Using Commons Exec for context-sensitive execution

Question

What I'm trying to do is simply run a batch file that does some preparatory work necessary for the subsequent commands to be executed successfully (setting environment variables and stuff). To prove this I put together a sample that uses Commons Exec

public class Tester {

    public static void main(String[] args) throws Exception {
        Tester tester = new Tester();
        MyResultHandler handler = tester.new MyResultHandler();
        CommandLine commandLine = CommandLine.parse("bash");
        PipedOutputStream ps = new PipedOutputStream();
        PipedInputStream is = new PipedInputStream(ps);
        BufferedWriter os = new BufferedWriter(new OutputStreamWriter(ps));
        Executor executor = new DefaultExecutor();
        PumpStreamHandler ioh = new PumpStreamHandler(System.out, System.err, is);
        executor.setStreamHandler(ioh);
        ioh.start();
        executor.execute(commandLine, handler);
        os.write("export MY_VAR=test");
        os.flush();
        os.write("echo $MY_VAR");
        os.flush();
        os.close();
    }

    private class MyResultHandler extends DefaultExecuteResultHandler {

        @Override
        public void onProcessComplete(final int exitValue) {
            super.onProcessComplete(exitValue);
            System.out.println("\nsuccess");
        }

        @Override
        public void onProcessFailed(final ExecuteException e) {
            super.onProcessFailed(e);
            e.printStackTrace();
        }
    }
}

But that prints empty string instead of the word "test". Any clues?

Answer 1

Answering my own question based on feedback from another forum. The trick is to add a new line character at the end of each command like this:

 os.write("export MY_VAR=test\n");
 os.flush();
 os.write("echo $MY_VAR\n");