Overview
patch is a utility that reads output files (also known as patch files) created by the diff command and applies changes to original files. These patch files typically record what content has been added, deleted, or modified line by line. The patch command modifies the original files based on this information. Before the advent of version control systems (like CVS, Git, etc.), it was a primary method for sharing code changes.
Key Features
The main features of the patch command are as follows:
- Uses patch files generated by the diff command.
- Widely used for updating source code, changing configuration files, etc.
- Can detect and apply some changes even if the original file does not exactly match the patch file.
- Also provides a function to revert changes to their original state (reverse).
Main Options
Frequently used patch command options are grouped by purpose.
1) Applying and Reverting Patches
2) Help
Generated command:
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Description:
`patch` Executes the command.
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Usage Examples
Learn the functionalities of the patch command through various usage examples.
Apply a Patch File
patch -p1 -i my_changes.patchApplies changes to the original file using 'my_changes.patch'. The `-p1` option ignores the first directory component in the patch file's path.
Revert Changes
patch -p1 -R -i my_changes.patchReverts the applied patch content to its original state using the `-R` option. Used to revert files to their pre-patched state.
Apply Patch via Pipe
diff -u original_file.txt new_file.txt | patch -p0 original_file.txtDirectly passes the output of the diff command to the patch command via a pipe (`|`), applying changes without creating a separate patch file.
Preview Patch Application
patch --dry-run -p1 -i my_changes.patchUses the `--dry-run` option to preview what changes would occur if the patch were applied.
Installation
patch is included by default in most Linux distributions. If the package is not present, you can install the `patch` or `diffutils` package as follows:
Debian/Ubuntu
sudo apt update && sudo apt install -y patchRHEL/CentOS/Fedora
sudo dnf install -y patchArch Linux
sudo pacman -S --needed patchTips & Cautions
Here are some important points to consider when using the patch command.
Tips
- The unified format generated by `diff -u` is the most common patch format. Using this format generally leads to a higher success rate for patch application.
- The `-p` option is crucial for ignoring path information in the patch file. You should check the patch file's header to specify the correct level. For example, if the path is `a/src/file.c`, using `-p1` will apply the patch to `src/file.c`.
- If a patch fails to apply, a file with a `.rej` extension is created. This file contains the rejected parts of the patch and can be referred to for manual correction.
- It is recommended to create a backup of your original files before applying a patch.