Mac Command Line: File System & Navigation

🏴‍☠️ Becoming a Cap10 of the Command Line

Objective: Teach absolute beginners how to confidently navigate and manage files in macOS using the Terminal.

Launching the Terminal

First, find the Terminal app in /Applications/Utilities or via Spotlight. When it opens, you’ll see a prompt—your helm for issuing commands.

$ pwd
/Users/YourName   # Shows you're in your Home directory (home is shown as ~)

Think of your Home directory as the captain’s quarters—your personal space where your files and folders reside.

1. Understanding the Mac File System

Before diving into the Terminal, let’s get a clear picture of how macOS organizes files.

Key Concepts

• Root Directory (/): The top-level directory where the entire file system begins.
• User Folders: Located in /Users/, each user has a home directory (e.g., /Users/yourname).
• Applications: Stored in /Applications.
• System Directories: Folders such as /Library, /System, and /usr.
• Paths: Absolute paths start with / and uniquely define a file’s location.

Example Structure

/
 ├── Applications
 ├── Library
 ├── System
 ├── Users
 │   └── yourname
 │       ├── Documents
 │       ├── Downloads
 │       ├── Desktop
 │       └── Pictures
        

2. Navigating the File System

Use these commands to move around and manage files:

pwd

pwd

Prints your current working directory.

ls

ls

Lists files and folders. Try ls -l for details or ls -a to include hidden files.

cd

cd /Users/yourname/Documents  # Move to Documents
cd ..                         # Up one level
cd ~                          # Go to Home
cd -                          # Switch to last directory
        

Change directories.

mkdir

mkdir MyFolder

Create a new folder.

touch

touch myfile.txt

Create an empty file or update its timestamp.

rm

rm myfile.txt         # Delete a file
rm -r MyFolder        # Delete a directory and its contents
        

Remove files or folders (permanent—no trash!).

cp / mv

cp myfile.txt Backup/   # Copy file
mv myfile.txt Backup/   # Move or rename file
        

Copy or move files.

Editing Files from the Command Line

Edit text right in Terminal with built-in editors:

• nano: nano file.txt. Type text, then Ctrl+X, Y to save, Enter to exit.
• vim: vim file.txt. Press i to insert, edit text, then Esc, :wq to save and quit.

Troubleshooting on the Command Line

When apps go rogue:

• Find a process: ps aux | grep AppName.
• Kill it: kill PID or kill -9 PID. Or killall AppName.
• Monitor system: top (press q to quit).
• Watch logs: tail -f /var/log/system.log (stop with Ctrl+C).

Backing Up Files

A savvy captain keeps backups:

• cp file1.txt file2.txt: Simple copy.
• cp -R folder1 folder2: Copy folders recursively.

rsync -av ~/Documents/ ~/Documents_backup/

Archive with tar:

tar -czvf backup.tar.gz folder_to_backup/

Unpack: tar -xzvf backup.tar.gz.

3. Intermediate Command Line Power Moves

Elevate your command-line mastery:

• Chaining: cmd1 && cmd2 runs second only if first succeeds (e.g., mkdir test && cd test).
• Piping: cmd1 | cmd2 sends output of one into another (e.g., ls | grep ".txt").
• Repeat Last: Type !! to rerun previous command.
• History: Use history or ↑/↓ arrows to browse past commands.
• Manual Pages: man command shows docs (press q to quit).
• Aliases: Create shortcuts in ~/.zshrc or ~/.bash_profile, e.g., alias ll="ls -la".

Developer Tools (Sneak Peek)

Your full command-line arsenal will include:

• Homebrew: Install with /bin/bash -c "$(curl -fsSL https://brew.sh)", then brew install git python.
• Git: Check with git --version to manage code versions.
• Python: Run scripts: python3 script.py.
• VS Code CLI: If VS Code is installed, use code . to open the current folder.

4. Final Challenge: Prove Your Command Line Captaincy

• Create a folder called Projects in Documents.
• Create readme.txt inside Projects and write “Hello, Cap10!”.
• Rename it to info.txt.
• Move it to Desktop, then delete it.
• List all .txt files in /Users/yourname/Documents/.

5. Key File Locations & Tools Available in the CLI

Here’s a treasure map of important places and tools on your Mac:

Common Directories

• /Applications: Where most of your apps live. Open apps via open -a AppName.
• /usr/local: Homebrew’s territory; check echo $PATH to see where executables live.
• ~/.bash_profile or ~/.zshrc: Your shell’s config file for aliases and environment tweaks.
• ~/Documents, ~/Downloads, ~/Desktop: Your personal folders—navigate with cd ~/Documents, etc.
• /etc/hosts: Map hostnames to IPs; view with cat /etc/hosts.
• /var/log: System logs—watch real-time with tail -f /var/log/system.log.

Handy Tools You’ll Encounter

• Homebrew (brew): Install packages (e.g., brew install git, brew install python).
• Git (git): Version control; start with git --version.
• Python (python3): Run scripts: python3 script.py.
• VS Code CLI (code): Open current folder in VS Code: code ..

That’s a lot of territory covered! Explore at your own pace, and remember, you can always consult man pages or use find if in doubt. In future posts, we’ll dive deeper into Git, Python, and more. Until then, fair winds and happy sailing, captain!