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Comparing and Merging Files ¶

This manual is for GNU Diffutils (version 3.11, 12 January 2025), and documents the GNU diff, diff3, sdiff, and cmp commands for showing the differences between files and the GNU patch command for using their output to update files.

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled “GNU Free Documentation License.”

Short Table of Contents

Overview
1 What Comparison Means
- 1.1 Hunks
- 1.2 Suppressing Differences in Blank and Tab Spacing
- 1.3 Suppressing Differences Whose Lines Are All Blank
- 1.4 Suppressing Differences Whose Lines All Match a Regular Expression
- 1.5 Suppressing Case Differences
- 1.6 Summarizing Which Files Differ
- 1.7 Binary Files and Forcing Text Comparisons
- 1.8 Comparing Files While They Are Changing
2 diff Output Formats
- 2.1 Two Sample Input Files
- 2.2 Showing Differences in Their Context
- 2.3 Showing Differences Side by Side
  - 2.3.1 Controlling Side by Side Format
  - 2.3.2 An Example of Side by Side Format
- 2.4 Showing Differences Without Context
  - 2.4.1 An Example of Normal Format
  - 2.4.2 Detailed Description of Normal Format
- 2.5 Making Edit Scripts
- 2.6 Merging Files with If-then-else
3 Incomplete Lines
4 Comparing Directories
5 Making diff Output Prettier
- 5.1 Preserving Tab Stop Alignment
- 5.2 Omitting trailing blanks
- 5.3 Paginating diff Output
6 diff Performance Tradeoffs
7 Comparing Three Files
- 7.1 A Third Sample Input File
- 7.2 An Example of diff3 Normal Format
- 7.3 Detailed Description of diff3 Normal Format
- 7.4 diff3 Hunks
8 Merging From a Common Ancestor
- 8.1 Selecting Which Changes to Incorporate
- 8.2 Marking Conflicts
- 8.3 Generating the Merged Output Directly
- 8.4 How diff3 Merges Incomplete Lines
- 8.5 Saving the Changed File
9 Interactive Merging with sdiff
- 9.1 Specifying diff Options to sdiff
- 9.2 Merge Commands
10 Merging with patch
- 10.1 Selecting the patch Input Format
- 10.2 Revision Control
- 10.3 Applying Imperfect Patches
- 10.4 Creating and Removing Files
- 10.5 Updating Timestamps on Patched Files
- 10.6 Multiple Patches in a File
- 10.7 Applying Patches in Other Directories
- 10.8 Backup Files
- 10.9 Backup File Names
- 10.10 Reject File Names
- 10.11 Messages and Questions from patch
- 10.12 patch and the POSIX Standard
- 10.13 GNU patch and Traditional patch
11 Tips for Making and Using Patches
- 11.1 Tips for Patch Producers
- 11.2 Tips for Patch Consumers
- 11.3 Avoiding Common Mistakes
- 11.4 Generating Smaller Patches
12 Invoking cmp
- 12.1 Options to cmp
13 Invoking diff
- 13.1 Options to diff
14 Invoking diff3
- 14.1 Options to diff3
15 Invoking patch
- 15.1 Options to patch
16 Invoking sdiff
- 16.1 Options to sdiff
17 Standards conformance
18 Future Projects
- 18.1 Suggested Projects for Improving GNU diff and patch
- 18.2 Reporting Bugs
Appendix A Copying This Manual
Appendix B Translations of This Manual
Appendix C Index