Fork off a process and specify a timeout value for it to complete in Java

I have a personal preference to code in C/C++ or Java. However, I'll swap between any other programming language I know if I think it will solve my problem. For what it's worth, people often get frustrated when they ask me what language is the best (or worse, or most important, etc..) because I'll often ask them what they know best, and state that as my answer.

Anyhow, I've had this need to interact with a couple of programs that have no API whatsoever. My solution has been to run the suckers and grab their output. For that reason, I got to learn a bit about how to execute a command in a separate process in Java. Through a class called ProcessBuilder (java.lang package), it allows one to get the input or output stream of the subprocess, as well as the exit status (among other available information).

Quick example:

import java.io.*;
import java.util.*;
public class MyExample {
  public static void main(String args[]) throws IOException {
    if (args.length <= 0) {
      System.err.println("What should I run?");
      System.exit(-1);
    }
    Process process = new ProcessBuilder(args).start();
    InputStream is = process.getInputStream();
    InputStreamReader reader = new InputStreamReader(is);
    BufferedReader buffer = new BufferedReader(reader);
    String line;
    System.out.printf("Output of running %s is:", Arrays.toString(args));
    while ((line = buffer.readLine()) != null) {
      System.out.println(line);
    }
  }
} 

And while I won't go into details of how to customize your ProcessBuilder inputs, you can try this out with > java MyExample ls.

My problem is that the software I'm executing in the subprocess, forks other threads and processes. Which screws up the process' signaling in Java. So I actually do the process forking in another C-based software I coded, and use Java to call that one. (Complicated tongue-twister, right?) But, this requires that the Java process waits until my C code finishes, which has to wait until the other programs finishes. For that reason, I had to include a  process.waitFor(); right after the start command.

This leads to the title of this post: How to specify a time out value to the waitFor()? Apparently waitFor() has no timeout. Which means that I need to create yet another Thread just to wait for it, and join both of the after the timeout expires.

1. Thread thread = new Thread(new Runnable()  
2. {  
3.     public void run()  
4.     {  
5.         try  
6.         {  
7.             process.waitFor();  
8.         }  
9.         catch (Exception e) { e.printStackTrace(); }  
10.     }  
11. });  
12. thread.start();  
13. thread.join(15000); // 15 seconds  

It's one of those things that I'm not necessarily bragging about, but not ashamed either. And most importantly, I don't want to forget. :)