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# Python modules
import time
import signal
# 3rd party modules
import posix_ipc
# Utils for this demo
import utils
MY_SIGNAL = signal.SIGUSR1
def handle_signal(signal_number, stack_frame):
message, priority = mq.receive()
print ("Ding! Message with priority %d received: %s" % (priority, message))
# Create the message queue.
mq = posix_ipc.MessageQueue(utils.QUEUE_NAME, posix_ipc.O_CREX)
# Request notifications
mq.request_notification(MY_SIGNAL)
# Register my signal handler
signal.signal(MY_SIGNAL, handle_signal)
# Get user input and send it to the queue.
print ("Enter a message:")
mq.send(utils.get_input())
# The signal fires almost instantly, but if I don't pause at least
# briefly then the main thread may exit before the notification fires.
print ("Sleeping for one second to allow the notification to happen.")
time.sleep(1)
print ("Destroying the message queue.")
mq.close()
# I could call simply mq.unlink() here but in order to demonstrate
# unlinking at the module level I'll do it that way.
posix_ipc.unlink_message_queue(utils.QUEUE_NAME)
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