Make multiple-select to adjust its height to fit options without scroll bar

Question

Apparently this doesn\'t work:

   select[multiple]{
     height: 100%;
   }

it makes the select have 100% page height...

auto

Answer 1

select could contain optgroup which takes one line each:

  
    1
  
  
    2
    3
  

In this example total size is (1+1)+(1+2)=5.