mq_setattr(2) set message queue attributes (REALTIME)


Lb librt


In mqueue.h Ft int Fo mq_setattr Fa mqd_t mqdes Fa const struct mq_attr *restrict mqstat Fa struct mq_attr *restrict omqstat Fc


The Fn mq_setattr system call sets attributes associated with the open message queue description referenced by the message queue descriptor specified by Fa mqdes . The message queue attributes corresponding to the following members defined in the Vt mq_attr structure will be set to the specified values upon successful completion of Fn mq_setattr :

The value of this member is zero or O_NONBLOCK

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


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.


The Fn mq_setattr system call will fail if:

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


The Fn mq_setattr system call conforms to St -p1003.1-2004 .


Support for POSIX message queues first appeared in Fx 7.0 .


Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2004 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2004 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