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// Copyright 2020 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package flag_test
import (
"errors"
"flag"
"fmt"
"net"
"os"
)
func ExampleFunc() {
fs := flag.NewFlagSet("ExampleFunc", flag.ContinueOnError)
fs.SetOutput(os.Stdout)
var ip net.IP
fs.Func("ip", "`IP address` to parse", func(s string) error {
ip = net.ParseIP(s)
if ip == nil {
return errors.New("could not parse IP")
}
return nil
})
fs.Parse([]string{"-ip", "127.0.0.1"})
fmt.Printf("{ip: %v, loopback: %t}\n\n", ip, ip.IsLoopback())
// 256 is not a valid IPv4 component
fs.Parse([]string{"-ip", "256.0.0.1"})
fmt.Printf("{ip: %v, loopback: %t}\n\n", ip, ip.IsLoopback())
// Output:
// {ip: 127.0.0.1, loopback: true}
//
// invalid value "256.0.0.1" for flag -ip: could not parse IP
// Usage of ExampleFunc:
// -ip IP address
// IP address to parse
// {ip: <nil>, loopback: false}
}
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