Fn::Sub

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