The format keyword in JSON Schema is used to define a regular expression pattern that a string value should match. It provides a way to validate that a string adheres to a specific format or pattern.
In cfn-lint, we have extended the format keyword to support custom formats that are specific to AWS resources. These custom formats help validate values against specific patterns or constraints defined by AWS.
cfn-lint supports the following custom formats:
This format ensures that the value is a valid VPC ID, which is a string of the pattern vpc-[0-9a-f]{8} or vpc-[0-9a-f]{17}.
This format validates that the value is a valid Security Group ID, which is a string of the pattern sg-[0-9a-f]{8} or sg-[0-9a-f]{17}.
This format validates that the value is a valid Security Group Name, which must be a string of 1 to 255 characters, starting with a letter, and containing only letters, numbers, and certain special characters.
This format validates that the value is a valid Amazon Machine Image (AMI), which is a string of the pattern ami-[0-9a-f]{8} or ami-[0-9a-f]{17}. More info in docs