flag
flag 是Go 标准库提供的解析命令行参数的包。
使用方式:
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flag.Type(name, defValue, usage)
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其中Type为String, Int, Bool等;并返回一个相应类型的指针。
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flag.TypeVar(&flagvar, name, defValue, usage)
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将flag绑定到一个变量上。
自定义flag
只要实现flag.Value接口即可:
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type Value interface {
String() string
Set(string) error
}
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通过如下方式定义该flag:
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flag.Var(&flagvar, name, usage)
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示例
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package main
import "flag"
import "fmt"
import "strconv"
type percentage float32
func (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)
}
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$ . /command-line-flags
name: lyh
age: 22
vip: true
email: lyhopq@gmail.com
other: []
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$ . /command-line-flags -name golang -age 4 -vip= true -pop 99 简洁 高并发 等等
name: golang
age: 4
vip: true
pop: 99
email: lyhopq@gmail.com
other: [简洁 高并发 等等]
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$ . /command-line-flags -h
Usage 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
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