mq

Note: You must be root to start this manager.

Syntax:

mq [options] &

Runs on:

Neutrino

Options:

-d

Don't daemonize.

-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.

-U user_name

-U uid[:gid[,sup_gid]*]]

Once running, run as the specified user, so that the program doesn't need to run as root:

In the first form, the service sets itself to be the named user and uses that user's groups. This form depends on the /etc/passwd and /etc/group files.
In the second form, the service sets its user ID, and optionally its group ID and supplementary groups, to the values provided.

Description:

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

Note: 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.

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.