Если не указан целевой файл - то вывод в stdout

cmd/go-tr/main.go

@@ -35,7 +35,7 @@ func getFlags() (int, string, string) {
 }
 
 func checkFlagsAreValid(source, target string) {
-	if source == "" || target == "" {
+	if source == "" {
 		printUsage()
 		os.Exit(1)
 	}
@@ -58,12 +58,16 @@ func safeTranspile(mode int, source, target string) {
 		os.Exit(1)
 	}
 	defer in.Close()
-	// Create the Arduino sketch file.
-	os.Remove(target)
-	out, err := os.OpenFile(target, os.O_CREATE|os.O_RDWR|os.O_SYNC, 0666)
-	if err != nil {
-		fmt.Fprintf(os.Stderr, "Arduino sketch file [%s] could not be opened! %v", target, err)
-		os.Exit(1)
+
+	out := os.Stdout
+	if target != "" {
+		// Create the Arduino sketch file.
+		os.Remove(target)
+		out, err = os.OpenFile(target, os.O_CREATE|os.O_RDWR|os.O_SYNC, 0666)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "Arduino sketch file [%s] could not be opened! %v", target, err)
+			os.Exit(1)
+		}
 	}
 	switch mode {
 	case CPP_MODE: