Add --run-and-exit flag to qrunweb and screenshot helper script

cmd/qrunweb/main.go

@@ -1,11 +1,15 @@
 package main
 
 import (
+	"context"
 	"embed"
 	"fmt"
 	"io/fs"
+	"net"
 	"net/http"
 	"os"
+	"os/exec"
+	"strings"
 )
 
 //go:embed static
@@ -13,8 +17,14 @@ var staticFS embed.FS
 
 func main() {
 	addr := ":8080"
-	if len(os.Args) > 1 {
-		addr = os.Args[1]
+	var runAndExit []string
+
+	for _, arg := range os.Args[1:] {
+		if v, ok := strings.CutPrefix(arg, "--run-and-exit="); ok {
+			runAndExit = strings.Fields(v)
+		} else {
+			addr = arg
+		}
 	}
 
 	sub, err := fs.Sub(staticFS, "static")
@@ -25,6 +35,27 @@ func main() {
 
 	http.Handle("/", http.FileServer(http.FS(sub)))
 
+	if len(runAndExit) > 0 {
+		ln, err := net.Listen("tcp", addr)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "Error: %v\n", err)
+			os.Exit(1)
+		}
+		srv := &http.Server{}
+		go srv.Serve(ln)
+
+		cmd := exec.Command(runAndExit[0], runAndExit[1:]...)
+		cmd.Stdout = os.Stdout
+		cmd.Stderr = os.Stderr
+		cmdErr := cmd.Run()
+		srv.Shutdown(context.Background())
+		if cmdErr != nil {
+			fmt.Fprintf(os.Stderr, "Error: %v\n", cmdErr)
+			os.Exit(1)
+		}
+		return
+	}
+
 	fmt.Printf("Listening on %s\n", addr)
 	if err := http.ListenAndServe(addr, nil); err != nil {
 		fmt.Fprintf(os.Stderr, "Error: %v\n", err)