title: grep pattern to exclude negative numbers from file
body: <p>I have been struggling trying to come up with an easier answer to this problem. But still using grep.</p>
  
  <p>I want to grep out the positive (and negative numbers) of myfile.dat. Myfile.dat look like this:</p>
  
  <pre><code>-1.4987 4.1354  -8.1235
  4.2322  -0.9842 -2.6845
  3.6845  1.5132  -2.8452
  0.0122  9.3542  -1.2354
  -7.2127 -1.1253 -4.3967
  0.3535  7.2416  -3.1277
  </code></pre>
  
  <p>No need to retain column format.
  So I have used the following grep patterns.</p>
  
  <p>Negative numbers:</p>
  
  <pre><code>grep -E -o [-][0-9]+.[0-9]+ myfile.dat
  </code></pre>
  
  <p>Positive numbers (here I have to pipe all numbers into another grep):</p>
  
  <pre><code>grep -Eo [-]\?[0-9]+.[0-9]+ myfile.dat | grep -v [-]
  </code></pre>
  
  <p>Here comes the question!
  Is there a grep pattern that allows me to extract positive numbers directly, without the use of a second grep command? </p>
  
  <p>This is all about the pattern, not whether I could use another command.</p>