Go語言－flag使用

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flag包

實現了命令列的flag解析

用法

• func String(name string, value string, usage string) *string
  String 定義了一個指定名字為name的string類型flag,預設值為value,用法usage.傳回值是string類型的地址，存放了flage對應的值

• func StringVar(p *string, name string, value string, usage string)
  StringVar 定義了指定名字為name的string類型的flage,預設值為value,用法為usage.參數p指標指向存在flag值的空間.

• func Var(value Value, name string, usage string)
  Var 定義了指定名字name和用法的flag.第一個入參為flag的值，類型為Value,可以存放使用者自訂實現的Value.舉個例子，使用者可以建立一個flag，傳入參數用逗號分割，放入一個切片裡.

• func Args() []string
  Args 返回沒有flag的命令列參數.

執行個體１

package mainimport (    "errors"    "flag"    "fmt"    "strings"    "time")var species = flag.String("species", "gopher", "the species we are studying")var gopherType stringvar gopherType1 stringvar intervalFlag intervalfunc 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.Durationfunc (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)}

編譯運行

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

運行結果

species: doggopherType: birdgopherType1: chickenintervalFlag: [10s 15s 1m0s 1h0m0s]

執行個體２

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

運行結果

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

執行個體３

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

運行結果

arg0: ./flag2arg1: 123 arg2: 123 arg3: 345 arg4: 678 

Go語言－flag使用