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I want to program a chess GUI in Java. The user can enter a move and then I want the program to make a move. Therefore I'll use an UCI (Universal Chess Interface). An UCI is a terminal/command line application (I'm using Mac OS X and Terminal) that calculates the best move in a position. Now what I need to do is write and read to this terminal application.

For example: I want the best move for a certain position, so I type: "go" (calculates the best move)

Let's say I get this answer: "e2e4" (means moving the Pawn (that's a piece in chess) from the e2-square to the e4-square)

Now I need to read that "e2e4" and then ask the user for his next move. So i kinda need to loop through these steps all the time until there is a checkmate: 1. Ask for a move 2. Calculate best response

I've already seen a lot of other StackOverflow questions asking the same question: How to run a command and get its output in Command Line/Terminal. But all answers only use one command, as for instance runtime.exec("ls"); But that's only one command. What I want is to enter a command, get the response, execute another command and so on, so basically I need to communicate with Mac OSX' Terminal app (alternating input and output). How do I accomplish that in Java?

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3 Answers 3

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You could execute the command that runs the chess program, and then check the command's output for the best move (using a Process).

For example:

String move = null;
Process process = Runtime.getRuntime().exec("go");
BufferedReader reader = new BufferedReader(new InputStreamReader(process.getOutputStream()));
move = reader.readLine();
// 'move'  now holds a reference to the chess program's output, or null if there was none.
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1

Just look up the return type of Runtime.exec(). It returns a java.lang.Process.

It offers two methods for input and output streaming: getOutputStream() and getInputStream()

You can read and write to the opened Process for ex. with BufferedReaders / BufferedWriters.

For Example: (see also https://stackoverflow.com/a/14745245/2358582)

import java.io.*;

public class c {
    public static void main(String[] args) throws Exception{
        Process p = Runtime.getRuntime().exec("cmd");
        BufferedReader inp = new BufferedReader(new InputStreamReader(p.getInputStream()));
        BufferedWriter out = new BufferedWriter(new OutputStreamWriter(p.getOutputStream()));

        //communication
        setUpStreamGobbler(p.getInputStream(), System.out);
        out.write("cmd\n");
        out.flush();
    }

    public static void setUpStreamGobbler(final InputStream is, final PrintStream ps) {
        final InputStreamReader streamReader = new InputStreamReader(is);
        new Thread(new Runnable() {
            public void run() {
                BufferedReader br = new BufferedReader(streamReader);
                String line = null;
                try {
                    while ((line = br.readLine()) != null) {
                        ps.println("process stream: " + line);
                    }
                } catch (IOException e) {
                    e.printStackTrace();
                } finally {
                    try {
                        br.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }
        }).start();
    }
}

Outputs:

process stream: Microsoft Windows [Version 6.1.7601]
process stream: Copyright (c) 2009 Microsoft Corporation. Alle Rechte vorbehalte
n.
process stream:
process stream: P:\Java\ExcecuteFile>cmd
process stream: Microsoft Windows [Version 6.1.7601]
process stream: Copyright (c) 2009 Microsoft Corporation. Alle Rechte vorbehalte
n.
process stream:
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7 Comments

This does not work, an Intellij IDEA marks this error: Error:(16, 30) java: no suitable constructor found for BufferedReader(java.io.OutputStreamWriter) constructor java.io.BufferedReader.BufferedReader(java.io.Reader) is not applicable (actual argument java.io.OutputStreamWriter cannot be converted to java.io.Reader by method invocation conversion) constructor java.io.BufferedReader.BufferedReader(java.io.Reader,int) is not applicable (actual and formal argument lists differ in length)
I found the error: should be BufferedWriter in the code
Now all is working fine, how do I output the result to the console? (using System.out.println()?)
Always try to think before post :) Yes you can output it with System.out.println(buf);
No, but it is not working, the out.write("command") is not executed
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I believe that this question might help you: I asked something similar, I hope that this will answer your question

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