There are lots of times that we want to have several logged in sessions open at once. Maybe you are logged in as different users in each one. Maybe you need to watch the output of a command while you are working in another window. Maybe you are working in multiple directories and don't want to have to "cd" so often. Opening up all those windows can be a bit of a hassle, especially if they are on a remote system, where you have to log in each time. Then there's the issue of screen clutter -- all those windows, so little screen real estate.

It sure would be helpful if there was a program to allow us to share a window between several "virtual" windows.

Enter GNU Screen. Screen allows users to set up virtual windows and easily interact with them -- just hit an escape key sequence to start a new window, kill an old one, or switch between your active windows. Rather than opening all those windows on your computer, you could open just one and then use Screen to create the virtual windows. Or even better, you could set up Screen's configuration file to open them for you on startup.

But wait, there's more! Here's a really great feature: if you have a Screen session running, you can detach from it and reattach later. Why is this great? Let's say at work you are running a bunch of things in a number of virtual windows. You'd like to go home, but you need to make sure that some long running command completes. No problem with Screen: just detach from your Screen session. When you get home, you can log in and reattach, and all the virtual windows will be just as you left them (the output doesn't block, so data may have been written to the screens while you were away). Sometimes I get so familiar with the virtual windows that I let the session run for several days and reattach every morning.

Have you ever had to scroll back into a console's history, but had trouble finding something? With Screen, that's no problem because not only can you scroll backward through history, you can also search for a string.

Need to copy something between windows?  Screen has the ability to copy and paste between the virtual windows.

One issue with virtual windows is that since you only view one at a time, you can't see what's happening on the other windows. Screen has a solution for that: there is an alert function you can turn on so that you are alerted (by ringing the console bell or with a message on the screen) if there is activity in another window.

Like most GNU projects, Screen is available on every UNIX-ish box known to mankind. Linux users will almost certainly have it included with their distribution.

Screen is one of those tools that has been around for ages, but despite it's usefulness, just hasn't had the notice that I think it deserves. Give it a try!