Merge pull request #779 from devlights/add-commanline-subcommand

Author: devlights

examples/singleapp/commandline_subcommands/.gitignore

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+app

examples/singleapp/commandline_subcommands/README.md

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+# これは何？
+
+```git``` コマンドのように サブコマンド を持つコマンドラインを ```flag``` パッケージを使って構築する方法についてのメモです。
+
+実行すると以下のように表示されます。
+
+```sh
+$ task
+task: [default] go build -o app
+task: [default] ./app
+Usage: app <cmd1|cmd2|version|help>
+Usage of cmd1:
+  -c int
+        option c
+Usage of cmd2:
+  -f string
+        option f
+task: [default] ./app help
+Usage: app <cmd1|cmd2|version|help>
+Usage of cmd1:
+  -c int
+        option c
+Usage of cmd2:
+  -f string
+        option f
+task: [default] ./app version
+version: vX.Y.Z (fe9c8eb719af1f17bcd9e2e7174c791e7ecd74c0)
+task: [default] ./app cmd1 -c 100
+option c is 100
+task: [default] ./app cmd2 -f helloworld
+option f is helloworld
+task: [default] ./app cmd1 -f helloworld
+flag provided but not defined: -f
+Usage of cmd1:
+  -c int
+        option c
+```
+
+## 参考情報
+
+- https://pkg.go.dev/flag@go1.22.1#FlagSet
+- https://gobyexample.com/command-line-subcommands

examples/singleapp/commandline_subcommands/Taskfile.yml

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+# https://taskfile.dev
+
+version: '3'
+
+tasks:
+  default:
+    cmds:
+      - go build -o app
+      - ./app
+      - ./app help
+      - ./app version
+      - ./app cmd1 -c 100
+      - ./app cmd2 -f helloworld
+      - ./app cmd1 -f helloworld
+    ignore_error: true

examples/singleapp/commandline_subcommands/main.go

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+package main
+
+import (
+	"flag"
+	"log"
+	"os"
+	"runtime/debug"
+)
+
+type subcommand string
+
+const (
+	subcmd1 subcommand = "cmd1"
+	subcmd2 subcommand = "cmd2"
+	subver  subcommand = "version"
+	subhelp subcommand = "help"
+)
+
+// cmd1 subcommand
+var (
+	cmd1     = flag.NewFlagSet("cmd1", flag.ExitOnError)
+	cmd1OptC = cmd1.Int("c", 0, "option c")
+)
+
+// cmd2 subcommand
+var (
+	cmd2     = flag.NewFlagSet("cmd2", flag.ExitOnError)
+	cmd2OptF = cmd2.String("f", "", "option f")
+)
+
+func init() {
+	log.SetFlags(0)
+}
+
+func main() {
+	if len(os.Args) < 2 {
+		help()
+		os.Exit(1)
+	}
+
+	var (
+		subcmd = subcommand(os.Args[1])
+		args   = os.Args[2:]
+	)
+
+	switch subcmd {
+	case subcmd1:
+		cmd1.Parse(args)
+		runCmd1()
+	case subcmd2:
+		cmd2.Parse(args)
+		runCmd2()
+	case subver:
+		version()
+		return
+	case subhelp:
+		help()
+		return
+	default:
+		help()
+		os.Exit(1)
+	}
+}
+
+func runCmd1() {
+	log.Printf("option c is %v", *cmd1OptC)
+}
+
+func runCmd2() {
+	log.Printf("option f is %v", *cmd2OptF)
+}
+
+func version() {
+	info, ok := debug.ReadBuildInfo()
+	if !ok {
+		log.Println("error: call debug.ReadBuildInfo()")
+		os.Exit(1)
+	}
+
+	for _, s := range info.Settings {
+		if s.Key == "vcs.revision" {
+			log.Printf("version: vX.Y.Z (%s)", s.Value)
+			return
+		}
+	}
+}
+
+func help() {
+	log.Println("Usage: app <cmd1|cmd2|version|help>")
+	cmd1.Usage()
+	cmd2.Usage()
+}