A Go library for implementing command-line interfaces

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


  • 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 (


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 {



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