prime.c

#include <stdio.h>
#include <math.h>
#include <stdlib.h>

int main(int argc, char *argv[]) {
	int n, x, i, s, f, l;

	if ( argc < 2 ) {
		printf("oi! Provide an argument!\n");
		return 1;
	}
	else if ( argc == 3 ) {
		l = atoi(argv[1]);
		n = atoi(argv[2]);
	}
	else {
		l = 2;
		n = atoi(argv[1]);
	}

	for ( x = l; x <= n; x++ ) {
		s = sqrt(x);
		f = 0;
		for ( i = 2; i <= s; i++ ) {
			if ( x % i == 0 ) {
				f = 1;
				break;
			}
		}
		if ( f == 0 ) {
			printf("%d\n", x);
		}
	}
	return 0;
}