Linux diff3 command: a powerful tool for comparing and merging three files

The diff3 command is a powerful tool in Linux that compares three files and shows their differences. This is very useful for programmers and system administrators who often deal with multiple versions of the same file, needing to merge these versions or identify changes between different versions.

This article will introduce the basic usage of the diff3 command, common options, and some examples to help you understand how it works in Linux.

What is diff3 command?

diff3 is a tool for comparing three files line by line, which recognizes differences and displays them in an easy to understand format.

It can be used for:

• Find the difference between the three files.
• Automatically merge content from different files.
• A conflict that occurs when merging file versions.

The diff3 command is similar to the diff command or the sdiff command, but it handles three files instead of two, which is especially useful when multiple contributors process the same file and need to merge their changes into a single version.

Basic syntax of diff3 command

The basic syntax of the diff3 command is as follows:

 diff3 [Options] File 1 File 2 File 3

Command explanation:

• 文件1 : The first version of the file.
• 文件2 : The second version of the file.
• 文件3 : The third version of the file.

Common options

Here are some common options for diff3 command:

• -e : Create an ed script that can be used to apply changes to files.
• -m : Automatically merge files.
• -A : Contains all changes to all files.
• -E : Try to merge files even if conflicts are found.
• -3 : Show only changes with differences between the three files.

Find differences between files in Linux

Suppose you have three files: file1.txt , file2.txt and file3.txt . Each file contains slightly different versions of the same content, and you want to compare them to see where the difference lies.

To compare these three files, you can use the following command:

 diff3 file1.txt file2.txt file3.txt 

Output result meaning:

• 1:2c : This means that in file1.txt , the change occurs on line 2, and the content of line 2 is This is line 2.
• 2:2c : This means that in file2.txt , the change also occurs on line 2, but the content of that line has been modified to This is modified line 2.
• 3:2,3c : This means that in file3.txt , there are changes in line 2 and line 3. Line 2 remains unchanged (This is line 2.), but line 3 is a new line with the content: This is an added line.

Merge files using diff3 in Linux

If you want to merge these three files and create a new file with all changes, you can use the -m option:

 diff3 -m file1.txt file2.txt file3.txt

This outputs the merged content and uses a conflict marker to show where there are conflicting changes.

Output result meaning:

• : This marks the beginning of the conflict and displays the version from <code>file1.txt .
• ||||||| file2.txt : This line displays the content from file2.txt (intermediate file in comparison).
• ======= : This separates the conflicting lines.
• >>>>>>> file3.txt : This tag comes from the version of file3.txt and the end of the conflict block.

You can edit this content manually to preserve the changes you want.

Use diff3 to apply changes to multiple files to one file

You can also create an ed script using diff3 that applies changes in file2.txt and file3.txt to file1.txt . This can be done using the -e option:

 diff3 -e file1.txt file2.txt file3.txt > scriptfile

This command creates a file named scriptfile that contains the generated ed script, which you can use ed command to apply from scriptfile file1.txt .

 ed file1.txt <p><img src="/static/imghw/default1.png" data-src="https://img.php.cn/upload/article/000/000/000/174692815950045.jpg" class="lazy" alt="How to Compare and Merge Files Using diff3 Command on Linux"></p><p> This is very useful when you want to use scripts to automatically merge files.</p><p></p><h2> Resolve conflicts in <code>diff3</code> merge</h2><p> When merging with <code>diff3</code> , conflicts may occur when there are differences in the three files in the same location. These conflicts will be marked in the output and you need to resolve them manually.</p><p> To resolve a conflict, open a file containing the conflict tag. Edit the file to delete unwanted lines and preserve the required changes. After resolving the conflict, save the file.</p><h5> in conclusion</h5><p> The <code>diff3</code> command is a powerful tool for comparing and merging three files in Linux, which is especially useful for handling multiple versions of the same file and resolving conflicts when merging changes. By understanding its basic usage and options, you can effectively manage file versions and collaborate with others in your project.</p>

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