Subprocesses on Windows
mail at timgolden.me.uk
Wed Oct 3 11:24:02 CEST 2007
Nachiket Joshi wrote:
> Well before I explain my problem, let me tell you all that
> I am not a professional programmer and new to python too.
Welcome to the world of Python, home to professional and
non-professional programmers alike!
> I just write some scripts as and when required
Same could be said of many of us.
> The problem is something like this.
> I am trying to run nmap scan on my network and for
> that I want to start multiple nmap instances (256 at once)
> togather and wait till those 256 are over before I start
> next lot of 256 instances.
My number one query is whether it's a great idea to
have *256* nmap instances running simultaneously.
But this is not my area, so maybe it's something people
commonly do. Howbeit, it's clear from your description
below that the problem is running *some number* of
> Well to test I have put in two
> nmap scans in my program and I have succeeded to start
> both of them simultaneously (in fact one after another) by using
> "subprocess module and Popen". But the problem is when I run a
> loop to start both of these nmap instances, they do start BUT
> the script then exits to command prompt completing all the executions.
> But this is not what I want. I want to wait till both of these nmap
> processes are finished and then only exit from script (in fact exit
> from that function or loop). Then only I would be able to call next
> lot of IP Ranges to scan. I did try os.waitpid() but it gives
> following error while running the program:
I admit I'm a bit confused both by the description and by the
code (not least because the code you're posting isn't
self-contained; it's not clear what the all-important
clas_c function is doing).
Assuming I have a (fake) nmap.py which looks like this:
then your code (if I understand it) wants to do this, in concept:
import os, sys
TEMPLATE = "192.168.%d.%d"
for network in range (256):
raw_input ("Network: %s - Press enter..." % (TEMPLATE % (network, 0)))
running_processes = 
for machine in range (256):
# start an nmap process which does whatever and returns
subprocess.Popen (["python", "nmap.py", TEMPLATE % (network, machine)])
# wait until all 256 nmap processes have finished
# before starting the next network
for process in running_processes:
if process.poll () is None:
Have I understood correctly? If you're not sure what my code
is doing, try saving it to two files and running it to see
if it gives the result you want.
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