SHM_RDONLY
shm_addr = shmat(shm_id, NULL, SHM_RDONLY);
(shmflg & SHM_RDONLY) ? IPC_R : IPC_R|IPC_W);
if ((shmflg & SHM_RDONLY) == 0)
if ((shmflg & SHM_RDONLY) == 0) {
if ((shmflg & SHM_RDONLY) == 0) {