_shmget
msqid = _shmget(key, size, msgflg, MSGGET);
semid = _shmget(key, size, semflg, SEMGET);
undoid = _shmget(IPC_PRIVATE, PAGE_SIZE, IPC_CREAT | IPC_EXCL | 0600,
return (_shmget(key, size, shmflg, SHMGET));
int _shmget(key_t, size_t, int, int);