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-rw-r--r--src/flag/example_textvar_test.go35
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diff --git a/src/flag/example_textvar_test.go b/src/flag/example_textvar_test.go
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+// Copyright 2022 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 (
+ "flag"
+ "fmt"
+ "net"
+ "os"
+)
+
+func ExampleTextVar() {
+ fs := flag.NewFlagSet("ExampleTextVar", flag.ContinueOnError)
+ fs.SetOutput(os.Stdout)
+ var ip net.IP
+ fs.TextVar(&ip, "ip", net.IPv4(192, 168, 0, 100), "`IP address` to parse")
+ fs.Parse([]string{"-ip", "127.0.0.1"})
+ fmt.Printf("{ip: %v}\n\n", ip)
+
+ // 256 is not a valid IPv4 component
+ ip = nil
+ fs.Parse([]string{"-ip", "256.0.0.1"})
+ fmt.Printf("{ip: %v}\n\n", ip)
+
+ // Output:
+ // {ip: 127.0.0.1}
+ //
+ // invalid value "256.0.0.1" for flag -ip: invalid IP address: 256.0.0.1
+ // Usage of ExampleTextVar:
+ // -ip IP address
+ // IP address to parse (default 192.168.0.100)
+ // {ip: <nil>}
+}