Lesson 2 — Navigation & File Operations

Time: ~30 minutes
Goal: Move confidently around your file system and manage files entirely from the command line.

📂 Get the Practice Files

Several commands in this lesson (cat, head, tail, grep, cp, mv, rm) need real files to work on. Set up a practice folder before you start — choose whichever option suits you.

Option A — Download only the practice files (recommended)

Use npx degit to download just the exercise files from the course repository — no course source code, no Ruby files, no .git history.

💡 npx ships with Node.js (a prerequisite for Lesson 3+). If you haven’t installed it yet, see the Prerequisites on the home page.

# Go to a safe working area
cd ~

# Download only the practice files into a new folder called cli-practice
npx degit ZEZE1020/cli-starter/practice cli-practice

# Enter the folder
cd cli-practice

You now have a clean folder containing only the exercise files:

cli-practice/
├── README.md        ← multi-line text — great for cat, head, tail, grep
├── app.log          ← simulated log file — great for tail, grep -i
├── file.txt         ← plain text — great for grep, cp, mv
├── notes.txt        ← course notes — great for grep -n, grep -r
├── original.txt     ← ready to copy with cp
├── old-name.txt     ← ready to rename with mv
└── src/
    ├── app.js       ← JavaScript with functions and TODOs
    ├── utils.js     ← more JS functions and TODOs
    └── style.css    ← CSS file for wildcard exercises

💡 Messed up a file? Delete the folder and re-download in seconds:
cd ~
rm -rf cli-practice
npx degit ZEZE1020/cli-starter/practice cli-practice
cd cli-practice

Option B — Create the practice files yourself

Prefer to build from scratch? This is great extra practice with the commands you’re about to learn. Run the commands below:

# Create and enter a practice folder
cd ~
mkdir -p cli-practice/src
cd cli-practice

# A multi-line README (good for head / tail / cat)
cat > README.md << 'EOF'
# Practice Project

This file is here so you can try out cat, head, tail, less and grep.

Line 1: The quick brown fox jumps over the lazy dog.
Line 2: Hello, CLI learner!
Line 3: Learning the terminal is a superpower.
Line 4: TODO: practice grep on this file.
Line 5: Every expert was once a beginner.
Line 6: Ctrl+C cancels a running command.
Line 7: Tab auto-completes file names.
Line 8: Use cd .. to go up one directory.
Line 9: pwd shows where you are right now.
Line 10: git init starts a new repository.
EOF

# A log file (good for tail -f, grep -i "error")
cat > app.log << 'EOF'
2026-03-01 08:00:12 INFO  Server started on port 3000
2026-03-01 08:01:10 WARN  Slow query detected
2026-03-01 08:01:20 ERROR Failed to send email: SMTP refused
2026-03-01 08:02:00 INFO  GET /api/orders 200 OK
2026-03-01 08:03:30 ERROR Database connection lost
2026-03-01 08:03:37 INFO  Database reconnected successfully
2026-03-01 08:05:05 INFO  POST /api/login 200 OK
EOF

# Plain text files for cp / mv / grep
echo "Hello, CLI learner! This file is great for grep and cp." > file.txt
echo "TODO: rename this file using mv." > old-name.txt
echo "Copy me with: cp original.txt copy.txt" > original.txt

# Notes file with TODOs (for cat and grep -n "TODO")
cat > notes.txt << 'EOF'
These are your course notes.

TODO: review navigation commands (cd, ls, pwd).
TODO: practice grep -n "TODO" notes.txt.
TODO: add your own notes as you learn.
EOF

# Source files with functions and TODOs (for grep -r and find)
cat > src/app.js << 'EOF'
function greet(name) {
  return "Hello, " + name + "!";
}
// TODO: add more functions here
function add(a, b) { return a + b; }
EOF

cat > src/utils.js << 'EOF'
function formatDate(date) { return new Date(date).toISOString().slice(0,10); }
// TODO: add unit tests
function isEmpty(v) { return v === null || v === undefined || v === ''; }
EOF

echo "/* TODO: add responsive styles */" > src/style.css

# Verify what you created
find . | sort

The File System — A Quick Mental Model

Think of your file system as a tree of folders. Every file lives at an absolute path starting from the root:

Mac / Git Bash: Root is /
Example: /Users/alex/Documents/project/index.html
Windows Git Bash: Root is /c/ (or /d/ for another drive)
Example: /c/Users/alex/Documents/project/index.html

The tilde ~ is a shortcut for your home folder:
~/Documents expands to /Users/alex/Documents (Mac) or /c/Users/alex/Documents (Windows).

Navigating the File System

`ls` — List Files

ls

Useful flags:

ls -l        # long format — shows permissions, size, date
ls -a        # show hidden files (files starting with .)
ls -la       # combine both
ls -lh       # human-readable file sizes (K, M, G)

Example output of ls -la:

drwxr-xr-x  5 alex staff  160 Mar  7 08:00 .
drwxr-xr-x 12 alex staff  384 Mar  7 07:55 ..
-rw-r--r--  1 alex staff  108 Mar  7 08:00 README.md
drwxr-xr-x  3 alex staff   96 Mar  7 08:00 src

💡 Windows Git Bash: ls works identically in Git Bash!

`cd` — Change Directory

cd Documents           # go into Documents folder
cd ..                  # go up one level
cd ../..               # go up two levels
cd ~                   # go to home directory (always works)
cd -                   # go back to previous directory
cd "My Projects"       # use quotes when the name has spaces

Absolute vs relative paths:

cd /Users/alex/Documents     # absolute — starts from root
cd Documents/projects        # relative — starts from current location

`pwd` — Where Am I?

A quick reminder: use pwd any time you want to confirm your location.

pwd
# /Users/alex/Documents/projects

Creating Directories and Files

`mkdir` — Make Directory

mkdir my-project             # create a folder
mkdir -p src/css/themes      # create nested folders in one command

`touch` — Create an Empty File (Mac / Git Bash)

touch index.html
touch style.css script.js    # create multiple files at once

💡 Windows Git Bash: touch works in Git Bash. In Command Prompt you’d use echo. > file.txt but since we’re using Git Bash throughout this course, touch is fine.

`echo` with Redirection — Create a File with Content

echo "# My Project" > README.md      # create/overwrite file
echo "More content" >> README.md     # append to existing file

Viewing File Contents

💡 Using practice files? Make sure you’re inside the practice folder (cd ~/cli-practice) before running the examples below.

`cat` — Print File Contents

cat README.md
cat file.txt
cat notes.txt

`less` — Scroll Through Long Files

less README.md
# Use arrow keys to scroll, q to quit
less app.log

`head` / `tail` — First or Last Lines

head -n 10 README.md     # first 10 lines
tail -n 20 app.log       # last 20 lines
tail -f app.log          # follow a file in real-time (Ctrl+C to stop)

Copying, Moving and Renaming

`cp` — Copy

cp original.txt copy.txt          # copy a file (original.txt is in the practice folder)
cp -r src/ backup/                # copy an entire directory (-r = recursive)
cp *.html dist/                   # copy all .html files into dist/

`mv` — Move or Rename

mv old-name.txt new-name.txt      # rename a file (old-name.txt is in the practice folder)
mv file.txt src/                  # move a file into a folder
mv src/ app/                      # rename a folder

Deleting Files and Folders

`rm` — Remove

rm file.txt                  # delete a file
rm -r my-folder/             # delete a folder and everything inside
rm -rf dist/                 # force delete without confirmation prompts

⚠️ Warning: There is no Recycle Bin in the terminal. rm permanently deletes files. Double-check before running rm -rf!

💡 Using the practice folder? If you delete a practice file by accident, reset with:
cd ~
rm -rf cli-practice
npx degit ZEZE1020/cli-starter/practice cli-practice
cd cli-practice

Practical Exercise

Let’s put it all together and build a simple project scaffold:

# 1. Go to a safe working area
cd ~

# 2. Create a projects folder (if it doesn't exist)
mkdir -p projects

# 3. Enter it
cd projects

# 4. Create a new project folder
mkdir my-first-project

# 5. Enter the project
cd my-first-project

# 6. Create a basic file structure
mkdir src
touch index.html
touch src/style.css
touch src/app.js
echo "# My First Project" > README.md

# 7. Verify the structure
ls -la
ls src/

# 8. Read the README
cat README.md

You should see:

.
..
README.md
index.html
src/

Searching and Finding Files

`find` — Find Files by Name

find . -name "*.js"            # find all JS files in current directory (try in practice/)
find . -name "*.md"            # find all Markdown files
find ~ -name "README.md"       # find README.md files in home directory
find . -type d                 # find all directories
find . -type f -name "*.js"    # find all JS files (practice/src has two)

`grep` — Search Inside Files

grep "hello" file.txt                  # search for "hello" in file.txt
grep -r "TODO" .                       # search recursively in all files
grep -rn "function" src/               # show line numbers too (src/ has JS files)
grep -i "error" app.log                # case-insensitive search in the log file
grep -n "TODO" notes.txt               # show which lines have TODOs

Wildcards (Glob Patterns)

Pattern	Matches
`*`	Any number of characters
`?`	Exactly one character
`[abc]`	One character from the set

ls *.md              # all markdown files
ls src/*.js          # all JS files in src/
rm -rf dist/**       # everything inside dist/

✅ Lesson 2 Checklist

← Lesson 1: CLI Basics

Lesson 3: Bootstrap a Project →

Lesson 2 — Navigation & File Operations

📂 Get the Practice Files

Option A — Download only the practice files (recommended)

Option B — Create the practice files yourself

The File System — A Quick Mental Model

Navigating the File System

ls — List Files

cd — Change Directory

pwd — Where Am I?

Creating Directories and Files

mkdir — Make Directory

touch — Create an Empty File (Mac / Git Bash)

echo with Redirection — Create a File with Content