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

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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.

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Legacy Version (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
    }
}

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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).