title: grep any word with any groups of (non-overlapping) consecutive letters
body: <p>I am trying to grep any word that has any specified groups of consecutive letters, and those groups must not overlap. To be specific, for example ,say I want to find 2 groups of consecutive letters, I have tried the following command, but it didn't work.
  PS: sample is a txt file that contains a word in each line.</p>
  
  <pre><code>grep -iE '.*([a-z])\1..*([a-z])\1.*' sample
  </code></pre>