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Go GitHub tag (latest SemVer) GoDoc FOSSA Status Go Report Card codecov Mentioned in Awesome Go

cmdr is a POSIX-compliant, command-line argument parser library in Golang. It is a getopt-like parser of command-line options, be compatible with the getopt_long command line UI, which is an extension of the syntax recommended by POSIX.

It's a replacement of the standard library flag.

Also, there is a fully-functional Options Store (configurations) integrated for your hierarchical configuration dataset.

The .netCore version Cmdr.Core is available now. A cxx version cmdr-cxx was released (Happy Spring Festival 2021).


See the image frames at #1.

See our extras:

and Bonus of #cmdr Series:


FRZ: It means I'm planning and in working for cmdr.v2, but the plan is delayed. In recently months, sadly, some things took my focus. But the v2 will be here soon.
In our v2's wishlist, codes will be rewritten completely since I understand coding more in golang, well, perhaps, I hope so.

  • docs (WIP):

  • v1.11.26 (FRZ)

    • security patch: upgrade to 0.17.0
  • v1.11.25 (FRZ)

    • security patch: google/x/net and more
    • upgrade deps
  • v1.11.23 (FRZ)

    • security patch: google/x/net and more
    • improved some writings
    • fixed/improved cmdr.Get() to extract some fields more deeply
    • added Flag.GetDottedNamePathEx()
    • improved defaultActionImpl to flush all outputs at once
    • make default action outputs colorful
  • v1.11.21 (FRZ)

    • NOTE: switched toolchain to go1.18 (see the go.mod)

    • now you may return ErrNotImpl to fallback to default action at early developing

      Expand to details

      There are 3 ways to make or fallback to cmdr default impl to get some debug information:

       1. set action to nil;
       2. use envvar `FORCE_DEFAULT_ACTION=1`;
       3. return `cmdr.ErrNotImpl` in your action handler:
      listCmd := cmdr.NewSubCmd().Titles("list", "ls").
        Description("list projects in .poi.yml").
        Action(func(cmd *cmdr.Command, args []string) (err error) {
          err = cmdr.ErrNotImpl // notify caller fallback to defaultAction

      The default action of a command handler will print flags hit info and others useful info.

  • More details at CHANGELOG



For Developer

For Developer

Fast Guide

See example-app, examples/, and cmdr-examples

Expand to source codes
package main

import (


func main() {

func Entry() {
	root := buildRootCmd()
	if err := cmdr.Exec(root, options...); err != nil {
		log.Fatalf("error occurs in app running: %+v\n", err)

func buildRootCmd() (rootCmd *cmdr.RootCommand) {
	root := cmdr.Root(appName, version).
		// AddGlobalPreAction(func(cmd *cmdr.Command, args []string) (err error) {
		//	// cmdr.Set("enable-ueh", true)
		//	return
		// }).
		// AddGlobalPreAction(func(cmd *cmdr.Command, args []string) (err error) {
		//	//fmt.Printf("# global pre-action 2, exe-path: %v\n", cmdr.GetExecutablePath())
		//	return
		// }).
		// AddGlobalPostAction(func(cmd *cmdr.Command, args []string) {
		//	//fmt.Println("# global post-action 1")
		// }).
		// AddGlobalPostAction(func(cmd *cmdr.Command, args []string) {
		//	//fmt.Println("# global post-action 2")
		// }).
		Copyright(copyright, "hedzr").
		Description(desc, longDesc).
	rootCmd = root.RootCommand()

	// for your biz-logic, constructing an AttachToCmdr(root *cmdr.RootCmdOpt) is recommended.
	// see our full sample and template repo:
	// core.AttachToCmdr(root.RootCmdOpt())

	// These lines are removable

		Titles("enable-ueh", "ueh").
		Description("Enables the unhandled exception handler?").
	// cmdrPanic(root)
	// pprof.AttachToCmdr(root.RootCmdOpt())

func cmdrSoundex(root cmdr.OptCmd) {
	cmdr.NewSubCmd().Titles("soundex", "snd", "sndx", "sound").
		Description("soundex test").
		TailPlaceholder("[text1, text2, ...]").
		Action(func(cmd *cmdr.Command, args []string) (err error) {
			for ix, s := range args {
				fmt.Printf("%5d. %s => %s\n", ix, s, tool.Soundex(s))

func onUnhandledErrorHandler(err interface{}) {
	if cmdr.GetBoolR("enable-ueh") {

	panic(err) // re-throw it

func dumpStacks() {
	fmt.Printf("\n\n=== BEGIN goroutine stack dump ===\n%s\n=== END goroutine stack dump ===\n\n", errors.DumpStacksAsString(true))

func init() {
	options = append(options,

		// cmdr.WithLogxShort(defaultDebugEnabled,defaultLoggerBackend,defaultLoggerLevel),
			defaultDebugEnabled, defaultLoggerBackend, defaultLoggerLevel,
			log.WithTimestamp(true, "")))),

# Type '-h'/'-?' or '--help' to get command help screen.
# Star me if it's helpful:

	if isDebugBuild() {
		options = append(options, pprof.GetCmdrProfilingOptions())

	// enable '--trace' command line option to toggle a internal trace mode (can be retrieved by cmdr.GetTraceMode())
	// import ""
	// trace.WithTraceEnable(defaultTraceEnabled)
	// Or:
	optAddTraceOption := cmdr.WithXrefBuildingHooks(func(root *cmdr.RootCommand, args []string) {
			Titles("trace", "tr").
			Description("enable trace mode for tcp/mqtt send/recv data dump", "").
			// Action(func(cmd *cmdr.Command, args []string) (err error) { println("trace mode on"); cmdr.SetTraceMode(true); return; }).
	}, nil)
	options = append(options, optAddTraceOption)
	// options = append(options, optAddServerExtOpt«ion)

	// allow and search '.<appname>.yml' at first
	locations := []string{".$APPNAME.yml"}
	locations = append(locations, cmdr.GetPredefinedLocations()...)
	options = append(options, cmdr.WithPredefinedLocations(locations...))

	// options = append(options, internal.NewAppOption())

var options []cmdr.ExecOption

func isDebugBuild() bool         { return isdelve.Enabled }
func isDockerBuild() bool        { return buildtags.IsDockerBuild() }
func isRunningInDockerEnv() bool { return cmdr.InDockerEnv() }

//goland:noinspection GoNameStartsWithPackageName
const (
	appName   = "example-app"
	version   = "0.2.5"
	copyright = "example-app - A devops tool - cmdr series"
	desc      = "example-app is an effective devops tool. It make an demo application for 'cmdr'"
	longDesc  = `example-app is an effective devops tool. It make an demo application for 'cmdr'.
	examples = `
$ {{.AppName}} gen shell [--bash|--zsh|--fish|--auto]
  generate bash/shell completion scripts
$ {{.AppName}} gen man
  generate linux man page 1
$ {{.AppName}} --help
  show help screen.
$ {{.AppName}} --help --man
  show help screen in manpage viewer (for linux/darwin).
	// overview = ``
	// zero = 0

	// defaultTraceEnabled  = true
	defaultDebugEnabled  = false
	defaultLoggerLevel   = "debug"
	defaultLoggerBackend = "logrus"

Tips for Building Your App

As building your app with cmdr, some build tags are suggested:

export GIT_REVISION="$(git rev-parse --short HEAD)"
export GIT_SUMMARY="$(git describe --tags --dirty --always)"
export GOVERSION="$(go version)"
export BUILDTIME="$(date -u '+%Y-%m-%d_%H-%M-%S')"
export VERSION="$(grep -E "Version[ \t]+=[ \t]+" doc.go|grep -Eo "[0-9.]+")"
export W_PKG=""
export LDFLAGS="-s -w \
    -X '$W_PKG.Githash=$GIT_REVISION' \
    -X '$W_PKG.GitSummary=$GIT_SUMMARY' \
    -X '$W_PKG.GoVersion=$GOVERSION' \
    -X '$W_PKG.Buildstamp=$BUILDTIME' \
    -X '$W_PKG.Version=$VERSION'"

go build -v -ldflags "$LDFLAGS" -o ./bin/your-app ./your-app/


Feel free to issue me bug reports and fixes. Many thanks to all contributors.

Thanks to JODL

Thanks to JetBrains for donating product licenses to help develop cmdr
jetbrains goland



FOSSA Status