To set a window's WM_ICON_NAME property, use XSetWMIconName().
To read a window's WM_ICON_NAME property, use XGetWMIconName().
The next two functions have been superseded by XSetWMIconName() and XGetWMIconName(), respectively. You can use these additional convenience functions for window names that are encoded as STRING properties.
To set the name to be displayed in a window's icon, use XSetIconName().
To get the name a window wants displayed in its icon, use XGetIconName().