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mqueue.h(7posix) [posix man page]

<mqueue.h>(P)						     POSIX Programmer's Manual						     <mqueue.h>(P)

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 sigevent structure (as described in <signal.h> ) and 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>, <sys/types.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 IEEE Std 1003.1-2001, mq_close(), mq_getattr(),
       mq_notify(), mq_open(), mq_receive(), mq_send(), mq_setattr(), mq_timedreceive(), mq_timedsend(), mq_unlink()

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technol-
       ogy -- 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							     <mqueue.h>(P)

Check Out this Related Man Page

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

PROLOG

       This  manual page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (consult the correspond-
       ing Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

NAME

       mq_getattr - get message queue attributes (REALTIME)

SYNOPSIS

       #include <mqueue.h>

       int mq_getattr(mqd_t mqdes, struct mq_attr *mqstat);

DESCRIPTION

       The mq_getattr() function shall obtain status information and attributes of the message queue and the open message queue description  asso-
       ciated with the message queue descriptor.

       The mqdes argument specifies a message queue descriptor.

       The results shall be returned in the mq_attr structure referenced by the mqstat argument.

       Upon  return,  the following members shall have the values associated with the open message queue description as set when the message queue
       was opened and as modified by subsequent mq_setattr() calls: mq_flags.

       The following attributes of the message queue shall be returned as set at message queue creation: mq_maxmsg, mq_msgsize.

       Upon return, the following members within the mq_attr structure referenced by the mqstat argument shall be set to the current state of  the
       message queue:

       mq_curmsgs
	      The number of messages currently on the queue.

RETURN VALUE

       Upon  successful completion, the mq_getattr() function shall return zero. Otherwise, the function shall return -1 and set errno to indicate
       the error.

ERRORS

       The mq_getattr() function shall fail if:

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

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       None.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       mq_open(),  mq_send(),  mq_setattr(),  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 Technol-
       ogy -- 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_GETATTR(3P)
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