#include<stdio.h>
#include<stdlib.h>
#include<sys/ipc.h>
#include<sys/sem.h>
#include<sys/signal.h>
#include<sys/time.h>
int semkey;
const struct sembuf  up = {0,1,SEM_UNDO};
const struct sembuf  down = {0,-1,SEM_UNDO};

void clearandexit(int r)
{
	int i;
	semctl(semkey,5,IPC_RMID);
	exit(r);
}

void philosopher(int i,int s1, int s2) 
{
	struct sembuf sb[2];
	srand(i+time(NULL));
	while (1) {
		sleep(rand()%2+1);
		sb[0]=down;sb[1]=down;
		sb[0].sem_num=s1; sb[1].sem_num=s2;
		semop(semkey,sb,2);
		printf("Philosopher %d is eating\n",i);
		sleep(rand()%4+1);
		printf("Philosopher %d finished eating\n",i);
		sb[0]=up;sb[1]=up;
		sb[0].sem_num=s1; sb[1].sem_num=s2;
		semop(semkey,sb,2);
	}
}
int main() 
{
	int i,n;
	struct sembuf sb[5];
	
	semkey=semget(IPC_PRIVATE,5,IPC_CREAT|0600);
	if (semkey<=0) {
		perror("Creating semaphore");
		clearandexit(-2);
	}
	for (i=0;i<5;i++) {
		sb[i].sem_num=i; sb[i].sem_op=1;
		sb[i].sem_flg=SEM_UNDO;
	}
	semop(semkey,sb,5);

	for (i=0;i<5;i++) {
		if (!fork()) {
			philosopher(i,i,(i+1)%5);
			return 0;
		}
	}
	signal(SIGINT,clearandexit); sleep(1000);
	clearandexit(0);
}