goopt: a flexible and powerful command-line parser

goopt is a flexible and powerful command-line option parser for Go. It provides a declarative, struct-first approach to building CLIs that are robust, maintainable, and user-friendly.

The library is designed to be intuitive for simple tools and scalable for complex applications, with "batteries-included" features like an advanced help system, a composable validation engine, command lifecycle hooks, and comprehensive internationalization (i18n) support.

Looking for the latest version? goopt v2 is here with major improvements!

👉 Check out v2 on GitHub or 📚 read the full docs

Installation (v2)

Version 2 is the recommended version for all new projects.

go get github.com/napalu/goopt/v2

Quick Start (v2)

Define your entire CLI structure—commands, flags, and descriptions—using a single Go struct.

package main

import (
    "fmt"
    "os"
    "github.com/napalu/goopt/v2"
)

type Config struct {
    // Global flags
    Verbose bool `goopt:"short:v;desc:Enable verbose output"`

    // 'create' command with a subcommand
    Create struct {
        Force bool `goopt:"short:f;desc:Force creation"`
        User struct {
            Username string `goopt:"short:u;desc:Username;required:true"`
            Password string `goopt:"short:p;desc:Password;secure:true"`
        } `goopt:"kind:command;name:user;desc:Create user"`
    } `goopt:"kind:command;name:create;desc:Create resources"`
}

func main() {
    cfg := &Config{}
    // Note: In v2, the parser type is simply `Parser`
    parser, err := goopt.NewParserFromStruct(cfg)
    if err != nil {
        fmt.Fprintf(os.Stderr, "Error creating parser: %v\n", err)
        os.Exit(1)
    }

    // Parse returns false on failure or if --help was requested
    if !parser.Parse(os.Args) {
        // goopt handles printing errors and help text by default
        os.Exit(1)
    }

    // Your application logic here...
    if parser.HasCommand("create", "user") {
        fmt.Printf("Creating user: %s\n", cfg.Create.User.Username)
    }
}

For more examples and advanced guides, please visit the v2 Documentation Site.

Legacy Version (v1.x)

Click to expand information for goopt v1.x

This version is in maintenance mode. For new projects, please use goopt v2.

Installation (v1): go get github.com/napalu/goopt@v1
Documentation (v1)
Migration Guide to v2

Quick Start (v1)

package main

import (
    "os"
    "fmt"
    "github.comcom/napalu/goopt"
)

// ...Config struct is identical to v2 example...

func main() {
    cfg := &Config{}
    parser, _:= goopt.NewCmdLineFromStruct(cfg)
    if !parser.Parse(os.Args) {
        parser.PrintUsage(os.Stdout)
        return
    }
}

License

goopt is licensed under the MIT License - see the LICENSE file for details.

Contributing

Contributions are welcome! Contributions should be based on open issues (feel free to open one).

📚 goopt - Awesome Go Library for Command Line