32c.c

/*
============================================================================
Name : 32c
Author : Piyush Singh
Description : Write a program to implement semaphore to protect any critical section.
a. rewrite the ticket number creation program using semaphore
b. protect shared memory from concurrent write access
c. protect multiple pseudo resources ( may be two) using counting semaphore
d. remove the created semaphore
Date: 26th Sep, 2025.
============================================================================
*/

// POSIX Counting Semaphore with fork() (macOS-compatible)
// <stdio.h>     → printf(), perror()
// <stdlib.h>    → exit()
// <semaphore.h> → sem_open(), sem_wait(), sem_post(), sem_close(), sem_unlink()
// <fcntl.h>     → O_CREAT, O_EXCL
// <unistd.h>    → fork(), sleep()

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

int main() 
{
    sem_t *resource_sem = sem_open("/resource_sem", O_CREAT | O_EXCL, 0666, 2);
    if (resource_sem == SEM_FAILED) 
    {
        perror("❌ sem_open failed");
        exit(1);
    }

    pid_t pid = fork();
    if (pid == 0) 
    {
        sem_wait(resource_sem);
        printf("👶 Child acquired resource\n");
        sleep(2);
        sem_post(resource_sem);
        printf("👶 Child released resource\n");
    } 
    else 
    {
        sem_wait(resource_sem);
        printf("👨 Parent acquired resource\n");
        sleep(2);
        sem_post(resource_sem);
        printf("👨 Parent released resource\n");
    }

    sem_close(resource_sem);
    sem_unlink("/resource_sem");
    return 0;
}

/*
Output:
╰─ ./32c                                                                      ─╯
👨 Parent acquired resource
👶 Child acquired resource
👨 Parent released resource
👶 Child released resource
*/