cobra

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 Go to latest Published: Apr 10, 2020 License: Apache-2.0 Imports: 16 Imported by: 126,261

README

cobra logo

Cobra is both a library for creating powerful modern CLI applications as well as a program to generate applications and command files.

Many of the most widely used Go projects are built using Cobra, such as: Kubernetes, Hugo, rkt, etcd, Moby (former Docker), Docker (distribution), OpenShift, Delve, GopherJS, CockroachDB, Bleve, ProjectAtomic (enterprise), Giant Swarm's gsctl, Nanobox/Nanopack, rclone, nehm, Pouch, Istio, Prototool, mattermost-server, Gardener, Linkerd, Github CLI etc.

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Table of Contents

Overview

Cobra is a library providing a simple interface to create powerful modern CLI interfaces similar to git & go tools.

Cobra is also an application that will generate your application scaffolding to rapidly develop a Cobra-based application.

Cobra provides:

  • Easy subcommand-based CLIs: app server, app fetch, etc.
  • Fully POSIX-compliant flags (including short & long versions)
  • Nested subcommands
  • Global, local and cascading flags
  • Easy generation of applications & commands with cobra init appname & cobra add cmdname
  • Intelligent suggestions (app srver... did you mean app server?)
  • Automatic help generation for commands and flags
  • Automatic help flag recognition of -h, --help, etc.
  • Automatically generated bash autocomplete for your application
  • Automatically generated man pages for your application
  • Command aliases so you can change things without breaking them
  • The flexibility to define your own help, usage, etc.
  • Optional tight integration with viper for 12-factor apps

Concepts

Cobra is built on a structure of commands, arguments & flags.

Commands represent actions, Args are things and Flags are modifiers for those actions.

The best applications will read like sentences when used. Users will know how to use the application because they will natively understand how to use it.

The pattern to follow is APPNAME VERB NOUN --ADJECTIVE. or APPNAME COMMAND ARG --FLAG

A few good real world examples may better illustrate this point.

In the following example, 'server' is a command, and 'port' is a flag:

hugo server --port=1313

In this command we are telling Git to clone the url bare.

git clone URL --bare

Commands

Command is the central point of the application. Each interaction that the application supports will be contained in a Command. A command can have children commands and optionally run an action.

In the example above, 'server' is the command.

More about cobra.Command

Flags

A flag is a way to modify the behavior of a command. Cobra supports fully POSIX-compliant flags as well as the Go flag package. A Cobra command can define flags that persist through to children commands and flags that are only available to that command.

In the example above, 'port' is the flag.

Flag functionality is provided by the pflag library, a fork of the flag standard library which maintains the same interface while adding POSIX compliance.

Installing

Using Cobra is easy. First, use go get to install the latest version of the library. This command will install the cobra generator executable along with the library and its dependencies:

go get -u github.com/spf13/cobra/cobra

Next, include Cobra in your application:

import "github.com/spf13/cobra"

Getting Started

While you are welcome to provide your own organization, typically a Cobra-based application will follow the following organizational structure:

  ▾ appName/
    ▾ cmd/
        add.go
        your.go
        commands.go
        here.go
      main.go

In a Cobra app, typically the main.go file is very bare. It serves one purpose: initializing Cobra.

package main

import (
  "{pathToYourApp}/cmd"
)

func main() {
  cmd.Execute()
}

Using the Cobra Generator

Cobra provides its own program that will create your application and add any commands you want. It's the easiest way to incorporate Cobra into your application.

Here you can find more information about it.

Using the Cobra Library

To manually implement Cobra you need to create a bare main.go file and a rootCmd file. You will optionally provide additional commands as you see fit.

Create rootCmd

Cobra doesn't require any special constructors. Simply create your commands.

Ideally you place this in app/cmd/root.go:

var rootCmd = &cobra.Command{
  Use:   "hugo",
  Short: "Hugo is a very fast static site generator",
  Long: `A Fast and Flexible Static Site Generator built with
                love by spf13 and friends in Go.
                Complete documentation is available at http://hugo.spf13.com`,
  Run: func(cmd *cobra.Command, args []string) {
    // Do Stuff Here
  },
}

func Execute() {
  if err := rootCmd.Execute(); err != nil {
    fmt.Println(err)
    os.Exit(1)
  }
}

You will additionally define flags and handle configuration in your init() function.

For example cmd/root.go:

package cmd

import (
	"fmt"
	"os"

	homedir "github.com/mitchellh/go-homedir"
	"github.com/spf13/cobra"
	"github.com/spf13/viper"
)

var (
	// Used for flags.
	cfgFile     string
	userLicense string

	rootCmd = &cobra.Command{
		Use:   "cobra",
		Short: "A generator for Cobra based Applications",
		Long: `Cobra is a CLI library for Go that empowers applications.
This application is a tool to generate the needed files
to quickly create a Cobra application.`,
	}
)

// Execute executes the root command.
func Execute() error {
	return rootCmd.Execute()
}

func init() {
	cobra.OnInitialize(initConfig)

	rootCmd.PersistentFlags().StringVar(&cfgFile, "config", "", "config file (default is $HOME/.cobra.yaml)")
	rootCmd.PersistentFlags().StringP("author", "a", "YOUR NAME", "author name for copyright attribution")
	rootCmd.PersistentFlags().StringVarP(&userLicense, "license", "l", "", "name of license for the project")
	rootCmd.PersistentFlags().Bool("viper", true, "use Viper for configuration")
	viper.BindPFlag("author", rootCmd.PersistentFlags().Lookup("author"))
	viper.BindPFlag("useViper", rootCmd.PersistentFlags().Lookup("viper"))
	viper.SetDefault("author", "NAME HERE <EMAIL ADDRESS>")
	viper.SetDefault("license", "apache")

	rootCmd.AddCommand(addCmd)
	rootCmd.AddCommand(initCmd)
}

func er(msg interface{}) {
	fmt.Println("Error:", msg)
	os.Exit(1)
}

func initConfig() {
	if cfgFile != "" {
		// Use config file from the flag.
		viper.SetConfigFile(cfgFile)
	} else {
		// Find home directory.
		home, err := homedir.Dir()
		if err != nil {
			er(err)
		}

		// Search config in home directory with name ".cobra" (without extension).
		viper.AddConfigPath(home)
		viper.SetConfigName(".cobra")
	}

	viper.AutomaticEnv()

	if err := viper.ReadInConfig(); err == nil {
		fmt.Println("Using config file:", viper.ConfigFileUsed())
	}
}
Create your main.go

With the root command you need to have your main function execute it. Execute should be run on the root for clarity, though it can be called on any command.

In a Cobra app, typically the main.go file is very bare. It serves, one purpose, to initialize Cobra.

package main

import (
  "{pathToYourApp}/cmd"
)

func main() {
  cmd.Execute()
}
Create additional commands

Additional commands can be defined and typically are each given their own file inside of the cmd/ directory.

If you wanted to create a version command you would create cmd/version.go and populate it with the following:

package cmd

import (
  "fmt"

  "github.com/spf13/cobra"
)

func init() {
  rootCmd.AddCommand(versionCmd)
}

var versionCmd = &cobra.Command{
  Use:   "version",
  Short: "Print the version number of Hugo",
  Long:  `All software has versions. This is Hugo's`,
  Run: func(cmd *cobra.Command, args []string) {
    fmt.Println("Hugo Static Site Generator v0.9 -- HEAD")
  },
}

Working with Flags

Flags provide modifiers to control how the action command operates.

Assign flags to a command

Since the flags are defined and used in different locations, we need to define a variable outside with the correct scope to assign the flag to work with.

var Verbose bool
var Source string

There are two different approaches to assign a flag.

Persistent Flags

A flag can be 'persistent' meaning that this flag will be available to the command it's assigned to as well as every command under that command. For global flags, assign a flag as a persistent flag on the root.

rootCmd.PersistentFlags().BoolVarP(&Verbose, "verbose", "v", false, "verbose output")
Local Flags

A flag can also be assigned locally which will only apply to that specific command.

localCmd.Flags().StringVarP(&Source, "source", "s", "", "Source directory to read from")
Local Flag on Parent Commands

By default Cobra only parses local flags on the target command, any local flags on parent commands are ignored. By enabling Command.TraverseChildren Cobra will parse local flags on each command before executing the target command.

command := cobra.Command{
  Use: "print [OPTIONS] [COMMANDS]",
  TraverseChildren: true,
}
Bind Flags with Config

You can also bind your flags with viper:

var author string

func init() {
  rootCmd.PersistentFlags().StringVar(&author, "author", "YOUR NAME", "Author name for copyright attribution")
  viper.BindPFlag("author", rootCmd.PersistentFlags().Lookup("author"))
}

In this example the persistent flag author is bound with viper. Note, that the variable author will not be set to the value from config, when the --author flag is not provided by user.

More in viper documentation.

Required flags

Flags are optional by default. If instead you wish your command to report an error when a flag has not been set, mark it as required:

rootCmd.Flags().StringVarP(&Region, "region", "r", "", "AWS region (required)")
rootCmd.MarkFlagRequired("region")

Positional and Custom Arguments

Validation of positional arguments can be specified using the Args field of Command.

The following validators are built in:

  • NoArgs - the command will report an error if there are any positional args.
  • ArbitraryArgs - the command will accept any args.
  • OnlyValidArgs - the command will report an error if there are any positional args that are not in the ValidArgs field of Command.
  • MinimumNArgs(int) - the command will report an error if there are not at least N positional args.
  • MaximumNArgs(int) - the command will report an error if there are more than N positional args.
  • ExactArgs(int) - the command will report an error if there are not exactly N positional args.
  • ExactValidArgs(int) - the command will report an error if there are not exactly N positional args OR if there are any positional args that are not in the ValidArgs field of Command
  • RangeArgs(min, max) - the command will report an error if the number of args is not between the minimum and maximum number of expected args.

An example of setting the custom validator:

var cmd = &cobra.Command{
  Short: "hello",
  Args: func(cmd *cobra.Command, args []string) error {
    if len(args) < 1 {
      return errors.New("requires a color argument")
    }
    if myapp.IsValidColor(args[0]) {
      return nil
    }
    return fmt.Errorf("invalid color specified: %s", args[0])
  },
  Run: func(cmd *cobra.Command, args []string) {
    fmt.Println("Hello, World!")
  },
}

Example

In the example below, we have defined three commands. Two are at the top level and one (cmdTimes) is a child of one of the top commands. In this case the root is not executable meaning that a subcommand is required. This is accomplished by not providing a 'Run' for the 'rootCmd'.

We have only defined one flag for a single command.

More documentation about flags is available at https://github.com/spf13/pflag

package main

import (
  "fmt"
  "strings"

  "github.com/spf13/cobra"
)

func main() {
  var echoTimes int

  var cmdPrint = &cobra.Command{
    Use:   "print [string to print]",
    Short: "Print anything to the screen",
    Long: `print is for printing anything back to the screen.
For many years people have printed back to the screen.`,
    Args: cobra.MinimumNArgs(1),
    Run: func(cmd *cobra.Command, args []string) {
      fmt.Println("Print: " + strings.Join(args, " "))
    },
  }

  var cmdEcho = &cobra.Command{
    Use:   "echo [string to echo]",
    Short: "Echo anything to the screen",
    Long: `echo is for echoing anything back.
Echo works a lot like print, except it has a child command.`,
    Args: cobra.MinimumNArgs(1),
    Run: func(cmd *cobra.Command, args []string) {
      fmt.Println("Echo: " + strings.Join(args, " "))
    },
  }

  var cmdTimes = &cobra.Command{
    Use:   "times [string to echo]",
    Short: "Echo anything to the screen more times",
    Long: `echo things multiple times back to the user by providing
a count and a string.`,
    Args: cobra.MinimumNArgs(1),
    Run: func(cmd *cobra.Command, args []string) {
      for i := 0; i < echoTimes; i++ {
        fmt.Println("Echo: " + strings.Join(args, " "))
      }
    },
  }

  cmdTimes.Flags().IntVarP(&echoTimes, "times", "t", 1, "times to echo the input")

  var rootCmd = &cobra.Command{Use: "app"}
  rootCmd.AddCommand(cmdPrint, cmdEcho)
  cmdEcho.AddCommand(cmdTimes)
  rootCmd.Execute()
}

For a more complete example of a larger application, please checkout Hugo.

Help Command

Cobra automatically adds a help command to your application when you have subcommands. This will be called when a user runs 'app help'. Additionally, help will also support all other commands as input. Say, for instance, you have a command called 'create' without any additional configuration; Cobra will work when 'app help create' is called. Every command will automatically have the '--help' flag added.

Example

The following output is automatically generated by Cobra. Nothing beyond the command and flag definitions are needed.

$ cobra help

Cobra is a CLI library for Go that empowers applications.
This application is a tool to generate the needed files
to quickly create a Cobra application.

Usage:
  cobra [command]

Available Commands:
  add         Add a command to a Cobra Application
  help        Help about any command
  init        Initialize a Cobra Application

Flags:
  -a, --author string    author name for copyright attribution (default "YOUR NAME")
      --config string    config file (default is $HOME/.cobra.yaml)
  -h, --help             help for cobra
  -l, --license string   name of license for the project
      --viper            use Viper for configuration (default true)

Use "cobra [command] --help" for more information about a command.

Help is just a command like any other. There is no special logic or behavior around it. In fact, you can provide your own if you want.

Defining your own help

You can provide your own Help command or your own template for the default command to use with following functions:

cmd.SetHelpCommand(cmd *Command)
cmd.SetHelpFunc(f func(*Command, []string))
cmd.SetHelpTemplate(s string)

The latter two will also apply to any children commands.

Usage Message

When the user provides an invalid flag or invalid command, Cobra responds by showing the user the 'usage'.

Example

You may recognize this from the help above. That's because the default help embeds the usage as part of its output.

$ cobra --invalid
Error: unknown flag: --invalid
Usage:
  cobra [command]

Available Commands:
  add         Add a command to a Cobra Application
  help        Help about any command
  init        Initialize a Cobra Application

Flags:
  -a, --author string    author name for copyright attribution (default "YOUR NAME")
      --config string    config file (default is $HOME/.cobra.yaml)
  -h, --help             help for cobra
  -l, --license string   name of license for the project
      --viper            use Viper for configuration (default true)

Use "cobra [command] --help" for more information about a command.
Defining your own usage

You can provide your own usage function or template for Cobra to use. Like help, the function and template are overridable through public methods:

cmd.SetUsageFunc(f func(*Command) error)
cmd.SetUsageTemplate(s string)

Version Flag

Cobra adds a top-level '--version' flag if the Version field is set on the root command. Running an application with the '--version' flag will print the version to stdout using the version template. The template can be customized using the cmd.SetVersionTemplate(s string) function.

PreRun and PostRun Hooks

It is possible to run functions before or after the main Run function of your command. The PersistentPreRun and PreRun functions will be executed before Run. PersistentPostRun and PostRun will be executed after Run. The Persistent*Run functions will be inherited by children if they do not declare their own. These functions are run in the following order:

  • PersistentPreRun
  • PreRun
  • Run
  • PostRun
  • PersistentPostRun

An example of two commands which use all of these features is below. When the subcommand is executed, it will run the root command's PersistentPreRun but not the root command's PersistentPostRun:

package main

import (
  "fmt"

  "github.com/spf13/cobra"
)

func main() {

  var rootCmd = &cobra.Command{
    Use:   "root [sub]",
    Short: "My root command",
    PersistentPreRun: func(cmd *cobra.Command, args []string) {
      fmt.Printf("Inside rootCmd PersistentPreRun with args: %v\n", args)
    },
    PreRun: func(cmd *cobra.Command, args []string) {
      fmt.Printf("Inside rootCmd PreRun with args: %v\n", args)
    },
    Run: func(cmd *cobra.Command, args []string) {
      fmt.Printf("Inside rootCmd Run with args: %v\n", args)
    },
    PostRun: func(cmd *cobra.Command, args []string) {
      fmt.Printf("Inside rootCmd PostRun with args: %v\n", args)
    },
    PersistentPostRun: func(cmd *cobra.Command, args []string) {
      fmt.Printf("Inside rootCmd PersistentPostRun with args: %v\n", args)
    },
  }

  var subCmd = &cobra.Command{
    Use:   "sub [no options!]",
    Short: "My subcommand",
    PreRun: func(cmd *cobra.Command, args []string) {
      fmt.Printf("Inside subCmd PreRun with args: %v\n", args)
    },
    Run: func(cmd *cobra.Command, args []string) {
      fmt.Printf("Inside subCmd Run with args: %v\n", args)
    },
    PostRun: func(cmd *cobra.Command, args []string) {
      fmt.Printf("Inside subCmd PostRun with args: %v\n", args)
    },
    PersistentPostRun: func(cmd *cobra.Command, args []string) {
      fmt.Printf("Inside subCmd PersistentPostRun with args: %v\n", args)
    },
  }

  rootCmd.AddCommand(subCmd)

  rootCmd.SetArgs([]string{""})
  rootCmd.Execute()
  fmt.Println()
  rootCmd.SetArgs([]string{"sub", "arg1", "arg2"})
  rootCmd.Execute()
}

Output:

Inside rootCmd PersistentPreRun with args: []
Inside rootCmd PreRun with args: []
Inside rootCmd Run with args: []
Inside rootCmd PostRun with args: []
Inside rootCmd PersistentPostRun with args: []

Inside rootCmd PersistentPreRun with args: [arg1 arg2]
Inside subCmd PreRun with args: [arg1 arg2]
Inside subCmd Run with args: [arg1 arg2]
Inside subCmd PostRun with args: [arg1 arg2]
Inside subCmd PersistentPostRun with args: [arg1 arg2]

Suggestions when "unknown command" happens

Cobra will print automatic suggestions when "unknown command" errors happen. This allows Cobra to behave similarly to the git command when a typo happens. For example:

$ hugo srever
Error: unknown command "srever" for "hugo"

Did you mean this?
        server

Run 'hugo --help' for usage.

Suggestions are automatic based on every subcommand registered and use an implementation of Levenshtein distance. Every registered command that matches a minimum distance of 2 (ignoring case) will be displayed as a suggestion.

If you need to disable suggestions or tweak the string distance in your command, use:

command.DisableSuggestions = true

or

command.SuggestionsMinimumDistance = 1

You can also explicitly set names for which a given command will be suggested using the SuggestFor attribute. This allows suggestions for strings that are not close in terms of string distance, but makes sense in your set of commands and for some which you don't want aliases. Example:

$ kubectl remove
Error: unknown command "remove" for "kubectl"

Did you mean this?
        delete

Run 'kubectl help' for usage.

Generating documentation for your command

Cobra can generate documentation based on subcommands, flags, etc. in the following formats:

Generating bash completions

Cobra can generate a bash-completion file. If you add more information to your command, these completions can be amazingly powerful and flexible. Read more about it in Bash Completions.

Generating zsh completions

Cobra can generate zsh-completion file. Read more about it in Zsh Completions.

Contributing

  1. Fork it
  2. Download your fork to your PC (git clone https://github.com/your_username/cobra && cd cobra)
  3. Create your feature branch (git checkout -b my-new-feature)
  4. Make changes and add them (git add .)
  5. Commit your changes (git commit -m 'Add some feature')
  6. Push to the branch (git push origin my-new-feature)
  7. Create new pull request

License

Cobra is released under the Apache 2.0 license. See LICENSE.txt

Documentation

Overview

Package cobra is a commander providing a simple interface to create powerful modern CLI interfaces. In addition to providing an interface, Cobra simultaneously provides a controller to organize your application code.

Index

Constants

View Source 
const (
	BashCompFilenameExt     = "cobra_annotation_bash_completion_filename_extensions"
	BashCompCustom          = "cobra_annotation_bash_completion_custom"
	BashCompOneRequiredFlag = "cobra_annotation_bash_completion_one_required_flag"
	BashCompSubdirsInDir    = "cobra_annotation_bash_completion_subdirs_in_dir"
)

Annotations for Bash completion.

View Source 
const (
	// ShellCompRequestCmd is the name of the hidden command that is used to request
	// completion results from the program.  It is used by the shell completion scripts.
	ShellCompRequestCmd = "__complete"
	// ShellCompNoDescRequestCmd is the name of the hidden command that is used to request
	// completion results without their description.  It is used by the shell completion scripts.
	ShellCompNoDescRequestCmd = "__completeNoDesc"
)

Variables

View Source 
var EnableCommandSorting = true

EnableCommandSorting controls sorting of the slice of commands, which is turned on by default. To disable sorting, set it to false.

View Source 
var EnablePrefixMatching = false

EnablePrefixMatching allows to set automatic prefix matching. Automatic prefix matching can be a dangerous thing to automatically enable in CLI tools. Set this to true to enable it.

View Source 
var MousetrapDisplayDuration = 5 * time.Second

MousetrapDisplayDuration controls how long the MousetrapHelpText message is displayed on Windows if the CLI is started from explorer.exe. Set to 0 to wait for the return key to be pressed. To disable the mousetrap, just set MousetrapHelpText to blank string (""). Works only on Microsoft Windows.

View Source 
var MousetrapHelpText = `This is a command line tool.

You need to open cmd.exe and run it from there.
`

MousetrapHelpText enables an information splash screen on Windows if the CLI is started from explorer.exe. To disable the mousetrap, just set this variable to blank string (""). Works only on Microsoft Windows.

Functions

func AddTemplateFunc 

func AddTemplateFunc(name string, tmplFunc interface{})

AddTemplateFunc adds a template function that's available to Usage and Help template generation.

func AddTemplateFuncs 

func AddTemplateFuncs(tmplFuncs template.FuncMap)

AddTemplateFuncs adds multiple template functions that are available to Usage and Help template generation.

func ArbitraryArgs 

func ArbitraryArgs(cmd *Command, args []string) error

ArbitraryArgs never returns an error.

func CompDebug added in v1.0.0 

func CompDebug(msg string, printToStdErr bool)

CompDebug prints the specified string to the same file as where the completion script prints its logs. Note that completion printouts should never be on stdout as they would be wrongly interpreted as actual completion choices by the completion script.

func CompDebugln added in v1.0.0 

func CompDebugln(msg string, printToStdErr bool)

CompDebugln prints the specified string with a newline at the end to the same file as where the completion script prints its logs. Such logs are only printed when the user has set the environment variable BASH_COMP_DEBUG_FILE to the path of some file to be used.

func CompError added in v1.0.0 

func CompError(msg string)

CompError prints the specified completion message to stderr.

func CompErrorln added in v1.0.0 

func CompErrorln(msg string)

CompErrorln prints the specified completion message to stderr with a newline at the end.

func Eq 

func Eq(a interface{}, b interface{}) bool

Eq takes two types and checks whether they are equal. Supported types are int and string. Unsupported types will panic.

func Gt 

func Gt(a interface{}, b interface{}) bool

Gt takes two types and checks whether the first type is greater than the second. In case of types Arrays, Chans, Maps and Slices, Gt will compare their lengths. Ints are compared directly while strings are first parsed as ints and then compared.

func MarkFlagCustom 

func MarkFlagCustom(flags *pflag.FlagSet, name string, f string) error

MarkFlagCustom instructs the various shell completion implementations to limit completions for this flag to the specified extensions (patterns).

Shell Completion compatibility matrix: bash, zsh

func MarkFlagDirname added in v0.0.5 

func MarkFlagDirname(flags *pflag.FlagSet, name string) error

MarkFlagDirname instructs the various shell completion implementations to complete only directories with this specified flag.

Shell Completion compatibility matrix: zsh

func MarkFlagFilename 

func MarkFlagFilename(flags *pflag.FlagSet, name string, extensions ...string) error

MarkFlagFilename instructs the various shell completion implementations to limit completions for this flag to the specified extensions (patterns).

Shell Completion compatibility matrix: bash, zsh

func MarkFlagRequired 

func MarkFlagRequired(flags *pflag.FlagSet, name string) error

MarkFlagRequired adds the BashCompOneRequiredFlag annotation to the named flag if it exists, and causes your command to report an error if invoked without the flag.

func NoArgs 

func NoArgs(cmd *Command, args []string) error

NoArgs returns an error if any args are included.

func OnInitialize 

func OnInitialize(y ...func())

OnInitialize sets the passed functions to be run when each command's Execute method is called.

func OnlyValidArgs 

func OnlyValidArgs(cmd *Command, args []string) error

OnlyValidArgs returns an error if any args are not in the list of ValidArgs.

Types

type Command 

type Command struct {
	// Use is the one-line usage message.
	Use string

	// Aliases is an array of aliases that can be used instead of the first word in Use.
	Aliases []string

	// SuggestFor is an array of command names for which this command will be suggested -
	// similar to aliases but only suggests.
	SuggestFor []string

	// Short is the short description shown in the 'help' output.
	Short string

	// Long is the long message shown in the 'help <this-command>' output.
	Long string

	// Example is examples of how to use the command.
	Example string

	// ValidArgs is list of all valid non-flag arguments that are accepted in bash completions
	ValidArgs []string
	// ValidArgsFunction is an optional function that provides valid non-flag arguments for bash completion.
	// It is a dynamic version of using ValidArgs.
	// Only one of ValidArgs and ValidArgsFunction can be used for a command.
	ValidArgsFunction func(cmd *Command, args []string, toComplete string) ([]string, ShellCompDirective)

	// Expected arguments
	Args PositionalArgs

	// ArgAliases is List of aliases for ValidArgs.
	// These are not suggested to the user in the bash completion,
	// but accepted if entered manually.
	ArgAliases []string

	// BashCompletionFunction is custom functions used by the bash autocompletion generator.
	BashCompletionFunction string

	// Deprecated defines, if this command is deprecated and should print this string when used.
	Deprecated string

	// Hidden defines, if this command is hidden and should NOT show up in the list of available commands.
	Hidden bool

	// Annotations are key/value pairs that can be used by applications to identify or
	// group commands.
	Annotations map[string]string

	// Version defines the version for this command. If this value is non-empty and the command does not
	// define a "version" flag, a "version" boolean flag will be added to the command and, if specified,
	// will print content of the "Version" variable. A shorthand "v" flag will also be added if the
	// command does not define one.
	Version string

	// The *Run functions are executed in the following order:
	//   * PersistentPreRun()
	//   * PreRun()
	//   * Run()
	//   * PostRun()
	//   * PersistentPostRun()
	// All functions get the same args, the arguments after the command name.
	//
	// PersistentPreRun: children of this command will inherit and execute.
	PersistentPreRun func(cmd *Command, args []string)
	// PersistentPreRunE: PersistentPreRun but returns an error.
	PersistentPreRunE func(cmd *Command, args []string) error
	// PreRun: children of this command will not inherit.
	PreRun func(cmd *Command, args []string)
	// PreRunE: PreRun but returns an error.
	PreRunE func(cmd *Command, args []string) error
	// Run: Typically the actual work function. Most commands will only implement this.
	Run func(cmd *Command, args []string)
	// RunE: Run but returns an error.
	RunE func(cmd *Command, args []string) error
	// PostRun: run after the Run command.
	PostRun func(cmd *Command, args []string)
	// PostRunE: PostRun but returns an error.
	PostRunE func(cmd *Command, args []string) error
	// PersistentPostRun: children of this command will inherit and execute after PostRun.
	PersistentPostRun func(cmd *Command, args []string)
	// PersistentPostRunE: PersistentPostRun but returns an error.
	PersistentPostRunE func(cmd *Command, args []string) error

	// SilenceErrors is an option to quiet errors down stream.
	SilenceErrors bool

	// SilenceUsage is an option to silence usage when an error occurs.
	SilenceUsage bool

	// DisableFlagParsing disables the flag parsing.
	// If this is true all flags will be passed to the command as arguments.
	DisableFlagParsing bool

	// DisableAutoGenTag defines, if gen tag ("Auto generated by spf13/cobra...")
	// will be printed by generating docs for this command.
	DisableAutoGenTag bool

	// DisableFlagsInUseLine will disable the addition of [flags] to the usage
	// line of a command when printing help or generating docs
	DisableFlagsInUseLine bool

	// DisableSuggestions disables the suggestions based on Levenshtein distance
	// that go along with 'unknown command' messages.
	DisableSuggestions bool
	// SuggestionsMinimumDistance defines minimum levenshtein distance to display suggestions.
	// Must be > 0.
	SuggestionsMinimumDistance int

	// TraverseChildren parses flags on all parents before executing child command.
	TraverseChildren bool

	// FParseErrWhitelist flag parse errors to be ignored
	FParseErrWhitelist FParseErrWhitelist
	// contains filtered or unexported fields
}

Command is just that, a command for your application. E.g. 'go run ...' - 'run' is the command. Cobra requires you to define the usage and description as part of your command definition to ensure usability.

func (*Command) AddCommand 

func (c *Command) AddCommand(cmds ...*Command)

AddCommand adds one or more commands to this parent command.

func (*Command) ArgsLenAtDash 

func (c *Command) ArgsLenAtDash() int

ArgsLenAtDash will return the length of c.Flags().Args at the moment when a -- was found during args parsing.

func (*Command) CalledAs added in v0.0.2 

func (c *Command) CalledAs() string

CalledAs returns the command name or alias that was used to invoke this command or an empty string if the command has not been called.

func (*Command) CommandPath 

func (c *Command) CommandPath() string

CommandPath returns the full path to this command.

func (*Command) CommandPathPadding 

func (c *Command) CommandPathPadding() int

CommandPathPadding return padding for the command path.

func (*Command) Commands 

func (c *Command) Commands() []*Command

Commands returns a sorted slice of child commands.

func (*Command) Context added in v0.0.6 

func (c *Command) Context() context.Context

Context returns underlying command context. If command wasn't executed with ExecuteContext Context returns Background context.

func (*Command) DebugFlags 

func (c *Command) DebugFlags()

DebugFlags used to determine which flags have been assigned to which commands and which persist.

func (*Command) ErrOrStderr added in v0.0.5 

func (c *Command) ErrOrStderr() io.Writer

ErrOrStderr returns output to stderr

func (*Command) Execute 

func (c *Command) Execute() error

Execute uses the args (os.Args[1:] by default) and run through the command tree finding appropriate matches for commands and then corresponding flags.

func (*Command) ExecuteC 

func (c *Command) ExecuteC() (cmd *Command, err error)

ExecuteC executes the command.

func (*Command) ExecuteContext added in v0.0.6 

func (c *Command) ExecuteContext(ctx context.Context) error

ExecuteContext is the same as Execute(), but sets the ctx on the command. Retrieve ctx by calling cmd.Context() inside your *Run lifecycle functions.

func (*Command) Find 

func (c *Command) Find(args []string) (*Command, []string, error)

Find the target command given the args and command tree Meant to be run on the highest node. Only searches down.

func (*Command) Flag 

func (c *Command) Flag(name string) (flag *flag.Flag)

Flag climbs up the command tree looking for matching flag.

func (*Command) FlagErrorFunc 

func (c *Command) FlagErrorFunc() (f func(*Command, error) error)

FlagErrorFunc returns either the function set by SetFlagErrorFunc for this command or a parent, or it returns a function which returns the original error.

func (*Command) Flags 

func (c *Command) Flags() *flag.FlagSet

Flags returns the complete FlagSet that applies to this command (local and persistent declared here and by all parents).

func (*Command) GenBashCompletion 

func (c *Command) GenBashCompletion(w io.Writer) error

GenBashCompletion generates bash completion file and writes to the passed writer.

func (*Command) GenBashCompletionFile 

func (c *Command) GenBashCompletionFile(filename string) error

GenBashCompletionFile generates bash completion file.

func (*Command) GenFishCompletion added in v1.0.0 

func (c *Command) GenFishCompletion(w io.Writer, includeDesc bool) error

GenFishCompletion generates fish completion file and writes to the passed writer.

func (*Command) GenFishCompletionFile added in v1.0.0 

func (c *Command) GenFishCompletionFile(filename string, includeDesc bool) error

GenFishCompletionFile generates fish completion file.

func (*Command) GenPowerShellCompletion added in v0.0.5 

func (c *Command) GenPowerShellCompletion(w io.Writer) error

GenPowerShellCompletion generates PowerShell completion file and writes to the passed writer.

func (*Command) GenPowerShellCompletionFile added in v0.0.5 

func (c *Command) GenPowerShellCompletionFile(filename string) error

GenPowerShellCompletionFile generates PowerShell completion file.

func (*Command) GenZshCompletion 

func (c *Command) GenZshCompletion(w io.Writer) error

GenZshCompletion generates a zsh completion file and writes to the passed writer. The completion always run on the root command regardless of the command it was called from.

func (*Command) GenZshCompletionFile 

func (c *Command) GenZshCompletionFile(filename string) error

GenZshCompletionFile generates zsh completion file.

func (*Command) GlobalNormalizationFunc 

func (c *Command) GlobalNormalizationFunc() func(f *flag.FlagSet, name string) flag.NormalizedName

GlobalNormalizationFunc returns the global normalization function or nil if it doesn't exist.

func (*Command) HasAlias 

func (c *Command) HasAlias(s string) bool

HasAlias determines if a given string is an alias of the command.

func (*Command) HasAvailableFlags 

func (c *Command) HasAvailableFlags() bool

HasAvailableFlags checks if the command contains any flags (local plus persistent from the entire structure) which are not hidden or deprecated.

func (*Command) HasAvailableInheritedFlags 

func (c *Command) HasAvailableInheritedFlags() bool

HasAvailableInheritedFlags checks if the command has flags inherited from its parent command which are not hidden or deprecated.

func (*Command) HasAvailableLocalFlags 

func (c *Command) HasAvailableLocalFlags() bool

HasAvailableLocalFlags checks if the command has flags specifically declared locally which are not hidden or deprecated.

func (*Command) HasAvailablePersistentFlags 

func (c *Command) HasAvailablePersistentFlags() bool

HasAvailablePersistentFlags checks if the command contains persistent flags which are not hidden or deprecated.

func (*Command) HasAvailableSubCommands 

func (c *Command) HasAvailableSubCommands() bool

HasAvailableSubCommands determines if a command has available sub commands that need to be shown in the usage/help default template under 'available commands'.

func (*Command) HasExample 

func (c *Command) HasExample() bool

HasExample determines if the command has example.

func (*Command) HasFlags 

func (c *Command) HasFlags() bool

HasFlags checks if the command contains any flags (local plus persistent from the entire structure).

func (*Command) HasHelpSubCommands 

func (c *Command) HasHelpSubCommands() bool

HasHelpSubCommands determines if a command has any available 'help' sub commands that need to be shown in the usage/help default template under 'additional help topics'.

func (*Command) HasInheritedFlags 

func (c *Command) HasInheritedFlags() bool

HasInheritedFlags checks if the command has flags inherited from its parent command.

func (*Command) HasLocalFlags 

func (c *Command) HasLocalFlags() bool

HasLocalFlags checks if the command has flags specifically declared locally.

func (*Command) HasParent 

func (c *Command) HasParent() bool

HasParent determines if the command is a child command.

func (*Command) HasPersistentFlags 

func (c *Command) HasPersistentFlags() bool

HasPersistentFlags checks if the command contains persistent flags.

func (*Command) HasSubCommands 

func (c *Command) HasSubCommands() bool

HasSubCommands determines if the command has children commands.

func (*Command) Help 

func (c *Command) Help() error

Help puts out the help for the command. Used when a user calls help [command]. Can be defined by user by overriding HelpFunc.

func (*Command) HelpFunc 

func (c *Command) HelpFunc() func(*Command, []string)

HelpFunc returns either the function set by SetHelpFunc for this command or a parent, or it returns a function with default help behavior.

func (*Command) HelpTemplate 

func (c *Command) HelpTemplate() string

HelpTemplate return help template for the command.

func (*Command) InOrStdin added in v0.0.5 

func (c *Command) InOrStdin() io.Reader

InOrStdin returns input to stdin

func (*Command) InheritedFlags 

func (c *Command) InheritedFlags() *flag.FlagSet

InheritedFlags returns all flags which were inherited from parent commands.

func (*Command) InitDefaultHelpCmd 

func (c *Command) InitDefaultHelpCmd()

InitDefaultHelpCmd adds default help command to c. It is called automatically by executing the c or by calling help and usage. If c already has help command or c has no subcommands, it will do nothing.

func (*Command) InitDefaultHelpFlag 

func (c *Command) InitDefaultHelpFlag()

InitDefaultHelpFlag adds default help flag to c. It is called automatically by executing the c or by calling help and usage. If c already has help flag, it will do nothing.

func (*Command) InitDefaultVersionFlag added in v0.0.2 

func (c *Command) InitDefaultVersionFlag()

InitDefaultVersionFlag adds default version flag to c. It is called automatically by executing the c. If c already has a version flag, it will do nothing. If c.Version is empty, it will do nothing.

func (*Command) IsAdditionalHelpTopicCommand 

func (c *Command) IsAdditionalHelpTopicCommand() bool

IsAdditionalHelpTopicCommand determines if a command is an additional help topic command; additional help topic command is determined by the fact that it is NOT runnable/hidden/deprecated, and has no sub commands that are runnable/hidden/deprecated. Concrete example: https://github.com/spf13/cobra/issues/393#issuecomment-282741924.

func (*Command) IsAvailableCommand 

func (c *Command) IsAvailableCommand() bool

IsAvailableCommand determines if a command is available as a non-help command (this includes all non deprecated/hidden commands).

func (*Command) LocalFlags 

func (c *Command) LocalFlags() *flag.FlagSet

LocalFlags returns the local FlagSet specifically set in the current command.

func (*Command) LocalNonPersistentFlags 

func (c *Command) LocalNonPersistentFlags() *flag.FlagSet

LocalNonPersistentFlags are flags specific to this command which will NOT persist to subcommands.

func (*Command) MarkFlagCustom 

func (c *Command) MarkFlagCustom(name string, f string) error

MarkFlagCustom adds the BashCompCustom annotation to the named flag, if it exists. Generated bash autocompletion will call the bash function f for the flag.

func (*Command) MarkFlagDirname added in v0.0.5 

func (c *Command) MarkFlagDirname(name string) error

MarkFlagDirname instructs the various shell completion implementations to complete only directories with this named flag.

Shell Completion compatibility matrix: zsh

func (*Command) MarkFlagFilename 

func (c *Command) MarkFlagFilename(name string, extensions ...string) error

MarkFlagFilename adds the BashCompFilenameExt annotation to the named flag, if it exists. Generated bash autocompletion will select filenames for the flag, limiting to named extensions if provided.

func (*Command) MarkFlagRequired 

func (c *Command) MarkFlagRequired(name string) error

MarkFlagRequired adds the BashCompOneRequiredFlag annotation to the named flag if it exists, and causes your command to report an error if invoked without the flag.

func (*Command) MarkPersistentFlagDirname added in v0.0.5 

func (c *Command) MarkPersistentFlagDirname(name string) error

MarkPersistentFlagDirname instructs the various shell completion implementations to complete only directories with this persistent named flag.

Shell Completion compatibility matrix: zsh

func (*Command) MarkPersistentFlagFilename 

func (c *Command) MarkPersistentFlagFilename(name string, extensions ...string) error

MarkPersistentFlagFilename instructs the various shell completion implementations to limit completions for this persistent flag to the specified extensions (patterns).

Shell Completion compatibility matrix: bash, zsh

func (*Command) MarkPersistentFlagRequired 

func (c *Command) MarkPersistentFlagRequired(name string) error

MarkPersistentFlagRequired adds the BashCompOneRequiredFlag annotation to the named persistent flag if it exists, and causes your command to report an error if invoked without the flag.

func (*Command) MarkZshCompPositionalArgumentFile added in v0.0.5 

func (c *Command) MarkZshCompPositionalArgumentFile(argPosition int, patterns ...string) error

MarkZshCompPositionalArgumentFile marks the specified argument (first argument is 1) as completed by file selection. patterns (e.g. "*.txt") are optional - if not provided the completion will search for all files.

func (*Command) MarkZshCompPositionalArgumentWords added in v0.0.5 

func (c *Command) MarkZshCompPositionalArgumentWords(argPosition int, words ...string) error

MarkZshCompPositionalArgumentWords marks the specified positional argument (first argument is 1) as completed by the provided words. At east one word must be provided, spaces within words will be offered completion with "word\ word".

func (*Command) Name 

func (c *Command) Name() string

Name returns the command's name: the first word in the use line.

func (*Command) NameAndAliases 

func (c *Command) NameAndAliases() string

NameAndAliases returns a list of the command name and all aliases

func (*Command) NamePadding 

func (c *Command) NamePadding() int

NamePadding returns padding for the name.

func (*Command) NonInheritedFlags 

func (c *Command) NonInheritedFlags() *flag.FlagSet

NonInheritedFlags returns all flags which were not inherited from parent commands.

func (*Command) OutOrStderr 

func (c *Command) OutOrStderr() io.Writer

OutOrStderr returns output to stderr

func (*Command) OutOrStdout 

func (c *Command) OutOrStdout() io.Writer

OutOrStdout returns output to stdout.

func (*Command) Parent 

func (c *Command) Parent() *Command

Parent returns a commands parent command.

func (*Command) ParseFlags 

func (c *Command) ParseFlags(args []string) error

ParseFlags parses persistent flag tree and local flags.

func (*Command) PersistentFlags 

func (c *Command) PersistentFlags() *flag.FlagSet

PersistentFlags returns the persistent FlagSet specifically set in the current command.

func (*Command) Print 

func (c *Command) Print(i ...interface{})

Print is a convenience method to Print to the defined output, fallback to Stderr if not set.

func (*Command) PrintErr added in v0.0.5 

func (c *Command) PrintErr(i ...interface{})

PrintErr is a convenience method to Print to the defined Err output, fallback to Stderr if not set.

func (*Command) PrintErrf added in v0.0.5 

func (c *Command) PrintErrf(format string, i ...interface{})

PrintErrf is a convenience method to Printf to the defined Err output, fallback to Stderr if not set.

func (*Command) PrintErrln added in v0.0.5 

func (c *Command) PrintErrln(i ...interface{})

PrintErrln is a convenience method to Println to the defined Err output, fallback to Stderr if not set.

func (*Command) Printf 

func (c *Command) Printf(format string, i ...interface{})

Printf is a convenience method to Printf to the defined output, fallback to Stderr if not set.

func (*Command) Println 

func (c *Command) Println(i ...interface{})

Println is a convenience method to Println to the defined output, fallback to Stderr if not set.

func (*Command) RegisterFlagCompletionFunc added in v1.0.0 

func (c *Command) RegisterFlagCompletionFunc(flagName string, f func(cmd *Command, args []string, toComplete string) ([]string, ShellCompDirective)) error

RegisterFlagCompletionFunc should be called to register a function to provide completion for a flag.

func (*Command) RemoveCommand 

func (c *Command) RemoveCommand(cmds ...*Command)

RemoveCommand removes one or more commands from a parent command.

func (*Command) ResetCommands 

func (c *Command) ResetCommands()

ResetCommands delete parent, subcommand and help command from c.

func (*Command) ResetFlags 

func (c *Command) ResetFlags()

ResetFlags deletes all flags from command.

func (*Command) Root 

func (c *Command) Root() *Command

Root finds root command.

func (*Command) Runnable 

func (c *Command) Runnable() bool

Runnable determines if the command is itself runnable.

func (*Command) SetArgs 

func (c *Command) SetArgs(a []string)

SetArgs sets arguments for the command. It is set to os.Args[1:] by default, if desired, can be overridden particularly useful when testing.

func (*Command) SetErr added in v0.0.5 

func (c *Command) SetErr(newErr io.Writer)

SetErr sets the destination for error messages. If newErr is nil, os.Stderr is used.

func (*Command) SetFlagErrorFunc 

func (c *Command) SetFlagErrorFunc(f func(*Command, error) error)

SetFlagErrorFunc sets a function to generate an error when flag parsing fails.

func (*Command) SetGlobalNormalizationFunc 

func (c *Command) SetGlobalNormalizationFunc(n func(f *flag.FlagSet, name string) flag.NormalizedName)

SetGlobalNormalizationFunc sets a normalization function to all flag sets and also to child commands. The user should not have a cyclic dependency on commands.

func (*Command) SetHelpCommand 

func (c *Command) SetHelpCommand(cmd *Command)

SetHelpCommand sets help command.

func (*Command) SetHelpFunc 

func (c *Command) SetHelpFunc(f func(*Command, []string))

SetHelpFunc sets help function. Can be defined by Application.

func (*Command) SetHelpTemplate 

func (c *Command) SetHelpTemplate(s string)

SetHelpTemplate sets help template to be used. Application can use it to set custom template.

func (*Command) SetIn added in v0.0.5 

func (c *Command) SetIn(newIn io.Reader)

SetIn sets the source for input data If newIn is nil, os.Stdin is used.

func (*Command) SetOut added in v0.0.5 

func (c *Command) SetOut(newOut io.Writer)

SetOut sets the destination for usage messages. If newOut is nil, os.Stdout is used.

func (*Command) SetOutput 

func (c *Command) SetOutput(output io.Writer)

SetOutput sets the destination for usage and error messages. If output is nil, os.Stderr is used. Deprecated: Use SetOut and/or SetErr instead

func (*Command) SetUsageFunc 

func (c *Command) SetUsageFunc(f func(*Command) error)

SetUsageFunc sets usage function. Usage can be defined by application.

func (*Command) SetUsageTemplate 

func (c *Command) SetUsageTemplate(s string)

SetUsageTemplate sets usage template. Can be defined by Application.

func (*Command) SetVersionTemplate added in v0.0.2 

func (c *Command) SetVersionTemplate(s string)

SetVersionTemplate sets version template to be used. Application can use it to set custom template.

func (*Command) SuggestionsFor 

func (c *Command) SuggestionsFor(typedName string) []string

SuggestionsFor provides suggestions for the typedName.

func (*Command) Traverse 

func (c *Command) Traverse(args []string) (*Command, []string, error)

Traverse the command tree to find the command, and parse args for each parent.

func (*Command) Usage 

func (c *Command) Usage() error

Usage puts out the usage for the command. Used when a user provides invalid input. Can be defined by user by overriding UsageFunc.

func (*Command) UsageFunc 

func (c *Command) UsageFunc() (f func(*Command) error)

UsageFunc returns either the function set by SetUsageFunc for this command or a parent, or it returns a default usage function.

func (*Command) UsagePadding 

func (c *Command) UsagePadding() int

UsagePadding return padding for the usage.

func (*Command) UsageString 

func (c *Command) UsageString() string

UsageString returns usage string.

func (*Command) UsageTemplate 

func (c *Command) UsageTemplate() string

UsageTemplate returns usage template for the command.

func (*Command) UseLine 

func (c *Command) UseLine() string

UseLine puts out the full usage for a given command (including parents).

func (*Command) ValidateArgs 

func (c *Command) ValidateArgs(args []string) error

func (*Command) VersionTemplate added in v0.0.2 

func (c *Command) VersionTemplate() string

VersionTemplate return version template for the command.

func (*Command) VisitParents 

func (c *Command) VisitParents(fn func(*Command))

VisitParents visits all parents of the command and invokes fn on each parent.

type FParseErrWhitelist added in v0.0.3 

type FParseErrWhitelist flag.ParseErrorsWhitelist

FParseErrWhitelist configures Flag parse errors to be ignored

type PositionalArgs 

type PositionalArgs func(cmd *Command, args []string) error

func ExactArgs 

func ExactArgs(n int) PositionalArgs

ExactArgs returns an error if there are not exactly n args.

func ExactValidArgs added in v0.0.4 

func ExactValidArgs(n int) PositionalArgs

ExactValidArgs returns an error if there are not exactly N positional args OR there are any positional args that are not in the `ValidArgs` field of `Command`

func MaximumNArgs 

func MaximumNArgs(n int) PositionalArgs

MaximumNArgs returns an error if there are more than N args.

func MinimumNArgs 

func MinimumNArgs(n int) PositionalArgs

MinimumNArgs returns an error if there is not at least N args.

func RangeArgs 

func RangeArgs(min int, max int) PositionalArgs

RangeArgs returns an error if the number of args is not within the expected range.

type ShellCompDirective added in v1.0.0 

type ShellCompDirective int

ShellCompDirective is a bit map representing the different behaviors the shell can be instructed to have once completions have been provided. 

const (
	// ShellCompDirectiveError indicates an error occurred and completions should be ignored.
	ShellCompDirectiveError ShellCompDirective = 1 << iota

	// ShellCompDirectiveNoSpace indicates that the shell should not add a space
	// after the completion even if there is a single completion provided.
	ShellCompDirectiveNoSpace

	// ShellCompDirectiveNoFileComp indicates that the shell should not provide
	// file completion even when no completion is provided.
	// This currently does not work for zsh or bash < 4
	ShellCompDirectiveNoFileComp

	// ShellCompDirectiveDefault indicates to let the shell perform its default
	// behavior after completions have been provided.
	ShellCompDirectiveDefault ShellCompDirective = 0
)

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