Mqueue

POSIX message queue server (QNX)

Syntax:

Mqueue [-anmrbd] [-s message size] [-S read_buffer_size]
       [-x max messages]

Options:

The following specify general behavior for the server:

-S read buffer size

Specifies the size of the read buffer. Messages smaller than this size will be read without an additional kernel call (defaults to 128).

The following specify which non-POSIX flags will be ORed into the mq_flags of a message queue if no structure is specified in the mq_open() call:

-a

(MQ_NOTIFY_ALWAYS) notify even if queue contains messages when you call mq_notify()

-b

(MQ_PRIO_BOOST) a 0 priority message will be boosted to the priority of the calling process

-d

(MQ_READBUF_DYNAMIC) a read() (or mq_receive()) buffer may be smaller than the maximum message size.

-m

(MQ_MULT_NOTIFY) more than one process can call mq_notify()

-n

(MQ_NONBLOCK) mq_send()'s and mq_receive()'s won't block

-r

(MQ_PRIO_RESTRICT) a process may not submit a message at a higher priority than itself

The following specify what values other fields of the mq_attr structure will default to if no structure is specified in the mq_open() call:

-s message size

The maximum size for any given message. If MQ_READBUF_DYNAMIC is not specified, this size also serves as a minimum.

-x max messages

The maximum number of messages on any message queue

Description:

The Mqueue manager is a POSIX 1003.1b message queue server which provides both the standard I/O API and the the POSIX 1003.1b message queue API to the programmer. The command-line options allow the default attributes of a queue to be set very explicitly. In the event that a queue is to be created, and the new attributes have not been specified, the defaults specified on the command line will be used.

See also:

• mq_*() library functions