aws cli command output as value in cloudformation template-CodePudding

I have an independent lambda layer, the arn is retrieved using the below CLI command.

aws lambda list-layer-versions --layer-name my-custom-lambda-layer --region us-east-1 --query 'LayerVersions[0].LayerVersionArn'

How can I refer this output to my cloud formation template, like below,

Resources:
  Parameters:
    MYLAYERARN: $(aws lambda list-layer-versions --layer-name my-custom-lambda-layer --region us-east-1 --query 'LayerVersions[0].LayerVersionArn')

Or use it directly in any of my lambda function as below,

Resources:
  MyLambdaFuntion:
    handler: Hello.lambda_handler
    timeout: 60
    memorySize: 256
    layers:
      - $(aws lambda list-layer-versions --layer-name my-custom-lambda-layer --region us-east-1 --query 'LayerVersions[0].LayerVersionArn')

Currenlty it is not executing the AWS CLI command, but taking the CLI command as the value

CodePudding user response：

That is not possible, as you can't evaluate such expressions in a CloudFormation template.

The easiest solution would be to pass in the already-evaluated expression as a parameter.

Alternatively, if you must use a CloudFormation solution, then you could leverage a CloudFormation macro to invoke a lambda function which executes custom code (in this case, the code would have the SDK equivalent of the AWS CLI command).

More on CloudFormation macros: https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/template-macros.html

Macro example: https://stackoverflow.com/a/70475459/3390419