Manual Pages  — MQ_GETATTR

mq_getattr – get 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_getattr(mqd_t mqdes, struct mq_attr *mqstat);

The mq_getattr() system call obtains status information and attributes of the message queue and the open message queue description associated with the message queue descriptor.

The mqdes argument specifies a message queue descriptor.

The results are returned in the mq_attr structure referenced by the mqstat argument.

Upon return, the following members will have the values associated with the open message queue description as set when the message queue was opened and as modified by subsequent mq_setattr() calls: mq_flags.

The following attributes of the message queue will be returned as set at message queue creation: mq_maxmsg, mq_msgsize.

Upon return, the following members within the mq_attr structure referenced by the mqstat argument will be set to the current state of the message queue:

mq_curmsgs
	The number of messages currently on the queue.

Upon successful completion, the value 0 is returned; otherwise the value -1 is returned and the global variable errno is set to indicate the error.

The mq_getattr() system call will fail if:

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

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

Support for POSIX message queues first appeared in FreeBSD 7.0 .