#include <mqueue.h> int mq_getattr(mqd_t mqdes, struct mq_attr *mqstat);
The mqdes argument specifies a message queue descriptor. The mq_getattr() function is used to get status information and attributes of the message queue and the open message queue description associated with the 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(3C) calls:
message queue flags
The following attributes of the message queue are returned as set at message queue creation:
maximum number of messages
maximum message size
number of messages currently on the queue.
Upon successful completion, the mq_getattr() function returns 0. Otherwise, the function returns −1 and sets errno to indicate the error.
The mq_getattr() function will fail if:
The mqdes argument is not a valid message queue descriptor.
The mq_getattr() function is not supported by the system.
See attributes(5) for descriptions of the following attributes: