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Module 1: Command Line Fundamentals

⏱ Estimated Time: 8-10 hours

Why This Matters

Every developer uses the command line. Every single one.

The command line, often referred to as the "terminal," "shell," or "CLI" (Command Line Interface), is your backstage pass to interacting with your computer in a way that goes beyond clicking and dragging. When you're deploying code, managing servers, running build tools, or using Git — you're in the terminal. Most tutorials assume you already know your way around. We're going to make sure you do.

By the end of this module, the command line will feel like home.

What is the Terminal?

The terminal (also called command line, shell, or console) is a text-based interface to your computer. Instead of clicking icons and menus, you type commands.

Why would anyone choose typing over clicking?

  • Speed — Once you know the commands, you can do things in seconds that would take minutes with a mouse
  • Power — Some tasks can only be done from the terminal
  • Automation — You can write scripts to do repetitive tasks for you
  • Remote access — When you're working on servers, the terminal is often your only option

Terminal vs Shell

Quick clarification:

  • Terminal — The application/window you type in
  • Shell — The program that interprets your commands

Common shells:

  • Bash — The classic, available everywhere
  • Zsh — Modern, powerful, default on Mac
  • PowerShell — Windows (we recommend using Git Bash or WSL instead)

If you're on Mac, you're using Zsh by default. If you're on Linux, probably Bash. Either works fine for this course.

Opening Your Terminal

Operating Systems and Access

Mac:

  • Press Cmd + Space, type "Terminal", hit Enter
  • Or navigate to Applications > Utilities > Terminal

Windows:

Linux:

  • Press Ctrl + Alt + T
  • Or find Terminal in your applications menu

The Prompt

When you open the terminal, you'll see something like this:

username@computer:~$

Or on Mac with Zsh:

username@computer ~ %

This is your prompt. It's waiting for you to type a command.

The ~ represents your home directory. The $ or % indicates you're a regular user (not root/admin).

Your First Commands

Where Am I? (Print Working Directory)

pwd

pwd stands for "print working directory." It tells you where you are in the file system.

Output:

/Users/username

Windows alternative:

cd

What's Here? (List Directories and Files)

Mac/Linux:

ls

Windows:

dir

ls (or dir on Windows) lists the contents of the current directory.

Desktop    Documents    Downloads    Pictures

See More Details

ls -l

The -l flag shows a "long" listing with more information:

drwxr-xr-x  5 username  staff   160 Jan 15 10:30 Desktop
drwxr-xr-x  8 username  staff   256 Jan 14 09:15 Documents

This shows permissions, owner, size, date modified, and name.

See Hidden Files

ls -a

Files starting with . are hidden by default. The -a flag shows all files.

.  ..  .zshrc  .gitconfig  Desktop  Documents

Combine Flags

ls -la

Shows all files with details. You'll use this constantly.

Navigating the File System

Moving Around (Changing Your Working Directory)

cd Documents

cd means "change directory." Now you're inside Documents.

pwd
/Users/username/Documents

Going Back (To the Previous Directory)

cd ..

.. means "parent directory" — one level up.

Going Home

cd ~

Or just:

cd

Both take you to your home directory.

Absolute vs Relative Paths

Absolute path — starts from root (/):

cd /Users/username/Documents/Projects

Relative path — starts from where you are:

cd Documents/Projects

If you're already in /Users/username, both commands take you to the same place.

Quick Navigation Tips

cd -

Takes you to the previous directory you were in. Great for bouncing between two locations.

cd ~/Documents/Projects

The ~ expands to your home directory, so this works from anywhere.

Working with Files and Directories

Creating Directories

Create a new directory called "VetsWhoCode":

mkdir VetsWhoCode

Creates a directory called VetsWhoCode.

Create nested directories:

mkdir -p projects/vwc/prework

The -p flag creates parent directories as needed. This creates the entire nested structure in one command.

Creating Files

touch index.html

Creates an empty file called index.html. If the file exists, it updates the timestamp.

Creating Multiple Files

touch index.html style.css script.js

Creates all three files at once.

Viewing File Contents

cat README.md

cat prints the entire file to the terminal. Good for short files.

less README.md

less lets you scroll through longer files. Press q to quit.

head -20 README.md

Shows the first 20 lines.

tail -20 README.md

Shows the last 20 lines.

Copying Files

cp index.html backup.html

Copies index.html to a new file called backup.html.

cp -r projects projects-backup

The -r flag copies directories recursively (including all contents).

Moving and Renaming

mv old-name.html new-name.html

Renames a file.

mv index.html ../

Moves index.html to the parent directory.

mv index.html ~/Documents/

Moves it to Documents.

Deleting a Directory (Oops!)

Mac/Linux:

rm unwanted-file.txt

Deletes the file. There is no trash. It's gone.

rm -r unwanted-folder

or

rm -r NameOfDirectory

Deletes a directory and everything inside it.

Windows:

rmdir /S NameOfDirectory

⚠️ Be careful with rm. There's no undo. Double-check before you hit Enter, especially with -r.

Safe Delete Practice

Before deleting, list what you're about to remove:

ls unwanted-folder

Then delete:

rm -r unwanted-folder

Finding Things

Find Files by Name

find . -name "*.html"

Finds all .html files starting from the current directory (.).

find ~/Documents -name "index.html"

Finds files named index.html in Documents.

Search Inside Files

grep "function" script.js

Finds lines containing "function" in script.js.

grep -r "TODO" .

Recursively searches all files in the current directory for "TODO".

grep -n "error" logfile.txt

The -n flag shows line numbers.

Pipes and Redirection

This is where the terminal gets powerful.

Pipes

The pipe | takes the output of one command and feeds it to another.

ls -la | less

Lists files and sends the output to less so you can scroll through it.

cat logfile.txt | grep "error"

Shows only lines containing "error".

history | grep "git"

Shows your command history filtered to only git commands.

Chaining Pipes

cat data.txt | grep "active" | wc -l

This:

  1. Reads the file
  2. Filters to lines with "active"
  3. Counts the lines (wc -l)

Output Redirection

ls -la > filelist.txt

The > redirects output to a file. Creates or overwrites the file.

echo "New line" >> notes.txt

The >> appends to a file instead of overwriting.

cat file1.txt file2.txt > combined.txt

Combines two files into one.

Command History and Shortcuts

History

history

Shows your recent commands.

Press Up Arrow to cycle through previous commands.

Press Ctrl + R to search your history. Start typing and it finds matching commands.

Keyboard Shortcuts

Shortcut Action
Ctrl + A Jump to beginning of line
Ctrl + E Jump to end of line
Ctrl + U Clear line before cursor
Ctrl + K Clear line after cursor
Ctrl + W Delete word before cursor
Ctrl + L Clear the screen
Ctrl + C Cancel current command
Tab Auto-complete files and commands

Tab completion is your best friend. Start typing a file or command name and press Tab. If there's one match, it completes. If there are multiple, press Tab twice to see options.

Customizing Your Shell

The Config File

Your shell reads a config file when it starts:

  • Zsh: ~/.zshrc
  • Bash: ~/.bashrc or ~/.bash_profile

Creating Aliases

Aliases are shortcuts for commands you use often. Add these to your config file:

# Open the config file
nano ~/.zshrc    # or ~/.bashrc for Bash

Add aliases like:

# Navigation
alias ..="cd .."
alias ...="cd ../.."
alias home="cd ~"
alias projects="cd ~/Documents/projects"

# List files
alias ll="ls -la"
alias la="ls -a"

# Git shortcuts (preview - more in Git module)
alias gs="git status"
alias ga="git add"
alias gc="git commit"
alias gp="git push"

# Safety nets
alias rm="rm -i"    # Asks for confirmation
alias mv="mv -i"    # Asks before overwriting
alias cp="cp -i"    # Asks before overwriting

# Clear screen
alias c="clear"

Save the file and reload:

source ~/.zshrc    # or source ~/.bashrc

Now ll works as ls -la, gs works as git status, etc.

Setting Your Editor

Add this to your config file:

export EDITOR="code"    # VS Code

Now when programs need to open an editor, they'll use VS Code.

Custom Prompt (Optional)

You can customize what your prompt displays. Here's a simple example:

# Shows: directory-name $
PS1="%1d $ "

Or with colors:

# Shows: directory-name in blue, then $
PS1="%F{blue}%1d%f $ "

Practical Exercises

Exercise 1: Navigation Drill

Without looking at notes, complete these tasks:

  1. Open your terminal
  2. Print your current directory
  3. Navigate to your Documents folder
  4. List all files including hidden ones
  5. Go back to your home directory using the shortcut
  6. Navigate to Documents using an absolute path

Exercise 2: File Operations

  1. Create a directory called vwc-prework
  2. Inside it, create three directories: html, css, js
  3. Inside html, create files: index.html, about.html, contact.html
  4. Copy index.html to the parent vwc-prework directory
  5. Rename the copy to home.html
  6. Delete home.html
  7. List the entire structure to verify

Exercise 3: Finding and Searching

  1. Find all .html files in your vwc-prework directory
  2. Create a file with some text: echo "Hello World" > greeting.txt
  3. Use grep to find "World" in that file
  4. Use cat to display the file contents

Exercise 4: Pipes Practice

  1. List all files in your home directory and count them: ls ~ | wc -l
  2. View your command history and filter to only cd commands
  3. List files and save the output to a file called my-files.txt

Exercise 5: Customize Your Shell

  1. Open your shell config file (~/.zshrc or ~/.bashrc)
  2. Add at least 5 aliases that will help your workflow
  3. Save and reload the config
  4. Test each alias

Common Mistakes and Fixes

"Command not found"

You mistyped the command or it's not installed.

# Wrong
lss -la

# Right
ls -la

"No such file or directory"

The file or path doesn't exist. Check your spelling and current location with pwd.

"Permission denied"

You don't have access. For your own files, this usually means the file isn't executable. For system files, you may need sudo (use carefully).

Accidentally Started Something

If a command is running and won't stop, press Ctrl + C to cancel it.

Terminal Looks Broken

If your terminal looks weird (no prompt, strange characters), type:

reset

This restores it to normal.

How to Know You're Ready

You should be able to do all of the following from memory, without looking anything up:

  • Navigate to any directory using both relative and absolute paths
  • Create nested directory structures in one command
  • Create, copy, move, and delete files and directories
  • View file contents using multiple methods
  • Find files by name
  • Search for text inside files
  • Use pipes to chain commands
  • Redirect output to files
  • Use keyboard shortcuts for efficiency
  • Set up useful aliases in your shell config

Your Gate

Take a screenshot of your terminal showing:

  1. Your custom aliases (run alias to list them)
  2. Your shell config file open, showing your customizations

This screenshot goes on your portfolio's About page.

Quick Reference

Navigation

Command Description
pwd Print working directory
ls / dir List files (Mac/Linux / Windows)
ls -la List all files with details
cd directory Change directory
cd .. Go up one level
cd ~ / cd Go to home
cd - Go to previous directory

Files and Directories

Command Description
mkdir name Create directory
mkdir -p path/to/dir Create nested directories
touch file Create file
cp source dest Copy file
cp -r source dest Copy directory
mv source dest Move or rename
rm file Delete file
rm -r directory / rmdir /S Delete directory (Mac/Linux / Windows)

Viewing Files

Command Description
cat file Print entire file
less file Scroll through file
head -n file First n lines
tail -n file Last n lines

Finding and Searching

Command Description
find . -name "pattern" Find files by name
grep "text" file Search in file
grep -r "text" . Search recursively

Pipes and Redirection

Symbol Description
| Pipe output to next command
> Redirect output to file (overwrite)
>> Redirect output to file (append)

Now, you're armed with the knowledge and tools to embark on your web development journey. Get ready to create, innovate, and make your mark on the digital world! 🚀

Next up: Module 2: Code Editor Setup