# Overview

W window has a `_NET_WM_PID` property set by the applicaiton. To really validate if the application has set this correctly is more work (see reference).

## Simple Example

Run command and click the window

```
$ xprop _NET_WM_PID
_NET_WM_PID(CARDINAL) = 11524
```

Get process info

```
$ ps -p 11524 -f
UID        PID  PPID  C STIME TTY          TIME CMD
a211278l 11524     1  1 11:10 tty2     00:00:06 /usr/bin/gnome-system-log
```


## Reference 

[StackExchange - What process created this X11 window?](http://unix.stackexchange.com/questions/5478/what-process-created-this-x11-window)