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

int main(int argc, char** argv) {
	if(argc != 2) {
		fprintf(stderr, "usage: %s n\n", argv[0]);
		return EXIT_FAILURE;
	}

	int n = atoi(argv[1]);

	printf("n: %d\n", n);

	sem_t* sem = sem_open("/cpt", O_CREAT, S_IRWXU, 4);

	sem_unlink("/cpt");

	for(int i=0; i<n; i++)
		fork();

	sem_wait(sem);

	printf("[%d] start job\n", getpid());
	sleep(1);
	printf("[%d] stop job\n", getpid());

	sem_post(sem);

	return EXIT_SUCCESS;
}