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NetBSD 6.1.5 - man page for mq_timedsend (netbsd section 3)

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MQ_SEND(3)			   BSD Library Functions Manual 		       MQ_SEND(3)

NAME
     mq_send, mq_timedsend -- send a message to a message queue (REALTIME)

LIBRARY
     POSIX Real-time Library (librt, -lrt)

SYNOPSIS
     #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);

DESCRIPTION
     The mq_send() function will add the message pointed to by the argument msg_ptr to the mes-
     sage 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 descrip-
     tion 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.

RETURN VALUES
     Upon successful completion, the 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.

ERRORS
     The mq_send() and mq_timedsend() functions fail if:

     [EAGAIN]		The O_NONBLOCK flag 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 writ-
			ing.

     [EINTR]		A signal interrupted the call to mq_send() or mq_timedsend().

     [EINVAL]		The value of msg_prio was outside the valid range, or the process or
			thread would have blocked, and the abs_timeout parameter specified a
			nanoseconds field value less than zero or greater than or equal to 1000
			million.

     [EMSGSIZE] 	The specified message length, msg_len, exceeds the message size attribute
			of the message queue.

     [ETIMEDOUT]	The 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.

SEE ALSO
     mq(3), mq_receive(3)

STANDARDS
     These functions are expected to conform to the IEEE Std 1003.1-2001 (``POSIX.1'') standard.

HISTORY
     The mq_send() and mq_timedsend() functions first appeared in NetBSD 5.0.

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 Insti-
     tute 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 .

BSD					   June 7, 2010 				      BSD
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