xprop is a program that can list and set X11 window properties. Listing properties is really simple: just run
xprop and click on the window that you are interested in, or use the
-id command line parameters to choose the “root” window or a window by ID. What’s not so clear is how the properties can be set; the manual does not give any examples.
In order to set a property you have to define the data format. This consists of the bit-width and data type: for example a string of 8-bit characters is
8s. A 32-bit hexadecimal integer is
32x, these are useful for example for window IDs. The widths and data types that can be used are documented in the manual page.
Here’s a simple example: PulseAudio uses a property called
PULSE_SERVER on the root window to know which audio server is used in the desktop session. To redirect the audio to a PulseAudio server on another host over TCP/IP you can use:
xprop -root -f PULSE_SERVER 8s -set PULSE_SERVER tcp:otherhost:4713