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NAME
     mq_setattr - set message queue attributes (REALTIME)


LIBRARY
     library “librt”


SYNOPSIS
     #include <mqueue.h>

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


DESCRIPTION
     The mq_setattr() system call 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 zero or O_NONBLOCK.

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


RETURN VALUES
     Upon successful completion, the function returns a value of 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
     error.


ERRORS
     The mq_setattr() system call will fail if:

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


SEE ALSO
     mq_open(2), mq_send(2), mq_timedsend(2)


STANDARDS
     The mq_setattr() system call conforms to .


HISTORY
     Support for POSIX message queues first appeared in FreeBSD 7.0.