mq_send(3c)

NAME
     mq_send - send a message to a queue

C SYNOPSIS
     #include <mqueue.h>

     int mq_send (mqd_t mqd, const char *msgptr, size_t msglen, unsigned int
     msg_prio);

DESCRIPTION
     mq_send sends the message at address msgptr, of size msglen bytes, to the
     message queue named by mqd.

     The message is queued in priority order, as specified by msgprio.  The
     larger the numerical value of the priority, the more important the
     message. Messages with same priorities are queued in FIFO order.  The
     value of msgprio must be less than {MQ_PRIO_MAX}.

     A message queue is full when the number of the messages queued equals the
     value the of mq_maxmsg attribute of the queue. If the O_NONBLOCK flag is
     set for the message queue descriptor mqd, mq_send will not block when the
     queue is full [see mq_setattr(3c)].  Otherwise, mq_send will block until
     either space becomes available to queue the message, or mq_send is
     interrupted by a signal.

     If multiple processes are waiting to send a message to the queue, the
     highest priority process will be unblocked to queue its message when
     space becomes available. Processes with equal priorities, blocked waiting
     to queue a message, are unblocked in FIFO order when queue space becomes
     available.

     mq_send will fail if one or more of the following conditions are true:

     [EAGAIN]       The O_NONBLOCK flag is set for the queue descriptor and
                    the queue is full.

     [EBADF]        The message queue descriptor, mqd, is not valid or the
                    queue was not opened for writing.

     [EINTR]        The mq_send system call was interrupted by a signal.

     [EINVAL]       The value of msgprio is not less than {MQ_PRIO_MAX}.

     [EMSGSIZE]     The size of the message, msglen, is greater than the value
                    of the mq_maxsize attribute of the queue.

SEE ALSO
     mq_open(3c), intro(3c), mq_unlink(3c), mq_receive(3c), mq_getattr(3c),
     mq_notify(3c),
DIAGNOSTICS
     Upon successful completion, a value of 0 is returned and the message is
     added to the queue.  Otherwise, the message is not added to the queue, a
     value of -1 is returned and errno is set to indicate the error.