gcc primenumbers.c -o primenumbers -lpthread

primenumbers.c

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <semaphore.h>

#define THREADS_NUM 8

long long int count_to = 100;

void *thread_isPrimeNumber(void *arg)
{
	long long int num = (long long int)arg;
	long long int i;
	char is_prime = 1;

	while (num++)
	{
		if (num > count_to && count_to != 0)
			break;

		if (num % THREADS_NUM == (long long int)arg && (num % 2 != 0 || num % 3 != 0 || num % 5 != 0 || num % 7 != 0 || num % 9 != 0))
		{
			is_prime = 1;
			for (i = 3; i < num; i=i+2)
			{
				if (num % i == 0)
				{
					is_prime = 0;
					break;
				}
			}
	
			if (is_prime)
				printf("%i\n", num);
			fflush(0);
		}
	}

	return 0;
}

int main(int argc, char* argv[])
{
	
	if (argc > 1)
		count_to = atoi(argv[1]);
	else
		count_to = 100;

	pthread_t pth[THREADS_NUM];

	long long int i;
	for (i = 0; i < THREADS_NUM; i++)
		pthread_create(&pth[i], NULL, thread_isPrimeNumber, i);

	for (i = 0; i < THREADS_NUM; i++)
		pthread_join(pth[i], NULL);
	
	printf("\n");

	return 0;
}