Go 自带 flag 包，可以用于解析命令行参数。但用起来非常繁琐，更谈不上优雅，远不如 Python 的 argparse 包简洁明了，易于使用。

语法

类型

• flag.Flag
• flag.FlagSet
• flag.Getter
• flag.Value

方法

func Bool(name string, value bool, usage string) *bool
func BoolVar(p *bool, name string, value bool, usage string)

func Duration(name string, value time.Duration, usage string) *time.Duration
func DurationVar(p *time.Duration, name string, value time.Duration, usage string)

func Float64(name string, value float64, usage string) *float64
func Float64Var(p *float64, name string, value float64, usage string)

func Func(name, usage string, fn func(string) error)

func Int(name string, value int, usage string) *int
func IntVar(p *int, name string, value int, usage string)

func Int64(name string, value int64, usage string) *int64
func Int64Var(p *int64, name string, value int64, usage string)

func String(name string, value string, usage string) *string
func StringVar(p *string, name string, value string, usage string)

func Uint(name string, value uint, usage string) *uint
func UintVar(p *uint, name string, value uint, usage string)

func Uint64(name string, value uint64, usage string) *uint64
func Uint64Var(p *uint64, name string, value uint64, usage string)

func Var(value Value, name string, usage string)

1. 带 Var 结尾的方法表示将值绑定到一个变量上。

func Arg(i int) string  // i-th argument
func Args() []string    // non-flag arguments

func NArg() int         // number of arguments remaining after flags have been processed
func NFlag() int        // number of command-line flags that have been set

func Parse()
func Parsed() bool
func Set(name, value string) error

func PrintDefaults()    // 帮助信息
func UnquoteUsage(flag *Flag) (name string, usage string)  // 返回 flag 的名称和用法

func Visit(fn func(*Flag))
func VisitAll(fn func(*Flag))

type ErrorHandling

FlagSet

func NewFlagSet(name string, errorHandling ErrorHandling) *FlagSet

上面的方法 FlagSet 也都有一份。

示例：Todo

package main

import (
    "flag"
    "fmt"
)

var (
    addFlag       = flag.String("add", "", "Add a new task")
    listFlag      = flag.Bool("list", false, "List all tasks")
    removeFlag    = flag.Int("remove", -1, "Remove a task by its index")
    removeAllFlag = flag.Bool("remove-all", false, "Remove all tasks")
    doneFlag      = flag.Int("done", -1, "Mark a task as done by its index")
    undoneFlag    = flag.Int("undone", -1, "Mark a task as undone by its index")
)

func main() {
    flag.Parse()
    args := make(map[string]interface{}, 10)
    args["add"] = *addFlag
    args["list"] = *listFlag
    args["remove"] = *removeFlag
    args["remove"] = *removeAllFlag
    args["done"] = *doneFlag
    args["undone"] = *undoneFlag
    fmt.Printf("%#v\n", args)
    // map[string]interface {}{"add":"", "done":-1, "list":false, "remove":false, "undone":-1}
    fmt.Println("Other arguments:", flag.Args())
    // Other arguments: []
}

参考资料与拓展阅读

• pkg.go.dev, flag package
• https://zhuanlan.zhihu.com/p/619004569