/* ** seminit.c -- sets up a semaphore for semdemo.c */ #include #include #include #include #include #include int main(void) { key_t key; int semid; union semun arg; if ((key = ftok("semdemo.c", 'J')) == -1) { perror("ftok"); exit(1); } /* create a semaphore set with 1 semaphore: */ if ((semid = semget(key, 1, 0666 | IPC_CREAT)) == -1) { perror("semget"); exit(1); } /* initialize semaphore #0 to 1: */ arg.val = 1; if (semctl(semid, 0, SETVAL, arg) == -1) { perror("semctl"); exit(1); } return 0; }