52.4. Message Queue Attributes

The mq_open(), mq_getattr(), and mq_setattr() functions all permit an argument that is a pointer to an mq_attr structure. This structure is defined in <mqueue.h> as follows:

struct mq_attr {
    long mq_flags;        /* Message queue description flags: 0 or
                             O_NONBLOCK [mq_getattr(), mq_setattr()] */
    long mq_maxmsg;       /* Maximum number of messages on queue
                             [mq_open(), mq_getattr()] */
    long mq_msgsize;      /* Maximum message size (in bytes)
                             [mq_open(), mq_getattr()] */
    long mq_curmsgs;      /* Number of messages currently in queue
                             [mq_getattr()] */
};