python - Java: is there a way to run a system command and print the output during execution?

Question

I have a python script and it takes a long time to finish. I would like to run it from Java, but also output the script's output while it is executing, so that I can tell if it is properly running.

I've searched and only found examples where we output the output after the system command has finished, rather than during its execution.

Any way to do it while the script is running?

Here's what I have

public void doSomething() throws IOException {
    String[] callAndArgs = {"python", "/hi.py"};
    Process p = Runtime.getRuntime().exec(callAndArgs);
    BufferedReader stdInput = new BufferedReader(new InputStreamReader(p.getInputStream()));
    BufferedReader stdError = new BufferedReader(new InputStreamReader(p.getErrorStream()));

    String s;
    while ((s = stdInput.readLine()) != null) {
        System.out.println(s);
    }

    while ((s = stdError.readLine()) != null) {
        System.out.println(s);
    }
}

Answer 1

i managed to get it working like this (Note it requires java7):

package test;
import java.lang.ProcessBuilder.Redirect;

public class Test {

    public static void main(String... args) throws Exception {
        ProcessBuilder pb = new ProcessBuilder("python","/home/foobar/Programming/test/src/test/test.py");
        pb.redirectOutput(Redirect.INHERIT);
        Process p = pb.start();
        p.waitFor();
    }

}

python (note i flush on python to make it work using sys.stdout.flush())

import time,sys
c =0
while c<=50:
    time.sleep(1)
    print("----")
    c = c +1
    sys.stdout.flush()

Note if you don't want to flush in a loop you can use this:

ProcessBuilder pb = new ProcessBuilder("python","-u","/home/foobar/Programming/NetBeansProjects/test/src/test/test.py");

Redirect.INHERIT

Indicates that subprocess I/O source or destination will be the same as those of the current process. This is the normal behavior of most operating system command interpreters (shells).