<pre>

!/usr/bin/python

import os
import tornado.ioloop
import tornado.web
import tornado.gen
import subprocess
import fcntl

class MainHandler(tornado.web.RequestHandler):
""" main handler """

def get(self):
    self.write("hello world, you requested me")

class MyHandler(tornado.web.RequestHandler):
""" my handler """

@tornado.web.asynchronous
def get(self):
    self.alldata = ""
    self.data = ""
    self.jobdone = 0
    self.sub("date && echo '<br/>' && echo 'start to sleep 5<br/>' && \
                sleep 5 && echo 'sleep again<br/>' && sleep 5 && echo done")

def done(self):
    ## callback is called when
    print "in done .... this is a callbck"
    print self.data
    self.write(self.data)
    self.flush()
    #self.finish()
    if self.jobdone == 1:
        self.finish()



def sub(self, cmd):

    p = subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE)
    pout = p.stdout
    self.process = p
    fd = pout.fileno()
    fl = fcntl.fcntl(fd, fcntl.F_GETFL)
    fcntl.fcntl(fd, fcntl.F_SETFL, fl | os.O_NONBLOCK)
    ioloop = tornado.ioloop.IOLoop.instance()
    self.ioloop = ioloop
    ioloop.add_handler(fd, self.__finish_handle, ioloop.READ)

def __finish_handle(self, fd, events):
    print "envent is ....  ",events

    ### this callback must be added everytime the event is called
    ### this callback is used for next event
    self.ioloop.add_callback(self.done)
    if self.process.poll() is not None:
        self.ioloop.remove_handler(fd)
    self.data = ""
    while True:
        try:
            data = os.read(self.process.stdout.fileno(), 10)
            # when the fd is closed
            if len(data)==0:
                print "job is done done"
                self.jobdone = 1
                break
            else:
                self.alldata += data
                self.data += data
                print "getdata    " + data
        except:
            break

app = tornado.web.Application([
(r'/', MainHandler),
(r'/my', MyHandler),
])

if name == 'main':
app.listen(8080)
tornado.ioloop.IOLoop.instance().start()

</pre>