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A Go library for building command line applications.


  • Advanced command line arguments handling
    • Subcommand handling
    • Short and long command line arguments
    • Multiple arguments (repeated or delimited)
    • Support for environment variables
    • Well formatted usage printing
    • Auto usage and version printing
    • Unknown argument handling
  • Output tables in the terminal
  • Template support for config files
  • No external dependency


go get github.com/devfacet/gocmd


A basic app

See basic for full code.

func main() {
	flags := struct {
		Help      bool `short:"h" long:"help" description:"Display usage" global:"true"`
		Version   bool `short:"v" long:"version" description:"Display version"`
		VersionEx bool `long:"vv" description:"Display version (extended)"`
		Echo      struct {
			Settings bool `settings:"true" allow-unknown-arg:"true"`
		} `command:"echo" description:"Print arguments"`
		Math struct {
			Sqrt struct {
				Number float64 `short:"n" long:"number" required:"true" description:"Number"`
			} `command:"sqrt" description:"Calculate square root"`
			Pow struct {
				Base     float64 `short:"b" long:"base" required:"true" description:"Base"`
				Exponent float64 `short:"e" long:"exponent" required:"true" description:"Exponent"`
			} `command:"pow" description:"Calculate base exponential"`
		} `command:"math" description:"Math functions" nonempty:"true"`

	// Echo command
	gocmd.HandleFlag("Echo", func(cmd *gocmd.Cmd, args []string) error {
		fmt.Printf("%s\n", strings.Join(cmd.FlagArgs("Echo")[1:], " "))
		return nil

	// Math commands
	gocmd.HandleFlag("Math.Sqrt", func(cmd *gocmd.Cmd, args []string) error {
		return nil
	gocmd.HandleFlag("Math.Pow", func(cmd *gocmd.Cmd, args []string) error {
		fmt.Println(math.Pow(flags.Math.Pow.Base, flags.Math.Pow.Exponent))
		return nil

	// Init the app
		Name:        "basic",
		Version:     "1.0.0",
		Description: "A basic app",
		Flags:       &flags,
		ConfigType:  gocmd.ConfigTypeAuto,
cd examples/basic/
go build .
$ ./basic
Usage: basic [options...] COMMAND [options...]

A basic app

  -h, --help         	Display usage
  -v, --version      	Display version
      --vv           	Display version (extended)

  echo               	Print arguments
  math               	Math functions
    sqrt             	Calculate square root
      -n, --number   	Number
    pow              	Calculate base exponential
      -b, --base     	Base
      -e, --exponent 	Exponent


go build .




git add CHANGELOG.md # update CHANGELOG.md
./release.sh v1.0.0  # replace "v1.0.0" with new version

git ls-remote --tags # check the new tag


  • Code contributions must be through pull requests
  • Run tests, linting and formatting before a pull request
  • Pull requests can not be merged without being reviewed
  • Use “Issues” for bug reports, feature requests and discussions
  • Do not refactor existing code without a discussion
  • Do not add a new third party dependency without a discussion
  • Use semantic versioning and git tags for versioning


Licensed under The MIT License (MIT)
For the full copyright and license information, please view the LICENSE.txt file.