AWS CloudFormation Concepts Intrinsic Functions

External

Intrinsic Function Reference

Internal

• AWS CloudFormation Concepts

Ref

Ref

The intrinsic function Ref returns the value of the object it refers to, such as a parameter or resource. When a parameter logical name is specified, it returns the value of the parameter. When a resource logical name is specified, it returns a value that can be typically used to refer to that resource, such as a physical ID.

!Ref AWS::StackName
!Ref MyParameter
!Ref MyResourceName

Join

Join

!Join [ delimiter, [ comma-delimited list of values ] ]

!Join ['-', [ a, b, c ]]

returns "a:b:c"

Split

Split

!Split ['.', "www.example.com"]

returns ["www", "example", "com"].

Select

Select

Sub

Sub

Sub substitutes variables in an input string with specified values.

If only template parameters, resource logical IDs and resource attributes are substituted in the String parameter, no variable map is required:

!Sub '${TemplateParameterA} is a ${TemplateParameterB}'
!Sub '${AWS::Region}-something'

ImportValue

ImportValue

The Fn::ImportValue returns the value of an output exported by another stack. The function is used to create cross-stack references.

Can be used as a key in a YAML structure:

...
ServiceRole:
  Fn::ImportValue: ...

or a value:

...
EnvironmentVariables:
  - Name: TARGET_BUCKET
     Value:
       Fn::ImportValue: !Sub '${AWS::Region}-BuildBucket'

FindInMap

!FindInMap [ MapName, TopLevelKey, SecondLevelKey ]