Go语言的参数解析(flag)

flag参数解析,我原以为会了,结果今天发现,原来比我印象中还强大些.
 索性记一下.
 第一个例子是常见用法:

//Flag例1
//author:Xiong Chuan Liang
//date:2015-4-10

package main

import (
	"flag"
	"fmt"
	"os"	
)

var (
	 levelFlag = flag.Int("level", 0, "级别")  
	 bnFlag int  
)

func init() {
	 flag.IntVar(&bnFlag, "bn", 3, "份数")  
}

func main() {

	flag.Parse()  
    count := len(os.Args)
    fmt.Println("参数总个数:",count)

    fmt.Println("参数详情:")
    for i := 0 ; i < count ;i++{
        fmt.Println(i,":",os.Args[i])
    }
   
    fmt.Println("\n参数值:")
	fmt.Println("级别:", *levelFlag)
	fmt.Println("份数:", bnFlag)
}


/*
运行结果:

C:\TEMP\testflag>go run tf2.go -level 3 -bn=2
参数总个数: 4
参数详情:
0 : C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp\go-build158983983\command-line-arguments\_obj\exe\tf2.exe
1 : -level
2 : 3
3 : -bn=2

参数值:
级别: 3
份数: 2


*/

  第二个例子,可以扩展功能:

//Flag例2
//author:Xiong Chuan Liang
//date:2015-4-10

package main

import (
	"flag"
	"fmt"
	"os"
	"time"
)

var (
/*
	参数解析出错时错误处理方式
	switch f.errorHandling {
		case ContinueOnError:
			return err
		case ExitOnError:
			os.Exit(2)
		case PanicOnError:
			panic(err)
		} 
		*/

	//flagSet = flag.NewFlagSet(os.Args[0],flag.PanicOnError) 
	flagSet = flag.NewFlagSet(os.Args[0],flag.ExitOnError) 
	//flagSet = flag.NewFlagSet("xcl",flag.ExitOnError) 
	verFlag = flagSet.String("ver", "", "version")
	xtimeFlag  = flagSet.Duration("time", 10*time.Minute, "time Duration")

	addrFlag = StringArray{}
)

func init() {
	flagSet.Var(&addrFlag, "a", "b")
}

func main() {
	fmt.Println("os.Args[0]:", os.Args[0])
	flagSet.Parse(os.Args[1:]) //flagSet.Parse(os.Args[0:])

	fmt.Println("当前命令行参数类型个数:", flagSet.NFlag())  
	 for i := 0; i != flagSet.NArg(); i++ {  
        fmt.Printf("arg[%d]=%s\n", i, flag.Arg(i))  
    }  

    fmt.Println("\n参数值:")
	fmt.Println("ver:", *verFlag)
	fmt.Println("xtimeFlag:", *xtimeFlag)
	fmt.Println("addrFlag:",addrFlag.String())

	for i,param := range flag.Args(){
        fmt.Printf("---#%d :%s\n",i,param)
    }
}


type StringArray []string

func (s *StringArray) String() string {
	return fmt.Sprint([]string(*s))
}

func (s *StringArray) Set(value string) error {
	*s = append(*s, value)
	return nil
}


/*
运行结果:
C:\TEMP\testflag>go run tfs.go -ver 9.0 -a ba -a ca -a d2 -ver 10.0 -time 2m0s
os.Args[0]: C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp\go-build341936307\command-line-arguments\_obj\exe\tfs.exe
当前命令行参数类型个数: 3

参数值:
ver: 10.0
xtimeFlag: 2m0s
addrFlag: [ba ca d2]



C:\TEMP\testflag>go run tfs.go -ver 9.0 -a ba -a ca -a d2 -ver 10.0
os.Args[0]: C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp\go-build712958211\command-line-arguments\_obj\exe\tfs.exe
当前命令行参数类型个数: 2

参数值:
ver: 10.0
xtimeFlag: 10m0s
addrFlag: [ba ca d2]



-- flagSet = flag.NewFlagSet(os.Args[0],flag.PanicOnError) 结果:
C:\TEMP\testflag>go run tfs.go -ver 9.0 -a ba -a ca -a d2 -ver 10.0 -time 2m0s33
os.Args[0]: C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp\go-build841833143\command-line-arguments\_obj\exe\tfs.exe
invalid value "2m0s33" for flag -time: time: missing unit in duration 2m0s33
Usage of C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp\go-build841833143\command-line-arguments\_obj\exe\tfs.exe:
  -a=[]: b
  -time=10m0s: time Duration
  -ver="": version
panic: invalid value "2m0s33" for flag -time: time: missing unit in duration 2m0s33

goroutine 1 [running]:
flag.(*FlagSet).Parse(0x10b18180, 0x10b42008, 0xc, 0xc, 0x0, 0x0)
        c:/go/src/flag/flag.go:814 +0xee
main.main()
        C:/TEMP/testflag/tfs.go:41 +0x163
exit status 2


-- flagSet = flag.NewFlagSet(os.Args[0],flag.ExitOnError) 结果:
C:\TEMP\testflag>go run tfs.go -ver 9.0 -a ba -a ca -a d2 -ver 10.0 -time 2m0s33
os.Args[0]: C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp\go-build501686683\command-line-arguments\_obj\exe\tfs.exe
invalid value "2m0s33" for flag -time: time: missing unit in duration 2m0s33
Usage of C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp\go-build501686683\command-line-arguments\_obj\exe\tfs.exe:
  -a=[]: b
  -time=10m0s: time Duration
  -ver="": version
exit status 2


*/

  flagSet类可以让参数处理更加灵活.
  其中NewFlagSet:
  flagSet = flag.NewFlagSet("xcl",flag.ExitOnError) 
  NewFlagSet的第一个参数是可以任意定的.但第二个参数,则决定了参数解析出错时错误处理方式.

 如果要扩展参数定义,只要实现下面的接口:

 type Value interface {
	String() string
	Set(string) error
}

 依例子中的 StringArray 一样.就可以实现如:
    -a ba -a ca -a d2 
     addrFlag: [ba ca d2]
   这种效果.

    要知道,同样的:

         -ver 9.0 -ver 10.0
    最后的结果是 ver: 10.0 即参数只识别最末一次的.

    没想到还能通过interface进行扩展,并且其使用比起Linux的getopt()系列函数.flag包这种方式还是更清晰直观.

BLOG: http://blog.csdn.net/xcl168

---