Amazon CodeCatalyst is no longer open to new customers. Existing customers can continue to use the service as normal. For more information, see [How to migrate from CodeCatalyst](migration.md).

# Referencing a predefined variable
<a name="workflows-working-with-variables-reference-output-vars"></a>

You can reference predefined variables in any action within an Amazon CodeCatalyst workflow.

Use the following instructions to reference a predefined variable in a workflow.

For more information about predefined variables, see [Using predefined variables](workflows-using-predefined-variables.md).

**Prerequisite**  
Determine the name of the predefined variable you want to reference, such as `CommitId`. For more information, see [Determining which predefined variables your workflow emits](workflows-working-with-variables-determine-output-vars.md).

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*Not available. Choose YAML to view the YAML instructions.*

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#### [ YAML ]

**To reference a predefined variable (YAML editor)**

1. Open the CodeCatalyst console at [https://codecatalyst.aws/](https://codecatalyst.aws/).

1. Choose your project.

1. In the navigation pane, choose **CI/CD**, and then choose **Workflows**.

1. Choose the name of your workflow. You can filter by the source repository or branch name where the workflow is defined, or filter by workflow name or status.

1. Choose **Edit**.

1. Choose **YAML**.

1. In a CodeCatalyst action, add the predefined variable reference using the following syntax:

   ```
   ${action-group-name.action-name-or-WorkflowSource.variable-name}
   ```

   Replace:
   + *action-group-name* with the name of the action group.
**Note**  
You can omit *action-group-name* if there is no action group, or if the variable is produced by an action in the same action group.
   + *action-name-or-WorkflowSource* with:

     The name of the action that outputs the variable.

     or

     `WorkflowSource`, if the variable is the `BranchName` or `CommitId` variable.
   + *variable-name* with the name of the variable.

   For example:

   ```
   MySecondAction:
       Configuration:
         Steps:
           - Run: echo ${MyFirstECSAction.cluster}
   ```

   Another example:

   ```
   MySecondAction:
       Configuration:
         Steps:
           - Run: echo ${WorkflowSource.CommitId}
   ```

   For more examples, see [Examples of referencing predefined variables](workflows-predefined-examples.md). For more information, see the [Workflow YAML definition](workflow-reference.md) for your action.

1. (Optional) Choose **Validate** to validate the workflow's YAML code before committing.

1. Choose **Commit**, enter a commit message, and choose **Commit** again.

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