CloudFormation – 2 – Intrinsic Functions

Intrinsic Functions

Fn::Ref

• The Fn::Ref function can be leveraged to reference
  • Parameters => returns the value of the parameter
  • Resources => returns the physical ID of the underlying resource (ex: EC2 ID)
• The shorthand for this in YA\/1_ is !Ref

 

Fn::GetAtt

• Attributes are attached to any resources you create
• To know the attributes of your resources, the best place to look at is the documentation.
• For example: the AZ of an EC2 machine !

 

 

Fn::FindInMap

Accessing Mapping Values

• We use Fn::FindInMap to return a named value from a specific key
• !FindInMap [ MapName, TopLevelKey, SecondLevelKey ]

 

Fn:ImportValue

• Import values that are exported in other templates
• For this, we use the Fn::ImportValue function

 

Fn::Join

• Join values with a delimiter

• This creates “a:b:c” :

 

Function 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 customize your templates.
• For example, you can combine Fn::Sub with References or AWS Pseudo variables !
• String must contain ${VariableName} and will substitute them

 

Conditions Functions

• The logical ID if for you to choose. It’s how you name condition
• The intrinsic function (logical) can be any of the following:
• Fn::And
• Fn::Equals
• Fn::If
• Fn::Not
• Fn::Or