title: Using curl with OpenWhisk
body: <p>I am trying to use IBM OpenWhisk. It has its own CLI, but I wanted to invoke a simple "echo" sample using <code>curl</code>.</p>
  
  <pre><code>curl -d-data '{"message": "hellow world"}' https://user:password@openwhisk.ng.bluemix.net:443/api/v1/namespaces/whisk.system/action/samples/echo
  curl: (6) Couldn't resolve host '"message": "hello world"'
  {
    "error": "HTTP method not allowed, supported methods: GET",
    "code": 81107
  }
  </code></pre>
  
  <p>How can I invoke it OpenWhisk via curl or similar tools, how do I authenticate?</p>