Linux command: Screen

screen is one of those commands that you just fall in love with immediately and once you start using it, you will start to find a many ways to use it to increase productivity.

When you type, screen, it does this:

It opens up a new screen(logical) in the shell, which can be “attached” to or “detached from” at any point in time without affecting the process running with in it.

Use case 1: This is obviously useful when you are working on SSH. For example, if you have to start a long running build process from a remote SSH, then you would need to be worried about the SSH connection breaking off, because if you loose that session the processes that were started within that are also killed.

screen will help you here, you can start your process from screen and then detach from it, it would be then running on in the background and you can get back to it whenever you want, even if you loose your SSH session.

Use case 2: You want to start build and then be able to connect to same session from other machines/location.

screen will let you take(connect, interact, view) your sessions where your go. Its like portable little shell :)

Small tutorial:

$> screen

This will open up a new screen.

Play around a bit, it is just like a bash shell. One difference : press “Ctrl+A”   and then “?” This will show your screen commands.

[screen] $> <start your longrunning process>

[screen] $> “Ctrl+A” and “d”

this will detach from the shell and return to the original prompt.

$> screen -ls

this will list the screens you currently have going on.

$> screen -r <screenid[listed above]

This will “reattach” you to the screen, and you will be happy to see your process still running :) Note: even if you loose the connection of the SSH.

This is probably the start, lot of other things that you could do with screen.

You could create new multiple windows, with in one screen.

Also, you might want to log the output of a screen, you can do that with “ctrl+a” + “H” (upper case) and that will create a .log file on the home directory.

That’s it I guess, to get started !

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