Xlib provides functions that you can use to obtain, change, update, or interchange window properties. In addition, Xlib provides other utility functions for inter-client communication (see "Inter-Client Communication Functions").
To obtain the type, format, and value of a property of a given window, use XGetWindowProperty().
To obtain a given window's property list, use XListProperties().
To change a property of a given window, use XChangeProperty().
To rotate a window's property list, use XRotateWindowProperties().
To delete a property on a given window, use XDeleteProperty().