#include <stdio.h>#include <sys/types.h>#include <sys/ipc.h>#include <sys/sem.h>int main(void){	key_t key;	int semid;	int nsems;	int proj_id;		key=IPC_PRIVATE;	nsems=2;	semid=semget(key,nsems,0666);	if(semid==-1)		perror("cannot create semaphore set");	else		printf("1. key=IPC_PRIVATE,  semid= %d\n",semid);	proj_id=1;	key=ftok("/home/program",proj_id);	if(key==-1)		perror("cannot generate IPC key");	semid=semget(key,nsems,IPC_CREAT|0666);        if(semid==-1)                perror("cannot create semphore set");	else        	printf("2. key=%d generated by ftok, semphore set semid= %d\n",key,semid);		semid=semget(key,nsems,IPC_CREAT |IPC_EXCL |0666);	if(semid==-1)		perror("cannot create semphore set");	semid=semget(key,nsems,IPC_CREAT |0666);	if(semid==-1)		perror("cannot create semphore set");		else		printf("Access the existing semphore set\n");	return 0;}