Embedded Linux System Design and Development

Real-Time Linux 229

/* Specify timeout as 10 seconds from now */

ts.tv_sec = time(NULL) + 10;

ts.tv_nsec = 0;

if (mq_timedsend(ds, text, SIZE,PRIOTITY, &ts) == -1){

if (errno == ETIMEDOUT){

printf("Timeout when waiting for message.");

return 0;

}

return -1;

}

/* receiving message */

if (mq_timedreceive(ds, new_text, SIZE, &prio, &ts) == -1){

if (errno == ETIMEDOUT){

printf("Timeout when waiting for message.");

return 0;

}

return -1;

}

Asynchronous Notification

The mq_notify function provides an asynchronous mechanism for processes

to receive notification that messages are available in a message queue rather

than synchronously blocking in

mq_receive or mq_timedreceive. This

interface is very useful for real-time applications. A process can call the

mq_notify ...