Question

Given this :

import os
import subprocess

def check_server():

    cl = subprocess.Popen(["nmap","10.7.1.71"], stdout=subprocess.PIPE)
    result = cl.communicate()
    print result

check_server()

check_server() returns this tuple:

('\nStarting Nmap 4.53 ( http://insecure.org ) at 2010-04-07 07:26 EDT\nInteresting ports on 10.7.1.71:\nNot shown: 1711 closed ports\nPORT   STATE SERVICE\n21/tcp open  ftp\n22/tcp open  ssh\n80/tcp open  http\n\nNmap done: 1 IP address (1 host up) scanned in 0.293 seconds\n', None)

Changing the second line in the method to

result, err = cl.communicate()

results in check_server() returning :

Starting Nmap 4.53 ( http://insecure.org ) at 2010-04-07 07:27 EDT
Interesting ports on 10.7.1.71:
Not shown: 1711 closed ports
PORT   STATE SERVICE
21/tcp open  ftp
22/tcp open  ssh
80/tcp open  http

Nmap done: 1 IP address (1 host up) scanned in 0.319 seconds

Looks to be the case that the tuple is converted to a string, and the \n’s are being stripped…. but how?

Answer 1

cl.communicate() is still returning a tuple. The assignment result, err = ... has the effect of unpacking the tuple into the variables result (a string) and err (an integer).

When you print the tuple, it uses the repr(...) of each element, but when you print the string, it just prints the string, hence the absence of delimiters and \ns.