Java command line parser with both an annotations API and a programmatic API, featuring usage help with ANSI colors, autocomplete and nested subcommands. In a single file, so you can include it in source form. This lets users run picocli-based applications without requiring picocli as an external dependency.

How it works: annotate your class and picocli initializes it from the command line arguments, converting the input to strongly typed data. Supports git-like subcommands (and nested sub-subcommands), any option prefix style, POSIX-style grouped short options, custom type converters, password options and more. Parser tracing facilitates troubleshooting. Command-line argument files (@-files) allow applications to handle very long command lines.

Distinguishes between named options and positional parameters and allows both to be strongly typed. Multi-valued fields can specify an exact number of parameters or a range (e.g., 0..*, 1..2). Supports Map options like -Dkey1=val1 -Dkey2=val2, where both key and value can be strongly typed.

Generates polished and easily tailored usage help and version help, using ANSI colors where possible. Works with Java 5 or higher (but is designed to facilitate the use of Java 8 lambdas).

Picocli-based command line applications can have TAB autocompletion, interactively showing users what options and subcommands are available. When an option has completionCandidates or has an enum type, autocompletion can also suggest option values. Picocli can generate completion scripts for bash and zsh, and offers picocli-shell-jline2 and picocli-shell-jline3 modules with JLine Completer implementations for building interactive shell applications.

Picocli-based applications can easily integrate with Dependency Injection containers.

• All Releases
• Latest: 4.0.1 Release Notes
• Older: Picocli 4.0 Release Notes
• Older: Picocli 3.0 Release Notes
• Older: Picocli 2.0 Release Notes

• 4.x User manual: https://picocli.info
• 4.x Quick Guide
• 4.x API Javadoc
• Command line autocompletion
• Programmatic API
• FAQ
• GraalVM AOT Compilation to Native Image

• 3.x User manual
• 3.x Quick Guide
• 3.x API Javadoc
• 2.x User manual
• 2.x API Javadoc
• 1.x User manual

• Create a Java Command Line Program with Picocli|Baeldung (2019-05-07) by François Dupire.
• A whirlwind tour of picocli JAX Magazine "Putting the spotlight on Java tools" (2019-04-08).
• An Introduction to PicoCLI (2019-02-10) by devop.
• Develop a CLI tool using groovy scripts (2018-10-26) by Chinthaka Dinadasa.
• Migrating from Commons CLI to picocli. You won't regret it! :-) (also on: DZone and Java Code Geeks).
• Groovy 2.5 CliBuilder Renewal (also on blogs.apache.org). In two parts: Part 1 (also on: DZone, Java Code Geeks), Part 2 (also on: DZone, Java Code Geeks).
• Micronaut user manual for running microservices standalone with picocli.
• Java Command-Line Interfaces (Part 30): Observations by Dustin Marx about picocli 2.0.1 (also on: DZone, Java Code Geeks)
• Java Command-Line Interfaces (Part 10): Picocli by Dustin Marx about picocli 0.9.7 (also on: DZone, Java Code Geeks)
• Picocli 2.0: Groovy Scripts on Steroids (also on: DZone, Java Code Geeks)
• Picocli 2.0: Do More With Less (also on: DZone, Java Code Geeks)
• Announcing picocli 1.0 (also on: DZone)

• Интерфейсы командной строки Java: picocli (2018-08-06): Russian translation by MaxRokatansky of Dustin Marx' blog post.

• [VIDEO] Des applications en ligne de commande avec Picocli et GraalVM (N. Peters) (2019-05-07): 15 minute presentation by Nicolas Peters during Devoxx FR. Presentation slides are available on GitHub.

• Picocli＋Spring Boot でコマンドラインアプリケーションを作成してみる (2019-07-20) by かんがるーさんの日記.
• GraalVM の native image を使って Java で爆速 Lambda の夢を見る (2019-05-02) by @kencharos

• 从Commons CLI迁移到Picocli (2019-03-13): Chinese translation of Migrating from Commons CLI to picocli, thanks to genghaihua.
• Picocli 2.0: Steroids上的Groovy脚本
• Picocli 2.0: 以少求多

Join the picocli Google group if you are interested in discussing anything picocli-related and receiving announcements on new releases.

• Check out Thibaud Lepretre's picocli Spring boot starter!

Reallinfo designed the new picocli logo! Many thanks!

• Picocli is now part of Groovy. From Groovy 2.5, all Groovy command line tools are picocli-based, and picocli is the underlying parser for Groovy's CliBuilder DSL.
• Picocli is now part of Micronaut. The Micronaut CLI has been rewritten with picocli, and Micronaut has dedicated support for running microservices standalone with picocli.
• Picocli is now part of JUnit 5. JUnit 5.3 migrated its ConsoleLauncher from jopt-simple to picocli to support @-files (argument files); this helps users who need to specify many tests on the command line and run into system limitations.
• Debian now offers a libpicocli-java package. Thanks to Miroslav Kravec.
• Picocli is used in the Intuit Karate standalone JAR / executable.
• Picocli is part of Ballerina. Ballerina uses picocli for all its command line utilities.
• Picocli is used in the CheckStyle standalone JAR / executable from Checkstyle 8.15.
• Picocli is included in the OpenJDK Quality Outreach list of Free Open Source Software (FOSS) projects that actively test against OpenJDK builds.
• Picocli is used in the Apache Hadoop Ozone/HDDS command line tools.
• Picocli is used in the Apache Hive benchmark CLI.
• Picocli is listed on StackShare. Please add it to your stack and add/upvote reasons why you like picocli!

Glad to see more people are using picocli. We must be doing something right. :-)

If you like picocli and your project is on GitHub, consider adding this badge to your README.md:

[![picocli](https://img.shields.io/badge/picocli-4.0.1-green.svg)](https://github.com/remkop/picocli)

Annotate fields with the command line parameter names and description. Optionally implement Runnable or Callable to delegate error handling and requests for usage help or version help to picocli. For example:

import picocli.CommandLine;
import picocli.CommandLine.Option;
import picocli.CommandLine.Parameters;
import java.io.File;

@Command(name = "example", mixinStandardHelpOptions = true, version = "Picocli example 4.0")
public class Example implements Runnable {
    @Option(names = { "-v", "--verbose" }, description = "Verbose mode. Helpful for troubleshooting. " +
                                                         "Multiple -v options increase the verbosity.")
    private boolean[] verbose = new boolean[0];

    @Parameters(arity = "1..*", paramLabel = "FILE", description = "File(s) to process.")
    private File[] inputFiles;
    
    public void run() {
        if (verbose.length > 0) {
            System.out.println(inputFiles.length + " files to process...");
        }
        if (verbose.length > 1) {
            for (File f : inputFiles) {
                System.out.println(f.getAbsolutePath());
            }
        }
    }
    
    public static void main(String[] args) {
        // By implementing Runnable or Callable, parsing, error handling and handling user
        // requests for usage help or version help can be done with one line of code.

        int exitCode = new CommandLine(new Example()).execute(args);
        System.exit(exitCode);
    }
}

If your command implements Runnable, all that is necessary to parse the command line and execute the command is a call to CommandLine.run with the command line parameters and the Runnable command. When the program is run on the command line, the command line arguments are converted to Java objects and assigned to the annotated fields. After the arguments are successfully parsed, picocli calls the command's run method.

$ java Example -v inputFile1 inputFile2

2 files to process...

The CommandLine.run convenience method automatically prints the usage help message if the user requested help or when the input was invalid.

If you want more control, you may be interested in the CommandLine.parse or CommandLine.parseWithHandlers methods. See the user manual for details.

Colors, styles, headers, footers and section headings are easily customized with annotations. For example:

See the source code.

Picocli annotations offer many ways to customize the usage help message.

If annotations are not sufficient, you can use picocli's Help API to customize even further. For example, your application can generate help like this with a custom layout:

See the source code.

You can add picocli as an external dependency to your project, or you can include it as source. See the source code. Copy and paste it into a file called CommandLine.java, add it to your project, and enjoy!

compile 'info.picocli:picocli:4.0.1'

<dependency>
  <groupId>info.picocli</groupId>
  <artifactId>picocli</artifactId>
  <version>4.0.1</version>
</dependency>

libraryDependencies += "info.picocli" % "picocli" % "4.0.1"

<dependency org="info.picocli" name="picocli" rev="4.0.1" />

@Grapes(
    @Grab(group='info.picocli', module='picocli', version='4.0.1')
)

[info.picocli/picocli "4.0.1"]

'info.picocli:picocli:jar:4.0.1'