Infrastructure as Code with AWS CloudFormation From Fundamentals to Production Patterns

Intrinsic functions in AWS CloudFormation are powerful tools that allow you to manipulate and reference data within your templates at deployment time. Here's an overview of the core intrinsic functions, including !Ref, !GetAtt, !Sub, !Join, !Select, !FindInMap, and !If.

Core Intrinsic Functions

!Ref

• Purpose: Returns a reference to a resource or parameter.

• Usage:

  • On a parameter: returns the value of the parameter.
  • On a resource: returns the primary identifier (e.g., instance ID, bucket name).

  yaml
   
  1InstanceType: !Ref InstanceTypeParam
  2SubnetId: !Ref MySubnet

!GetAtt

• Purpose: Returns an attribute of a resource.

• Usage:

  • Useful for retrieving specific attributes like ARNs, DNS names, etc.

  yaml
   
  1FunctionArn: !GetAtt MyLambdaFunction.Arn
  2LoadBalancerDNS: !GetAtt MyLoadBalancer.DNSName

!Sub

• Purpose: Substitutes variables in a string with values from parameters or

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