Sub

The intrinsic function Fn::Sub substitutes variables in an input string with values that you specify. In your templates, you can use this function to construct commands or outputs that include values that aren’t available until you create or update a stack.

The sub method is the CloudFormation Fn::Sub equivalent.

Example Snippet

resource("Instance", "AWS::EC2::Instance",
  InstanceType: ref("InstanceType"),
  ImageId: "ami-0de53d8956e8dcf80",
  UserData: sub("hello ${k1} ${k2}", k1: "v1", k2: "v2")
)

Example Output

Resources:
  Instance:
    Type: AWS::EC2::Instance
    Properties:
      InstanceType:
        Ref: InstanceType
      ImageId: ami-0de53d8956e8dcf80
      UserData:
        Fn::Sub:
        - hello ${k1} ${k2}
        - k1: v1
          k2: v2

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