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patch Command in Linux

patch Command in Linux

By Team Scaler
2 mins read
Last updated: 31 Dec 2023
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Overview

In the Linux operating system, the 'patch' command is a nifty tool designed to apply changes to text files. It operates by reading a diff file, commonly produced by the 'diff' command that outlines the changes between two files. The patch command then applies these changes, or 'patches', to a set of original files, effectively updating them. This is highly useful in code maintenance and version control, especially in open-source development.

Syntax of patch Command in Linux

The basic syntax of the patch command in Linux is as follows:

Where:

  • patch: This is the command itself. It invokes the patch program.
  • [options]: This part represents any optional flags or parameters that can be applied to modify the behavior of the command.
  • [originalfile [patchfile]]: These represent the files to be patched. 'originalfile' is the file to be modified, and 'patchfile' is the file containing the differences.

Options in patch Command in Linux

  1. -p or --strip: This option tells patch how many leading components from file names to strip (default is 0).

    For example -

    Output:

    The patch is applied to example.txt with the path stripped by one component.

  2. -R or --reverse: Apply the patch in reverse to undo it.

    For example -

    Output:

    The patch is reversed and the original changes are undone.

  3. -N or --forward: Ignore patches that seem to be already applied.

    For example -

    Output:

    The patch is applied, but patches that seem already applied are ignored.

Example Usages

  • Applying a patch to a single file:

    Output:

    Explanation: The differences outlined in myfile.patch are applied to myfile.txt.

  • Applying a patch with filename in the patch file:

    Output:

    Explanation: This applies the patch to the filename included in the patch file.

Tips

  • Always keep a backup of your original files before applying a patch.

  • Use the -R option to undo a patch if it causes any unforeseen issues.

Advanced Use Cases of patch Command in Linux

  • Applying a patch to multiple files in a directory:

    Output:

    Explanation: This applies each patch in the directory to the respective file.

  • Testing a patch before applying it:

    Output:

    Explanation: The patch command checks if the patch can be applied successfully without actually modifying the file.

  • Applying a patch with file path:

    Output:

    Explanation: The patch is applied to example.txt by specifying the full path to the patch file.

Conclusion

  • The patch command in Linux is a powerful tool for applying changes to files, useful in code versioning and maintenance.

  • Various options can be used with the patch command to modify its behavior, such as -p1 for stripping file paths, or -R for reversing a patch.

  • Always remember to keep a backup of your original files before patching to prevent accidental data loss.