def shell_out command=nil
      $shell_history ||= []
      command ||= get_string("Enter system command:", :maxlen => 50) do |f|
        require 'canis/core/include/rhistory'
        f.extend(FieldHistory)
        f.history($shell_history)
      end
      ##w = @window || @form.window
      #w.hide
      Ncurses.endwin
      ret = system command
      Ncurses.refresh
      #Ncurses.curs_set 0  # why ?
      #w.show
      return ret
    end
def shell_out command=nil
      $shell_history ||= []
      command ||= get_string("Enter system command:", :maxlen => 50) do |f|
        require 'canis/core/include/rhistory'
        f.extend(FieldHistory)
        f.history($shell_history)
      end
      ##w = @window || @form.window
      #w.hide
      Ncurses.endwin
      ret = system command
      Ncurses.refresh
      #Ncurses.curs_set 0  # why ?
      #w.show
      return ret
    end
takes a unix command (system) and executes the same. No output
 @return return value of system command