Golang之flage

golang的flage包提供了对命令行参数的解析。

1. flage提供的几个基本函数

package mainimport (    "flag"    "fmt")func main() {    //1.参数的名字 2.默认的参数 3.参数详情    name := flag.String("name", "happy", "input into your name")    age := flag.Int("age", 23, "your age")    sex := flag.Bool("sex", true, "your sex")    flag.Parse()    fmt.Println("name:", *name)    fmt.Println("age:", *age)    fmt.Println("vip:", *sex)}

运行程序

***.exe -name haha -age 18 -sex true

输出结果

如果运行程序时不输入参数的话，则输出为默认的参数

另外可以将解析出来的参数绑定到变量上

    var Name string    flag.StringVar(&Name , "name", "happy", "input into your name")    flag.Parse()    fmt.Println("name:",Name)

2. 自定义flage

用户可以使用flage.Value()定义一个flage。
flage.Value()的声明如下：

// Var defines a flag with the specified name and usage string. The type and// value of the flag are represented by the first argument, of type Value, which// typically holds a user-defined implementation of Value. For instance, the// caller could create a flag that turns a comma-separated string into a slice// of strings by giving the slice the methods of Value; in particular, Set would// decompose the comma-separated string into the slice.func Var(value Value, name string, usage string) {    CommandLine.Var(value, name, usage)}

根据如上描述，我们需要先自定义类型并实现Value 接口：
type Value interface {
String() string
Set(string) error
}

代码如下：

package mainimport (    "flag"    "fmt")type flagestring stringfunc (p *flagestring) Set(s string) error {    *p = flagestring(s)    return nil}func (p *flagestring) String() string {    return fmt.Sprintf("%f", *p)}func main() {    var Name flagestring    //设置默认的参数为 new flage    Name.Set("happy")    //1.参数变量 2.参数名字 3.参数描述    flag.Var(&Name, "name", "input your name")    flag.Parse()    fmt.Println("name:", Name)}

运行程序：

***.exe -name gaoxing

运行结果：

3. Arge 和Arges

分别获得所有的参数和某个参数

// Args returns the non-flag command-line arguments.func Args() []string { return CommandLine.args }

// Arg returns the i'th command-line argument. Arg(0) is the first remaining argument// after flags have been processed. Arg returns an empty string if the// requested element does not exist.func Arg(i int) string {    return CommandLine.Arg(i)}