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...

1
0
.
2
4
3

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

Answer 1

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.