GNU Screen

GNU Screen is a terminal multiplexer that lets you manage multiple shell sessions within a single terminal. Acting like an electronic MUX, it handles several inputs (shells) to one output (your terminal). Key features include:

• Multiple sessions, each containing one or more windows
• Independent windows running separate programs
• Splitting windows into regions (panes)
• A command prefix (default Ctrl-a) followed by command keys
• Detachable sessions that continue running in the background
• Socket connections, copy/scrollback mode, and extensive customization

Table of Contents

• History
• Getting Started
• Prefix & Window Management
• Navigating & Closing Windows
• Splitting into Regions (Panes)
• Sessions: Listing, Naming & Killing
• Detaching & Reattaching
• Copy/Scrollback Mode
• Configuration
• Links & References

History

In the era of physical VT100 terminals (1970s/80s), users had no windowing system. GNU Screen, introduced in 1987, emulated multiple VT100 sessions on a single terminal, transforming remote and local shell workflows.

Getting Started

To launch a new Screen session:

$ screen
GNU Screen version 4.05.00 (GNU) 10-Dec-16
...

Press Space or Enter to dismiss the welcome message. Behind the scenes, Screen has created session 0 and window 0, presenting you with a familiar shell prompt.

Prefix & Window Management

All Screen commands begin with the default prefix: Ctrl-a (denoted C-a), followed by a command key.

Example: Managing Windows

1. In window 0, run:

   $ ps
   PID TTY          TIME CMD
   974 pts/2    00:00:00 bash
   981 pts/2    00:00:00 ps
   

2. Press C-a c to create window 1, then run ps again.
3. Press C-a w to view the window list:

   Num  Name  Flags
   0    bash  $
   1    bash  *$
   

4. Rename window 1:
   • Press C-a A
   • Enter ps
5. Create window 2 named “yetanotherwindow”:

   $ screen -t yetanotherwindow
   

Navigating & Closing Windows

Switching Windows

After C-a ", use ↑/↓ and Enter:

Num  Name               Flags
0    bash               $
1    ps                 $
2    yetanotherwindow   $

Closing Windows

• Exit the shell/program inside the window
• Or press C-a k, then confirm with y:

  Really kill this window [y/n] y
  Window 0 (bash) killed.
  

Splitting into Regions (Panes)

Divide your window into multiple regions for side-by-side workflows.

Empty regions display as two hyphens. Closing a region does not kill its window; it simply hides the view.

Sessions: Listing, Naming & Killing

Listing Active Sessions

$ screen -ls
There is a screen on:
	1037.pts-0.debian (Attached)
1 Socket in /run/screen/S-user.

• 1037: Session PID
• pts-0.debian: Terminal and host

Naming a New Session

$ screen -S "my session"

Now screen -ls shows:

There are screens on:
	1009.my session   (Attached)
	1037.pts-0.debian (Attached)
2 Sockets in /run/screen/S-user.

Killing a Session

$ screen -S 1037 -X quit

You can use the session name instead of the PID.

Detaching & Reattaching

Copy/Scrollback Mode

Screen’s scrollback mode allows you to browse history and copy text across windows:

1. Enter mode: C-a [
2. Move cursor to the start of the text (arrow keys)
3. Press Space to begin selection
4. Move to the end of the text
5. Press Space to complete selection
6. Paste with: C-a ]

Configuration

Screen reads two primary config files:

Each config file may include:

1. General settings

   defscrollback 10000
   

2. Key bindings

   bind | split ____
   

3. Terminal settings

   defnonblock 5
   

4. Startup screens

   screen -t top top
   

Edit these files to tailor Screen’s behavior. Consult the GNU Screen man page for a full directive reference.

Links & References

• GNU Screen Home Page
• Linux Journal: GNU Screen Tutorial
• man screen (official)