File-like interface

Message queues resemble files, at least as far as their interface is concerned.

You open a message queue with mq_open(), close it with mq_close(), and destroy it with mq_unlink(). And to put data into (“write”) and take it out of (“read”) a message queue, you use mq_send() and mq_receive().

For strict POSIX conformance, you should create message queues that start with a single slash (/) and contain no other slashes. But note that we extend the POSIX standard by supporting pathnames that may contain multiple slashes. This allows, for example, a company to place all its message queues under its company name and distribute a product with increased confidence that a queue name will not conflict with that of another company.

In QNX Neutrino, all message queues created will appear in the filename space under the directory:

For example, with the traditional implementation:

mq_open() name: Pathname of message queue:
/data /dev/mqueue/data
/acme/data /dev/mqueue/acme/data
/qnx/data /dev/mqueue/qnx/data

You can display all message queues in the system using the ls command as follows:

ls -Rl /dev/mqueue

The size printed is the number of messages waiting.