using screen to keep unix sessions active

In Unix, what is screen, and how do I use it?

The screen program allows you to use multiple windows (virtual VT100 terminals) in Unix.

Note: UITS does not support screen.


  1. If your local computer crashes, or you are connected via a modem and lose the connection, the processes or login sessions you establish through screen don’t go away. You can resume your screen sessions with the following command:
  screen -r

In some cases you may have to manually “detach” your screen session before resuming it. For more information, see the Knowledge Base document Using screen, why can’t I re-attach to my session after a lost connection?

  1. The screen program creates multiple processes instead of multiple Unix login sessions, which means that it is resource-efficient.

  2. You can cut and paste between different screens without using a mouse. Thus, you don’t need to be on a computer with a windowing environment such as Mac OS, Mac OS X, Windows, or the X Window System.

  3. It has a block copy feature which is similar to the kill rectangle feature of Emacs.

  4. You can copy and paste more than one page at a time, which you cannot do with some clients. You can scroll up more than one page, depending on how many scrolling lines you have set with the -h option.

  5. Using the detach feature, you can save screen processes when logging out and resume where you left off, saving the trouble of restarting them.

###Starting screen###

To start screen, enter the following command:


###General commands###

Note: Every screen command begins with Ctrl-a .

Ctrl-a c Create new window (shell)
Ctrl-a k Kill the current window
Ctrl-a w List all windows (the current window is marked with "*")
Ctrl-a 0-9 Go to a window numbered 0-9
Ctrl-a n Go to the next window
Ctrl-a Ctrl-a Toggle between the current and previous window
Ctrl-a [ Start copy mode
Ctrl-a ] Paste copied text
Ctrl-a ? Help (display a list of commands)
Ctrl-a Ctrl-\ Quit screen
Ctrl-a D (Shift-d) Power detach and logout
Ctrl-a d Detach but keep shell window open

Press the Spacebar or Enter to end a command.

To copy a block

To get into copy mode, press Ctrl-a [ .

To move the cursor, press the h , j , k , and l (the letter l) keys. The 0 (the number 0) or ^ (the caret) moves to the start of the line and $ (the dollar sign) moves to the end of the line. Ctrl-b scrolls the cursor back one page and Ctrl-f scrolls forward one page. To set the left and right margins of copy, press c and C (Shift-c). The Spacebar starts selecting the text and ends selecting the text. To abort copy mode, press Ctrl-g .

To paste a block

To paste the copied text to the current window (as many times as you want), press Ctrl-a ] .

Other commands

To run a program or execute any Unix command in a new window, at the Unix prompt, enter:

  screen unixcommand

Above, replace unixcommand with the appropriate command name.

To automatically start several windows when you run screen, create a .screenrc file in your home directory and put screen commands in it.

To quit screen (kill all windows in the current session), press Ctrl-a Ctrl-\ .

The man pages for screen are quite readable and make a good tutorial. At the Unix prompt, enter:

  man screen

###[Source Link][]###

###If your unix server does not support screen. It is always a better to run some commands with nohup.###

Any questions on this, please feel free to ask. We’re here to help…