... include <sys/sem.h> int semget(key_t key , int nsems , int semflg ); . ... All operations that set, get, or test-n-set a semaphore use the semop() system call. ... include stdio.h # include stdlib.h # include errno.h # include sys/types.h # include sys/ipc.h # include sys/sem.h int main(void) { key _t key ; int semid ; struct sembuf sb = {0, -1, 0}; /* set to allocate resource */ if (( key = ftok( semdemo.c , 'J')) == -1) { perror( ftok ); exit(1); } /* grab the ...