title: Curly braces in awk reg exp
body: <p>I am trying to match a fixed number of digits using curly braces in <code>awk</code>but I get no result.</p>
  
  <pre><code># This outputs nothing
  echo "123" | awk '/^[0-9]{3}$/ {print $1;}' 
  
  # This outputs 123
  echo "123" | awk '/^[0-9]+$/ {print $1;}' 
  </code></pre>
  
  <p>Do I need to do something specific to use curly braces?</p>