Kotlin Formatter

A command-line tool for formatting Kotlin source code files, implemented as a wrapper around ktfmt.

It can be used to automate code formatting, ensuring a clean and consistent codebase, while integrating seamlessly into development workflows.

The tool can:

• Format files and directories: Apply consistent formatting to files, directories, or standard input.
• Integrate with Git workflows:
  • Pre-commit: Format staged files before committing.
  • Pre-push: Check committed files before pushing.

Usage

kotlin-format [OPTIONS] [FILES...]

Options

Option	Description
--set-exit-if-changed	Exit with a non-zero code if any files needed changes.
--dry-run	Display the changes that would be made without writing them to disk.
--pre-commit	Format staged files as part of the pre-commit process. Mutually exclusive with --pre-push.
--pre-push	Check committed files as part of the pre-push process. Mutually exclusive with --pre-commit.
--push-commit=<text>	The SHA of the commit to use for pre-push. Defaults to HEAD.
--print-stats	Emit performance-related statistics to help diagnose performance issues.
-h, --help	Show help message and exit.

Arguments

Argument	Description
<files>	Files or directories to format. Use - for standard input.

Installing CLI

There are multiple ways to install and use the Kotlin Formatter CLI:

1. Using Hermit

If you don't have Hermit installed, follow the Hermit Getting Started Guide to install it first. Once Hermit is installed, you can install the Kotlin Formatter CLI using:

hermit install kotlin-format

Once installed, you can run the CLI with:

kotlin-format [OPTIONS] [FILES...]

2. Downloading the pre-packaged distribution with a script

A pre-packaged distribution is available on Maven Central and GitHub Releases

VERSION=X.Y.Z
curl -L -o kotlin-formatter-dist.zip https://github.com/block/kotlin-formatter/releases/download/$VERSION/kotlin-formatter-dist-$VERSION.zip
unzip kotlin-formatter-dist.zip
cd kotlin-format-shadow-$VERSION

Once downloaded and extracted, you can run the CLI with:

./bin/kotlin-format [OPTIONS] [FILES...]

3. Downloading the JAR manually

A fat JAR of the CLI is available on Maven Central and GitHub Releases. Once downloaded, you can run the CLI with:

java -jar path/to/kotlin-formatter-$version-all.jar [OPTIONS] [FILES...]