msgrcv
ssize_t msgrcv(int, void *, size_t, long, int);
msgrcv((key_t)msgID, (void *)&msg, 20, 0, IPC_NOWAIT);
msgrcv((key_t)msgID, (void *)&msg, 10, 0, IPC_NOWAIT);
= msgrcv((key_t)msgID, (void *)&msg, 10, 0, IPC_NOWAIT | MSG_NOERROR);