check output from CalledProcessError

Question

I am using subprocess.check_output from pythons subprocess module to execute a ping command. Here is how I am doing it:

output = subprocess.check_output([\"p         


        

Answer 1

According to the Python os module documentation os.popen has been deprecated since Python 2.6.

I think the solution for modern Python is to use check_output() from the subprocess module.

From the subprocess Python documentation:

subprocess.check_output(args, *, stdin=None, stderr=None, shell=False, universal_newlines=False) Run command with arguments and return its output as a byte string.

If the return code was non-zero it raises a CalledProcessError. The CalledProcessError object will have the return code in the returncode attribute and any output in the output attribute.

If you run through the following code in Python 2.7 (or later):

import subprocess

try:
    print subprocess.check_output(["ping", "-n", "2", "-w", "2", "1.1.1.1"])
except subprocess.CalledProcessError, e:
    print "Ping stdout output:\n", e.output

You should see an output that looks something like this:

Ping stdout output:

Pinging 1.1.1.1 with 32 bytes of data:
Request timed out.
Request timed out.

Ping statistics for 1.1.1.1:
Packets: Sent = 2, Received = 0, Lost = 2 (100% loss),

The e.output string can be parsed to suit the OPs needs.

If you want the returncode or other attributes, they are in CalledProccessError as can be seen by stepping through with pdb

(Pdb)!dir(e)   

['__class__', '__delattr__', '__dict__', '__doc__', '__format__',
 '__getattribute__', '__getitem__', '__getslice__', '__hash__', '__init__',
 '__module__', '__new__', '__reduce__', '__reduce_ex__', '__repr__',
 '__setattr__', '__setstate__', '__sizeof__', '__str__', '__subclasshook__', 
 '__unicode__', '__weakref__', 'args', 'cmd', 'message', 'output', 'returncode']