Keyboard issue with Java Console App in rc.local

Question

I am trying to run a java console app in Raspbian rc.local.

It is a boot menu to select a menu item based on a keyboard input. The program runs fine, if running at command prompt.

However, when starting the java console app within rc.local

java -jar /home/pi/RaspPiStartup/RaspPiStartup.jar

the application is not able to read keyboard inputs.

    Scanner in = new Scanner(System.in);
    Console con=System.console();
    AtomicInteger num=new AtomicInteger(-1);

    Thread thread = new Thread() {
        public void run() {
            try {
                int i1;
                if (con==null) {
                    System.out.println("KeyScan In");
                    i1=in.nextInt();
                    System.out.println("KeyScan "+i1);
                }
                else {
                    System.out.println("KeyCon In");
                    i1=Integer.parseInt(con.readLine());
                    System.out.println("KeyCon "+i1);
                }
                num.set(i1 );
            }
            catch(Exception e) {
                System.out.println("Fehler Keyboard In"+e.toString());
            }
        }
    };

    thread.start();        

I tried several ways, as you see. This solution gives me an Exception. As con == null in rc.local, the scanner tries to read. Thus resulting in an java.util.NoSuchElementException.

What do I need to do, to read a keyboard input in rc.local? Thanks...

Answer 1

1. NoSuchElementException is thrown when you attempt to read from a stream that has no (more) characters to be read.

2. The getConsole() method is defined to return null when there is no interactive "console" available.

When you are executing an application from an "rc.local" script on a Raspberry Pi, that (presumably) happens before there is a console configured for you to read from. That is most likely an OS limitation. (There is a similar limitation in classic Linux systems, etc)

What do I need to do, to read a keyboard input in rc.local?

I suspect that what you need to do is to have your "rc.local" script launch a virtual console and run the java application from that.