HowTo: Create Patch Using Diff Command – Linux

If you have made some changes to the code and you would like to share these changes with others – the best way is to provide them as a patch file.

diff is the Linux command line tool that is used for creating patches (sometimes called diffs) and requires that you have two copies of the code: one with your changes and one without.

This article explains how to create a patch for a single file or for a whole directory using diff and how to apply this patch after.

Create a Patch for a Single File in Linux

Let’s say you have some original file.

You make some changes in it and save the result to a new updated file.

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To create a patch file containing the changes you’ve made, run the following command:

$ diff -u OriginalFile UpdatedFile > PatchFile

Option	Description
-u	Create a diff file in the unified format

Apply a Patch to a File

A person, who has the original file and wants to apply the changes you’ve made, can patch the original file with the below command:

$ patch OriginalFile < PatchFile

Now the original file has the same content as the updated file.

Undo a Patch

To revert a previously applied to a file patch, use this command:

$ patch -R OriginalFile < PatchFile

Option	Description
-R, –reverse	Undo changes

Create a Patch for a Directory in Linux

Assume you have a directory with some files and subdirectories inside.

You recursively copy its content to some new directory and do the necessary updates in it.

To create a patch file containing the modifications you’ve made, run the following command:

$ diff -ruN OriginalDir UpdatedDir > PatchFile

Option	Description
-r	Recursively compare any subdirectories found
-u	Create a diff file in the unified format
-N	Treat absent files as empty

Apply a Patch to a Directory

A person, who has the original directory and wants to apply the changes you’ve made, has to copy the original directory and the patch file to some location (e.g. /tmp), go to that location and apply the patch with this command:

$ patch -p0 < PatchFile

Option	Description
-p0	Apply the patch to the same directory structure as when the patch was created

Now the original directory contains the content of the updated directory.

Undo a Patch

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To revert a previously applied to a directory patch, use this command:

$ patch -R -p0 OriginalFile < PatchFile

Option	Description
-R, –reverse	Undo changes