Chapter 1: Getting Started with Bash on macOS¶

Learning Objectives¶

By the end of this chapter, you will be able to:

• Understand what Bash is and how it fits into the macOS terminal environment
• Identify differences between Bash and Zsh on macOS
• Configure your terminal environment to use Bash effectively
• Write and run your first Bash script on macOS
• Understand basic shell concepts: shell sessions, prompts, commands, and scripts
• Recognize security best practices for running scripts
• Troubleshoot common first-time scripting issues

Introduction: Why Learn Bash on macOS?¶

While macOS now defaults to Zsh, Bash remains a widely used and essential shell, especially in scripting for automation, enterprise administration, and cross-platform tasks. Learning Bash on macOS helps you:

• Automate repetitive tasks - From simple file organization to complex deployment workflows
• Build secure, portable scripts - Write code that runs reliably across different systems
• Work effectively in mixed environments - Seamlessly transition between Linux servers and macOS workstations
• Prepare for real-world security use cases - Script vulnerability scans, compliance checks, and security automation
• Integrate with enterprise tools - Connect with MDM systems, security tools, and modern DevOps practices

As a system administrator or security engineer, mastering Bash on macOS empowers you to automate security hardening, manage endpoints at scale, and respond quickly to threats. This book bridges fundamental Bash concepts with advanced macOS-specific security practices, preparing you for enterprise-grade automation.

1.1 The Terminal on macOS¶

The Terminal is your command-line interface (CLI). On macOS, you can find it under:

Applications → Utilities → Terminal

You can also use third-party terminals like iTerm2 for enhanced features such as split panes, profiles, and hotkeys.

1.2 Bash vs Zsh on macOS¶

As of macOS Catalina (10.15), Apple switched the default shell from Bash to Zsh. Here's a quick comparison:

To switch to Bash temporarily:

bash

To make Bash your default shell:

chsh -s /bin/bash

You’ll be prompted to enter your password. This only applies to your user account.

1.3 Your First Bash Script¶

Let’s create a simple Bash script to print “Hello, Secure Bash!” to the Terminal.

1. Open your terminal.
2. Create a new script file:

nano hello.sh

1. Add the following code:

#!/bin/bash
echo "Hello, Secure Bash!"

1. Save and exit (Ctrl+O to write out, then Ctrl+X to exit).
2. Make it executable:

chmod +x hello.sh

1. Run the script:

./hello.sh

Output:

Hello, Secure Bash!

Congratulations! You’ve just written and run your first Bash script on macOS.

1.4 Security Tip: Trusting Scripts¶

Never run scripts from the internet blindly. Review their contents first with cat or nano. If you're unsure where the script came from or what it does, don’t execute it.

1.5 Key Concepts¶

Chapter 1 Exercise¶

Create a startup script:

Write a script that:

1. Prints your username.
2. Prints today’s date.
3. Prints the number of files in your Desktop folder.

Hint:

#!/bin/bash
echo "User: $USER"
echo "Date: $(date)"
echo "Files in Desktop: $(ls ~/Desktop | wc -l)"

Save it as startup.sh, make it executable, and run it!

macOS Scripting Tips¶

• macOS Bash is older (3.2) — avoid Bash 4+ features unless you're using Homebrew to install a newer version.
• Use pbcopy and pbpaste to work with the clipboard.
• Use open to open files and apps from scripts:

open -a "Safari" https://apple.com