shmem.py

import mmap
import posix_ipc
import os
import sys

def create_shared_mem(sm_name, size):
    sm = posix_ipc.SharedMemory(sm_name, flags=posix_ipc.O_CREX, size=size)
    return mmap.mmap(sm.fd, sm.size)

def open_shared_mem(sm_name):
    sm = posix_ipc.SharedMemory(sm_name,flags=0)
    return mmap.mmap(sm.fd, sm.size)

def worker(sm_name):
    id = os.getpid()
    mem  = open_shared_mem( sm_name )

    while True:
        mem.seek(0)
        x =  mem.read(5)
        mem.seek(0)
        mem.write("%5d" % id)
        print "read '%s' wrote '%5d'" % (x, id)

def master():
    sm_name = '/shared-memory-%d' % os.getpid()
    m = create_shared_mem( sm_name, size=1000 )
    print sm_name
    raw_input("press <return> to start")

    for i in range(3):
        if True:
            os.system('python %s %s &' % (sys.argv[0], sm_name))
        else:
            import multiprocessing
            multiprocessing.Process(target=worker, args=(sm_name,)).start()

    worker(sm_name)

if __name__ == '__main__':
    if len(sys.argv) == 1:
        master()
    else:
        worker(sm_name=sys.argv[1])