title: How to pass a variable to EMR addStep in AWS StepFunctions
body: <p>AWS Stepfunctions recently added EMR integration, which is cool, but i couldn't find a way to pass a variable from step functions into the addstep args.
  For example i would like to pass "$.dayid" variable into "Parameters">"Step">"HadoopJarStep">Args. Similar to "ClusterId.$": "$.ClusterId" (this cluster id variable works).</p>
  
  <pre><code>{
      "Step_One": {
      "Type": "Task",
      "Resource": "arn:aws:states:::elasticmapreduce:addStep.sync",
      "Parameters": {
          "ClusterId.$": "$.ClusterId",
          "Step": {
              "Name": "The first step",
              "ActionOnFailure": "CONTINUE",
              "HadoopJarStep": {
                  "Jar": "command-runner.jar",
                  "Args": [
                      "hive-script",
                      "--run-hive-script",
                      "--args",
                      "-f",
                      "s3://&lt;region&gt;.elasticmapreduce.samples/cloudfront/code/Hive_CloudFront.q",
                      "-d",
                      "INPUT=s3://&lt;region&gt;.elasticmapreduce.samples",
                      "-d",
                      "OUTPUT=s3://&lt;mybucket&gt;/MyHiveQueryResults/$.dayid"
                  ]
              }
          }
      },
      "End": true
  }
  </code></pre>