# File vpp, line 316
def find_viewer
  if @viewer 
    # before looking for this program, strip off any arguments:
    executable(@viewer.split.shift) or
      quit("\#{@viewer} was specified for viewing\nin an rc file, but is was not found in PATH\n(rc files: \#{@rcfiles}\n",1)
  else
    VIEWERS.each do |v|
      if executable(v)
        @viewer = v
        break
      end
    end
    @viewer or quit("no valid pdf viewer could be found",1)
  end
end