!How_exec_works_in_Java.md

Non-blocking

The System.lang.Runtime.exec() method is non-blocking, so you call it and it spawns a background process.

Unfortunately the java.lang.Process thingy in Java 8 has no way to get a PID, so you need a cheesy hack to find it.

Main.java

/* javac Main.java && CLASSPATH=. java Main */

import java.lang.Runtime;
import java.lang.Process;
import java.io.InputStreamReader;
import java.io.BufferedReader;

public class Main {
    public static void main(String[] args) throws Exception {
        System.out.println("Here we go");
        String commandLine = "./yoyoyo.sh";
        Runtime.getRuntime().exec(commandLine);
        Process proc = Runtime.getRuntime().exec("ps aux");
        BufferedReader br = new BufferedReader(new InputStreamReader(proc.getInputStream()));
        int pid = -1;
        String line = null;
        while ((line = br.readLine()) != null) {
            String cmd = line.substring(65);
            if (commandLine.equals(cmd) || ("/bin/sh " + commandLine).equals(cmd)) {
                String[] fields = line.split(" +");
                pid = Integer.parseInt(fields[1]);
                break;
            }
        }
        System.out.println(pid);
    }
}

yoyoyo.sh

#!/bin/sh

sleep 5
touch yoyoyo.txt