AWS CloudFormation
User Guide (API Version 2010-05-15)

Specifying Intrinsic Functions

AWS CloudFormation intrinsic functions are special actions you use in your template to assign values to properties not available until runtime. Each function is declared with a double-quoted name, a single colon, and its parameters. When an argument is a literal string, it is enclosed in double quotes (""). When arguments are in a list of any kind, they are enclosed in brackets ([ ]). If an argument is a value that is returned from an intrinsic function, it is enclosed in braces ({ }).

The following example shows the function "Fn::GetAtt" being used to assign a value to the MyLBDNSName, which it does by retrieving the value of the attribute DNSName from the Elastic Load Balancing load balancer named MyLoadBalancer.

"Properties" : {
   "MyMyLBDNSName" : {
      "Fn::GetAtt" : [ "MyLoadBalancer", "DNSName" ]

For more information about intrinsic functions, see Intrinsic Function Reference.