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pipe and fork - communicating with your children
this example from a Well House Consultants training course
More on this [link]

This example is described in the following article(s):
   • Multiple processes (forking) in Python - [link]

Source code: t3 Module: Y303

# A demonstration of how a process can be forked and
# the parent and child can later communicate via a
# pipe set up prior to forking. Signals and / or
# buffer tests on the file handle (not shown in this
# example) can be used to check whether or not parent
# and child have data to exchange without one of them
# blocking on a read

import re
from os import *

def lifetest(ip):
      status = -1
      pingaling = popen("ping -q -c2 "+ip,"r")
      while 1:
        line = pingaling.readline()
        if not line: break
        igot = re.findall(lifeline,line)
        if igot:
           status = int(igot[0])
      return status

lifeline = re.compile(r"(\d) packets received")

# Single process ...
print "hello - multipinger"

# becomes two processes!

while True:
        iptest = raw_input("What IP to test ")
        if iptest == "": break

        rend, wend = pipe()
        gerald = fork()
        if not gerald:
                print "testing ",iptest
                about = lifetest(iptest)
                print "tested ",iptest
                rz = "Result %s %d\n" % (iptest,about)
                # convert file descriptor to file handle
                whand = fdopen(wend,'w',0)
                whand.write(rz)
                exit()

        print "Off for a nice hot curry"
        rhand = fdopen(rend,'r',0)
        report = rhand.readline()
        print report

print "done"
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