Ruby does not output in real time

I'm having problems with Project Euler . One of the questions:

The main factors of 13195 are 5, 7, 13 and 29. What is the maximum prime coefficient of the number 600851475143?

I have code written ... and it works:

class Integer

  def primeFactors
  load('/home/arseno/ruby/lib/prime.rb')
  a = []

    for i in (1..self)
      div = self.to_f/i.to_f
      if((div==div.to_i)&&(Prime.prime?(i)))
        a << i
      end
    end
  a
  end
end

puts 13195.primeFactors

Outputs:

5
7
13
29

So far so good! Now, when I put in 600851475143 instead, my terminal freezes (by right, it calculates a lot of everything!) So what I tried to do was put puts iinside the / if loop so that I capture the output when it repeats through ... in mode real time.

But by putting this puts iin a loop, Ruby does not output the variable during the iteration; instead, it holds the values ​​in some kind of buffer and flushes them when the calculation is complete.

Ruby ( 10 ), , .

Ruby ( ?) ? , ? ?