Linux Shell Programming for Beginners

What is Shell

The shell is a command-line interpreter and scripting environment that serves as an interface between the user and the operating system’s core, known as the kernel. It allows users to interact with the system by typing human-readable commands in a terminal, which the shell then translates into instructions the kernel can understand and execute.

Shell Scripting Language

Shell scripting is a command-line programming language used to automate tasks in Unix-based systems like Linux and macOS. Common shell scripting languages are Bourne Shell (sh), GNU Bourne-Again Shell (Bash), C Shell (csh), KornShell (ksh), Z shell (Zsh), Debian Almquist shell (dash), Fish shell (fish), PowerShell (pwsh), Nushell (nu).

Script

A script is a text file that contains a sequence of commands, variables, functions, and control structures (like loops and if-else statements)

Shebang

The first line of a shell script, starting with #! (e.g., #!/bin/bash ), is called the shebang. It tells the system which interpreter to use for running the script.

Permissions

For security, Linux does not allow a file to be executed by default. You must explicitly grant execute permissions using the chmod command (e.g., chmod +x script.sh )

ls Command

The ls (list) command in Linux lists directory contents, displaying files and subdirectories. It provides detailed information such as file names, permissions, sizes, and modification dates.

The ls command syntax is:

ls [options]