title: What are double colons :: in a shell script?
body: <p>What is double colon <code>::</code> in shell scripts? like this piece of script:</p>
  
  <pre><code>function guess_built_binary_path {
    local hyperkube_path=$(kube::util::find-binary "hyperkube")
    if [[ -z "${hyperkube_path}" ]]; then
      return
    fi
    echo -n "$(dirname "${hyperkube_path}")"
  }
  </code></pre>
  
  <p>I found it in here: </p>
  
  <p><a href="https://github.com/kubernetes/kubernetes/blob/master/hack/local-up-cluster.sh" rel="noreferrer">https://github.com/kubernetes/kubernetes/blob/master/hack/local-up-cluster.sh</a></p>