blocks - send input to python subprocess pipeline

Question

I\'m testing subprocesses pipelines with python. I\'m aware that I can do what the programs below do in python directly, but that\'s not the point. I just want to test the pipel

Answer 1

Here's an example of using Popen together with os.fork to accomplish the same thing. Instead of using close_fds it just closes the pipes at the right places. Much simpler than trying to use select.select, and takes full advantage of system pipe buffers.

from subprocess import Popen, PIPE
import os
import sys

p1 = Popen(["cat"], stdin=PIPE, stdout=PIPE)

pid = os.fork()

if pid: #parent
    p1.stdin.close()
    p2 = Popen(["cat"], stdin=p1.stdout, stdout=PIPE)
    data = p2.stdout.read()
    sys.stdout.write(data)
    p2.stdout.close()

else: #child
    data_to_write = 'hello world\n' * 100000
    p1.stdin.write(data_to_write)
    p1.stdin.close()