Use Fn::Sub to perform string substitution. Consider this:
DSN: "Fn::Sub" - mysql://${db_user}:${db_pass}@${db_host}:3306/wordpress - { db_user: lchan, db_pass: ch33s3, db_host: localhost }
This would yield the following value:
mysql://lchan:ch33s3@localhost:3306/wordpress
When you combine these functions with Ref and Fn::GetAtt, you can start doing some really powerful stuff, as we'll be seeing in the recipes throughout this book.
Other available inbuilt functions include:
- Fn::Base64
- Fn::FindInMap
- Fn::GetAZs
- Fn::ImportValue
- Fn::Select
Documentation on all of these functions is available here http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/intrinsic-function-reference.html.
