function! GrepOperator(type, ...)
  " We will select and yank to perform the operation.
  " So, saving the previous selection and default register
  " content, so that we can reset it after the operation is complete.
  let sel_save = &selection
  let &selection = "inclusive"
  let reg_save = @@

  if a:0  " Invoked from Visual mode, use gv command.
    silent exe "normal! gvy"
  elseif a:type == 'line'
    silent exe "normal! '[V']y"
  else
    silent exe "normal! `[v`]y"
  endif

  " Grep and open if there are results
  execute "silent grep ". shellescape(@@) ." | cwindow"

  " Restore the default register content and previous selection
  let &selection = sel_save
  let @@ = reg_save
endfunction

nnoremap <silent> ,n :set opfunc=GrepOperator<CR>g@
vnoremap <silent> ,n :<C-U>call GrepOperator(visualmode(), 1)<CR>