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mq_send(3)
NAME
  mq_send - Places a message in the message queue (P1003.1b)

SYNOPSIS
  #include <mqueue.h>

  int mq_send (
  mqd_t mqdes,
  const char *msg_ptr,
  size_t msg_len,
  unsigned int msg_prio);

LIBRARY
  Realtime Library (librt.so, librt.a)

PARAMETERS
  mqdes
      Specifies a message queue descriptor.

  *msg_ptr
      Specifies a pointer to a buffer containing the message to be sent.

  msg_len
      Indicates the number of bytes of the message to be sent.

  msg_prio
      Indicates the priority of the message being sent.

DESCRIPTION
  The mq_send function places a message in the message queue. This function
  inserts the message in the queue at the position indicated by the msg_prio
  argument.  A message with a relatively large numeric value for the msg_prio
  argument has a high priority, and it is therefore inserted before messages
  with lower values for the msg_prio argument.	This function inserts
  messages with equal priority into the queue in first-in/first-out order.
  Thus the function inserts a message with a given priority after already-
  queued messages that have the same priority.

  If the message queue is full, and the O_NONBLOCK option associated with it
  is not set, the mq_send function blocks until sufficient space in the
  message queue becomes available or until a signal interrupts the mq_send
  function.

  If two or more processes are waiting to send messages when space becomes
  available in the queue, the highest-priority process that has been waiting
  the longest sends the message first.

  The mq_send function returns an error if the specified queue is full and
  the O_NONBLOCK option is set for that queue.

RETURN VALUES
  On successful completion, the mq_send function returns a value of 0 (zero).

  Otherwise, no message is sent, -1 is returned, and errno is set to indicate
  the error.

ERRORS
  The mq_send function fails under the following conditions:

  [EAGAIN]
      The O_NONBLOCK option is set in the message queue description
      associated with mqdes, and the specified message queue is full.

  [EBADF]
      The mqdes argument is not a valid message queue descriptor open for
      writing.

  [EFAULT]
      An internal virtual memory error occurred.

  [EINTR]
      A signal interrupted the call to mq_send.

  [EINVAL]
      The value of msg_prio is outside the valid range.

  [EMSGSIZE]
      The specified message length, msg_len, exceeds the message size
      attribute of the message queue. Note that a zero-length message is
      valid.

SEE ALSO
  Functions: mq_receive(3), mq_setattr(3)

  Guide to Realtime Programming

Index for Section 3

Alphabetical listing for M

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