os.system for submitting command

Question

I am using os.system to submit a command to the system.

I.e.,

import os
os.system(my_cmd)

But I was wondering how could I obtain the output, i.e., let us say i am in the bash and I type in my cmd, I'd get an output of this form:

Job <57960787> is submitted to queue <queueq>.

How can I, in python, using the os.system(cmd), also obtain the text output, and parse it to obtain the job id, 57960787.

Thanks!

Answer 1

It is better to use the subprocess module documentation here, example below:

import subprocess,re
p = subprocess.Popen('commands',stdout=subprocess.PIPE,stderr=subprocess.PIPE)
results, errors = p.communicate()
print results
re.search('<(\d+)>', results).group(1) #Cheers, Jon Clements

Or you can even use os.popen documentation here,

p_os = os.popen("commands","r")
line = p_os.readline()
print line
re.search('<(\d+)>', line).group(1) #Cheers, Jon Clements

Or as John Clements kindly suggested, you can use subprocess.check_output, Documentation here

>>> subprocess.check_output(["echo", "Hello World!"])
'Hello World!\n' 

Answer 2

A simple example:

>>> import os, sys
>>> cmd = "uname"
>>> b = os.popen(cmd, 'r', 1)
>>> b.read()
'Linux\n'

I am running Linux uname command.

os.popen() executes command and return a file type object using that you can read command's output.

Answer 3

os.system does not return output. So instead you can use the commands module.

Example:

import commands
my_cmd = 'ls -l'
status, output = commands.getstatusoutput(my_cmd)
print output