screen

What is screen?

screen is a powerful terminal multiplexer that lets you manage multiple terminal sessions within a single window. It’s particularly useful for:

• Running long-running processes: Keep your processes running even after you close your terminal.
• Managing multiple sessions: Work on many tasks concurrently within a single terminal.
• Remote access: Access your sessions from different terminals.
• Session restoration: Recover sessions after unexpected disconnections.

Getting Started with screen

Before diving into detailed examples, ensure screen is installed on your system. Most Linux distributions include it by default. If not, use your distribution’s package manager (e.g., apt-get install screen on Debian/Ubuntu, yum install screen on CentOS/RHEL).

Basic screen Commands

Let’s look at fundamental screen commands with practical examples.

1. Starting a screen session:

Simply type screen in your terminal. This will create a new screen session. You’ll now be working within this session. Any commands you run here will continue running even if you detach from the session.

2. Detaching from a screen session:

Press Ctrl+a followed by d. This detaches you from the current session without terminating the running processes. Your session remains active in the background.

3. Listing existing screen sessions:

Use the command screen -ls. This lists all active screen sessions, showing their process ID and status. The output looks something like this:

There are screens on:
    1234.pts-1.myuser    (Detached)
    5678.pts-2.myuser    (1 Socket)

4. Reattaching to a screen session:

Use screen -r <session_number> or screen -r <session_name>. Replace <session_number> with the number from the screen -ls output or <session_name> (if you’ve named your session using the -S option during launch). For example, to reattach to session 1234.pts-1.myuser, use:

screen -r 1234.pts-1.myuser

5. Killing a screen session:

Use screen -X quit within the session itself to gracefully exit, or screen -S <session_name> -X quit from outside the session. Forcibly killing a session requires using the process ID and kill command (obtained from screen -ls), which is generally discouraged unless absolutely necessary.

Advanced screen Usage: Splitting Windows and more

screen provides features to split your terminal into multiple windows, improving your workflow.

1. Splitting the screen:

Within a screen session, press Ctrl+a followed by S. This splits the current window horizontally. You can now navigate between the split windows using Ctrl+a then Tab.

2. Creating new windows:

Press Ctrl+a followed by c to create a new window within the screen session.

3. Switching between windows:

Use Ctrl+a followed by n (for next window) or p (for previous window).

4. Closing a window:

Press Ctrl+a followed by k within the window you want to close.

5. Naming a session:

You can name your sessions at launch using the -S option:

screen -S my_long_running_process

Example: Running a long process

Let’s say we want to run a long-running process, like a web server:

1. Start a screen session: screen
2. Start your process within the session (replace python your_script.py with your actual command): python your_script.py
3. Detach from the session: Ctrl+a, d
4. Later, reattach: screen -r

This ensures your web server continues running even if you close your terminal or lose your network connection. You can reattach at any point to monitor its progress or make changes.

Conclusion (Not included as per instructions)