In the dynamic realm of command-line interfaces, the terminal serves as a potent hub for executing tasks, running scripts, and managing server operations. However, a common challenge arises when you need to keep processes running in the background, especially when working over SSH. Enter the ‘screen’ command—a versatile and powerful tool that unlocks a world of possibilities for persistent task management.

In this blog post, we will embark on a journey into the realm of ‘screen,’ demystifying its functionalities and showcasing how it can be a game-changer for users who wish to ensure the continuity of their tasks even when the SSH session is closed. Whether you’re a system administrator, developer, or enthusiast seeking to enhance your command-line prowess, understanding ‘screen’ can open doors to uninterrupted workflows and increase productivity.

Join us as we explore the ins and outs of the ‘screen’ command, from its basic usage to advanced features, empowering you to keep your tasks alive, thriving, and resilient to the ephemeral nature of SSH connections. Let’s dive into the terminal and discover the art of background task management with ‘screen.’

What’s the screen command?

The screen command in the terminal is a powerful tool that provides a virtual terminal multiplexer. It enables users to create multiple terminal sessions within a single window or terminal session. This functionality becomes especially useful when working remotely over SSH or when you need to run processes that should persist even if the SSH connection is terminated.

Basic Usage:

Start a New Session:

To start a new session, simply type screen and press Enter in your terminal. This creates a new terminal session within the existing one.

screen

Navigate Between Sessions:

If you have multiple screen sessions running, you can switch between them using the command:

screen -ls          # List existing sessions
screen -r SESSION_ID # Resume a specific session

Use Ctrl+A followed by N to switch to the next session and Ctrl+A followed by P to switch to the previous session.

Detach from a Session:

To detach from a screen session while keeping it running in the background, press Ctrl+A followed by D. This returns you to the original terminal.

# Detach from the current session
Ctrl+A, D

Reattach to a Session:

To reattach to a detached session, use the following command:

screen -r SESSION_ID

Running Processes in the Background:

Start a Process:

Inside a screen session, start a process as you normally would.

# Example: Run a script in the background
./myscript.sh &

Detach and Keep Running:

Detach from the screen session, allowing the process to continue running in the background.

# Detach from the current session
Ctrl+A, D

Reattach to Check Progress:

Later, you can reattach to the screen session to check on the progress of your background process.

screen -r SESSION_ID

Additional Commands:

Create a Named Session:

screen -S session_name

Lock a Session:

Ctrl+A, X

Split the Screen Horizontally:

Ctrl+A, S

Split the Screen Vertically:

Ctrl+A, |

The screen command offers a plethora of features, making it a versatile tool for managing terminal sessions and background processes. Its ability to persist sessions even when the SSH connection is closed makes it particularly valuable for long-running tasks and remote server management.

-Tiago