Linux: Get WM_CLASS of Window

Objective: Get the WM_CLASS property of a X Window application on Linux.

The WM_CLASS property and various other properties are used by X window managers to track applications and to retrieve the application’s resources from the resource database.

To retrieve the WM_CLASS property of an application, for example, Google Chrome, run the following command on the terminal.

The mouse pointer would have changed after running xprop to indicate that it’s waiting for input. Use the mouse to select the target window. Below is the output that I got after selecting Android Studio IDE window.

If you are having issues with application icons not displaying correctly on Linux, most probably it has something to do with window matching using WM_CLASS property. Most Java applications running on Linux are affected by this issue.

You can manually define the WM_CLASS property of an application by modifying the appropriate desktop entry file. Desktop entries for applications, or .desktop files, are generally a combination of meta information resources and a shortcut of an application. These files usually reside in /usr/share/applications or /usr/local/share/applications for applications installed system-wide, or ~/.local/share/applications for user-specific applications. User entries take precedence over system entries.

Below is the config of my android-studio.desktop file that is used to launch Android Studio. The WM_CLASS property is set to jetbrains-studio using the StartupWMClass property.

Without the StartupWMClass line, Docky (application shortcut bar that I am using) was not matching the window properly – both the name and icon were incorrect.