Output styles available:

name | description
--- | ---
list | display a full list of all violations, with preview of the current item (large dialog)
simple | a small & simple dialog that navigates the user through the violations one by one, sequentially
print | print the list to stdout in human readable form
log | print the list as INFO lines in the log in human readable form
dump | print the list to stdout in script readable form

Note that the design rule check uses the current board rule settings, not the current style settings.