Updated: 2021/Apr/14

MQ_SETATTR(3)              Library Functions Manual              MQ_SETATTR(3)

     mq_setattr - set message queue attributes (REALTIME)

     POSIX Real-time Library (librt, -lrt)

     #include <mqueue.h>

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

     The mq_setattr() function sets 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 will 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 will be ignored by mq_setattr().

     If omqstat is non-NULL, the mq_setattr() function will store, in the
     location referenced by omqstat the previous message queue attributes and
     the current queue status.  These values are the same as would be returned
     by a call to mq_getattr(3) at that point.

     Upon successful completion, the mq_setattr() function returns zero and
     the attributes of the message queue will have been changed as specified.
     Otherwise, the message queue attributes are unchanged, and the function
     returns a value of -1 and sets the global variable errno to indicate the

     The mq_setattr() function fails if:

     [EBADF]            The mqdes argument is not a valid message queue

     mq(3), mq_getattr(3)

     This function conforms to the IEEE Std 1003.1-2001 ("POSIX.1") standard.

     This function first appeared in NetBSD 5.0.

     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 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

NetBSD 9.99                      June 7, 2010                      NetBSD 9.99