inline_prime.rb

#!/usr/bin/env ruby

require 'inline'

class Primes
  inline do |builder|
    builder.c '
        void prime(unsigned long amount) {
                int *list;
                unsigned long i,x,d;
                list = malloc(sizeof(int)*(amount));
                for (i=2; i <= amount; i++){
                        list[i] = 1;
                }
                for(x=2; x<=amount; x++) {
                        if (list[x]) {
                                for (d = x; d * x < amount ; d++) {
                                        list[d * x] = 0;
                                }
                        }
                }
                for (i=2; i < amount; i++){
                        if (list[i]){
                                printf("%d\n",i);
                        }
                }
        }'
  end
end

def help
  puts "#{$0} <primes_up_to>"
end
begin
  unless ARGV.length == 1
    help
    exit(1)
  end
  prime = Primes.new
  prime.prime(ARGV[0].to_i)
end