Command line

Command Line usage

If you don't plan to use ktlint's command line interface then you can skip this section.

Download and verification¶

Download manually from github¶

All releases of ktlint can be downloaded from the releases page.

Download using curl¶

A particular version of ktlint can be downloaded with next command which also changes the file to an executable in directory /usr/local/bin:

Download

curl -sSLO https://github.com/pinterest/ktlint/releases/download/1.4.0/ktlint && chmod a+x ktlint && sudo mv ktlint /usr/local/bin/

Curl not installed or behind proxy

If you don't have curl installed - replace curl -sL with wget -qO-.
If you are behind a proxy see - curl / wget manpage. Usually simple:

http_proxy=http://proxy-server:port https_proxy=http://proxy-server:port curl -sL ...

Verification of download¶

ktlint.asc contains PGP signature which you can verify with:

Verify releases 0.32.0 and above

curl -sS https://keybase.io/ktlint/pgp_keys.asc | gpg --import && gpg --verify ktlint.asc

Verify releases up through 0.31.0

curl -sS https://keybase.io/shyiko/pgp_keys.asc | gpg --import && gpg --verify ktlint.asc

Package managers¶

ktlint can be installed via several OS specific package managers.

Install with brew on macOS or Homebrew on Linux

brew install ktlint

Install with MacPorts

port install ktlint

Command line usage¶

Rule set(s)¶

When no arguments are specified, the style of all Kotlin files (ending with '.kt' or '.kts') inside the current dir (recursively) are validated with the rules from the standard ruleset. Hidden folders will be skipped.

Default validation with standard ruleset

ktlint

Note

The experimental rules in the standard rule set will only be run when .editorconfig property ktlint_experimental = enabled is set.

To validate with a custom ruleset run command below:

Validation with standard and a custom ruleset

ktlint --ruleset=/path/to/custom-ruleset.jar
# or
ktlint -R /path/to/custom-ruleset.jar

Note

If the custom rule set contains rules that are marked as experimental, those rule will only be run when .editorconfig property ktlint_experimental = enabled is set.

Format (autocorrect)¶

Most style violations can be corrected automatically. Errors that can not be corrected, are printed to stderr.

Autocorrect style violations

ktlint --format
# or
ktlint -F

Globs¶

Globs can be used to specify more exactly what files and directories are to be validated. ktlint uses the .gitignore pattern style syntax for globs. Globs are processed from left to right. Prepend a glob with ! to negate it. Hidden folders will be skipped.

Check only certain locations starting from the current directory

# Check all '.kt' files in 'src/' directory, but ignore files ending with 'Test.kt':
ktlint 'src/**/*.kt' '!src/**/*Test.kt'

# Check all '.kt' files in 'src/' directory, but ignore 'generated' directory and its subdirectories:
ktlint 'src/**/*.kt' '!src/**/generated/**'

Violation reporting¶

ktlint supports different type of reporters for lint violations. When not specified the plain reporter is used. Optionally the plain reporter can group the violations per file.

Style violation grouped by file

$ ktlint --reporter=plain?group_by_file

When using ktlint on an existing project, the number of violations can be huge. To get more insights in which rules are causing the most violations, the plain-summary reporter can be used.

Style violations counted per rule

$ ktlint --reporter=plain-summary

Other built-in reporters are: json, sarif, checkstyle, and html

Style violations can be written to an output file which is convenient when multiple reporters are specified. In example below, the plain reporter is used to write to the console while the checkstyle reports is written to a file:

Multiple reporters

ktlint --reporter=plain --reporter=checkstyle,output=ktlint-report-in-checkstyle-format.xml

If resolving all existing errors in a project is unwanted, it is possible to create a baseline and in following invocations compare violations against this baseline. Violations that are registered in the baseline, will be ignored silently. Remove the baseline file in case you want to reset it.

Check against a baseline file

ktlint --baseline=ktlint-baseline.xml # Baseline is created when not existing

Logging¶

Logging information is written to stdout. The amount of logging can be influenced by setting the minimal log level using option --log-level or -l to one of values trace, debug, info, warn, error, or none to suppress all logging.

By default, the info log level is used meaning that all log lines at level info, warn and error are shown while suppressing log lines at level debug or trace.

Rule configuration (`.editorconfig`)¶

Some rules can be tweaked via the editorconfig file.

A scaffold of the .editorconfig file can be generated with command below. Note: that the generated file only contains configuration settings which are actively used by the rules which are loaded:

Generate .editorconfig

# Specify the code style(ktlint_official, intellij_idea or android_studio) to be used when generating the .editorconfig
ktlint generateEditorConfig ktlint_official
# or
ktlint --ruleset=/path/to/custom-ruleset.jar generateEditorConfig android_studio

Normally the .editorconfig file is located in the root of your project directory. In case the file is located in a sub folder of the project, the settings of that file only applies to that subdirectory and its folders (recursively). Ktlint automatically detects and reads all .editorconfig files in your project.

Use command below, to specify a default editorconfig. In case a property is not defined in any .editorconfig file on the path to the file, the value from the default file is used. The path may point to any valid file or directory. The path can be relative or absolute. Depending on your OS, the "~" at the beginning of a path is replaced by the user home directory.

Override '.editorconfig'

ktlint --editorconfig=/path/to/.editorconfig

Overrides '.editorconfig' in project directory" in KtLint 0.46 and older

When specifying this option using ktlint 0.46 or older, all .editorconfig files in the project directory are being ignored. Starting from KtLint 0.47 the properties in this file are used as fallback.

Stdin && stdout¶

With command below, the input is read from stdin and the violations are printed to stderr. Logging is written to stdout.

Lint from stdin

ktlint --stdin

When combined with the --format option, the formatted code is written to stdout and the violations are printed to stderr:

Format from stdin and write to stdout

ktlint --stdin -F

Suppress logging and error output

Logging output printed to stdout can be suppressed by setting --log-level=none (see logging). Output printed to stderr can be suppressed in different ways. To ignore all error output, add 2> /dev/null to the end of the command line. Otherwise, specify a reporter to write the error output to a file.

If input from stdin represents the contents of a file, the file path can be supplied with stdin-path. This path is made available for rules to use, the --format option will not modify this file.

file path from stdin-path

ktlint --stdin --stdin-path /path/to/file/Foo.kt

Git hooks¶

Predefined git hooks can be installed, to automatically validate lint errors before commit or push.

Install git pre-commit hook

ktlint installGitPreCommitHook

Install git pre-push hook

ktlint installGitPrePushHook

Miscellaneous flags and commands¶

--color and --color-name=<colorName>: Make output colorful and optionally set the color name to use.

-h or --help: Prints help information.

--limit=<limit>: Maximum number of errors to show (default: show all)

--relative: Print files relative to the working directory (e.g. dir/file.kt instead of /home/user/project/dir/file.kt)

--patterns-from-stdin[=<delimiter>]: Reads additional patterns from stdin, where the patterns are separated by <delimiter>. If =<delimiter> is omitted, newline is used as fallback delimiter. If an empty string is given, the NUL byte is used as delimiter instead. If this option is given, then the default patterns are disabled. Options --stdin and --patterns-from-stdin are mutually exclusive, only one of them can be given at a time.

-V or --version: Prints version information and exit.

Microsoft Windows users¶

Microsoft Windows is not able to run the ktlint command directly. Ktlint can be run in following ways on Microsoft Windows:

Use the ktlint.bat batch file provided as part of the release. Add the batch file to your %PATH% environment variable for easy access
Run ktlint using Git Bash
Run as java -jar ktlint