Linux diff Guide

Complete beginner-friendly guide to diff on Linux, covering Arch Linux, CachyOS, and other distributions including comparing files, finding differences, and generating patches.

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Table of Contents

1. Understanding diff
2. diff Basics
3. Comparing Files
4. Comparing Directories
5. Generating Patches
6. Troubleshooting

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Understanding diff

What is diff?

diff compares files and shows differences.

Uses:

• Compare files: Find differences between files
• Generate patches: Create patch files
• Version control: See what changed
• Code review: Review changes

Why it matters:

• File comparison: Compare file versions
• Change tracking: See what changed
• Patch creation: Create patches for updates

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diff Basics

Compare Files

Basic usage:

# Compare two files
diff file1.txt file2.txt

# Shows differences

Unified Format

Unified output:

# Unified format
diff -u file1.txt file2.txt

# -u = unified (easier to read)

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Comparing Files

Context Lines

Add context:

# Context lines
diff -c file1.txt file2.txt

# Shows surrounding lines

Ignore Case

Case insensitive:

# Ignore case
diff -i file1.txt file2.txt

# -i = ignore case

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Comparing Directories

Compare Directories

Directory comparison:

# Compare directories
diff -r dir1/ dir2/

# -r = recursive

Brief Output

Summary only:

# Brief summary
diff -rq dir1/ dir2/

# -q = quiet (only names)

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Generating Patches

Create Patch

Generate patch:

# Create patch file
diff -u old.txt new.txt > patch.diff

# Unified patch format

Apply Patch

Apply patch:

# Apply patch
patch file.txt < patch.diff

# Updates file

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Troubleshooting

diff Not Found

Check installation:

# Check diff
which diff

# Usually in diffutils
# Install if missing
sudo pacman -S diffutils

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Summary

This guide covered diff usage, file comparison, and patch generation for Arch Linux, CachyOS, and other distributions.

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Next Steps

• patch Guide - Applying patches
• Git Guide - Version control
• diff Documentation: man diff

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This guide covers Arch Linux, CachyOS, and other Linux distributions. For distribution-specific details, refer to your distribution's documentation.