Wait for process to finish before proceeding in Java

Question

Essentially, I\'m making a small program that\'s going to install some software, and then run some basic commands afterwards to prep that program. However, what is happening

Answer 1

If you are running a system command that returns a very long response string, stdin buffer fills up and the process appears to hang. This happened to me with sqlldr. If that appears to be the case then just read from stdin as the process is running.

    try {
        ProcessBuilder pb = new ProcessBuilder("myCommand");
        Process p = pb.start();
        BufferedReader stdInput = new BufferedReader(new 
                InputStreamReader(p.getInputStream()));

        BufferedReader stdError = new BufferedReader(new 
                InputStreamReader(p.getErrorStream()));
        StringBuffer response = new StringBuffer();
        StringBuffer errorStr = new StringBuffer();
        boolean alreadyWaited = false;
        while (p.isAlive()) {
            try {
                if(alreadyWaited) {

                    // read the output from the command because
                    //if we don't then the buffers fill up and
                    //the command stops and doesn't return
                    String temp;

                    while ((temp = stdInput.readLine()) != null) {
                        response.append(temp);
                    }


                    String errTemp;
                    while ((errTemp = stdError.readLine()) != null) {
                        errorStr.append(errTemp);
                    }                                                   
                }
                Thread.sleep(1000);
                alreadyWaited = true;
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            logger.debug("Response is " + response);
            logger.debug("Error is: " + errorStr);
        }

    } catch (IOException e) {
        logger.error("Error running system command", e);
    }