• Linux originated in the 1990s when Linus Torvalds developed a free, open source version of the Unix kernel it is most used.

• Anyone who have programming knowledge can modify it because of open source.

• Linux is widely used today in many devices, desktops, supercomputers, data centers, and cloud servers.

• Linux distributions include Red Hat Enterprise Linux (RHEL), Debian, Ubuntu, Suse (SLES, SLED, OpenSuse), Fedora, Mint, and Arch.

• The Linux system consists of five key layers:

  - user

  - application - Operating System

  - kernel

  and hardware.

Linux Commands

• You .can use the “curl” and “wget” commands to display and download files from URLs

• The “echo” command prints string or variable values.

• The “cat” and “tail” commands display file contents.

• You can get user information with the "whoami" and "id" commands.

• The “ls” command lists all files and directories contained within a specified directory tree.

• The “cd” command allows you to navigate directories.

• The “touch” command allows you to create a file or update its last–modified timestamp.

• The “mkdir” command creates directories and “rmdir” deletes empty directories.

• The “tar” command decompresses and unpacks a “tar.gz” archive.

Linux Shell

The Linux OS is a set of programs that acts as a link between the computer and the user. Linux has a kernel which interact to the hardware. But a kernel does not understand the language of a user. And this is where a shell comes into the game. A shell act as an interpreter between the kernel and the user. A Linux shell is a command-line interpreter that provides a command-line user interface for Linux operating systems. It gathers input from the users and executes the programs, and displays the output of a program after executing the same. There are various types of shell present which are listed below –

1. Bourne shell (sh)

2. Korn shell (ksh)

3. C shell (csh)

4. POSIX shell (sh)

5. TENEX/TOPS C shell (tcsh)

Shell scripting

Shell scripts are used to run commands and programs and can interpret command line arguments.A shell script is an executable text file that begins with a ‘shebang’ interpreter directive.Shell variables can be assigned values with ‘=’ and listed using ‘set’.Environment variables are shell variables with extended scope; create with ‘export,’ list with ‘env’.Jobs can be scheduled to run periodically at selected times.A shell script is a file containing a sequence of commands that are executed by the bash program line by line. It allows you to perform a series of actions, such as navigating to a specific directory, creating a folder, and launching a process using the command line.

BASH script = Bourne Again SHell script

Advantages of Shell scripting

Shell scripting is a powerful and versatile tool for automating system administration tasks, managing system resources, and performing other routine tasks Linux systems.Some advantages given below :-

Automation

Portability

Integration

Debugging