Listening to console command output

Question

I want to run a console command in my Java application which listens for incoming messages and logs to the console when it receives one. The console command runs fine when I execute it in the terminal. So I want to run the command and then do something when it outputs a line and after that keep on running and listen for other new messages. I tried this through the following code:

try {
    ProcessBuilder builder = new ProcessBuilder(PYTHON_PATH, YOWSUP_CLI_PATH, "demos", "-r", "-c", YOWSUP_CONFIG);
    builder.redirectErrorStream(true);
    Process p = builder.start();
    BufferedReader reader = new BufferedReader(new InputStreamReader(p.getInputStream()));

    String line = "";
    log.info("Started listening...");

    // It does nothing from here on
    while ((line = reader.readLine()) != null) {
        log.info(line);
    }
    log.info("Stopped listening.");
} catch (Exception e) {
    e.printStackTrace();
}

But when I run this code, it logs the "Started listening..." string, so I send a message to try it out but it doesn't log anything and just keeps on running without doing anything.

If I didn't explain something correctly just say so!

Answer 1

I fixed it using the "-u" parameter in my command, using this answer from MadProgrammer.