patch – Install patches for open source software

The patch command is a Linux utility that is used to apply patches to source code. Patches are files that contain changes to a source code file or a set of files. The patch command reads these patch files and applies the changes to the corresponding files. This command is particularly useful for open source software development, where developers can submit patches to improve the software.

Overview

The basic syntax of the patch command is as follows:

patch [options] [original-file [patch-file]]

Here, original-file is the file that needs to be patched, and patch-file is the patch file that contains the changes. If original-file is not specified, patch will look for the file in the current directory. If patch-file is not specified, patch will read the patch file from standard input.

Applying a patch

To apply a patch to a file, use the following command:

patch original-file patch-file

For example, to apply a patch file named my-patch.patch to a file named original-file.txt, use the following command:

patch original-file.txt my-patch.patch

Creating a patch

To create a patch file, use the diff command. The diff command compares two files and outputs the differences between them. To create a patch file that contains the differences between two files, use the following command:

diff -u original-file new-file > my-patch.patch

Here, original-file is the original file, new-file is the modified file, and my-patch.patch is the name of the patch file.

Applying a patch with backup

To apply a patch with a backup of the original file, use the -b option. This option creates a backup of the original file before applying the patch.

patch -b original-file patch-file

Applying a patch with dry-run

To test the patch file before applying it, use the -p option. This option performs a dry-run of the patch file and shows the changes that will be made without actually making them.

patch -p1 --dry-run original-file patch-file

Applying a patch with verbose output

To display verbose output during the patching process, use the -v option.

patch -v original-file patch-file

Options

Here are the available options for the patch command:

Option	Description
-b	Create a backup of the original file before patching
-c	Ignore whitespace changes when comparing files
-d	Change to the directory specified before patching
-E	Ignore changes that add or remove blank lines
-f	Force patching, even if the patch file seems to be reversed
-i	Read the patch file from standard input
-N	Apply patches even if the target file is missing
-p	Strip the specified number of leading slashes from file names in the patch file
-R	Reverse the patch, undoing the changes
-s	Silent mode, suppress output
-t	Print the file name and line number before each change
-u	Use unified diff format

Troubleshooting tips

• If the patch file fails to apply, make sure that the target file matches the expected version. The patch file may be for a different version of the file.
• If the patch file fails to apply, check the line numbers in the patch file. The patch file may be for a different version of the file, or the file may have been modified since the patch file was created.
• If the patch file fails to apply, make sure that the patch file is in the correct format. The patch file should be in unified diff format.

Notes

• The patch command is a powerful tool for applying patches to source code. However, it can also be dangerous if used improperly. Always make sure to test patches thoroughly before applying them to production systems.
• The patch command can be used with a variety of programming languages, including C, C++, Java, and Python.
• The patch command can also be used to apply patches to non-source code files, such as configuration files or data files.