How to get PID of java.lang.Process in linux by JAVA

I think out two method to resolve this question but they can’t reach the expectation .

1. I use the ‘Process’ to exec “ps -ef”

   I can through this method to get all lines and I can filter them by my running command.But If I have many same command process.This isn’t work.

2. I use the JNA to get PID

    Field field = null;
    Integer pid = -1;
    try {
        Class clazz = Class.forName("java.lang.UNIXProcess");
        field = clazz.getDeclaredField("pid");
        field.setAccessible(true);
        pid = (Integer) field.get(process);
    } catch (Throwable e) {
        e.printStackTrace();
    }

This way only can get the PID of running window. It isn’t the true PID of process.

what should I do?

Thanks!

Answer

Java 9

Java 9 introduces a number “nice” changes, one is the inclusion of the native PID of a Process – see Process#pid for more details

import java.io.IOException;
import java.io.InputStream;

public class Test {

    public static void main(String[] args) throws IOException, InterruptedException {
        ProcessBuilder pb = new ProcessBuilder("/Applications/Xcode.app/Contents/MacOS/Xcode");
        pb.redirectErrorStream(true);
        Process p = pb.start();
        // Yes, I'm a bad developer, but I just want to demonstrate
        // the use of the PID method :/
        new Thread(new Consumer(p.getInputStream())).start();
        System.out.println("PID = " + p.pid());
        p.waitFor();
        System.out.println("Exit with " + p.exitValue());
    }

    public static class Consumer implements Runnable {
        private InputStream is;

        public Consumer(InputStream is) {
            this.is = is;
        }

        @Override
        public void run() {
            try {
                int value = -1;
                while ((value = is.read()) != -1) {
                    // I'm ignoring it for brevity
                }
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }
    }

}

You can also obtain a reference to the ProcessHandle for the Process via the Process#toHandle method, which is kind of nice