mqueue.h(0P)		   POSIX Programmer's Manual		  mqueue.h(0P)

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
       mqueue.h — message queues (REALTIME)

SYNOPSIS
       #include <mqueue.h>

DESCRIPTION
       The <mqueue.h> header shall define the mqd_t type, which is used for
       message queue descriptors. This is not an array type.

       The <mqueue.h> header shall define the pthread_attr_t, size_t, and
       ssize_t types as described in <sys/types.h>.

       The <mqueue.h> header shall define the struct timespec structure as
       described in <time.h>.

       The tag sigevent shall be declared as naming an incomplete structure
       type, the contents of which are described in the <signal.h> header.

       The <mqueue.h> header shall define the mq_attr structure, which is used
       in getting and setting the attributes of a message queue. Attributes
       are initially set when the message queue is created. An mq_attr
       structure shall have at least the following fields:


	   long	   mq_flags    Message queue flags.
	   long	   mq_maxmsg   Maximum number of messages.
	   long	   mq_msgsize  Maximum message size.
	   long	   mq_curmsgs  Number of messages currently queued.

       The following shall be declared as functions and may also be defined as
       macros. Function prototypes shall be provided.


	   int	    mq_close(mqd_t);
	   int	    mq_getattr(mqd_t, struct mq_attr *);
	   int	    mq_notify(mqd_t, const struct sigevent *);
	   mqd_t    mq_open(const char *, int, ...);
	   ssize_t  mq_receive(mqd_t, char *, size_t, unsigned *);
	   int	    mq_send(mqd_t, const char *, size_t, unsigned);
	   int	    mq_setattr(mqd_t, const struct mq_attr *restrict,
			struct mq_attr *restrict);
	   ssize_t  mq_timedreceive(mqd_t, char *restrict, size_t,
			unsigned *restrict, const struct timespec *restrict);
	   int	    mq_timedsend(mqd_t, const char *, size_t, unsigned,
			const struct timespec *);
	   int	    mq_unlink(const char *);

       Inclusion of the <mqueue.h> header may make visible symbols defined in
       the headers <fcntl.h>, <signal.h>, and <time.h>.

       The following sections are informative.

APPLICATION USAGE
       None.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       <fcntl.h>, <signal.h>, <sys_types.h>, <time.h>

       The System Interfaces volume of POSIX.1‐2017, mq_close(), mq_getattr(),
       mq_notify(), mq_open(), mq_receive(), mq_send(), mq_setattr(),
       mq_unlink()

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 .

       Any typographical or formatting errors that appear in this page are
       most likely to have been introduced during the conversion of the source
       files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group		     2017			  mqueue.h(0P)