title: bash: extract double from string
body: <p>I have this string in bash:</p>
  
  <pre><code>str=sdk.iphoneos4.1.sdk
  </code></pre>
  
  <p>and I would like to have a variable with '4.1' in it</p>
  
  <p>is there any way to parse a float/double value in bash ?</p>