#include <stdio.h>
#include "SDL.h"

static int oldtime;
static int newtime;

int timer (int interval)
{
  return (oldtime/interval) != (newtime/interval);
}

int main(int argc, char *argv[])
{
  ...

  for (;;)
    {
      oldtime = newtime;
      newtime = SDL_GetTicks ();

      if (timer (1000))
    {
      fputs ("1000\n", stdout);
    }
      if (timer (2000))
    {
      fputs ("2000\n", stdout);
    }
      if (timer (3000))
    {
      fputs ("3000\n", stdout);
    }
    }
  ...
}