pipe.py

import subprocess
import signal

def pipeline(cmds, first_stdin=None, last_stdout=None):
    """Pipe together programs using subprocess"""
    pcount = len(cmds)
    plist = []
    for i, cmd in enumerate(cmds):
        stdin = None
        stdout = None
        stderr = None
        if i == 0:
            #First process
            stdin = first_stdin
        else:
            stdin = plist[i-1].stdout

        if i == len(cmds) - 1:
            #Last process
            stdout = last_stdout
        else:
            stdout = subprocess.PIPE

        #print cmd, stdin, stdout
        plist.append(subprocess.Popen(cmd, close_fds=True, stdin=stdin, stdout=stdout, preexec_fn=lambda: signal.signal(signal.SIGPIPE, signal.SIG_DFL)))

    ret = plist
    #for proc in ret:
    #    print proc, proc.stdin, proc.stdout
    return ret

#-------------------

import os
import sys

def test(argv):
  procs = pipeline([['/bin/echo', 'hello\nthere'], ['/bin/grep', 'hel']])[-1].wait()
  procs = pipeline([['/bin/echo', 'end\nof\nworld'], ['/bin/grep', 'wor']])[-1].wait()
  return 0
  
if __name__ == '__main__':
  sys.exit(test(sys.argv))