title: xxd output only the binary
body: <p>Using the command :</p>
  
  <p><code>xxd -b some_text</code></p>
  
  <p>will output the binary representation and the original text:</p>
  
  <pre><code>000054c: 11101111 10100001 10110110 00010000 01011011 10000110  ....[.
  0000552: 01111000 11001000 01010101 11000101 11101111 10101111  x.U...
  0000558: 10010111 11101010 00011001 01010100 10101010 10001110  ...T..
  </code></pre>
  
  <p>How can I have the utility output only the binary without anything else?</p>