sp-lab/4.c

#include<stdio.h>
#include<fcntl.h>
#include<semaphore.h>

int main(){
    int n, phil, ch;
    printf("Enter number of philosophers: ");
    scanf("%d", &n);

    int eating[n];
    for(int i =0;i<n;i++)
        eating[i]=0;
    sem_t *chopstick[n];
    char name[20];

    for(int i=0;i<n;i++){
        sprintf(name, "/c%d",i);
        sem_unlink(name);
        chopstick[i] = sem_open(name, O_CREAT, 0644, 1);
    }
    sem_unlink("/room");
    sem_t *room = sem_open("/room", O_CREAT, 0644, n-1);

    while(1){
        printf("---\nDIning philosopher problem----\n");
        printf("\n1.Pick chopstick(eat)");
        printf("\n2.Put chopstick(think)");
        printf("\n3.Exit");
        printf("\nENter your choice: ");
        scanf("%d", &ch);

        if(ch==1){
            printf("\nEnter the philosopher number (0 to %d): ", n-1);
            scanf("%d",&phil);

            if(eating[phil]){
                printf("\nprofessor already eating");
                continue;
            }
            sem_wait(room);
            sem_wait(chopstick[phil]);
            sem_wait(chopstick[(phil+1)%n]);
            eating[phil] = 1;
            printf("\nprofessor %d eating", phil);
        }
        else if(ch ==2){
            printf("\nEnter the philosopher number (0 to %d): ",n-1);
            scanf("%d", &phil);

            if(!eating[phil]){
                printf("\nphilosopher not eating");
                continue;
            }
            sem_post(chopstick[phil]);
            sem_post(chopstick[(phil+1)%n]);
            sem_post(room);
            eating[phil] = 0;
            
            printf("Philosopher %d finished eating\n",
                   phil);
        }
        else if (ch == 3) {
            break;
        }

        else {
                printf("Invalid choice\n");
        }
    
    }

    for(int i =0;i<n;i++){
        sprintf(name, "/c%d", i);
        sem_close(chopstick[i]);
        sem_unlink(name);
    }
    sem_close(room);
    sem_unlink("/room");
    return 0;
}