mq_setattr man page


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.

mq_setattr — set message queue attributes (REALTIME)


#include <mqueue.h>

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


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():


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.


The mq_setattr() function shall fail if:


The mqdes argument is not a valid message queue descriptor.

The following sections are informative.



Application Usage




Future Directions


See Also

mq_open(), mq_send(), msgctl(), msgget(), msgrcv(), msgsnd()

The Base Definitions volume of POSIX.1‐2008, <mqueue.h>


2013 IEEE/The Open Group POSIX Programmer's Manual