pipeliner.py

import os
import sys
from subprocess import PIPE, STDOUT, Popen


bash_commands = sys.argv[1:]
procs = []


for n, cmd in enumerate(bash_commands):
    kwargs = {
        'stdout': PIPE,
        'env': os.environ.copy()
    }
    if n == 0:
        kwargs['stdin'] = PIPE
    proc = Popen(['bash', '-c', cmd], **kwargs)
    procs.append(proc)


exited = 0
while exited < len(procs) - 1:
    exited = 0
    for n, proc in enumerate(procs):
        returncode = proc.poll()
        if returncode is not None:
            exited += 1
            if returncode > 0:
                for sproc in procs:
                    if sproc.returncode is None:
                        sproc.terminate()
                sys.exit(returncode)

    next_proc = None
    if n + 1 < len(procs):
        next_proc = proc[n]

    for line in iter(proc.stdout.readline, b''):
        if next_proc:
            next_proc.communicate(input=line)
        else:
            sys.stdout.write(line)