main()

This next section of code is the mainline. It's responsible for:

• creating the channel (via ChannelCreate()),
• calling the setupPulseAndTimer() routine (to set up a once-per-second timer, with a pulse as the event delivery method), and then
• sitting in a “do-forever” loop waiting for pulses or messages and processing them.

Notice the check against the return value from MsgReceive(); a zero indicates it's a pulse (and we don't do any strong checking to ensure that it's our pulse), a nonzero indicates it's a message. The processing of the pulse or message is done by gotAPulse() and gotAMessage().

int
main (void)                 // ignore command-line arguments
{
    int rcvid;              // process ID of the sender
    MessageT msg;           // the message itself

    if ((chid = ChannelCreate (0)) == -1) {
        fprintf (stderr, "%s:  couldn't create channel!\n",
                 progname);
        perror (NULL);
        exit (EXIT_FAILURE);
    }

    // set up the pulse and timer
    setupPulseAndTimer ();

    // receive messages
    for (;;) {
        rcvid = MsgReceive (chid, &msg, sizeof (msg), NULL);

        // determine who the message came from
        if (rcvid == 0) {
            // production code should check "code" field...
            gotAPulse ();
        } else {
            gotAMessage (rcvid, &msg.msg);
        }
    }

    // you'll never get here
    return (EXIT_SUCCESS);
}