go get -u github.com/spf13/cobra/cobra
go mod init blog
go get -u github.com/spf13/cobra/cobra

具体写一个例子, 设计一个命令叫 blog， 有四个子命令

blog new [post-name] ：创建一篇新的blog
blog list   ：列出当前有哪些文章
blog delete [post-name]: 删除某一篇文章
blog edit [post-name]：编辑某一篇文章

> cobra init -h
Initialize (cobra init) will create a new application, with a license
and the appropriate structure for a Cobra-based CLI application.

  * If a name is provided, a directory with that name will be created in the current directory;
  * If no name is provided, the current directory will be assumed;

Usage:
  cobra init [name] [flags]

Aliases:
  init, initialize, initialise, create

Flags:
  -h, --help              help for init
      --pkg-name string   fully qualified pkg name

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

创建应用

> cobra init --pkg-name blog -a raoxiaoya -l mit
Your Cobra application is ready at
D:\dev\php\magook\trunk\server\golang\project\blog

会生成目录

./cmd
./cmd/root.go
./go.mod
./go.sum
./LICENSE
./main.go

编译运行

> go build main.go
> main.exe -h
A longer description that spans multiple lines and likely contains
examples and usage of using your application. 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.

commandflagargs
go get -u test.com/a/b

这里 get 就是 commond（这里比较特殊）， -u 就是 flag， test.com/a/b 就是 args

那么命令行就是有三部分构成，所以需要定义好这个

命令自身的一些基本信息，用command表示，具体对象是 cobra.Command
命令的一些标致或者选项，用flag表示，具体对象是 flag.FlagSet
最后的参数，用args表示，通常是[]string

还有一个概念是子命令，比如get就是go的子命令，这是一个树状结构的关系。

我可以使用go命令，也可以使用 go get命令

例如: root.go，定义了root命令，另外在init里面 定义了flag，如果它本身有具体执行，就填充Run字段。

rootCmd.AddCommand()
cobra add new
cobra add delete
cobra add list
cobra add edit

new.go, delete.go,list.go,edit.go

添加逻辑代码

new.go
var newCmd = &cobra.Command{
	Use:   "new",
	Short: "create new post",
	Long:  `create new post `,
	Args: func(cmd *cobra.Command, args []string) error {
		if len(args) != 1 {
			return errors.New("requires a color argument")
		}
		return nil
	},
	Run: func(cmd *cobra.Command, args []string) {
		floder := "posts/"
		fileName := floder + args[0]

		if _, err := os.Stat(floder); os.IsNotExist(err) {
			err := os.Mkdir(floder, 644)
			if err != nil {
				log.Fatal(err)
			}
		}

		_, err := os.Stat(fileName)
		if os.IsNotExist(err) {
			file, err := os.Create(fileName)
			if err != nil {
				log.Fatal(err)
			}
			log.Printf("create file %s", fileName)
			defer file.Close()
		} else {
		}
	},
}

list.go
var listCmd = &cobra.Command{
    Use:   "list",
    Short: "list all blog in posts",
    Long: `list all blog in posts `,
    Run: func(cmd *cobra.Command, args []string) {
        _, err := os.Stat("posts")
        if os.IsNotExist(err) {
            log.Fatal("posts dir is not exits")
        }
        dirs, err := ioutil.ReadDir("posts")
        if err != nil {
            log.Fatal("read posts dir fail")
        }
        fmt.Println("------------------")
        for _, dir := range dirs {
            fmt.Printf(" %s\n", dir.Name() )
        }
        fmt.Println("------------------")
        fmt.Printf("total: %d blog\n", len(dirs))
    },
}

delete.go
var deleteCmd = &cobra.Command{
    Use:   "delete",
    Short: "delete a post",
    Long: `delete a post`,
    Args: func(cmd *cobra.Command, args []string) error {
        if len(args) != 1 {
            return errors.New("requires a color argument")
        }
        if strings.Contains(args[0],"/") || strings.Contains(args[0],"..") {
            return errors.New("posts name should not contain / or .. ")
        }
        return nil
    },
    Run: func(cmd *cobra.Command, args []string) {
        fileName := "./posts/" +  args[0]
        stat, err := os.Stat(fileName)
        if os.IsNotExist(err) {
            log.Fatalf("post %s is not exist", fileName)
        }
        if stat.IsDir() {
            log.Fatalf("%s is dir ,can not be deleted", fileName)
        }
        err = os.Remove(fileName)
        if err != nil {
            log.Fatalf("delete %s fail, err %v", fileName, err)
        } else {
            log.Printf("delete post %s success", fileName)
        }
    },
}

测试

go build main.go
main.exe list
main.exe new blog1.md
main.exe new blog2.md
main.exe new blog3.md
main.exe list
main.exe delete blog1.md
main.exe list