goopt: A Flexible, Feature-Rich CLI Parser for Go

goopt is a powerful command-line option parser for Go, designed to be intuitive for simple tools and scalable for complex, enterprise-grade applications. It provides a uniquely flexible, struct-first approach to building CLIs that are robust, maintainable, and user-friendly.

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Why goopt? More Than Just Parsing

goopt stands out by providing built-in solutions for the complex challenges of modern CLI development.

🌐 Low-Config Internationalization (i18n)

Ship a single binary that speaks your users’ language. goopt provides out-of-the-box i18n for all system messages and a powerful code generation tool (goopt-i18n-gen) to automate the entire translation workflow for your application.
Read the Internationalization Guide

πŸš€ An Advanced, Interactive Help System

Stop writing boilerplate help text. goopt features an adaptive help system that automatically chooses the best display style for your CLI’s complexity. Its interactive parser lets users search and filter help (--help --search "db"), providing a superior experience.
Learn more about the Help System

βœ… Powerful, Composable Validation

Define complex validation rules directly in your struct tags. Chain built-in validators like email, port, and range, or compose them with logical operators (oneof, all, not) to ensure your application receives correct data.
See the Validation Guide

ν›… Command Lifecycle Hooks

Implement cross-cutting concerns cleanly with a powerful pre- and post-execution hook system. Manage authentication, database connections, logging, and resource cleanup with ease by attaching logic to the command lifecycle.
Explore Execution Hooks

Key Features at a Glance

  • Flexible Definition: Build your CLI with a declarative struct-first approach, a programmatic builder, or a hybrid of both.
  • Hierarchical Structure: Natively supports nested commands, command-specific flags, and intelligent flag inheritance.
  • Advanced Flag Handling: Includes support for positional arguments, repeated flags (-v -v -v), and flag dependencies.
  • Automatic Conveniences: Zero-config support for --help and --version flags.
  • Broad Shell Support: Generate completion scripts for Bash, Zsh, Fish, and PowerShell.
  • Extensive Configuration: Load options from environment variables and external config files with a clear precedence order.

Where to Next?

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