Finding the key symbol used for a keyboard key in X11
In X11, each keyboard key has a macro defined for it in /usr/include/X11/keysymdef.h .
In order to find out the key symbol for a desired keyboard key to use in software like dwm, you can run the debugging tool xev.
The reason to use xev over just looking at /usr/include/X11/keysymdef.h , is that sometimes keys that are used in combination with other keys ( Like for example Alt+Shift ) produce different key symbols than when used alone, this is especially true for numpad keys.
However since xev outputs a lot of other debugging information that we do not need, it is recommended to run the following command instead:
xev 2>&1 | grep -F keysym