58 lines
1.5 KiB
Go
58 lines
1.5 KiB
Go
// Copyright 2023 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package flag_test
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import (
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"flag"
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"fmt"
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"time"
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)
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func ExampleFlagSet() {
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start := func(args []string) {
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// A real program (not an example) would use flag.ExitOnError.
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fs := flag.NewFlagSet("start", flag.ContinueOnError)
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addr := fs.String("addr", ":8080", "`address` to listen on")
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if err := fs.Parse(args); err != nil {
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fmt.Printf("error: %s", err)
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return
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}
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fmt.Printf("starting server on %s\n", *addr)
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}
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stop := func(args []string) {
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fs := flag.NewFlagSet("stop", flag.ContinueOnError)
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timeout := fs.Duration("timeout", time.Second, "stop timeout duration")
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if err := fs.Parse(args); err != nil {
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fmt.Printf("error: %s", err)
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return
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}
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fmt.Printf("stopping server (timeout=%v)\n", *timeout)
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}
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main := func(args []string) {
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subArgs := args[2:] // Drop program name and command.
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switch args[1] {
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case "start":
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start(subArgs)
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case "stop":
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stop(subArgs)
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default:
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fmt.Printf("error: unknown command - %q\n", args[1])
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// In a real program (not an example) print to os.Stderr and exit the program with non-zero value.
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}
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}
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main([]string{"httpd", "start", "-addr", ":9999"})
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main([]string{"httpd", "stop"})
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main([]string{"http", "start", "-log-level", "verbose"})
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// Output:
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// starting server on :9999
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// stopping server (timeout=1s)
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// error: flag provided but not defined: -log-level
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}
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