| MQ_SEND(3) | Library Functions Manual | MQ_SEND(3) | 
mq_send, mq_timedsend —
#include <mqueue.h>
int
  
  mq_send(mqd_t mqdes,
    const char *msg_ptr, size_t
    msg_len, unsigned msg_prio);
#include
    <mqueue.h>
  
  #include <time.h>
int
  
  mq_timedsend(mqd_t mqdes,
    const char *msg_ptr, size_t
    msg_len, unsigned msg_prio,
    const struct timespec *abs_timeout);
mq_send() function will add the message pointed to
  by the argument msg_ptr to the message queue specified
  by mqdes. The msg_len argument
  specifies the length of the message, in bytes, pointed to by
  msg_ptr. The value of msg_len will
  be less than or equal to the mq_msgsize attribute of the
  message queue, or mq_send() will fail.
If the specified message queue is not full,
    mq_send() behaves as if the message is inserted into
    the message queue at the position indicated by the
    msg_prio argument. A message with a larger numeric
    value of msg_prio will be inserted before messages
    with lower values of msg_prio. A message will be
    inserted after other messages in the queue, if any, with equal
    msg_prio. The value of msg_prio
    will be less than {MQ_PRIO_MAX}.
If the specified message queue is full and
    O_NONBLOCK is not set in the message queue
    description associated with mqdes,
    mq_send() blocks until space becomes available to
    enqueue the message, or until mq_send() is
    interrupted by a signal. If more than one thread is waiting to send when
    space becomes available in the message queue, then the thread of the highest
    priority that has been waiting the longest will be unblocked to send its
    message. If the specified message queue is full and
    O_NONBLOCK is set in the message queue description
    associated with mqdes, the message will not be queued
    and mq_send() will return an error.
The mq_timedsend() function will add a
    message to the message queue specified by mqdes in the
    manner defined for the mq_send() function. However,
    if the specified message queue is full and
    O_NONBLOCK is not set in the message queue
    description associated with mqdes, the wait for
    sufficient room in the queue will be terminated when the specified timeout
    expires. If O_NONBLOCK is set in the message queue
    description, this function will be equivalent to
    mq_send().
The timeout will expire when the absolute time specified by abs_timeout passes, as measured by the clock on which timeouts are based (that is, when the value of that clock equals or exceeds abs_timeout), or if the absolute time specified by abs_timeout has already been passed at the time of the call.
The resolution of the timeout is based on the CLOCK_REALTIME
    clock. The timespec argument is defined in the
    <time.h> header.
Under no circumstance will the operation fail with a timeout if there is sufficient room in the queue to add the message immediately. The validity of the abs_timeout parameter need not be checked when there is sufficient room in the queue.
mq_send() and
  mq_timedsend() functions return a value of zero.
  Otherwise, no message will be enqueued, the functions will return -1, and the
  global variable errno will be set to indicate the error.
mq_send() and mq_timedsend()
  functions fail if:
EAGAIN]O_NONBLOCK flag is set in the message queue
      description associated with mqdes, and the specified
      message queue is full.EBADF]EINTR]mq_send() or
      mq_timedsend().EINVAL]EMSGSIZE]ETIMEDOUT]O_NONBLOCK flag was not set when the message
      queue was opened, but the timeout expired before the message could be
      added to the queue.mq_send() and mq_timedsend()
  functions first appeared in NetBSD 5.0.
| June 7, 2010 | NetBSD 9.4 |