Skipping a pause command in a batch file when executing from a Java Process

Question

Sorry if this is a duplicate, but no other solution has worked.

I'm trying to write a Java app that will call a batch file, print out what the batch file is doing, and wait for it to finish execution, then do whatever else. I've read that sending a linefeed through Process.getOutputStream() would trigger the "Press any key to continue..." prompt, but it's not doing it for me.

Here's my test.bat:

@echo off
echo This is a test batch file.
echo This text should be readable in the console window
echo Pausing...
pause
echo done.
exit

And here is my Java driver:

public class Tester {

    String cmd[] = { "cmd", "/c", "C:/Test Folder/test.bat" };

    BufferedReader in = null;
    BufferedWriter out = null;
    Process p = null;

    public Tester() {
        System.out.println( "Starting process..." );
        ProcessBuilder pb = new ProcessBuilder( cmd ).redirectErrorStream( true );
        try {
            p = pb.start();
            System.out.println( "Started process " + p.hashCode() );
            in = new BufferedReader( new InputStreamReader( p.getInputStream() ) );
            out = new BufferedWriter( new PrintWriter( p.getOutputStream() ) );
            String line = "";
            while ( ( line = in.readLine() ) != null ) {
                System.out.println( "INFO [" + p.hashCode() + "] > " + line );

                // Wait for "Press any key to continue . . . from batch"

                if ( line.startsWith( "Press" ) ) {
                    System.out.println( "INFO [ SYS ] > Script may have called PAUSE" );
                    out.write( "\n\r" );
                }
            }
            int e = p.waitFor();
            if ( p.exitValue() != 0 )
                System.err.println( "Process did not finish successfully with code " + e );
            else
                System.out.println( "Process finished successfully with code " + e );
        } catch ( IOException ioe ) {
            System.err.println( "I/O: " + ioe.getMessage() );
        } catch ( InterruptedException ie ) {
            System.err.println( "Interrupted: " + ie.getMessage() );
        } catch ( Exception e ) {
            System.err.println( "General Exception: " + e.getMessage() );
        } finally {
            try {
                in.close();
                out.close();
                p.destroy();
            } catch ( Exception e ) {
                System.err.println( "Error closing streams: " + e.getMessage() );
            }
        }
        System.out.println( "Tester has completed" );
    }
    public static void main( String[] args ) {
        new Tester();
    }
}

In the while loop, it'll print out:

Starting process...
Started process 2018699554
INFO [2018699554] > This is a test batch file.
INFO [2018699554] > This text should be readable in the console window
INFO [2018699554] > Pausing...

And never go pass the pause statement. I've tried redirecting error output, sending VK_ENTER, and sending random keys all to no avail.

Any ideas?

Answer 1

With buffered writers, you have to flush the buffer before they actually write. Call out.flush() after out.write().