Thanks for your answers. Phillip and Dwayne, your answer was very useful, I did not know some commands and such softwares exist for this application (but as I'm on windows, the diff command was not working because of my file size) and I did not only see the difference, but create a new file with some specific things. As Bartosz and Brian said I'll try with your solution, the file is not so big (~300k text each) Only because I think it could be good to know, someone have some kind of solution if files are bigger ? I was thinking of sorting lines in the files before removing lines in the 2nd file. I'll try with your ideas and maybe think about an alternate method in case of .. thanks again for your help. -- Posted via http://www.ruby-forum.com/.