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