I want to know the process ID of a particular window. I have seen and used the Force close panel applet, and I'd like something similar that would report me the process ID of the window I select.
If a tool for this purpose exists, that'd be great. Although, I am willing even to write a simple python script if it can be done.
Edit: In a more specific case, I want to get the process ID of a java swing window. (The
xprop solution some answers suggest is not working).