golang CLI框架--cobra

https://github.com/spf13/cobra.git

使用golang可以很方便把代码编译成二进制，但是如何写出类似linux工具那样，符合posix标准的工具呢？答案是cobra。

kubectl使用cobra框架实现。

快速开始

使用cobra-cli脚手架快速创建项目

go install github.com/spf13/[email protected]

cobra-cli应该安装到$GOPATH/bin目录下,确保$GOPATH/bin在PATH目录下

运行下面命令快速初始化：

cobra-cli init

会生成如下结构：

- main.go
+ cmd
  - root.go

此时就已经可以运行项目简单的试试效果：

$ go run main.go -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.

Usage:
  cobra-test [flags]
  cobra-test [command]

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

Flags:
  -h, --help            help for cobra-test
  -t, --toggle          Help message for toggle	

添加一个子命令

比如：

git clone xxx 

其中clone即是一个子命令，如何添加一个类似的？

运行下面命令，即会生成一个serve.go

cobra-cli add serve

添加开关参数

• 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 command",
	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")
		// 位置参数
		fmt.Println(args)
		// 开关参数
		fmt.Println(cmd.Flags().GetBool("toggle"))
	},
}

func init() {
    
	rootCmd.AddCommand(serveCmd)

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

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

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

args代表位置参数，toggle代表开关参数

$ go run main.go serve -t hello
serve called
[hello]
true <nil>

长参数

git clone --config /etc/config.yaml

其中--config /etc/config.yaml这种是符合POSIX标准的长参数。

package cmd

import (
	"fmt"
	"os"

	"github.com/spf13/cobra"
)

// config file path
var cfgFile string


// rootCmd represents the base command when called without any subcommands
var rootCmd = &cobra.Command{
    
	Use:   "cobra-test",
	Short: "A brief description of your application",
	Long: `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.`,
	// Uncomment the following line if your bare application
	// has an action associated with it:
	Run: func(cmd *cobra.Command, args []string) {
    
        // 这里根据参数获取情况，执行相关逻辑
		fmt.Println(cfgFile)
	},
}

// Execute adds all child commands to the root command and sets flags appropriately.
// This is called by main.main(). It only needs to happen once to the rootCmd.
func Execute() {
    
	err := rootCmd.Execute()
	if err != nil {
    
		os.Exit(1)
	}
}

func init() {
    
	// Here you will define your flags and configuration settings.
	// Cobra supports persistent flags, which, if defined here,
	// will be global for your application.

	// rootCmd.PersistentFlags().StringVar(&cfgFile, "config", "", "config file (default is $HOME/.cobra-test.yaml)")

	// Cobra also supports local flags, which will only run
	// when this action is called directly.
	rootCmd.Flags().BoolP("toggle", "t", false, "Help message for toggle")
	// 这一行定义类似 go run main.go --config xxx.yaml 
	rootCmd.PersistentFlags().StringVar(&cfgFile, "config", "", "config file (default is $HOME/.cobra.yaml)")
}