Window Management – How to Find Out the Application Under the Mouse

window-management

It often happens to me, that an application pops up a question and I wonder to which exact application this window belongs, because if I look in the Launcher there is no application that currently has focus (no white triangle on the right side of the icon when I focus the message window)

Is there a way to find out the belonging of an open window?

Best Answer

Using xdotool

First make sure xdotool is available on your system:

sudo apt-get install xdotool

The following command will print the process name of the window currently in focus:

cat "/proc/$(xdotool getwindowpid "$(xdotool getwindowfocus)")/comm"

To give yourself more time to focus the window / click on it you can prepend a small sleep duration:

sleep 5 && cat "/proc/$(xdotool getwindowpid "$(xdotool getwindowfocus)")/comm"

The process name should be displayed after a short amount of time.

Using wininfo

Wininfo is a graphical utility that displays various information on windows and their properties, including the PID (process ID) associated with the window:

image of PID in wininfo

wininfo should be available in the official repositories:

sudo apt-get install wininfo

Having determined the PID of the window you can then look up the process name associated with it. There are various ways to do this, e.g. by looking at /proc:

$ cat /proc/17002/comm
gnome-terminal

This would be the process name associated with the PID 17002.

A more elegant way that allows inspecting the process tree context, as suggested by @Rmano:

$ pstree -a -s -l -p -u 17002
init,1
  └─lightdm,1900
      └─lightdm,3202 --session-child 12 19
          └─lxsession,3307,glutanimate -s LXDE -e LXDE
              └─openbox,3362 --config-file /home/glutanimate/.config/openbox/lxde-rc.xml
                  └─gnome-terminal,17002
                      ├─bash,1841
                      ├─bash,2332
                      ├─bash,2424
                      │   └─pstree,2484 -a -s -l -p -u 17002
                      ├─gnome-pty-helpe,1840
                      ├─{gnome-terminal},1835
                      ├─{gnome-terminal},1836
                      ├─{gnome-terminal},1842
                      └─{gnome-terminal},2269

Of course you can also combine pstree with the xdotool option above (thanks to @rubo77 for pointing this out!):

sleep 2; pstree -spaul $(xdotool getwindowpid "$(xdotool getwindowfocus)")

Sources:

https://unix.stackexchange.com/q/38867/29245

http://www.linuxquestions.org/questions/debian-26/how-to-find-the-process-associated-with-a-top-level-x-window-907125/

https://superuser.com/q/632979/170160

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