mkdir cobra_app

cd cobra_app

go mod init cobra_app

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

go install github.com/spf13/cobra-cli@latest

cobra-cli init

go run main.go

cobra-cli add serve
cobra-cli add sum
cobra-cli add version

cmd/serve.go

package cmd

import (
    "fmt"

    "github.com/spf13/cobra"
)

// serveCmd represents the serve command
var serveCmd = &cobra.Command{
    Use:   "serve",
    Short: "A brief description of your serve",
    Long: `A longer description that spans multiple lines and likely contains examples
and usage of using your command. For example:

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.`,
    Run: func(cmd *cobra.Command, args []string) {
        fmt.Println("serve called")

        x_foo, err := cmd.Flags().GetString("foo")

        if err == nil {
            fmt.Printf("foo = %s\n", x_foo)

        }

        x_toggle, err := cmd.Flags().GetBool("toggle")

        if err == nil {
            fmt.Printf("toggle = %t\n", x_toggle)

        }

        x_port, err := cmd.Flags().GetInt64("port")

        if err == nil {
            fmt.Printf("port = %d\n", x_port)

        }
    },
}

func init() {
    rootCmd.AddCommand(serveCmd)

    serveCmd.Flags().Int64P("port", "p", 8081, "指定端口")
    // go run .\main.go serve --foo "hello wold" -t true -p 8090
    serveCmd.PersistentFlags().String("foo", "", "A help for foo")
    serveCmd.Flags().BoolP("toggle", "t", false, "Help message for toggle")
}

cmd/sum.go

package cmd

import (
    "fmt"
    "strconv"

    "github.com/spf13/cobra"
)

// sumCmd represents the sum command
var sumCmd = &cobra.Command{
    Use:   "sum",
    Short: "求和计算",
    Long:  ` app sum 1 2 `,
    Run: func(cmd *cobra.Command, args []string) {
        result := 0
        for _, value := range args {
            v1, _ := strconv.Atoi(value)
            result += v1
        }
        fmt.Println(result)

    },
}

func init() {
    rootCmd.AddCommand(sumCmd)
    // 触发方式
    //  go run .\main.go sum 1 3 5 6 8
}

cmd/version.go

/*
Copyright © 2024 NAME HERE <EMAIL ADDRESS>
*/
package cmd

import (
    "fmt"

    "github.com/spf13/cobra"
)

const current_version = "1.2.0"

var author = "apple"

// versionCmd represents the version command
var versionCmd = &cobra.Command{
    Use:   "version",
    Short: "当前版本",
    Long:  `输出当前版本信息`,
    Run: func(cmd *cobra.Command, args []string) {
        fmt.Println("当前版本为： " + current_version)
        x_author, _ := cmd.Flags().GetString("author")
        fmt.Println("作者是：" + x_author)
    },
}

func init() {
    rootCmd.AddCommand(versionCmd)
    rootCmd.PersistentFlags().StringVar(&author, "author", "YOUR NAME", "Author name for copyright attribution")

    // 运行方式
    //  go run .\main.go version --author  zhangsan
    //  go run .\main.go version --author apple

    // Here you will define your flags and configuration settings.

    // Cobra supports Persistent Flags which will work for this command
    // and all subcommands, e.g.:
    // versionCmd.PersistentFlags().String("foo", "", "A help for foo")

    // Cobra supports local flags which will only run when this command
    // is called directly, e.g.:
    // versionCmd.Flags().BoolP("toggle", "t", false, "Help message for toggle")
}

go build -o greet.exe

.\greet.exe version --author apple

.\greet.exe sum 1 3 5 7

.\greet.exe serve --foo "hello wold" -t true -p 8090

参考连接：https://github.com/spf13/cobra-cli/blob/main/README.md

Installing

Using Cobra is easy. First, use go get to install the latest version of the library.

go get -u github.com/spf13/cobra@latest
Next, include Cobra in your application:

import "github.com/spf13/cobra"

Usage

cobra-cli is a command line program to generate cobra applications and command files. It will bootstrap your application scaffolding to rapidly develop a Cobra-based application. It is the easiest way to incorporate Cobra into your application.

It can be installed by running:

go install github.com/spf13/cobra-cli@latest

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.

Install the cobra generator with the command go install github.com/spf13/cobra-cli@latest.
Go will automatically install it in your $GOPATH/bin directory which should be in your $PATH.

Once installed you should have the cobra-cli command available. Confirm by typing cobra-cli at a
command line.

There are only two operations currently supported by the Cobra generator:

cobra-cli init

The cobra-cli init [app] command will create your initial application code
for you. It is a very powerful application that will populate your program with
the right structure so you can immediately enjoy all the benefits of Cobra.
It can also apply the license you specify to your application.

With the introduction of Go modules, the Cobra generator has been simplified to
take advantage of modules. The Cobra generator works from within a Go module.

Initalizing a module

If you already have a module, skip this step.

If you want to initialize a new Go module:

1. Create a new directory
2. cd into that directory
3. run go mod init <MODNAME>

e.g.

cd $HOME/code 
mkdir myapp
cd myapp
go mod init github.com/spf13/myapp

Initalizing a Cobra CLI application

From within a Go module run cobra-cli init. This will create a new barebones project
for you to edit.

You should be able to run your new application immediately. Try it with
go run main.go.

You will want to open up and edit 'cmd/root.go' and provide your own description and logic.

e.g.

cd $HOME/code/myapp
cobra-cli init
go run main.go

cobra-cli init can also be run from a subdirectory such as how the cobra generator itself is organized.
This is useful if you want to keep your application code separate from your library code.

Optional flags:

You can provide it your author name with the --author flag.
e.g. cobra-cli init --author "Steve Francia spf@spf13.com"

You can provide a license to use with --license
e.g. cobra-cli init --license apache

Use the --viper flag to automatically setup viper

Viper is a companion to Cobra intended to provide easy handling of environment variables and config files and seamlessly connecting them to the application flags.

Add commands to a project

Once a cobra application is initialized you can continue to use the Cobra generator to
add additional commands to your application. The command to do this is cobra-cli add.

Let's say you created an app and you wanted the following commands for it:

• app serve
• app config
• app config create

In your project directory (where your main.go file is) you would run the following:

cobra-cli add serve
cobra-cli add config
cobra-cli add create -p 'configCmd'

cobra-cli add supports all the same optional flags as cobra-cli init does (described above).

You'll notice that this final command has a -p flag. This is used to assign a
parent command to the newly added command. In this case, we want to assign the
"create" command to the "config" command. All commands have a default parent of rootCmd if not specified.

By default cobra-cli will append Cmd to the name provided and uses this name for the internal variable name. When specifying a parent, be sure to match the variable name used in the code.

Note: Use camelCase (not snake_case/kebab-case) for command names.
Otherwise, you will encounter errors.
For example, cobra-cli add add-user is incorrect, but cobra-cli add addUser is valid.

Once you have run these three commands you would have an app structure similar to
the following:

  ▾ app/
    ▾ cmd/
        config.go
        create.go
        serve.go
        root.go
      main.go

At this point you can run go run main.go and it would run your app. go run main.go serve, go run main.go config, go run main.go config create along
with go run main.go help serve, etc. would all work.

You now have a basic Cobra-based application up and running. Next step is to edit the files in cmd and customize them for your application.

For complete details on using the Cobra library, please read the The Cobra User Guide.

Have fun!

User Guide

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

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 https://gohugo.io/documentation/`,
  Run: func(cmd *cobra.Command, args []string) {
    // Do Stuff Here
  },
}

func Execute() {
  if err := rootCmd.Execute(); err != nil {
    fmt.Fprintln(os.Stderr, 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"

    "github.com/spf13/cobra"
    "github.com/spf13/viper"
)

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

    rootCmd = &cobra.Command{
        Use:   "cobra-cli",
        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 initConfig() {
    if cfgFile != "" {
        // Use config file from the flag.
        viper.SetConfigFile(cfgFile)
    } else {
        // Find home directory.
        home, err := os.UserHomeDir()
        cobra.CheckErr(err)

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

Organizing subcommands

A command may have subcommands which in turn may have other subcommands. This is achieved by using
AddCommand. In some cases, especially in larger applications, each subcommand may be defined in
its own go package.

The suggested approach is for the parent command to use AddCommand to add its most immediate
subcommands. For example, consider the following directory structure:

├── cmd
│   ├── root.go
│   └── sub1
│       ├── sub1.go
│       └── sub2
│           ├── leafA.go
│           ├── leafB.go
│           └── sub2.go
└── main.go

In this case:

• The init function of root.go adds the command defined in sub1.go to the root command.
• The init function of sub1.go adds the command defined in sub2.go to the sub1 command.
• The init function of sub2.go adds the commands defined in leafA.go and leafB.go to the
  sub2 command.

This approach ensures the subcommands are always included at compile time while avoiding cyclic
references.

Returning and handling errors

If you wish to return an error to the caller of a command, RunE can be used.

package cmd

import (
  "fmt"

  "github.com/spf13/cobra"
)

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

var tryCmd = &cobra.Command{
  Use:   "try",
  Short: "Try and possibly fail at something",
  RunE: func(cmd *cobra.Command, args []string) error {
    if err := someFunc(); err != nil {
    return err
    }
    return nil
  },
}

The error can then be caught at the execute function call.

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, and 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: the variable author will not be set to the value from config,
when the --author flag is 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")

Or, for persistent flags:

rootCmd.PersistentFlags().StringVarP(&Region, "region", "r", "", "AWS region (required)")
rootCmd.MarkPersistentFlagRequired("region")

Flag Groups

If you have different flags that must be provided together (e.g. if they provide the --username flag they MUST provide the --password flag as well) then
Cobra can enforce that requirement:

rootCmd.Flags().StringVarP(&u, "username", "u", "", "Username (required if password is set)")
rootCmd.Flags().StringVarP(&pw, "password", "p", "", "Password (required if username is set)")
rootCmd.MarkFlagsRequiredTogether("username", "password")

You can also prevent different flags from being provided together if they represent mutually
exclusive options such as specifying an output format as either --json or --yaml but never both:

rootCmd.Flags().BoolVar(&ofJson, "json", false, "Output in JSON")
rootCmd.Flags().BoolVar(&ofYaml, "yaml", false, "Output in YAML")
rootCmd.MarkFlagsMutuallyExclusive("json", "yaml")

If you want to require at least one flag from a group to be present, you can use MarkFlagsOneRequired.
This can be combined with MarkFlagsMutuallyExclusive to enforce exactly one flag from a given group:

rootCmd.Flags().BoolVar(&ofJson, "json", false, "Output in JSON")
rootCmd.Flags().BoolVar(&ofYaml, "yaml", false, "Output in YAML")
rootCmd.MarkFlagsOneRequired("json", "yaml")
rootCmd.MarkFlagsMutuallyExclusive("json", "yaml")

In these cases:

• both local and persistent flags can be used
  • NOTE: the group is only enforced on commands where every flag is defined
• a flag may appear in multiple groups
• a group may contain any number of flags

Positional and Custom Arguments

Validation of positional arguments can be specified using the Args field of Command.
The following validators are built in:

• Number of arguments:
  • NoArgs - report an error if there are any positional args.
  • ArbitraryArgs - accept any number of args.
  • MinimumNArgs(int) - report an error if less than N positional args are provided.
  • MaximumNArgs(int) - report an error if more than N positional args are provided.
  • ExactArgs(int) - report an error if there are not exactly N positional args.
  • RangeArgs(min, max) - report an error if the number of args is not between min and max.
• Content of the arguments:
  • OnlyValidArgs - report an error if there are any positional args not specified in the ValidArgs field of Command, which can optionally be set to a list of valid values for positional args.

If Args is undefined or nil, it defaults to ArbitraryArgs.

Moreover, MatchAll(pargs ...PositionalArgs) enables combining existing checks with arbitrary other checks.
For instance, if you want to 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, you can call MatchAll on ExactArgs and OnlyValidArgs, as
shown below:

var cmd = &cobra.Command{
  Short: "hello",
  Args: cobra.MatchAll(cobra.ExactArgs(2), cobra.OnlyValidArgs),
  Run: func(cmd *cobra.Command, args []string) {
    fmt.Println("Hello, World!")
  },
}

It is possible to set any custom validator that satisfies func(cmd *cobra.Command, args []string) error.
For example:

var cmd = &cobra.Command{
  Short: "hello",
  Args: func(cmd *cobra.Command, args []string) error {
    // Optionally run one of the validators provided by cobra
    if err := cobra.MinimumNArgs(1)(cmd, args); err != nil {
        return err
    }
    // Run the custom validation logic
    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-cli 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-cli [command]

Available Commands:
  add         Add a command to a Cobra Application
  completion  Generate the autocompletion script for the specified shell
  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-cli
  -l, --license string   name of license for the project
      --viper            use Viper for configuration

Use "cobra-cli [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.

Grouping commands in help

Cobra supports grouping of available commands in the help output. To group commands, each group must be explicitly
defined using AddGroup() on the parent command. Then a subcommand can be added to a group using the GroupID element
of that subcommand. The groups will appear in the help output in the same order as they are defined using different
calls to AddGroup(). If you use the generated help or completion commands, you can set their group ids using
SetHelpCommandGroupId() and SetCompletionCommandGroupId() on the root command, respectively.

Defining your own help

You can provide your own Help command or your own template for the default command to use
with the 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-cli --invalid
Error: unknown flag: --invalid
Usage:
  cobra-cli [command]

Available Commands:
  add         Add a command to a Cobra Application
  completion  Generate the autocompletion script for the specified shell
  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-cli
  -l, --license string   name of license for the project
      --viper            use Viper for configuration

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.

Error Message Prefix

Cobra prints an error message when receiving a non-nil error value.
The default error message is Error: <error contents>.
The Prefix, Error: can be customized using the cmd.SetErrPrefix(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. The *PreRun and *PostRun functions will only be executed if the Run function of the current command has been declared. 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]

By default, only the first persistent hook found in the command chain is executed.
That is why in the above output, the rootCmd PersistentPostRun was not called for a child command.
Set EnableTraverseRunHooks global variable to true if you want to execute all parents' persistent hooks.

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 automatically generated based on existing subcommands 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 make sense in your set of commands but for 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.
Read more about it in the docs generation documentation.

Generating shell completions

Cobra can generate a shell-completion file for the following shells: bash, zsh, fish, PowerShell.
If you add more information to your commands, these completions can be amazingly powerful and flexible.
Read more about it in Shell Completions.

Providing Active Help

Cobra makes use of the shell-completion system to define a framework allowing you to provide Active Help to your users.
Active Help are messages (hints, warnings, etc) printed as the program is being used.
Read more about it in Active Help.

Creating a plugin

When creating a plugin for tools like kubectl, the executable is named
kubectl-myplugin, but it is used as kubectl myplugin. To fix help
messages and completions, annotate the root command with the
cobra.CommandDisplayNameAnnotation annotation.

Example kubectl plugin

package main

import (
    "fmt"

    "github.com/spf13/cobra"
)

func main() {
    rootCmd := &cobra.Command{
        Use: "kubectl-myplugin",
        Annotations: map[string]string{
            cobra.CommandDisplayNameAnnotation: "kubectl myplugin",
        },
    }
    subCmd := &cobra.Command{
        Use: "subcmd",
        Run: func(cmd *cobra.Command, args []string) {
            fmt.Println("kubectl myplugin subcmd")
        },
    }
    rootCmd.AddCommand(subCmd)
    rootCmd.Execute()
}

Example run as a kubectl plugin:

$ kubectl myplugin
Usage:
  kubectl myplugin [command]

Available Commands:
  completion  Generate the autocompletion script for the specified shell
  help        Help about any command
  subcmd

Flags:
  -h, --help   help for kubectl myplugin

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