What Is Bash? Features, Major Concepts, Commands, & More!

Bash, short for Bourne-again shell, is a command-line shell and scripting language used on Linux, macOS, and other Unix-like operating systems. Its name comes from its predecessor Bourne Shell after its original developer Stephen Bourne. Bash is the default shell on most Linux distributions and is used for executing chains of commands and scripts. In this article, we will discuss what is Bash scripting, the history of Bash script, features, commands, etc. 

What Is Bash?

To begin with, Bash is the command language interpreter for the operating system and is compatible with Bourne shell programs. In other words, it provides users with a simple and efficient way to interact with the system and perform a variety of tasks, such as creating files, editing text, and managing processes.

• Commands are the fundamental building blocks of Bash.
• Arguments, variables, functions, pipes, redirection, and wildcards are used to modify and extend the behavior of bash commands.
• Bash scripts are programs written in Bash that can automate tasks, perform complex operations, and create custom tools. 

To use Bash, you need to open a terminal or console window. In Linux, you can usually open a terminal by pressing Ctrl+Alt+T. In macOS, you can open a terminal by searching for 'Terminal' in Spotlight or opening it from the utility folder in the 'Applications folder'. Once you have a terminal window open, you can start using Bash by typing commands and pressing 'Enter'.

History Of Bash

Bash was created by Brian Fox in 1987 as a free software replacement for the original Unix shell- the Bourne shell (often referred to as 'sh'). It was developed as part of the GNU Project and was designed to be a versatile shell that could be used in a variety of Unix environments. Over time, Bash has become the most widely used shell on Unix systems.

It incorporates features from other shells, such as the C shell (csh) and the Korn shell (ksh), and has additional new features of its own, such as command-line editing and command-line completion. The Linux shell is based on the Bash scripting language and provides a wide range of built-in commands and features like double brackets that allow users to perform various tasks. There are two types of shell i.e. Command-line interface(CLI) and Graphical user interface (GUI). Bash commonly uses a Command-line interface for Unix OS.

Features of Bash

Over the years, Bash has continued to evolve, with new features and improvements being added with each release. Some of the notable features of Bash include:

• Command-line editing: Bash allows users to edit their commands using the arrow keys and other editing keys, making it easier to correct mistakes and modify commands.
• Command history: Bash keeps a history of the commands that have been entered, making it easy to recall and reuse previous ones when needed.
• Job control: Bash allows users to run multiple commands in the background and switch between them, making it easier to manage and monitor long-running tasks.
• Shell scripting: Bash includes a powerful scripting language that allows users to automate tasks and perform complex operations.

Bash: Some Important Concepts

The following are some basic concepts of Bash that every user should be familiar with:

1. Commands: A command is an instruction that tells the shell what to do. Commands can be typed in the terminal and can be simple or complex.

2. Arguments: Arguments are additional information that is passed to a command to modify its behavior. They can be options, filenames, or other types of data.

3. Variables: Variables are used to store data that can be used by the shell or by scripts. They can be assigned values and used in commands or scripts.

4. Functions: Functions are used to group commands together and perform specific tasks. They can be called from the command line or from within a Bash script.

5. Pipes: Pipes allow users to chain commands together and create more complex workflows.

6. Redirection: Redirection is used to redirect the output of a command to a file or to another command. This allows users to save the output to a file or to use it as input for another command in the command prompt.

7. Wildcards: Wildcards are used to match patterns in filenames or other data. They can be used to select multiple files or to perform operations on groups of files.

What Is Bash Scripting?

Bash scripting refers to the process of writing shell scripts using the Bash shell. These scripts are essentially a series of commands that are executed sequentially and can be used to automate repetitive tasks or perform complex operations. Bash scripts are executed by typing the name of the script in the terminal window.

Here are some basic concepts and commands related to Bash scripting :

1. Shebang: The first line of a Bash script is known as the "shebang" and specifies the interpreter to be used to run the script.It is basically an absolute path to the bash interpreter. The shebang for Bash scripts is usually-
   #!/bin/bash

2. Variables: Variables are used to store values and can be referenced later in the script. To assign a value to a variable, use the syntax varname=value.

3. Command substitution: Command substitution is a way to use the output of a command as part of another command. It is done by enclosing the command in $(command) or command.

4. Conditional statements: Conditional statements allow users to execute certain commands based on whether a condition is true or false.

5. Loops: Loops allow users to execute a set of commands repeatedly. The two main types of loops in Bash scripting are- for loops and while loops.

6. Functions: Functions are used to group commands together and can be called later in the script. To define a function, use the syntax-
   function_name() { commands }

7. Input/output: Bash provides several simple commands for reading input and writing output. The most common ones are- read and echo.

Also read - Prepare For Linux Interview Questions

Commonly Used Bash Commands 

There are countless Linux Bash commands at the disposal of all its users. Experienced users can easily use these commands and complete the task they want to, with some guidance. Below are a few of the most commonly used Linux Bash commands: 

1. Command cd: Changes the current directory to the specified directory. For example, "cd /home/user" changes the current directory to /home/user.

2. Command ls: List directory contents and file type in the current directory. The most commonly used options are -l (long format) and -a (show hidden files).

3. Command mkdir: Creates a new directory with the specified name. For example, "mkdir mydir" creates a new directory called mydir in the current directory.

4. Command touch: Creates a new file with the specified name. For example, "touch myfile.txt" creates a new file called myfile.txt in the current directory.

5. Command rm: Deletes a file or directory. For example, "rm myfile.txt" deletes the file myfile.txt, and "rm -r mydir" deletes the directory mydir and all its contents.

6. Command mv: Renames or moves a file or directory. For example, "mv myfile.txt newname.txt" renames the file myfile.txt to newname.txt, and "mv mydir /home/user" moves the directory mydir to the /home/user directory.

7. Command cp: Copies a file or directory. For example, "cp myfile.txt myfile_copy.txt" creates a copy of the file myfile.txt called myfile_copy.txt, and "cp -r mydir mydir_copy" creates a copy of the directory mydir called mydir_copy.

8. Command cat: Concatenates and displays the contents of one or more files. For example, "cat myfile.txt" displays the contents of the file myfile.txt.

9. Command grep Searches for a specific pattern in a file or input. For example, "grep 'example' myfile.txt" searches for the word "example" in the file myfile.txt.

10. Command echo: Prints a message to the terminal or writes it to a file. For example, "echo 'Hello, world!'" prints the message "Hello, world!" to the terminal.

Conclusion

This brings us to the end of our discussion on what is Bash and important concepts, Linux Bash scripts, Linux Bash commands, etc. We now know that Bash is a versatile and powerful shell and scripting language that provides a way to interact with Unix-based operating systems. It allows users to execute commands, perform complex operations, and automate tasks. Also, it is some of the most widely used and essential tools for Linux and macOS users.

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