python formatting return value of subprocess

Question

I am attempting on Python 2.6.6 to get the routing table of a system (for a interface) into a python list to parse; but I cannot seem to solve why the entire result is stored into one variable.

The loop seems to iterate over one characters at a time, while the behavior I wanted was one line at a time.

what I get is one character; short example below...

what I'd like line to return; so I can run other commands against each line..

10.243.186.1    0.0.0.0         255.255.255.255 UH        0 0          0 eth0
10.243.188.1    0.0.0.0         255.255.255.255 UH        0 0          0 eth0
10.243.184.0    10.243.186.1    255.255.255.128 UG        0 0          0 eth0

Here is the code below...

def getnet(int):
    int = 'eth0' ####### for testing only
    cmd = ('route -n | grep ' + int)
    routes = subprocess.Popen([cmd], shell=True, stdout=subprocess.PIPE)
    routes, err = routes.communicate()
    for line in routes:
        print line

score 0 · Answer 1 · edited May 23 '17 at 11:43

routes in your case is a bytestring that contains the entire output from the shell command. for character in astring statement produces one character at a time as the example in your question demonstrates. To get lines as a list of strings instead, call lines = all_output.splitlines():

from subprocess import check_output

lines = check_output("a | b", shell=True, universal_newlines=True).splitlines()

Here's a workaround if your Python version has no check_output(). If you want to read one line at a time while the process is still running, see Python: read streaming input from subprocess.communicate().

You could try to use os, ctypes modules, to get the info instead of grepping the output of an external command.

python formatting return value of subprocess

1 Answers1