title: Unix shell script to sort files depending on the 'date string' present in their file name
body: <p>I am trying to sort files in a directory, depending on the 'date string' attached in the file name, for example files looks as below
  <code>SSA_F12_05122013.request.done</code>
  <code>SSA_F13_12142012.request.done</code>
  <code>SSA_F14_01062013.request.done</code>
  Where 05122013,12142012 and 01062013 represents the dates in  format.
  Please help me in providing a unix shell script to sort these files on the date string present in their file name(in descending and ascending order).</p>
  
  <p>Thanks in advance.</p>