how do you know that I didn't read about sed. I am reading many pages especially about sed (because you insisted on the solution can only be possible with using sed) for last two days.
I can introduce you the best page (in my opinion) among that many pages about sed on the net:
but I couldn't find my question's answer on that pages, that is why I requested help here. But if you don't want, forget about it, nevermind.