title: grepping multiple lines from a file
body: <p>I would like to grep in order multiple lines of a file.
  An example of the file <code>originalfile.txt</code> could be:</p>
  
  <pre><code>num=12
  workers not specified
  length= 128
  Using array element 
  num= 24 
  workers not specified
  length= 128
  Using array element 
  ......
  </code></pre>
  
  <p>I want to <code>grep</code> only valuable lines like all those with <code>num</code> and <code>length</code>:</p>
  
  <pre><code>num=12
  length= 128
  num= 24 
  length= 128
  ......
  </code></pre>
  
  <p>I know how to <code>grep</code> for just one pattern, say <code>num</code> but I don't know how to do it for more than one pattern.</p>
  
  <pre><code>$ grep "num" originalfile.txt
  </code></pre>
  
  <p>It turns out that I have some parameters in the same line that  <code>awk</code> does not seem to find,i.e:</p>
  
  <p><code>.... time=  1.234 Gflop/s=  3.4556  .....</code></p>
  
  <p>It filters the first one, but not Gflop/s. Is there a way to recursvely find on the same line?</p>