huschi.net

MQ_NOTIFY(3P)              POSIX Programmer's Manual             MQ_NOTIFY(3P)

PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the  corresponding
       Linux  manual page for details of Linux behavior), or the interface may
       not be implemented on Linux.
NAME
       mq_notify - notify process that a message is available (REALTIME)
SYNOPSIS
       #include <mqueue.h>
       int mq_notify(mqd_t mqdes, const struct sigevent *notification);

DESCRIPTION
       If the argument notification is not NULL, this function shall  register
       the  calling process to be notified of message arrival at an empty mes-
       sage queue associated with  the  specified  message  queue  descriptor,
       mqdes. The notification specified by the notification argument shall be
       sent to the process when the message queue transitions  from  empty  to
       non-empty.  At any time, only one process may be registered for notifi-
       cation by a message queue. If the calling process or any other  process
       has already registered for notification of message arrival at the spec-
       ified message queue, subsequent attempts to register for  that  message
       queue shall fail.
       If  notification  is  NULL  and the process is currently registered for
       notification by the specified message queue, the existing  registration
       shall be removed.
       When  the notification is sent to the registered process, its registra-
       tion shall be removed. The message queue shall then  be  available  for
       registration.
       If  a  process  has registered for notification of message arrival at a
       message queue and some thread is blocked  in  mq_receive()  waiting  to
       receive  a  message  when  a message arrives at the queue, the arriving
       message shall satisfy  the  appropriate  mq_receive().   The  resulting
       behavior  is as if the message queue remains empty, and no notification
       shall be sent.
RETURN VALUE
       Upon successful completion, the mq_notify()  function  shall  return  a
       value  of  zero; otherwise, the function shall return a value of -1 and
       set errno to indicate the error.
ERRORS
       The mq_notify() function shall fail if:
       EBADF  The mqdes argument is not a valid message queue descriptor.
       EBUSY  A process is already registered for notification by the  message
              queue.

       The following sections are informative.
EXAMPLES
       None.
APPLICATION USAGE
       None.
RATIONALE
       None.
FUTURE DIRECTIONS
       None.
SEE ALSO
       mq_open(),  mq_send(),  mq_timedsend(),  msgctl(),  msgget(), msgrcv(),
       msgsnd(),  the  Base  Definitions   volume   of   IEEE Std 1003.1-2001,
       <mqueue.h>
COPYRIGHT
       Portions  of  this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
       Specifications Issue 6, Copyright (C) 2001-2003  by  the  Institute  of
       Electrical  and  Electronics  Engineers, Inc and The Open Group. In the
       event of any discrepancy between this version and the original IEEE and
       The  Open Group Standard, the original IEEE and The Open Group Standard
       is the referee document. The original Standard can be  obtained  online
       at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group                  2003                        MQ_NOTIFY(3P)