title: how to break one column into multiple columns in Linux
body: <p>I want to break a column into different rows. e.g.,</p>
  
  <pre><code>test.dat
  1
  4
  3
  4
  6
  2
  4
  6
  8
  </code></pre>
  
  <p>What I want is to break it into a 3 x 3 matrix</p>
  
  <pre><code>out.dat
  1   4   4
  4   6   6
  3   2   8
  </code></pre>