Complete Shell Scripting Tutorial

Sourin
3 min readSep 3, 2023

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What is a Shell?

A shell is a command-line interface (CLI) program that provides a user-friendly way to interact with an operating system (OS) or a computer system. It serves as a bridge between the user and the kernel (core of OS) by interpreting and executing commands entered by the user or by script

Step-by-step Guide (Including Source Codes): https://github.com/heysourin/Shell-Scripting

Different Types of Shells

  1. Bash (Bourne-Again Shell): Bash is one of the most widely used shells and is the default shell on many Linux distributions. It is a powerful and versatile shell that supports scripting, interactive use, and command-line automation.
  2. Zsh (Z Shell): Zsh is known for its extensive customization options and interactive features. It offers advanced auto-completion, syntax highlighting, and theming. Many users prefer Zsh for its user-friendly experience.
  3. Fish (Friendly Interactive Shell): Fish is designed to be a user-friendly shell with a focus on interactive use. It provides helpful features like auto-suggestions, syntax highlighting, and an easy-to-understand scripting syntax.
  4. Dash: Dash is a minimalistic POSIX-compliant shell optimized for scripting. It is often used as the default /bin/sh shell on many Unix systems because of its speed and efficiency.
  5. Tcsh: Tcsh is an enhanced version of the C shell (csh) with additional features like command-line history, command-line editing, and job control. It’s popular among some Unix users.
  6. Ksh (Korn Shell): The Korn Shell is known for its scripting capabilities and is compatible with the Bourne Shell (sh). It offers advanced scripting features like associative arrays and floating-point arithmetic.
  7. Ash (Almquist Shell): Ash is a lightweight and efficient shell that adheres to the POSIX shell standard. It is often used in embedded systems and as the basis for other shells like Dash.
  8. Csh (C Shell): The C shell is an early Unix shell with C-like syntax. It offers some unique features but is less commonly used today, especially for scripting.
  9. PowerShell: While primarily associated with Microsoft Windows, PowerShell has also been developed for Linux and macOS. It is a powerful and object-oriented shell designed for automation and system administration.

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What is shell scripting?

  • Shell scripting is a way to automate tasks and create programs using shell commands. A shell script is a sequence of commands that can be executed in a shell environment. Shell scripts are commonly used for system administration, automation, and other tasks.
  • All the commands execute sequentially.
  • Some important tasks engineers do with shell scripting is file manipulation, program execution, user interaction, automation etc.

Key characteristics and functions of a shell include

  • Command Interpretation: The shell interprets commands entered by the user and translates them into instructions that the operating system can understand and execute.
  • Command Execution: It runs programs, utilities, and scripts on behalf of the user. This includes both built-in shell commands and external programs.
  • Scripting: Shells support scripting languages that allow users to automate tasks by writing sequences of commands in script files.
  • I/O Redirection: Shells allow users to redirect input and output streams (e.g., redirecting output to a file) to manipulate and process data.
  • Variables: Users can create and manipulate variables to store and retrieve data within the shell environment.
  • Control Structures: Shells support conditional statements (e.g., if-else), loops (e.g., for, while), and other control structures for scripting and automation.
  • Environment Management: Shells manage environment variables, which are used to store configuration information and data that can be accessed by programs and scripts.
  • Customization: Users can customize their shell environment by defining aliases, setting prompts, and configuring various settings.

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