Linux Shell

The Linux shell is a unique program that acts as a bridge between the user and the services of the operating system. It takes commands entered in a human-readable format, such as text typed on a keyboard or stored in a file, and translates them into a form that the operating system's kernel can process. The shell functions essentially as a command-language interpreter, executing these instructions. It becomes active automatically when users log into their accounts or start a terminal session.

In Linux, there are two main types of shells: Command Line and Graphical Interface.

Command Line

The command-line shell is accessible to users through a text-based interface. Users can enter commands into a specific application known in Linux as the Terminal. Commands like

cat,ls, and others are written into this interface, processed, and executed. The results of these commands are displayed directly in the terminal window.

A terminal on Linux looks like this:

In the given screenshot, the

lscommand is executed with the-loption. This command lists all files in the current directory in a long format.

Using the command line can be challenging at first because remembering commands might be difficult. However, its power lies in its flexibility and strength; users can compile scripts and execute them simultaneously, making it easy to automate repetitive tasks. In the Linux context, these scripts are often referred to as shell scripts.

Graphical Interface

The graphical interface offers a user-friendly way to interact with programs. It allows users to perform actions like opening, closing, moving, and resizing windows without needing to type commands. Operating systems like Windows or Ubuntu provide a graphical interface to simplify user interaction with the system.

A graphical interface on a typical Linux system looks like this:

Linux operating systems offer various shells, each with unique features and command syntax:

• BASH (Bourne Again SHell): The most widely used Linux shell, serving as the default shell on Linux and macOS. BASH is known for its comprehensive scripting capabilities and extensive support.

• CSH (C Shell): The syntax and usage of C Shell are similar to the C programming language, making it appealing for users familiar with C.

• KSH (Korn Shell): The Korn Shell, which forms the basis for the POSIX Shell standard features, combines elements from BASH and CSH, offering powerful scripting abilities and command-line editing features.

• ZSH (Z Shell): ZSH incorporates features from BASH, KSH, and TCSH, offering robust auto-completion functions, customizable prompts, and numerous plugins and themes through frameworks like Oh My Zsh.

• Fish (Friendly Interactive SHell): Known for its user-friendly interface, Fish provides features like syntax highlighting, auto-suggestions, and tab completions without requiring additional configuration.

While all these shells perform the basic task of command interpretation, they vary in the specific commands they support, built-in functionalities, and scripting capabilities, allowing users to choose the shell that best fits their preferences and needs.

What is a Terminal?

The terminal application serves as a gateway for users to interact with the shell, providing a text-based interface where commands can be entered and their outputs viewed. It is a critical tool for executing commands directly and is also used to run larger scripts designed to automate and perform repetitive and complex tasks.

To open the terminal, you can usually find it by typing 'terminal' into the search box in the graphical interface and launching it by double-clicking the result.