46.4. Message Queue Associated Data Structure

Each message queue has an associated msqid_ds data structure of the following form:

struct msqid_ds {
    struct ipc_perm msg_perm;           /* Ownership and permissions */
    time_t          msg_stime;          /* Time of last msgsnd() */
    time_t          msg_rtime;          /* Time of last msgrcv() */
    time_t          msg_ctime;          /* Time of last change */
    unsigned long   __msg_cbytes;       /* Number of bytes in queue */
    msgqnum_t       msg_qnum;           /* Number of messages in queue */
    msglen_t        msg_qbytes;         /* Maximum bytes in queue */
    pid_t           msg_lspid;          /* PID of last msgsnd() */
    pid_t           msg_lrpid;          /* PID of last msgrcv() */
};