int msgctl (int, int, struct msqid_ds *);
int msgget (key_t, int);
ssize_t msgrcv (int, void *, size_t, long, int);
int msgsnd (int, const void *, size_t, int);
int msgctl (int, int, struct msqid_ds *);
int msgget (key_t, int);
ssize_t msgrcv (int, void *, size_t, long, int);
int msgsnd (int, const void *, size_t, int);