golang flag test

README.md

Flag!

arg.go

package main

import (
	"flag"
	"fmt"
)

func main() {
	flag.Parse()

	n := flag.NArg()
	fmt.Printf("flag.NArgs() = %v\n", n)
	for i := 0; i < n; i++ {
		fmt.Printf("flag.Arg(%d) = %v\n", i, flag.Arg(i))
	}

	fmt.Printf("flag.Args() = %v\n", flag.Args())
}

custom-var.go

package main

import (
	"flag"
	"fmt"
)

type MyValue int

func (i *MyValue) String() string {
	return fmt.Sprintf("%d", *i)
}

func (i *MyValue) Set(s string) error {
	fmt.Printf("Set: %v\n", s)
	switch s {
	case "one":
		*i = 1
	case "two":
		*i = 2
	case "three":
		*i = 3
	default:
		*i = 0
	}
	return nil
}

func main() {
	var myValue MyValue
	flag.Var(&myValue, "value", "customized value")
	flag.Parse()
	fmt.Printf("myValue = %d\n", myValue)
}

flag_set.go

package main

import (
	"flag"
	"fmt"
)

func main() {
	flagSet := flag.NewFlagSet("HogeHoge", flag.ContinueOnError)
	boolVar := flagSet.Bool("bool", false, "flag.BoolVar")
	intVar := flagSet.Int("int", 0, "flag.IntVar")
	int64Var := flagSet.Int64("int64", 0, "flag.Int64Var")
	uintVar := flagSet.Uint("uint", 0, "flag.IntVar")
	uint64Var := flagSet.Uint64("uint64", 0, "flag.Int64Var")
	float64Var := flagSet.Float64("float64", 0, "flag.Float64Var")
	stringVar := flagSet.String("string", "", "flag.StringVar")
	durationVar := flagSet.Duration("duration", 0, "flag.DurationVar")

	flagSet.Parse([]string{
		"--bool",
		"--int=12",
		"--int64=123",
		"--uint=1234",
		"--uint64=12345",
		"--float64=3.1415926535",
		"--string", "some string",
		"--duration", "12h30m",
	})

	fmt.Printf("flag.NFlag() = %d\n", flagSet.NFlag())
	fmt.Printf("boolVar = %v\n", *boolVar)
	fmt.Printf("intVar = %v\n", *intVar)
	fmt.Printf("int64Var = %v\n", *int64Var)
	fmt.Printf("uintVar = %v\n", *uintVar)
	fmt.Printf("uint64Var = %v\n", *uint64Var)
	fmt.Printf("float64Var = %v\n", *float64Var)
	fmt.Printf("stringVar = %v\n", *stringVar)
	fmt.Printf("durationVar = %v\n", *durationVar)
}

lookup.go

package main

import (
	"flag"
	"fmt"
)

func main() {
	flag.Bool("bool", false, "flag.BoolVar")
	flag.Int("int", 0, "flag.IntVar")
	flag.Int64("int64", 0, "flag.Int64Var")
	flag.Uint("uint", 0, "flag.IntVar")
	flag.Uint64("uint64", 0, "flag.Int64Var")
	flag.Float64("float64", 0, "flag.Float64Var")
	flag.String("string", "", "flag.StringVar")
	flag.Duration("duration", 0, "flag.DurationVar")

	flag.Parse()

	fmt.Println(flag.Lookup("bool"))
	fmt.Println(flag.Lookup("int"))
	fmt.Println(flag.Lookup("int64"))
	fmt.Println(flag.Lookup("uint64"))
	fmt.Println(flag.Lookup("float64"))
	fmt.Println(flag.Lookup("string"))
	fmt.Println(flag.Lookup("duration"))
}

non-var.go

package main

import (
	"flag"
	"fmt"
)

func main() {
	boolVar := flag.Bool("bool", false, "flag.BoolVar")
	intVar := flag.Int("int", 0, "flag.IntVar")
	int64Var := flag.Int64("int64", 0, "flag.Int64Var")
	uintVar := flag.Uint("uint", 0, "flag.IntVar")
	uint64Var := flag.Uint64("uint64", 0, "flag.Int64Var")
	float64Var := flag.Float64("float64", 0, "flag.Float64Var")
	stringVar := flag.String("string", "", "flag.StringVar")
	durationVar := flag.Duration("duration", 0, "flag.DurationVar") // time.ParseDuration で解析してくれる

	flag.Parse()

	fmt.Printf("flag.NFlag() = %d\n", flag.NFlag())
	fmt.Printf("boolVar = %v\n", *boolVar)
	fmt.Printf("intVar = %v\n", *intVar)
	fmt.Printf("int64Var = %v\n", *int64Var)
	fmt.Printf("uintVar = %v\n", *uintVar)
	fmt.Printf("uint64Var = %v\n", *uint64Var)
	fmt.Printf("float64Var = %v\n", *float64Var)
	fmt.Printf("stringVar = %v\n", *stringVar)
	fmt.Printf("durationVar = %v\n", *durationVar)
}

usage.go

package main

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

func main() {
	flag.Usage = func() {
		fmt.Fprintf(os.Stderr, "Custom usage of %s:\n", os.Args[0])
		flag.PrintDefaults()
	}
	flag.Parse()
}

var.go

package main

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

func main() {
	var boolVar bool
	var intVar int
	var int64Var int64
	var uintVar uint
	var uint64Var uint64
	var float64Var float64
	var stringVar string
	var durationVar time.Duration

	flag.BoolVar(&boolVar, "bool", false, "flag.BoolVar")
	flag.IntVar(&intVar, "int", 0, "flag.IntVar")
	flag.Int64Var(&int64Var, "int64", 0, "flag.Int64Var")
	flag.UintVar(&uintVar, "uint", 0, "flag.IntVar")
	flag.Uint64Var(&uint64Var, "uint64", 0, "flag.Int64Var")
	flag.Float64Var(&float64Var, "float64", 0, "flag.Float64Var")
	flag.StringVar(&stringVar, "string", "", "flag.StringVar")
	flag.DurationVar(&durationVar, "duration", 0, "flag.DurationVar") // time.ParseDuration で解析してくれる

	flag.Parse()

	fmt.Printf("flag.NFlag() = %d\n", flag.NFlag())
	fmt.Printf("boolVar = %v\n", boolVar)
	fmt.Printf("intVar = %v\n", intVar)
	fmt.Printf("int64Var = %v\n", int64Var)
	fmt.Printf("uintVar = %v\n", uintVar)
	fmt.Printf("uint64Var = %v\n", uint64Var)
	fmt.Printf("float64Var = %v\n", float64Var)
	fmt.Printf("stringVar = %v\n", stringVar)
	fmt.Printf("durationVar = %v\n", durationVar)
}

visit.go

package main

import (
	"flag"
	"fmt"
)

func main() {
	flag.Bool("bool", false, "flag.BoolVar")
	flag.Int("int", 0, "flag.IntVar")
	flag.Int64("int64", 0, "flag.Int64Var")
	flag.Uint("uint", 0, "flag.IntVar")
	flag.Uint64("uint64", 0, "flag.Int64Var")
	flag.Float64("float64", 0, "flag.Float64Var")
	flag.String("string", "", "flag.StringVar")
	flag.Duration("duration", 0, "flag.DurationVar")

	flag.Parse()

	fmt.Println("----- Visit -----")
	flag.Visit(func(f *flag.Flag) {
		fmt.Println(f)
	})

	fmt.Println("")
	fmt.Println("----- VisitAll -----")
	flag.VisitAll(func(f *flag.Flag) {
		fmt.Println(f)
	})
}