CloudFormation Intrinsic Functions

Links: 102 AWS DVA Index

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Ref

• Fn::Ref
• YAML short hand !Ref
• If we refer parameters it returns the value of the parameter
• If we refer resources it returns the physical ID of the underlying resource (ex: EC2 ID)

GetAtt

• Fn:GetAtt
• Attributes are attached to any resources you create
• We can get a lot of attributes depending on the resource. To know what is exposed by the resource we will have to go through the documentation.
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FindInMap

• Accessing map values
• Fn::FindInMap to return a named value from a specific key.
• Another notation !FindInMap [MapName, TopLevelKey, SecondLevelKey]

ImportValue

• Import values that are exported In other templates
• Fn:ImportValue

Join

• Fn::Join
• To create a:b:c we can use !Join [":",[a, b, c]]

Sub

• Fn::Sub
• Fn::Sub, or !Sub as a shorthand, is used to substitute variables from a text. It's a very handy function that will allow you to fully customise your templates.
• For example, you can combine Fn::Sub with references or AWS Pseudo variables
• String must contain ${VariableName} and will substitute them.
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Last updated: 2022-06-09