getopt-like behavior in Go

Question

How do I nicely parse a list of program parameters and automate handling \"--help\" and/or \"--version\" (such as \"program [-d value] [--abc] [FILE1]\") in Go?

Answer 1

Another option is Kingping which provides support for all the standard goodies you have come to expect from a modern command line parsing library. It has --help in multiple formats, sub-commands, requirements, types, defaults, etc. It's also still under development. It seems like the other suggestions here haven't been updated in a while.

package main

import (
  "os"
  "strings"
  "gopkg.in/alecthomas/kingpin.v2"
)

var (
  app      = kingpin.New("chat", "A command-line chat application.")
  debug    = app.Flag("debug", "Enable debug mode.").Bool()
  serverIP = app.Flag("server", "Server address.").Default("127.0.0.1").IP()

  register     = app.Command("register", "Register a new user.")
  registerNick = register.Arg("nick", "Nickname for user.").Required().String()
  registerName = register.Arg("name", "Name of user.").Required().String()

  post        = app.Command("post", "Post a message to a channel.")
  postImage   = post.Flag("image", "Image to post.").File()
  postChannel = post.Arg("channel", "Channel to post to.").Required().String()
  postText    = post.Arg("text", "Text to post.").Strings()
)

func main() {
  switch kingpin.MustParse(app.Parse(os.Args[1:])) {
  // Register user
  case register.FullCommand():
    println(*registerNick)

  // Post message
  case post.FullCommand():
    if *postImage != nil {
    }
    text := strings.Join(*postText, " ")
    println("Post:", text)
  }
}

And the --help output:

$ chat --help
usage: chat []  [] [ ...]

A command-line chat application.

Flags:
  --help              Show help.
  --debug             Enable debug mode.
  --server=127.0.0.1  Server address.

Commands:
  help []
    Show help for a command.

  register  
    Register a new user.

  post []  []
    Post a message to a channel.