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
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
etc
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.
