Æsh, Another Extensible SHellSkip to content

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Æsh

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Æsh - Java Libraries for Command-Line Interfaces<br>Æsh (Another Extendable SHell) is a collection of Java libraries for building command-line interfaces, interactive shells, and terminal applications.<br>Overview

The Æsh project provides two complementary libraries:<br>Æsh - High-level command framework with annotation-based definitions<br>Æsh Readline - Low-level terminal input/output and line editing<br>Both libraries are production-ready, cross-platform (POSIX and Windows), and actively maintained.<br>Æsh - Command Framework

Æsh provides a high-level API for building CLI applications with commands, options, and arguments. It handles parsing, validation, type conversion, and help generation automatically.<br>Example

@CommandDefinition(name = "deploy", description = "Deploy an application")<br>public class DeployCommand implements CommandCommandInvocation> {

@Option(shortName = 'e', defaultValue = "production",<br>description = "Target environment")<br>private String environment;

@Option(shortName = 'f', hasValue = false,<br>description = "Force deployment")<br>private boolean force;

@Argument(description = "Application name", required = true)<br>private String application;

@Override<br>public CommandResult execute(CommandInvocation invocation) {<br>invocation.println("Deploying " + application + " to " + environment);<br>if (force) {<br>invocation.println("Force flag enabled");<br>return CommandResult.SUCCESS;

Start an interactive console or execute single commands:<br>// Interactive console with history and tab completion<br>AeshConsoleRunner.builder()<br>.command(DeployCommand.class)<br>.prompt("[deploy-tool]$ ")<br>.start();

// Single command execution (for CLI tools)<br>AeshRuntimeRunner.builder()<br>.command(DeployCommand.class)<br>.args(args)<br>.execute();

Key Capabilities

Command Definition<br>Annotation-based (@CommandDefinition, @Option, @Argument) or builder API<br>Optional compile-time annotation processor eliminates runtime reflection<br>Automatic parsing and type conversion (String, Integer, Boolean, File, Enum, custom types)<br>Support for short (-v) and long (--verbose) option names<br>Required and optional parameters with default values<br>Command Organization<br>Command groups and subcommands (e.g., git remote add, docker container start)<br>Unlimited nesting depth for complex hierarchies<br>Dynamic command registration and removal at runtime<br>User Experience<br>Automatic help generation (--help) with visibility levels<br>Tab completion for commands, options, and values<br>Shell completion script generation for bash, zsh, and fish<br>Built-in completers for files, booleans, enums<br>Ghost text suggestions as you type<br>Command history and line editing (via Readline)<br>Clear error messages and validation feedback<br>Extensibility<br>Validators - Custom validation rules for options and arguments<br>Converters - Convert string input to custom types<br>Completers - Domain-specific tab completion<br>Activators - Conditionally enable/disable options based on other options<br>Renderers - Customize help output format<br>Execution Modes<br>Console mode - Interactive shell with readline features<br>Runtime mode - Single command execution from command-line arguments<br>Programmatic - Direct command invocation from Java code<br>Performance & Native Images<br>Annotation processor shifts all reflection to compile time – 3-4x faster startup than the reflection path<br>67-655x faster command registration than picocli in benchmarks<br>8-21x faster command-line parsing than picocli<br>GraalVM native-image friendly – generated code uses direct new calls, no reflection configuration needed<br>Zero external dependencies<br>Coming from picocli? See the Migration Guide.<br>Use Cases

CLI tools and utilities<br>Interactive shells and REPLs<br>Build...