title: Sed replace asterisk symbols
body: <p>I'm am trying to replace a series of asterix symbols in a text file with a -999.9 using sed. However I can't figure out how to properly escape the wildcard symbol.</p>
  
  <p>e.g.</p>
  
  <pre><code>$ echo "2006.0,1.0,************,-5.0" | sed 's/************/-999.9/g'
  sed: 1: "s/************/-999.9/g": RE error: repetition-operator operand invalid
  </code></pre>
  
  <p>Doesn't work. And</p>
  
  <pre><code>$ echo "2006.0,1.0,************,-5.0" | sed 's/[************]/-999.9/g'
  2006.0,1.0,-999.9-999.9-999.9-999.9-999.9-999.9-999.9-999.9-999.9-999.9-999.9-999.9,-5.0
  </code></pre>
  
  <p>puts a -999.9 for every * which isn't what I intended either.</p>
  
  <p>Thanks!</p>