// Eratosthenes' sieve
    
#include <stdio.h>
#include <stdlib.h>

#define SIZE 10000000

int fill_sieve(int *psieve);
int sort_sieve(int *psieve);
int print_sieve(int *psieve);

int main(void)
{
    int *psieve = NULL;

    psieve = (int *)malloc(SIZE*sizeof(int));
    if(psieve == NULL)
    {
        printf("\nNot enough memory.\n");
        return 1;
    }
    
    fill_sieve(psieve);
    sort_sieve(psieve);    
    print_sieve(psieve);
    
    free(psieve);
    
    return 0;
}

int fill_sieve(int *psieve)
{
    for(int i = 0; i < SIZE; i++)
        psieve[i] = i;
    return 0;
}

int sort_sieve(int *psieve)
{
    for(int i = 2; i < SIZE; i++)
            for(int j = i * 2; j < SIZE; j += i)
                psieve[j] = 0;
    return 0;
}

int print_sieve(int *psieve)
{
    FILE *pfile = NULL;
    char *filename = "primes.txt";
    
    if(!(pfile = fopen(filename, "w")))
    {
        printf("Error opening %s for writing.", filename);
        exit(1);
    }

    for(int i = 2; i < SIZE; i++)
        if(psieve[i] != 0)
            fprintf(pfile, "%d\n", psieve[i]);
    
    fclose(pfile);
    
    return 0;
}