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mq_notify(3)
NAME
  mq_notify - Attaches a request for asynchronous signal notification to a
  message queue (P1003.1b)

SYNOPSIS
  #include <mqueue.h>

  int mq_notify (
  mqd_t mqdes,
  const struct sigevent *notification);

PARAMETERS
  mqdes	     Specifies a message queue descriptor.

  *notification
	     Specifies a signal to be sent when the specified  queue accepts
	     a message.	 If the notification argument is NULL, and the
	     process has previously attached a notification request to the
	     message queue with this mqdes argument, notification request is
	     detached and the queue is available for another process to
	     attach a notification request.

DESCRIPTION
  Attaches a request for asynchronous signal notification to a message queue
  for the calling process.  Following a call to this function, the specified
  signal is sent to the calling process when the queue transitions from empty
  to non-empty.	 Two or more processes cannot attach notification requests to
  the same queue at the same time.

  If a process has attached a notification request and any process is blocked
  in the execution of the mq_receive function waiting to receive a message
  when a message arrives at the queue, then the appropriate mq_receive
  function is completed and the notification remains pending.

  When the notification has been sent, the registration is canceled.  In
  effect, it is a one-shot notification and must be re-registered if
  required.

  Note that the POSIX IPC functions are not reentrant with respect to
  signals.  For example, if your application were to use a signal to notify
  it that a queue has become non-empty and then attempt to call mq_receive
  from the signal handler, the signal handler must reside in a thread other
  than the tread that called mq_send.  Otherwise, a deadlock on internal
  locks would occur.

RETURN VALUES
  On successful completion, the function returns the value 0; otherwise, the
  function returns the value -1 and sets errno to indicate the error.

ERRORS
  The mq_notify function fails under the following conditions:

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

  [EBUSY]	 A process has already attached to this message queue for
		 asynchronous notification, or the calling process attempted
		 to cancel a request that was attached by another process.

  [EINVAL]	 The requested signo is invalid, or the sigev_notify field of
		 the notification structure does not equal SIGEV_SIGNAL.

RELATED INFORMATION
  Functions: mq_open(3), mq_send(3)

Index for Section 3

Alphabetical listing for M

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