picocli - a mighty tiny command line interface

Picocli aims to be the easiest-to-use way to create rich command line applications that can run on and off the JVM.

Picocli is a modern library and framework, written in Java, that contains both an annotations API and a programmatic API. It features usage help with ANSI colors and styles, TAB autocompletion 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.

Picocli-based applications can be ahead-of-time compiled to a native image, with extremely fast startup time and lower memory requirements, which can be distributed as a single executable file. Picocli comes with an annotation processor that automatically Graal-enables your jar during compilation.

Picocli applications can be very compact with no boilerplate code: your command (or subcommand) can be executed with a single line of code. Simply implement Runnable or Callable, or put the business logic of your command in a @Command-annotated method.

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.

Picocli 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. Parser tracing facilitates troubleshooting. Command-line argument files (@-files) allow applications to handle very long command lines.

Generates polished and easily tailored usage help and version help, using ANSI colors where possible. Requires at minimum Java 5, but is designed to facilitate the use of Java 8 lambdas. Tested on all Java versions between 5 and 15-ea (inclusive).

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.

Unique features in picocli include support for negatable options, advanced quoted values, and argument groups. Argument groups can be used to create mutually exclusive options, mutually dependent options, option sections in the usage help message and repeating composite arguments like ([-a=<a> -b=<b> -c=<c>] (-x | -y | -z)).... For advanced use cases, applications can access the picocli command object model with the @Spec annotation, and implement custom parameter processing for option parameters if the built-in logic is insufficient.

Picocli-based applications can easily integrate with Dependency Injection containers. The Micronaut microservices framework has built-in support for picocli. Picocli ships with a picocli-spring-boot-starter module that includes a PicocliSpringFactory and Spring Boot auto-configuration to use Spring dependency injection in your picocli command line application. The user manual has an example of integrating with Guice.

Releases

All Releases
Latest: 4.3.2 Release Notes
Older: Picocli 4.0 Release Notes
Older: Picocli 3.0 Release Notes
Older: Picocli 2.0 Release Notes

Documentation

Older

Articles & Presentations

English

Quarkus guide for Quarkus command mode with picocli, thanks to a picocli extension by Michał Górniewski included in Quarkus 1.5 (2020-06-03).
CLI applications with Micronaut and Picocli (2020-06-01) by Λ: Olivier Revial.
Building Native Covid19 Tracker CLI using Java, PicoCLI & GraalVM (2020-05-11) by Mohammed Aboullaite.
Creating CLI tools with Scala, Picocli and GraalVM (2020-03-09) by Naoki Takezoe
Building native Java CLIs with GraalVM, Picocli, and Gradle (2020-03-08) by Mitch Seymour
Build Great Native CLI Apps in Java with Graalvm and Picocli (2020-03-07)
Picocli Structured Objects (2019-09-10) by Philipp Hanslovsky explains how to use picocli's support for repeating argument groups to add or configure structured objects from the command line.
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.
Corda CLI UX (User Experience) Guide (2018 by R3 Limited) gives useful advice.
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)

русский

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

Español

[VIDEO] Picocli - Spring Boot example (2020-05-24) 7-minute quick introduction by Gonzalo H. Mendoza.

Mailing List

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

Credit

Reallinfo designed the new picocli logo! Many thanks!

Commitments

This project follows semantic versioning and adheres to the Zero Bugs Commitment.

Adoption

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, the Apache Hive benchmark CLI, Apache Ignite TensorFlow, and Apache Sling Feature Model Converter.
Picocli is listed on StackShare. Please add it to your stack and add/upvote reasons why you like picocli!
Picocli is used in Pinterest ktlint.
Picocli is used in Spring IO nohttp-cli.
The MinecraftPicocli library allows the use of picocli in Minecraft Forge.
Simple Java Mail now offers a picocli-based CLI.
jbang not only uses picocli internally, but also has a CLI template to generate an initial script: use jbang --init=cli helloworld.java to generate a sample picocli-enabled jbang script. See asciinema.

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

Help to promote picocli

If you like picocli, there are a few things you can do to help:

Upvote my Quora answer to "What is the best way to parse command-line arguments with Java?"
Upvote my StackOverflow answer to "How do I parse command line arguments in Java?"
Tweet about picocli! What do you like about it? How has it helped you? How is it different from the alternatives?

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-4.3.2-green.svg)](https://github.com/remkop/picocli)

Example

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);
    }
}

Implement Runnable or Callable, and your command can be executed in one line of code. The example above uses the CommandLine.execute method to parse the command line, handle errors, handle requests for usage and version help, and invoke the business logic. Applications can call System.exit with the returned exit code to signal success or failure to their caller.

$ java Example -v inputFile1 inputFile2

2 files to process...

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

This can be customized in many ways. See the user manual section on Executing Commands for details.

Usage Help with ANSI Colors and Styles

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

See the source code.

Usage Help API

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: