add start, fgstart, stop, status subcommands

Modelled after 9p/main.go. Pid file in 9P namespace dir; running check
via TCP dial to -listen address. No-subcommand path preserved for
backwards compatibility.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

main.go

@@ -17,9 +17,14 @@ import (
 	"fmt"
 	"io"
 	"log"
+	"net"
 	"net/http"
+	"os"
+	"os/exec"
 	"path"
+	"path/filepath"
 	"strings"
+	"syscall"
 
 	"9fans.net/go/plan9"
 	"9fans.net/go/plan9/client"
@@ -35,8 +40,100 @@ var (
 	addr    = flag.String("addr", "", "9P server address; empty = use namespace service")
 )
 
+const pidFile = "ollie-httpgw.pid"
+
 func main() {
+	if len(os.Args) >= 2 {
+		subcmd := os.Args[1]
+		switch subcmd {
+		case "start", "fgstart", "stop", "status":
+			flag.CommandLine.Parse(os.Args[2:]) //nolint:errcheck
+			ns := client.Namespace()
+			if ns == "" {
+				fmt.Fprintln(os.Stderr, "no namespace")
+				os.Exit(1)
+			}
+			pidPath := filepath.Join(ns, pidFile)
+			switch subcmd {
+			case "start":
+				if gwRunning() {
+					fmt.Println("ollie-httpgw already running")
+					os.Exit(0)
+				}
+				daemonize()
+			case "fgstart":
+				if gwRunning() {
+					fmt.Println("ollie-httpgw already running")
+					os.Exit(0)
+				}
+				runGateway(pidPath)
+			case "stop":
+				stopGateway(pidPath)
+			case "status":
+				if gwRunning() {
+					fmt.Println("ollie-httpgw running")
+				} else {
+					fmt.Println("ollie-httpgw not running")
+					os.Exit(1)
+				}
+			}
+			return
+		}
+	}
+	// Legacy: no subcommand — run in foreground directly (no pid file).
 	flag.Parse()
+	serve()
+}
+
+func gwRunning() bool {
+	conn, err := net.Dial("tcp", *listen)
+	if err == nil {
+		conn.Close()
+		return true
+	}
+	return false
+}
+
+func daemonize() {
+	exe, _ := os.Executable()
+	args := []string{"fgstart", "-listen", *listen, "-service", *service}
+	if *network != "" {
+		args = append(args, "-net", *network)
+	}
+	if *addr != "" {
+		args = append(args, "-addr", *addr)
+	}
+	cmd := exec.Command(exe, args...)
+	cmd.SysProcAttr = &syscall.SysProcAttr{Setsid: true}
+	if err := cmd.Start(); err != nil {
+		fmt.Fprintf(os.Stderr, "failed to start: %v\n", err)
+		os.Exit(1)
+	}
+	fmt.Printf("ollie-httpgw started (pid %d)\n", cmd.Process.Pid)
+}
+
+func stopGateway(pidPath string) {
+	data, err := os.ReadFile(pidPath)
+	if err != nil {
+		fmt.Println("ollie-httpgw not running")
+		return
+	}
+	var pid int
+	fmt.Sscanf(string(data), "%d", &pid)
+	if pid > 0 {
+		syscall.Kill(pid, syscall.SIGTERM) //nolint:errcheck
+	}
+	os.Remove(pidPath) //nolint:errcheck
+	fmt.Println("ollie-httpgw stopped")
+}
+
+func runGateway(pidPath string) {
+	os.WriteFile(pidPath, fmt.Appendf(nil, "%d", os.Getpid()), 0644) //nolint:errcheck
+	serve()
+	os.Remove(pidPath) //nolint:errcheck
+}
+
+func serve() {
 	http.HandleFunc("/openapi.json", func(w http.ResponseWriter, r *http.Request) {
 		w.Header().Set("Content-Type", "application/json")
 		w.Write(openapiSpec)