cli is a library for implementing command-line interfaces in Go. cli is the library that powers the CLI for Packer, Consul, Vault, Terraform, Nomad, and more.

• Easy sub-command based CLIs: cli foo, cli bar, etc.

• Support for nested subcommands such as cli foo bar.

• Optional support for default subcommands so cli does something other than error.

• Support for shell autocompletion of subcommands, flags, and arguments with callbacks in Go. You don't need to write any shell code.

• Automatic help generation for listing subcommands.

• Automatic help flag recognition of -h, --help, etc.

• Automatic version flag recognition of -v, --version.

• Helpers for interacting with the terminal, such as outputting information, asking for input, etc. These are optional, you can always interact with the terminal however you choose.

• Use of Go interfaces/types makes augmenting various parts of the library a piece of cake.

Below is a simple example of creating and running a CLI

package main

import (
	"log"
	"os"

	"github.com/hashicorp/cli"
)

func main() {
	c := cli.NewCLI("app", "1.0.0")
	c.Args = os.Args[1:]
	c.Commands = map[string]cli.CommandFactory{
		"foo": fooCommandFactory,
		"bar": barCommandFactory,
	}

	exitStatus, err := c.Run()
	if err != nil {
		log.Println(err)
	}

	os.Exit(exitStatus)
}