How do I find the X window ID under the mouse pointer in bash?

Question

From a bash script, is there some way to get the ID of the X window under the mouse pointer?

(edit) I need the process to be non-interactive.

Answer 1

xdotool exposes the pointer location (xdotool getmouselocation). None of xdotool, xwininfo or wmctrl appear to have a way to match a window by a screen position where it's visible.

The underlying X library call is XQueryPointer (corresponding to a QueryPointer message). Here's a simple Python wrapper script around this call (using ctypes). Error checking largely omitted. Assumes you're using screen 0 (if you didn't know that displays could have more than one screen, ignore this).

#! /usr/bin/env python
import sys
from ctypes import *
Xlib = CDLL("libX11.so.6")
display = Xlib.XOpenDisplay(None)
if display == 0: sys.exit(2)
w = Xlib.XRootWindow(display, c_int(0))
(root_id, child_id) = (c_uint32(), c_uint32())
(root_x, root_y, win_x, win_y) = (c_int(), c_int(), c_int(), c_int())
mask = c_uint()
ret = Xlib.XQueryPointer(display, c_uint32(w), byref(root_id), byref(child_id),
                         byref(root_x), byref(root_y),
                         byref(win_x), byref(win_y), byref(mask))
if ret == 0: sys.exit(1)
print child_id.value

Usage example:

xwininfo -tree -id $(XQueryPointer)

Answer 2

The xwininfo command gives this kind of output, but you do have to click on the window you want info on:

% xwininfo
xwininfo: Please select the window about which you
          would like information by clicking the
          mouse in that window.

xwininfo: Window id: 0xa0000d "flask"

...

So doing: xwininfo | grep 'Window id:' might give you something you can parse the ID out of.

Answer 3

try this, it uses only xdotool, but its version is at least "2.20110530.1"

eval `xdotool getmouselocation --shell 2>/dev/null |grep WINDOW`
echo $WINDOW

to get the window id directly you can use this:

sedGetValue='s".*=\(.*\)"\1"'
windowId=`xdotool getmouselocation --shell 2>/dev/null |grep WINDOW |sed "$sedGetValue"`
echo $windowId

Answer 4

I toyed around with the answer from Peter.O and came up with:

xdotool click 1|xwininfo|grep 'Window id:'