mq

Manage message queues (QNX Neutrino)

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You must be root to start this manager.

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Syntax:

mq [options] &

Runs on:

Neutrino

Options:

-m num_msgs

Set the default for the maximum number of messages, for use if the mq_attr argument to mq_open() is NULL. The default is 64 messages.

-N path

Set the pathname of the directory for message queues. The default is /dev/mq.

-s size

Set the default message size, for use if the mq_attr argument to mq_open() is NULL. The default is 256 bytes.

Description:

The mq manager implements POSIX 1003.1b message queues. When you create a queue, it appears in the pathname space under /dev/mq.

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The /dev/mq directory doesn't appear until you actually create a queue. You can change this directory to union over the directory exported by the mqueue server by using the mq -N/dev/mqueue option, but we don't recommend this, because it may cause some user-namespace confusion.

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This implementation uses the kernel's asynchronous messaging facility to buffer the messages within the kernel itself, and eliminates the context-switching overheads of using an external server (i.e. mqueue) in each message-queue operation, thus greatly improving the performance of POSIX message queues.

In order to use the mq implementation, you must link your application(s) against the libmq library. In a manual build, specify the -l mq option; in automatic/recursive builds, use this setting in your common.mk file:

LIBS += mq

For more information, see the Managing POSIX Message Queues technote.

See also:

mqueue, procnto*

mq_close(), mq_getattr(), mq_notify(), mq_open(), mq_receive(), mq_send(), mq_setattr(), mq_unlink() in the Neutrino Library Reference

Controlling How Neutrino Starts in the Neutrino User's Guide

Managing POSIX Message Queues technote