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58 lines
1.5 KiB
Go
58 lines
1.5 KiB
Go
// Some command-line tools, like the `go` tool or `git`
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// have many *subcommands*, each with its own set of
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// flags. For example, `go build` and `go get` are two
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// different subcommands of the `go` tool.
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// The `flag` package lets us easily define simple
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// subcommands that have their own flags.
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package main
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import (
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"flag"
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"fmt"
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"os"
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)
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func main() {
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// We declare a subcommand using the `NewFlagSet`
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// function, and proceed to define new flags specific
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// for this subcommand.
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fooCmd := flag.NewFlagSet("foo", flag.ExitOnError)
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fooEnable := fooCmd.Bool("enable", false, "enable")
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fooName := fooCmd.String("name", "", "name")
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// For a different subcommand we can define different
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// supported flags.
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barCmd := flag.NewFlagSet("bar", flag.ExitOnError)
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barLevel := barCmd.Int("level", 0, "level")
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// The subcommand is expected as the first argument
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// to the program.
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if len(os.Args) < 2 {
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fmt.Println("expected 'foo' or 'bar' subcommands")
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os.Exit(1)
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}
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// Check which subcommand is invoked.
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switch os.Args[1] {
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// For every subcommand, we parse its own flags and
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// have access to trailing positional arguments.
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case "foo":
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fooCmd.Parse(os.Args[2:])
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fmt.Println("subcommand 'foo'")
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fmt.Println(" enable:", *fooEnable)
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fmt.Println(" name:", *fooName)
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fmt.Println(" tail:", fooCmd.Args())
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case "bar":
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barCmd.Parse(os.Args[2:])
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fmt.Println("subcommand 'bar'")
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fmt.Println(" level:", *barLevel)
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fmt.Println(" tail:", barCmd.Args())
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default:
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fmt.Println("expected 'foo' or 'bar' subcommands")
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os.Exit(1)
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}
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}
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