flag
flag 是Go 標(biāo)準(zhǔn)庫提供的解析命令行參數(shù)的包。
使用方式：
flag.Type(name, defValue, usage)
其中Type為String, Int, Bool等；并返回一個(gè)相應(yīng)類型的指針。
flag.TypeVar(&flagvar, name, defValue, usage)
將flag綁定到一個(gè)變量上。
自定義flag
只要實(shí)現(xiàn)flag.Value接口即可：
type Value interface { String() string Set(string) error} 通過如下方式定義該flag：
flag.Var(&flagvar, name, usage)
示例
package mainimport "flag"import "fmt"import "strconv"type percentage float32func (p *percentage) Set(s string) error { v, err := strconv.ParseFloat(s, 32) *p = percentage(v) return err}func (p *percentage) String() string { return fmt.Sprintf("%f", *p) }func main() { namePtr := flag.String("name", "lyh", "user's name") agePtr := flag.Int("age", 22, "user's age") vipPtr := flag.Bool("vip", true, "is a vip user") var email string flag.StringVar(&email, "email", "lyhopq@gmail.com", "user's email") var pop percentage flag.Var(&pop, "pop", "popularity") flag.Parse() others := flag.Args() fmt.Println("name:", *namePtr) fmt.Println("age:", *agePtr) fmt.Println("vip:", *vipPtr) fmt.Println("pop:", pop) fmt.Println("email:", email) fmt.Println("other:", others)} $ ./command-line-flagsname: lyhage: 22vip: trueemail: lyhopq@gmail.comother: []
$ ./command-line-flags -name golang -age 4 -vip=true -pop 99 簡潔 高并發(fā) 等等name: golangage: 4vip: truepop: 99email: lyhopq@gmail.comother: [簡潔 高并發(fā) 等等]
$ ./command-line-flags -hUsage of ./command-line-flags: -age=22: user's age -email="lyhopq@gmail.com": user's email -name="lyh": user's name -pop=0.0: popularity -vip=true: is a vip user
