Golang 命令行(CMD)开发指南

1. 标准库 flag 包基础用法

package main

import (
    "flag"
    "fmt"
)

func main() {
    // 定义命令行参数
    var (
        host     = flag.String("host", "localhost", "Server host")
        port     = flag.Int("port", 8080, "Server port")
        debug    = flag.Bool("debug", false, "Enable debug mode")
        username string
    )
    
    // 自定义变量绑定
    flag.StringVar(&username, "user", "", "Username for authentication")
    
    // 解析参数
    flag.Parse()
    
    fmt.Printf("Starting server at %s:%d (debug=%t)\n", *host, *port, *debug)
    if username != "" {
        fmt.Println("Authenticated user:", username)
    }
}

使用方式:

$ go run main.go -host=0.0.0.0 -port=9000 -user=admin -debug=true

2. Cobra - 专业级CLI框架

安装:

go get github.com/spf13/cobra@latest

基本项目结构:

myapp/
├── cmd/
│   ├── root.go      # 根命令
│   ├── serve.go     # serve子命令 
│   └── version.go   # version子命令
└── main.go          # 程序入口

root.go示例:

package cmd

import (
	"fmt"
	"os"

	"github.com/spf13/cobra"
)

var rootCmd = &cobra.Command{
	Use:   "myapp",
	Short: "MyApp is a demo CLI application",
	Long: `A longer description that spans multiple lines and likely contains examples 
and usage of using your application`,
}

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

serve子命令示例:

package cmd

import (
	"fmt"
	
	"github.com/spf13/cobra"
)

var (
	serveHost string
	servePort int
)

var serveCmd = &cobra.Command{
	Use:   "serve",
	Short: "Start the server",
	Run: func(cmd *cobra.Command, args []string) {
		fmt.Printf("Starting server on %s:%d\n", serveHost, servePort)
		
		// 实际服务启动代码...
		
	},
}

func init() {
	rootCmd.AddCommand(serveCmd)
	
	// Flags配置
	serveCmd.Flags().StringVarP(&serveHost, 
	    "host", "", "localhost", 
	    "Server host address")
	
	serveCmd.Flags().IntVarP(&servePort,
	    "port", "p", 8080,
	    "Server port number")
}

3. Viper集成配置管理

结合Cobra实现配置加载:

import (
    "github.com/spf13/viper"
)

func initConfig() {
    // Config文件自动搜索路径 (./config.yaml等)
    viper.AutomaticEnv()
    
    if cfgFile != "" { // --config参数指定的配置文件路径  
        viper.SetConfigFile(cfgFile)
        
        if err := viper.ReadInConfig(); err != nil {
            fmt.Println("Can't read config:", err)
            os.Exit(1)
        }
        
        fmt.Println("Using config file:", viper.ConfigFileUsed())
        
        // Watch配置热更新 (可选)  
        viper.WatchConfig()
        viper.OnConfigChange(func(e fsnotify.Event) {
            fmt.Println("Config file changed:", e.Name)
            
            // Reload逻辑...
            
        })
        
    }
}

4. Go-Args高级特性库

对于复杂参数解析需求，推荐使用:

go get github.com/alexflint/go-arg@latest

示例:

package main

import (
    "fmt"
    
    "github.com/alexflint/go-arg"
)

type Args struct {
	Name      string `arg:"required"`
	DockerTag string `arg:"env:DOCKER_TAG"`
	
	structTags struct { ... } `arg:"subcommand"`
	
	listen struct { ... } `arg:"subcommand"`
}

func main() {
	var args Args
	
	p := arg.MustParse(&args)  
	if p.Subcommand() == nil {  
	    p.Fail("missing subcommand")  
	    return  
	  }  

	switch p.Subcommand().Name() { ... }
}

需要我针对某个具体场景提供更详细的实现方案吗？

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