example_test.go

// Example of use of the flags package.
package flags

import (
	"fmt"
	"os/exec"
)

func Example() {
	var opts struct {
		// Slice of bool will append 'true' each time the option
		// is encountered (can be set multiple times, like -vvv)
		Verbose []bool `short:"v" long:"verbose" description:"Show verbose debug information"`

		// Example of automatic marshalling to desired type (uint)
		Offset uint `long:"offset" description:"Offset"`

		// Example of a callback, called each time the option is found.
		Call func(string) `short:"c" description:"Call phone number"`

		// Example of a required flag
		Name string `short:"n" long:"name" description:"A name" required:"true"`

		// Example of a value name
		File string `short:"f" long:"file" description:"A file" value-name:"FILE"`

		// Example of a pointer
		Ptr *int `short:"p" description:"A pointer to an integer"`

		// Example of a slice of strings
		StringSlice []string `short:"s" description:"A slice of strings"`

		// Example of a slice of pointers
		PtrSlice []*string `long:"ptrslice" description:"A slice of pointers to string"`

		// Example of a map
		IntMap map[string]int `long:"intmap" description:"A map from string to int"`

		// Example of a filename (useful for completion)
		Filename Filename `long:"filename" description:"A filename"`

		// Example of positional arguments
		Args struct {
			ID   string
			Num  int
			Rest []string
		} `positional-args:"yes" required:"yes"`
	}

	// Callback which will invoke callto:<argument> to call a number.
	// Note that this works just on OS X (and probably only with
	// Skype) but it shows the idea.
	opts.Call = func(num string) {
		cmd := exec.Command("open", "callto:"+num)
		cmd.Start()
		cmd.Process.Release()
	}

	// Make some fake arguments to parse.
	args := []string{
		"-vv",
		"--offset=5",
		"-n", "Me",
		"-p", "3",
		"-s", "hello",
		"-s", "world",
		"--ptrslice", "hello",
		"--ptrslice", "world",
		"--intmap", "a:1",
		"--intmap", "b:5",
		"--filename", "hello.go",
		"id",
		"10",
		"remaining1",
		"remaining2",
	}

	// Parse flags from `args'. Note that here we use flags.ParseArgs for
	// the sake of making a working example. Normally, you would simply use
	// flags.Parse(&opts) which uses os.Args
	_, err := ParseArgs(&opts, args)

	if err != nil {
		panic(err)
	}

	fmt.Printf("Verbosity: %v\n", opts.Verbose)
	fmt.Printf("Offset: %d\n", opts.Offset)
	fmt.Printf("Name: %s\n", opts.Name)
	fmt.Printf("Ptr: %d\n", *opts.Ptr)
	fmt.Printf("StringSlice: %v\n", opts.StringSlice)
	fmt.Printf("PtrSlice: [%v %v]\n", *opts.PtrSlice[0], *opts.PtrSlice[1])
	fmt.Printf("IntMap: [a:%v b:%v]\n", opts.IntMap["a"], opts.IntMap["b"])
	fmt.Printf("Filename: %v\n", opts.Filename)
	fmt.Printf("Args.ID: %s\n", opts.Args.ID)
	fmt.Printf("Args.Num: %d\n", opts.Args.Num)
	fmt.Printf("Args.Rest: %v\n", opts.Args.Rest)

	// Output: Verbosity: [true true]
	// Offset: 5
	// Name: Me
	// Ptr: 3
	// StringSlice: [hello world]
	// PtrSlice: [hello world]
	// IntMap: [a:1 b:5]
	// Filename: hello.go
	// Args.ID: id
	// Args.Num: 10
	// Args.Rest: [remaining1 remaining2]
}