💻 Mastering the Terminal (Windows, Mac, Linux)

🎯 Lesson Objectives

By the end of this lesson, learners will be able to:

• Understand what the terminal is and how it differs across platforms.
• Navigate directories using standard commands.
• Create, view, copy, move, rename, and delete files and folders using the CLI.

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⌨️ What is the Terminal?

The terminal (also called the command line) allows you to interact with your computer using text commands instead of a mouse.

Developers use the terminal to:

• Manage files and folders efficiently.
• Run programs and automated scripts.
• Use version control (Git).
• Control development servers and tools.

🛡️ One Language, Many Platforms

In modern software engineering, the Terminal is the universal language. However, how you access it depends on your operating system:

• Mac Users: macOS is built on a Unix foundation; your native Terminal app supports these commands natively.
• Linux Users: This is your natural environment.
• Windows Users: This is critical. Standard Windows tools like "Command Prompt" (CMD) or "PowerShell" follow different rules. To run these standard developer commands on Windows, you must use a compatibility tool like Git Bash or the Windows Subsystem for Linux (WSL).

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📂 Understanding Directories

A directory is simply another name for a folder. The terminal lets you move between directories and manage what’s inside them.

The Shell Prompt

Every line starts with a prompt, giving you context: dev@machine:~/projects$

• dev: The current user.
• ~: Shortcut for your Home Directory.
• $: Indicates you are a standard user.

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🔑 Essential Commands

📍 pwd — Print Working Directory

Shows the folder you are currently inside.

pwd

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📄 ls — List Files and Folders

Shows the contents of the current directory.

ls

Useful Flags

• ls -a: Shows hidden files (files starting with a .).
• ls -l: Shows a detailed list (size, date, permissions).
• ls -la: Combines both—shows hidden files in a detailed view.

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📁 cd — Change Directory

• Move into a folder: cd projects
• Move back one level: cd ..
• Go to home directory: cd ~

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🧹 clear — Clear the Screen

Removes previous commands from view (start with a fresh slate).

clear

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🆕 mkdir & touch — Create Things

• mkdir website: Creates a new folder.
• touch index.html: Creates an empty file.

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🗣️ echo — Print and Write Content

1️⃣ Print Text

echo Hello World

2️⃣ Create or Overwrite (>)

Using > writes text into a file. If the file exists, it replaces everything inside. echo "My first webpage" > index.html

3️⃣ Append Content (>>)

Using >> adds text to the end of a file without deleting what is already inside. echo "This line was added later" >> index.html

Command	What It Does
echo "text" > file.txt	Creates or overwrites existing content
echo "text" >> file.txt	Appends text to the end of the file

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📖 cat — View and Create Content

• View: cat index.html (Displays what is inside).
• Create/Overwrite: cat > notes.txt (Type content, then press CTRL+D to save).
• Append: cat >> notes.txt (Add content, press CTRL+D to save).

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📋 cp & mv — Copy and Move

• Copy File: cp index.html about.html
• Copy Folder: cp -r website backup-website (The -r is required for folders).
• Rename/Move: mv index.html home.html

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❌ rm & rmdir — Delete

• Delete Empty Folder: rmdir old-folder
• Delete File: rm file.txt
• Delete Folder & Content: rm -r website

⚠️ CAUTION: Deletions are instantaneous and permanent. There is no Recycle Bin.

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🧪 Practice Exercise

Try the following commands step by step:

mkdir web-practice
cd web-practice
touch index.html
echo "Hello Web" > index.html
echo "Learning terminal commands" >> index.html
cat index.html
mkdir assets
cp index.html assets/
ls -l

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🖼️ Terminal Example

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🎥 Lesson Video

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📝 Project Task: Terminal Mastery

Using only the terminal:

1. Create a folder named my-first-website
2. Inside it, create index.html and about.html.
3. Add the text "Welcome to my website" inside index.html using echo.
4. Append another line to index.html using echo >>.
5. Create a file called notes.txt using cat and write two lines inside.
6. Append a third line to notes.txt using cat >>.
7. Copy index.html into a new folder called backup.
8. Rename about.html to about-me.html.
9. Verify your folder structure using ls -l.