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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?

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2 Answers 2

up vote 9 down vote accepted

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

Sources:

http://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/

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

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1  
+1 for the nice answer. If the PID is of a child of the main application, you can suggest the use of pstree -a -s -l -p -u $PID which is quite nice... –  Rmano Aug 8 at 9:48
    
@Rmano: Oh, that's neat! I added it to the answer. –  Glutanimate Aug 8 at 10:04
    
The echo $() in your commands isn't necessary. –  Dennis Williamson Aug 8 at 15:08
    
@DennisWilliamson Thanks for the pointer. Edited. –  Glutanimate Aug 8 at 15:20
    
Perfect! didn't know this option of xdotool –  Jacob Vlijm Aug 31 at 19:57

You can create a keyboard-shortcut with this command:

zenity --info --text $(xprop $win_id WM_CLASS | cut -d" " -f4-)
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1  
That's a very nice solution, +1. However, one smaller issue: if the application doesn't assign a proper WMCLASS (which is oftentimes the case with cryptic dialogs), xprop won't be of any help. –  Glutanimate Aug 8 at 9:02
    
Did you have an example for an application (popup) that didn't work, thank you. –  TuKsn Aug 8 at 9:06
1  
I don't have anything specific at hand but I do remember having issues with several Java applications and other obscure programs that didn't have WMCLASS set (or set to something generic like java-window). I ran into these kinds of issues a while ago when I was trying to implement application-specific rules in my window manager configuration. –  Glutanimate Aug 8 at 9:09
1  
You are right there is a similar problem with apps created with qml/qt -> bugreports.qt-project.org/browse/QTBUG-29396 –  TuKsn Aug 8 at 9:24

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