Walk the active msqid_ds structures corresponding to message queue identifiers. This structure is defined in <sys/msg.h>.
Iterate over the message structures that are currently enqueued on the specified message queue.
Walk the active semid_ds structures corresponding to semaphore identifiers. This structure is defined in <sys/sem.h>.
Walk the active shmid_ds structures corresponding to shared memory segment identifiers. This structure is defined in <sys/shm.h>.