#!/usr/bin/python
try:
    from argparse import ArgumentParser, RawTextHelpFormatter
except:
    sys.exit('argparse module is required (available in Python 2.7.2+ or Python 3.2.1+)')
import sys, os, re
from multiprocessing import Process, Queue

class Worker(Process):
    def __init__(self, queue):
        Process.__init__(self)
        self.queue = queue

    def run(self):
        while True:
            try:
                cmd = self.queue.get()
                if cmd is None:
                    break
                else:
                    os.system(cmd)
            except KeyboardInterrupt:
                break
        
def run(cmds, ncpu):
    try:
        jobs = []
        queue = Queue()
        for i in cmds:
            queue.put(i)
        for i in range(ncpu):
            p = Worker(queue)
            p.start()
            jobs.append(p)
            queue.put(None)
        for j in jobs:
            j.join()
    except KeyboardInterrupt:
        sys.exit(1)

if __name__ == '__main__':
    parser = ArgumentParser(description='''Run input commands in parallel.
    Example: "cat jobs.sh | {} --jobs 8"'''.format(sys.argv[0]), formatter_class=RawTextHelpFormatter)
    parser.add_argument('-j','--jobs', metavar = 'N', type = int, default = 1, help = 'number of jobs')
    args = parser.parse_args()
    try:
        cmds = [re.sub('\r\n|(\s*);(\s*)','\n', x) for x in sys.stdin.readlines() \
                     if not x.startswith('#') and len(x.strip()) > 0]
    except KeyboardInterrupt:
        sys.exit("Standard input stream expected")
    run(cmds, args.jobs if args.jobs > 1 else 1)