What is a Shell in Linux [A Comprehensive Summary]

The shell exposes the operating system to the user. It provides a way for a user to interact with the system and control it. A shell can have a graphical or command-line interface. In the command-line interface, a user can provide commands, scripts, or other programs and execute them. For instance, you want to know the current date. You can type “date” on a terminal in your Linux, and the shell will run the necessary program to show you the date. In this article, you will learn everything you need to know about shell in Linux.

What is A Shell in Linux?

A shell is a program. It takes commands from the keyboard and gives them to the operating system to execute. However, nowadays most operating systems provide GUI (Graphical User Interface) to provide commands. Linux systems use a shell named bash, whereas Windows uses powershell. Command formatting can be different on different shells. Bash commands are Unix-styled and powershell commands are based on OOP (Object Oriented Programming). For instance, the ls command in bash performs the same task as the “Get-ChildItem” command in powershell which is listing files in the current directory. There are different types of shells available as different users have different needs and preferences.

How Does Shell Work?

Here are the detailed steps of how the shell works:

  1. First, the user provides a command.
  2. Shell divides the command into individual words.
  3. Shell looks for an executable file having the same name of the command in the PATH environment.
  4. Shell launches the program and provides necessary arguments and input.
  5. The program runs based on the inputs and returns an exit status at the end.
  6. Shell displays the output on the screen.
  7. Shell waits for a new command.

Command-line Shell and Graphical Shell

Linux shells are broadly categorized into 2 types:

  1. command line shell and
  2. graphical shell.

1. Command Line shell

  • It uses text-based interface.
  • More flexible and powerful, especially in scripting.
  • Require some knowledge of commands and their usage.
  • Faster for working with large data sets or repetitive tasks.
  • Preferable for purposes like scripting and automation.

2. Graphical Shell

  • It uses graphical user interface (GUI) interaction instead of text-based interaction.
  • Suitable for any type of user.
  • Includes drag and drop.
  • It provides a wide range of applications for web browsers to media players.
  • It has a lot of keyboard shortcuts and GUI-based features.

Different Types of Shell for Linux Systems

There are different types of shells available nowadays for Linux systems. Here I have listed some of them:

  • Bourne Shell (sh): It is used for executing basic commands and script.
  • Bourne Again Shell (bash): It is the upgraded version of Bourne shell. It has features like command-line editing, job control, history Also it provides support for advanced scripting.
  • C Shell (csh): It has syntax like C programming language. It also provides features like command-line editing, job control, history.
  • Korn Shell (ksh): It is also an improved version of Bourne shell. It also provides advanced features.
  • Z shell (zsh): It includes features from Bourne, C and Korn shells. Also, it provides some advanced features like spelling correction and advanced globbing. Globbing helps to specify multiple files or directories without typing their names.
  • Fish Shell (fish): It provides a more user-friendly It also includes features like text highlighting.

Terminal Vs Shell

Some people think terminal and shell are the same. But they are different from one another.

  • Terminal: It can be physical or virtual. It is a text based interface that allows a user to enter commands and display them.
  • Shell: It is a program that interprets the commands entered via the terminal and provides a way to interact with the operating system.

Benefits of a Shell

Shell in Linux offers several benefits, making them essential to interact with the operating system:

  1. Command Execution: Enabling users to execute commands, the shell provides an efficient and faster way to perform tasks and control system processes.
  2. Automation and Scripting: Shell Linux supports scripting languages, allowing users to automate repetitive tasks and create programs for complex problems.
  3. Flexibility and Control: It provides greater control and flexibility by allowing users to run shell scripts in the current shell environment.
  4. Accessibility: Shells can used remotely and the Linux system can be managed from anywhere with an internet connection.

What is Shell Scripting?

Shell scripting in Linux is creating a sequence of commands written in a scripting language that is specific to a shell for interpretation. The main goal of shell scripting is to automate tasks and perform repetitive tasks quickly and efficiently. The basic element is a list of commands, listed in order of execution. The files in which the commands are listed and executed are called shell scripts or shell programs. Each shell script is saved with “.sh” file extension, for example, my_script.sh.

A shell script has syntax like another programming language. There are conditional tests, and loops that assist users in handling massive data, and the shell can also include functions. A quality shell script has comments preceded by the sign “#”, that describes each step.

Advantages of Shell Scripts in Linux

Using shell scripts is beneficial in many ways. Some of them are listed below:

  • Portable: A shell script developed in one machine can run on different machines.
  • Fast: It is faster than GUI.
  • Less Resource Hungry: It needs fewer computer resources to run whereas GUI consumes a lot of resources.
  • Good for Automation and Scripting: It is more flexible, efficient, and powerful for automation and scripting.

 Disadvantages of Shell Scripts in Linux

Using shell scripts in Linux also has some disadvantages:

  • Less Intuitive: It is less intuitive than GUI. It is hard to tell what is going on.
  • Not Beginner Friendly: It requires a steep learning curve. That’s why it isn’t suitable for all types of users.
  • Not as Powerful as Programming Language: Programming languages are faster than shell script. Also, programming languages provide a lot of functionality and flexibility than shell.

Conclusion

In this article, I have tried to provide you with some basic concepts on shell Linux. Hopefully, now you have a better understanding of shell Linux than before.

People Also Ask

How to find out which Linux shell I am using?

Run the command echo $SHELL to know the Linux shell type that your system is using. For example, if you are using the bash shell, the mentioned command will display /bin/bash as output denoting that your system is using the bash (bourne again shell) shell.

Can I find out how many shells are installed in my Linux system?

Yes, you can. You have to look into the file named /etc/shells to see all the installed Linux shells in your system which you can do using the cat command for instance. The complete command is mentioned below:

cat /etc/shells

This will display the list of installed shells, showcasing their respective paths.

How does a shell differ from a Linux kernel?

A kernel is the core of an operating system responsible for managing hardware, memory, processes, and other fundamental resources. On the other hand, the shell is a user interface that allows users to interact with the kernel. It allows users to issue commands that the kernel can understand and thus execute.

Is it possible to change my default shell in Linux?

Yes, it’s possible. You can use the chsh command and change the default Linux shell. Now, to change the shell, mention the -s option after the command chsh and input the shell path afterward. For example, to change the default shell to z shell, run the below command:

chsh -s /usr/bin/zsh

What is the kernel?

The kernel is the core of an operating system with full control over everything in the system. It acts as a bridge between the hardware and applications running in the system. The kernel manages the following resources of a Linux system:

  1. File management
  2. Process management
  3. I/O management’
  4. Memory management etc.

What is a terminal in Linux?

A terminal in Linux is a command-line program that provides users with an interface to access the shell. It permits users to enter commands and see the command outputs in a text-based interface. So, in brief, the terminal acts as a bridge between the users and the operating system, enabling them to run programs, manage files, and configure system settings.

Who invented the shell?

The journey of shells started in the 1960s and 1970s when computers had just begun to become more than just calculators. In 1971, Ken Thompson introduced the first Unix shell, which is called the Thompson shell. The shell allowed users to provide commands using natural language like syntax. It was more user-friendly than previous techniques. Then Stephen Bourne developed the Bourne shell which replaced the Thomson Shell as it is more powerful and flexible. However, more advanced shells like Bash(Bourne Again Shell) arrived later.


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Walid Al Asad

Hello Everyone! I am Walid Al Asad. Currently, I am working at a tech company named Softeko as a Linux Content Developer Executive. I live in Dhaka, Bangladesh. I have completed my BSc. in Mechanical Engineering from Bangladesh University of Engineering and Technology (BUET). You can find me on LinkedIn, and ResearchGate. Read Full Bio

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