type Flag struct {Name     string // flag在命令行中的名字Usage    string // 帮助信息Value    Value  // 要设置的值DefValue string // 默认值(文本格式)，用于使用信息
}

type FlagSet struct {// Usage函数在解析flag出现错误时会被调用// 该字段为一个函数(而非采用方法)，以便修改为自定义的错误处理函数Usage func()// 内含隐藏或非导出字段
}

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

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

package mainimport ("flag""fmt"
)func main() {married := flag.Bool("married", false, "Are you married?")age := flag.Int("age", 22, "How old are you?")name := flag.String("name", "", "What your name?")var address string//flag.StringVar这样的函数第一个参数换成了变量地址，后面的参数和flag.String是一样的。flag.StringVar(&address, "address", "GuangZhou", "Where is your address?")flag.Parse() //解析输入的参数fmt.Println("输出的参数married的值是:", *married)//不加*号的话,输出的是内存地址fmt.Println("输出的参数age的值是:", *age)fmt.Println("输出的参数name的值是:", *name)fmt.Println("输出的参数address的值是:", address)
}

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

func Set(name, value string) error

func Visit(fn func(*Flag))

func VisitAll(fn func(*Flag))

package mainimport ("flag""fmt"
)func main() {// golang的flag包的一些基本使用方法// 待使用的变量var id intvar name stringvar male bool// 是否已经解析fmt.Println("parsed? = ", flag.Parsed())// 设置flag参数 (变量指针，参数名，默认值，帮助信息)// 也可以用以下带返回值的方法代替，不过他们返回的是指针，比较麻烦点// Int(name string, value int, usage string) *int// String(name string, value string, usage string) *string// Bool(name string, value bool, usage string) *boolflag.IntVar(&id, "id", 123, "help msg for id")flag.StringVar(&name, "name", "default name", "help msg for name")flag.BoolVar(&male, "male", false, "help msg for male")// 解析flag.Parse()// 是否已经解析fmt.Println("parsed? = ", flag.Parsed())//// 获取非flag参数fmt.Println(flag.NArg())fmt.Println("------ Args start ------")fmt.Println(flag.Args())for i, v := range flag.Args() {fmt.Printf("arg[%d] = (%s).\n", i, v)}fmt.Println("------ Args end ------")//// visit只包含已经设置了的flagfmt.Println("------ visit flag start ------")flag.Visit(func(f *flag.Flag) {fmt.Println(f.Name, f.Value, f.Usage, f.DefValue)})fmt.Println("------ visit flag end ------")//// visitAll只包含所有的flag(包括未设置的)fmt.Println("------ visitAll flag start ------")flag.VisitAll(func(f *flag.Flag) {fmt.Println(f.Name, f.Value, f.Usage, f.DefValue)})fmt.Println("------ visitAll flag end ------")//// flag参数fmt.Printf("id = %d\n", id)fmt.Printf("name = %s\n", name)fmt.Printf("male = %t\n", male)// flag参数默认值fmt.Println("------ PrintDefaults start ------")flag.PrintDefaults()fmt.Println("------ PrintDefaults end ------")//非flag参数个数fmt.Printf("NArg = %d\n", flag.NArg())// 已设置的flag参数个数fmt.Printf("NFlag = %d\n", flag.NFlag())
}

# go run demo2_flag.go -id 234 -name "xx" -male=true p1 p2 p3
parsed? =  false
parsed? =  true
3
------ Args start ------
[p1 p2 p3]
arg[0] = (p1).
arg[1] = (p2).
arg[2] = (p3).
------ Args end ------
------ visit flag start ------
id 234 help msg for id 123
male true help msg for male false
name xx help msg for name default name
------ visit flag end ------
------ visitAll flag start ------
id 234 help msg for id 123
male true help msg for male false
name xx help msg for name default name
------ visitAll flag end ------
id = 234
name = xx
male = true
------ PrintDefaults start -------id inthelp msg for id (default 123)-malehelp msg for male-name stringhelp msg for name (default "default name")
------ PrintDefaults end ------
NArg = 3
NFlag = 3