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_setattr — set message queue attributes (REALTIME)

SYNOPSIS

       #include <mqueue.h>

       int mq_setattr(mqd_t mqdes, const struct mq_attr *restrict mqstat,
           struct mq_attr *restrict omqstat);

DESCRIPTION

       The  mq_setattr()  function  shall  set  attributes associated with the open message queue
       description referenced by the message queue descriptor specified by mqdes.

       The message queue attributes corresponding to the following members defined in the mq_attr
       structure shall be set to the specified values upon successful completion of mq_setattr():

       mq_flags    The  value  of  this  member  is  the  bitwise-logical  OR  of zero or more of
                   O_NONBLOCK and any implementation-defined flags.

       The values of the mq_maxmsg, mq_msgsize, and mq_curmsgs members of the  mq_attr  structure
       shall be ignored by mq_setattr().

       If  omqstat is non-NULL, the mq_setattr() function shall store, in the location referenced
       by omqstat, the previous message queue attributes and the  current  queue  status.   These
       values shall be the same as would be returned by a call to mq_getattr() at that point.

RETURN VALUE

       Upon  successful  completion, the function shall return a value of zero and the attributes
       of the message queue shall have been changed as specified.

       Otherwise, the message queue attributes shall be unchanged, and the function shall  return
       a value of -1 and set errno to indicate the error.

ERRORS

       The mq_setattr() 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(), msgctl(), msgget(), msgrcv(), msgsnd()

       The Base Definitions volume of POSIX.1‐2017, <mqueue.h>

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 .