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:2015-4-10package mainimport ("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.exe1 : -level2 : 33 : -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:2015-4-10package mainimport ("flag""fmt""os""time")var (/*参数解析出错时错误处理方式switch f.errorHandling {case ContinueOnError:return errcase 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 []stringfunc (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 2m0sos.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: 10.0xtimeFlag: 2m0saddrFlag: [ba ca d2]C:\TEMP\testflag>go run tfs.go -ver 9.0 -a ba -a ca -a d2 -ver 10.0os.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: 10.0xtimeFlag: 10m0saddrFlag: [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 2m0s33os.Args[0]: C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp\go-build841833143\command-line-arguments\_obj\exe\tfs.exeinvalid value "2m0s33" for flag -time: time: missing unit in duration 2m0s33Usage 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="": versionpanic: invalid value "2m0s33" for flag -time: time: missing unit in duration 2m0s33goroutine 1 [running]:flag.(*FlagSet).Parse(0x10b18180, 0x10b42008, 0xc, 0xc, 0x0, 0x0)c:/go/src/flag/flag.go:814 +0xeemain.main()C:/TEMP/testflag/tfs.go:41 +0x163exit 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 2m0s33os.Args[0]: C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp\go-build501686683\command-line-arguments\_obj\exe\tfs.exeinvalid value "2m0s33" for flag -time: time: missing unit in duration 2m0s33Usage 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="": versionexit 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() stringSet(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.
比起Linux的getopt()系列函数.flag包这种方式还是更清晰直观点.
BLOG:
，生命不是一场赛跑，而是一次旅行。比赛在乎终点，而旅行在乎沿途风景。
