Chapter 3: File System Navigation and Manipulation¶

Learning Objectives¶

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

• Navigate the macOS file system using Bash commands
• Understand relative vs absolute paths
• Manage files and directories: create, delete, move, and copy
• Use wildcards and globbing for pattern matching
• Apply file permissions and understand chmod, chown, and umask
• Use macOS-specific tools like open, xattr, and mdls

Introduction: The Shell as Your Filesystem Interface¶

The command line isn't just a place to run commands — it's a powerful interface to the file system. In this chapter, we'll explore how to traverse, inspect, and modify files and directories using Bash, with a focus on macOS's quirks and features.

3.1 Paths: Absolute vs Relative¶

• Absolute path: starts from root /
• Example: /Users/sammy/Documents/report.txt (use $HOME/Documents/report.txt in scripts)
• Relative path: based on your current directory
• Example: ../Documents/report.txt

Check your current directory:

pwd

Move to another directory:

cd /path/to/folder

Return to previous directory:

cd -

3.2 Listing and Inspecting Files¶

List directory contents:

ls -l    # Long format
ls -a    # Include hidden files
ls -lh   # Human-readable sizes

Inspect file metadata:

stat file.txt

macOS-specific:

mdls file.txt      # Show Spotlight metadata
xattr file.txt     # Show extended attributes

3.3 Creating and Removing Files and Directories¶

Create a file or folder:

touch notes.txt
mkdir projects

Delete files or folders:

rm file.txt
rm -r projects     # Recursively delete folder

Be cautious with rm -rf. It will remove without confirmation.

3.4 Moving, Copying, and Renaming¶

Move or rename:

mv old.txt new.txt
mv file.txt ~/Desktop/

Copy files and folders:

cp file.txt backup.txt
cp -r myfolder/ archive/

Use -i to confirm before overwriting.

3.5 Wildcards and Globbing¶

Use wildcards to match file patterns:

• * matches any characters
• ? matches a single character
• [] matches a character set

Examples:

ls *.txt         # All .txt files
ls report?.pdf   # report1.pdf, report2.pdf, etc.
ls data[1-3].csv # data1.csv, data2.csv, data3.csv

Combine with commands like rm, cp, echo, etc.

3.6 Permissions and Ownership¶

Check permissions:

ls -l

Modify permissions:

chmod 755 script.sh   # rwxr-xr-x
chmod +x script.sh    # Add execute bit

Change ownership (admin required):

sudo chown sammy file.txt

Default permission mask:

umask

3.7 macOS-Specific File Tips¶

• Use open . to launch Finder
• open file.pdf opens with default app
• Use mdls, xattr, GetFileInfo for metadata
• Spotlight indexing can interfere with scripting; exclude folders via:

sudo mdutil -i off /path/to/dir

Chapter 3 Exercise¶

Write a script named organize_downloads.sh that:

• Scans your ~/Downloads directory
• Moves .zip files to ~/Downloads/zips
• Moves .dmg files to ~/Downloads/installers
• Creates folders if they don’t exist

Hint:

#!/bin/bash
mkdir -p ~/Downloads/zips ~/Downloads/installers
for file in ~/Downloads/*; do
  case "$file" in
    *.zip) mv "$file" ~/Downloads/zips/ ;;
    *.dmg) mv "$file" ~/Downloads/installers/ ;;
  esac
done
echo "Downloads organized."

macOS Scripting Tips¶

• open -R filename reveals a file in Finder
• Use tmutil to interact with Time Machine in scripts
• Use diskutil list to inspect drives and volumes
• Use find or mdfind for search with greater flexibility