One of the more unusual Linux commands is named “yes”. It’s a very simple tool intended to help you avoid having to answer a lot of questions that might be asked when you run a script or a program that needs a series of responses to do its work.
If you type “yes” by itself at the command prompt, your screen is going to start filling up with the just the letter “y” (one per line) until you hit control-C to stop it. It’s also incredibly fast. Unlike what you see displayed below, yes will likely spit out more than a million y’s in the time it likely takes you to reach down and press control-C. Fortunately, that’s not all that this command can do.
Source:: Network World – Data Center