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 .