#!/usr/bin/python

from __future__ import print_function
import subprocess
import select

# can even be wrapped without change by "stdbuf -oL sh -c ..."
PROG = """
echo 'xxxxxxxxxxxx'
echo 'yyyyyyyyyyyyyyy'
read something
echo 'aaaaaaaa'
echo 'bbbbbbbb'
echo 'cccccccc'
echo 'dddddddd'
echo 'FINISHED'
read something
"""

process = subprocess.Popen(
    PROG,
    shell=True,
    stdin=subprocess.PIPE,
    stdout=subprocess.PIPE,
    stderr=subprocess.PIPE,
    bufsize=0,              # python2 default, broken since 3.3.1 ?
    universal_newlines=True)

poll = select.poll()
poll.register(process.stdout, select.POLLIN|select.POLLHUP|select.POLLERR)

process.stdin.write("go\n")

while True:
    matches = poll.poll()
    if not matches: continue
    for fd, event in matches:
        if event & select.POLLIN:
            l = process.stdout.readline().strip()
            print(">" + l)
            if l == "FINISHED":
                process.stdin.write("quit\n")
        if event & select.POLLHUP:
            print("pipe closed")
            exit(0)
        if event & select.POLLERR:
            print("process error")
            exit(1)