title: How to print week number of previous week in shell
body: <p>Can anyone please help me to get the previous week number ?</p>
  
  <p>I tried following before askign this here.</p>
  
  <p>This one works but not able to couple it with year number.</p>
  
  <pre><code>echo `date +%W `-1 | bc``
  2
  </code></pre>
  
  <p>Here are the failures I am getting while coupling year and previous week number</p>
  
  <pre><code>echo `date +%Y`wk`date +%W `-1 | bc``
  (standard_in) 1: parse error
  
  echo "`date +%Y`wk`date +%W `-1 | bc``"
  2016wk03-1 | bc
  </code></pre>
  
  <h1>Outupt desired :</h1>
  
  <p>CUrrentYEARwkPREVIOUSWEEK</p>
  
  <p>like </p>
  
  <pre><code>2016wk02
  </code></pre>
  
  <p><strong>Note: I am trying to get this done using oneliner , trying to avoide use of variable here.</strong> </p>