Redirect process output to stdout

Question

I would like to execute foo.bat from within a Groovy program and have the resulting process' output redirected to stdout. Either a Java or Groovy code example would be fine.

foo.bat can take several minutes to run and generates a lot of output, so I would like to see the output as soon as it is generated, rather than having to wait until the process has completed before seeing all the output at once.

Answer 1

It is simple to redirect all your stream to standard output using inheritIO() method. This will print the output to the stdout of the process from which you are running this command.

ProcessBuilder pb = new ProcessBuilder("command", "argument"); pb.directory(new File(<directory from where you want to run the command>)); pb.inheritIO(); Process p = pb.start(); p.waitFor(); 

There exist other methods too, like as mentioned below. These individual methods will help redirect only required stream.

    pb.redirectInput(Redirect.INHERIT)     pb.redirectOutput(Redirect.INHERIT)     pb.redirectError(Redirect.INHERIT) 

Answer 2

This uses a class which reads all output the executed program generates and displays it in it's own stdout.

class StreamGobbler extends Thread {     InputStream is;      // reads everything from is until empty.      StreamGobbler(InputStream is) {         this.is = is;     }      public void run() {         try {             InputStreamReader isr = new InputStreamReader(is);             BufferedReader br = new BufferedReader(isr);             String line=null;             while ( (line = br.readLine()) != null)                 System.out.println(line);             } catch (IOException ioe) {             ioe.printStackTrace();           }     } }  Runtime rt = Runtime.getRuntime(); Process proc = rt.exec("javac"); //output both stdout and stderr data from proc to stdout of this process StreamGobbler errorGobbler = new StreamGobbler(proc.getErrorStream()); StreamGobbler outputGobbler = new StreamGobbler(proc.getInputStream()); errorGobbler.start(); outputGobbler.start(); proc.waitFor();