get matrix

IN OPEN INVENTOR: I want to retrieve the cumulative matrix within the scene graph. Say, after several transformations and before the objects drawing, I want to know what’s the exact position in the world coordniate system.
Use SoGetMatrixAction or other functions?
But the documentation is too simple to use this kind function and other stuff like SoPath…
Some simple code will be greatly appreciated.

because very few people in high API furums, have to ask here for kind help.