of Python you’d write to process data file-like objects.

Answered By: Kirk Strauser

Answer #3:

import subprocess

process = subprocess.Popen("ps cax | grep something",
                             shell=True,
                             stdout=subprocess.PIPE,
                           )
stdout_list = process.communicate()[0].split('n')
Answered By: instigator

Answer #4:

Drop that ‘ps’ subprocess and back away slowly! 🙂

Use the psutil module instead.

Answered By: Michael Kent

Answer #5:

import os

os.system('ps -cax|grep something')

If you wanna replace grep argument with some variable:

os.system('ps -cax|grep '+your_var)
Answered By: Mark Ma

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