Hi,

I call a program with ProcessBuilder.  From
http://www.javaworld.com/javaworld/jw-12-2000/jw-1229-traps.html?page=4
I copied over the class StreamGobbler, to redirect the output.  However,
sometimes this doesn’t work.  I have to do the whole process twice, then
it works.  I’m out of ideas what the cause could be, and don’t know how
to debug this.  The SSCCE I extracted does not work at all, in that it
doesn’t write anything to the output file.  It does write to the
console, though.

I read Roedy’s page on exec() and more.

Any ideas mostly appreciated.  Classes found below.

==StreamGobbler.java==

import java.io.*;

public class StreamGobbler extends Thread {

   private final InputStream is;

   private final String type;

   private final OutputStream os;

   public StreamGobbler(InputStream is, String type, OutputStream
redirect) {
       this.is = is;
       this.type = type + ">";
       os = redirect;
   }

   @Override
   public void run() {
       try {
           PrintWriter pw = null;
           if (os != null) {
               pw = new PrintWriter(os);
           }
           final InputStreamReader isr = new InputStreamReader(is);
           final BufferedReader br = new BufferedReader(isr);
           String line = null;
           while ((line = br.readLine()) != null) {
               if (pw != null) {
                   pw.println(line);
               }
               System.out.println(type + line);
           }
           if (pw != null) {
               pw.flush();
           }
       } catch (final IOException ioe) {
           ioe.printStackTrace();
       }
   }
}

==MonaCaller.java==

import java.io.*;

public class MonaCaller {

   public static void main(String[] args) throws IOException,
           FileNotFoundException, InterruptedException {
       final File automFile = new File("test.out");
       final ProcessBuilder monaCaller = new ProcessBuilder("echo",
"test");
       final Process mona = monaCaller.start();
       final StreamGobbler monaError = new StreamGobbler(
               mona.getErrorStream(), "test error", null);
       final FileOutputStream monaAutomaton = new
FileOutputStream(automFile);
       final StreamGobbler monaOutput = new StreamGobbler(mona
               .getInputStream(), "test output", monaAutomaton);
       monaError.start();
       monaOutput.start();
       mona.waitFor();
       monaAutomaton.close();
   }

}

TIA, H.