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

Question

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

The subprocess module seems complex...

Is there something like

output,error = `ps ca         


        

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.

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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'))