Introduction to Bash

What is Bash?

Bash (Bourne Again SHell) is the most widely used Unix/Linux shell and command language. It's the default shell on most Linux distributions and was the default on macOS until Catalina (which switched to Zsh).

Bash serves two purposes:

1. Interactive Shell — A command-line interface where you type commands
2. Scripting Language — Write scripts to automate tasks

A Brief History

• 1971 — Thompson Shell (the first Unix shell)
• 1977 — Bourne Shell (sh) by Stephen Bourne at Bell Labs
• 1978 — C Shell (csh) by Bill Joy at UC Berkeley
• 1983 — Korn Shell (ksh) by David Korn at Bell Labs
• 1989 — Bash by Brian Fox for the GNU Project (free replacement for sh)
• 2019 — macOS switches default to Zsh

Bash combines the best features of sh, csh, and ksh while adding its own improvements.

Why Learn Bash?

• Ubiquitous — Available on virtually every Linux/macOS/Unix system
• Server Management — Most servers run Linux; Bash is how you manage them
• DevOps Essential — CI/CD pipelines, Docker, Kubernetes all use Bash scripts
• Automation — Automate backups, deployments, system maintenance
• Text Processing — Powerful tools for processing logs, data, and configurations
• Career Growth — Required skill for SysAdmin, DevOps, SRE, and Cloud roles

Bash vs Other Shells

Key Concepts

Before diving in, here's what you'll learn:

1. Commands — Built-in commands and external programs
2. Files & Directories — Navigating and managing the filesystem
3. Pipes & Redirection — Connecting commands and redirecting output
4. Variables & Environment — Storing data and configuring the shell
5. Scripting — Writing automated scripts with logic and loops
6. Text Processing — Using grep, sed, awk, and other tools
7. Process Management — Managing running processes and jobs
8. Regular Expressions — Pattern matching and text manipulation

The Terminal vs Shell vs Console

These terms are often confused:

• Terminal (Terminal Emulator) — The window/application (e.g., GNOME Terminal, iTerm2, Windows Terminal)
• Shell — The program that interprets your commands (Bash, Zsh, Fish)
• Console — Historically, the physical hardware; now often used interchangeably with terminal

When you open a terminal application, it launches a shell (usually Bash) inside it.

What You'll Build

By the end of these tutorials, you'll be able to:

• Navigate the Linux filesystem efficiently
• Write Bash scripts to automate system tasks
• Process text data with grep, sed, and awk
• Manage processes and system services
• Create cron jobs for scheduled tasks
• Write deployment and backup scripts
• Handle errors and debug scripts

Let's start by setting up your Bash environment!