Go语言－flag使用

flag包

实现了命令行的flag解析

用法

• func String(name string, value string, usage string) *string
  String 定义了一个指定名字为name的string类型flag,默认值为value,用法usage.返回值是string类型的地址，存放了flage对应的值

• func StringVar(p *string, name string, value string, usage string)
  StringVar 定义了指定名字为name的string类型的flage,默认值为value,用法为usage.参数p指针指向存在flag值的空间.

• func Var(value Value, name string, usage string)
  Var 定义了指定名字name和用法的flag.第一个入参为flag的值，类型为Value,可以存放用户自定义实现的Value.举个例子，用户可以创建一个flag，传入参数用逗号分割，放入一个切片里.

• func Args() []string
  Args 返回没有flag的命令行参数.

实例１

package main

import (
    "errors"
    "flag"
    "fmt"
    "strings"
    "time"
)

var species = flag.String("species", "gopher", "the species we are studying")

var gopherType string
var gopherType1 string
var intervalFlag interval

func init() {

    const (
        defaultGopher = "pocket"
        usage         = "the variety of gopher"
    )
    flag.StringVar(&gopherType, "gopher_type", defaultGopher, usage)
    flag.StringVar(&gopherType1, "g", defaultGopher, usage+" (shorthand)")
    flag.Var(&intervalFlag, "deltaT", "comma-separated list of intervals to use between events")
}

type interval []time.Duration

func (i *interval) String() string {
    return fmt.Sprint(*i)
}

func (i *interval) Set(value string) error {
    if len(*i) > 0 {
        return errors.New("interval flag already set")
    }

    for _, dt := range strings.Split(value, ",") {
        duration, err := time.ParseDuration(dt)
        if err != nil {
            return err
        }

        *i = append(*i, duration)
    }

    return nil
}

func main() {
    flag.Parse()
    fmt.Println("species:", *species)
    fmt.Println("gopherType:", gopherType)
    fmt.Println("gopherType1:", gopherType1)
    fmt.Println("intervalFlag:", intervalFlag)
}

编译运行

     go build flag.go 

    ./flag  -species dog -g chicken -gopher_type bird -deltaT 10s,15s,1m,1h

运行结果

species: dog
gopherType: bird
gopherType1: chicken
intervalFlag: [10s 15s 1m0s 1h0m0s]

实例２

package main

import (
    "fmt"
    "flag"
)

func main() {
    flag.Parse()
    args := flag.Args()

    for index, val := range args {
        fmt.Printf("arg%v: %v \n", index, val)
    }
    return
}

运行结果

arg0: 123 
arg1: 123 
arg2: 345 
arg3: 678 

实例３

package main

import (
    "fmt"
    "os"
)

func main() {
    for index, val := range os.Args {
        fmt.Printf("arg%v: %v \n", index, val)
    }
    return
}

运行结果

arg0: ./flag2
arg1: 123 
arg2: 123 
arg3: 345 
arg4: 678