Which is the best way to get a list of running processes in unix with python?

Question

I'm trying:

import commands
print commands.getoutput("ps -u 0")

But it doesn't work on os x. os instead of commands gives the same output: USER PID %CPU %MEM VSZ RSS TT STAT STARTED TIME COMMAND

nothing more

Answer 1

It works if you use os instead of commands

import os

print os.system("ps -u 0")

Answer 2

The cross-platform replacement for commands is subprocess. See the subprocess module documentation. The 'Replacing older modules' section includes how to get output from a command.

Of course, you still have to pass the right arguments to 'ps' for the platform you're on. Python can't help you with that, and though I've seen occasional mention of third-party libraries that try to do this, they usually only work on a few systems (like strictly SysV style, strictly BSD style, or just systems with /proc.)

Answer 3

I've tried in on OS X (10.5.5) and seems to work just fine:

print commands.getoutput("ps -u 0")

UID PID TTY TIME CMD

0 1 ?? 0:01.62 /sbin/launchd

0 10 ?? 0:00.57 /usr/libexec/kextd

etc.

Python 2.5.1

Answer 4

This works on Mac OS X 10.5.5. Note the capital -U option. Perhaps that's been your problem.

import subprocess
ps = subprocess.Popen("ps -U 0", shell=True, stdout=subprocess.PIPE)
print ps.stdout.read()
ps.stdout.close()
ps.wait()

Here's the Python version

Python 2.5.2 (r252:60911, Feb 22 2008, 07:57:53) 
[GCC 4.0.1 (Apple Computer, Inc. build 5363)] on darwin