Manual Pages  — MQ_SETATTR

mq_setattr – set message queue attributes (REALTIME)

LIBRARY SYNOPSIS DESCRIPTION RETURN VALUES ERRORS SEE ALSO STANDARDS HISTORY COPYRIGHT

POSIX Real\-time Library (librt, -lrt)

#include <mqueue.h>

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

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().

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 mq_setattr() system call will fail if:

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

The mq_setattr() system call conforms to IEEE Std 1003.1-2004 ("POSIX.1").

Support for POSIX message queues first appeared in FreeBSD 7.0 .