Linux diff3 Command with Practical Examples

Introduction

In this lab, you will learn how to use the Linux diff3 command to compare and merge three files with conflicting changes. The diff3 command is a powerful tool that helps you identify and resolve conflicts when working with multiple versions of a file. You will start by understanding the purpose and syntax of the diff3 command, and then learn how to use it to merge conflicting files. This lab will provide you with practical examples and steps to help you become proficient in using the diff3 command for your scripting and programming tasks.

The diff3 command is a useful tool for resolving conflicts in a three-way merge, which is a common scenario when working with version control systems or collaborating on shared files. By the end of this lab, you will be able to effectively use the diff3 command to merge conflicting files and choose the desired changes to create a unified version.

Linux Commands Cheat Sheet

Skills Graph

Understand the Purpose and Syntax of diff3 Command

In this step, you will learn about the purpose and syntax of the diff3 command in Linux. The diff3 command is used to compare three files and identify the differences between them.

The syntax of the diff3 command is as follows:

diff3 [options] file1 file2 file3

Here, file1, file2, and file3 are the three files you want to compare.

Some common options for the diff3 command include:

• -E: Treat all files as text and compare them line-by-line.
• -a: Treat all files as text, even if they do not contain text.
• -L label: Use the given label instead of the file name.
• -m: Show the merged output, highlighting conflicts.

To understand the purpose of the diff3 command, let's consider a scenario where you have three files with some conflicting changes. You can use the diff3 command to merge these files and resolve the conflicts.

Merge Conflicting Files Using diff3

In this step, you will learn how to use the diff3 command to merge conflicting files.

Let's create three files with some conflicting changes:

$ cd ~/project
$ echo "Line 1" > file1.txt
$ echo "Line 2" >> file1.txt
$ echo "Line 3" >> file1.txt

$ echo "Line 1" > file2.txt
$ echo "Line 2 - Modified" >> file2.txt
$ echo "Line 4" >> file2.txt

$ echo "Line 1" > file3.txt
$ echo "Line 2 - Another Modification" >> file3.txt
$ echo "Line 3" >> file3.txt

Now, we can use the diff3 command to merge these files:

$ diff3 file1.txt file2.txt file3.txt
=======
Line 1
Line 2 - Another Modification
Line 3
-------
Line 1
Line 2 - Modified
Line 4

The diff3 command identifies the conflicting changes and presents them in a merged output. The lines starting with ======= and ------- indicate the conflicting sections.

To resolve the conflicts, you can manually edit the files and choose the desired changes.

Example output:

Line 1
Line 2 - Modified
Line 3

In this example, we have chosen to keep the modified version of "Line 2" from file2.txt.

Resolve Conflicts in a Three-Way Merge

In this step, you will learn how to resolve conflicts in a three-way merge using the diff3 command.

Let's continue with the previous example, where we have three files with conflicting changes:

$ cd ~/project
$ cat file1.txt
Line 1
Line 2
Line 3

$ cat file2.txt
Line 1
Line 2 - Modified
Line 4

$ cat file3.txt
Line 1
Line 2 - Another Modification
Line 3

To resolve the conflicts, we can use the diff3 command with the -m option, which will show the merged output with conflict markers:

$ diff3 -m file1.txt file2.txt file3.txt
Line 1
<<<<<<< file1.txt
Line 2
=======
Line 2 - Another Modification
>>>>>>> file3.txt
Line 3
Line 4

The conflict markers <<<<<<< file1.txt, =======, and >>>>>>> file3.txt indicate the conflicting sections. You can now manually edit the file and choose the desired changes.

Let's resolve the conflict by keeping the modified version of "Line 2" from file3.txt:

$ cat resolved.txt
Line 1
Line 2 - Another Modification
Line 3
Line 4

Example output:

Line 1
Line 2 - Another Modification
Line 3
Line 4

Now, the conflicts have been resolved, and the merged file resolved.txt contains the desired changes.

Summary

In this lab, you learned about the purpose and syntax of the diff3 command in Linux, which is used to compare three files and identify the differences between them. You also learned how to use the diff3 command to merge conflicting files and resolve conflicts in a three-way merge. The diff3 command presents the conflicting changes in a merged output, allowing you to manually edit the files and choose the desired changes.

Linux Commands Cheat Sheet