How to monitor external process ran by ProcessBuilder?

Question

This should be rather simple, but I don\'t see anything helpful in JavaDocs.

What I need is to run some external process from my Java code and then be able to monito

Answer 1

I'm not sure I'm understanding the question but one way to do this is to call process.exitValue();. It throws an exception if process has not yet terminated:

/**
 * Returns the exit value for the subprocess.
 *
 * @return  the exit value of the subprocess represented by this 
 *          Process object. by convention, the value 
 *          0 indicates normal termination.
 * @exception  IllegalThreadStateException  if the subprocess represented 
 *             by this Process object has not yet terminated.
 */
abstract public int exitValue();

If you don't mind a hack, you can do something like the following if you are working on a ~Unix system which uses the UNIXProcess class. This does use reflection however:

ProcessBuilder pb = new ProcessBuilder("/bin/sleep", "5");
Process process = pb.start();
// open accessability of the UNIXProcess.hasExited field using reflection
Field field = process.getClass().getDeclaredField("hasExited");
field.setAccessible(true);
// now we can get the field using reflection
while (!(Boolean) field.get(process)) {
    ...
}