Runtime exec() Problem, change working dir

Question

Hi!
I have following problem:
I want to call an executable from my home-directory under Linux this way:
Runtime rt = Runtime.getRuntime();
Process pr = rt.exec("/home/tom/prog/exec-command");
Unfortunately I'm getting either exception "file not found" (but it's there) or no complain but no program run...
perhaps something's wrong with the path-name?
If I call the program in the directory with a shell it works fine.
Would be very happy if anybody can give a hint!
Thanks a lot,
Manuel

Answer 1

You are interested in the programs output? Does it write to stdout or stderr or both? In any case, my advice is to go multithreading and use one thread to wait for the program to exit, one to read stdout and one to read stderr. If you just use one thread for reading, the program might block. I normally use something like this:
  final int BUFFER = 2048;
  final Process p = Runtime.getRuntime().exec(args);
  //read standard out output of the external executable
  //in seperate thread to avoid I/O deadlocks
  new Thread()
    public void run()
       try
         BufferedInputStream in =  new BufferedInputStream (p.getInputStream());
         int i;
         byte[] buf = new byte[BUFFER];
         while ( (i = in.read(buf, 0, BUFFER)) != -1 )
            System.out.write(buf, 0, i);
         in.close();
       catch (IOException e)
         e.printStackTrace();
  }.start();
  //read standard error output of the external executable
  //in seperate thread for symmetry
  new Thread()
    public void run()
       try
         BufferedInputStream in =  new BufferedInputStream (p.getErrorStream());
         int i;
         byte[] buf = new byte[BUFFER];
         while ( (i = in.read(buf, 0, BUFFER)) != -1 )
            System.err.write(buf, 0, i);
         in.close();
       catch (IOException e)
         e.printStackTrace();
  }.start();
  //Wait for the external process to finish     
  int exitCode = p.waitFor();          
  if ( exitCode != 0 )
    throw new IOException("Executable stopped with error code "+exitCode); Cheers, HJK