Fn::GetAtt - AWS CloudFormation
DeclarationParametersReturn valueExamplesSupported functions

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Fn::GetAtt

The Fn::GetAtt intrinsic function returns the value of an attribute from a resource in the template.

Declaration

JSON

{ "Fn::GetAtt" : [ "logicalNameOfResource", "attributeName" ] }

YAML

Syntax for the full function name:

Fn::GetAtt: [ logicalNameOfResource, attributeName ]

Syntax for the short form:

!GetAtt logicalNameOfResource.attributeName

Parameters

logicalNameOfResource

The logical name (also called logical ID) of the resource that contains the attribute that you want.

attributeName

The name of the resource-specific attribute whose value you want. See the resource's reference page for details about the attributes available for that resource type.

Return value

The attribute value. For information about GetAtt return values for resources, see the documentation for the resources in the Resource and property reference.

Examples

Return an attribute value

The following examples return a string containing the DNS name of the load balancer with the logical name myELB.

JSON

"Fn::GetAtt" : [ "myELB" , "DNSName" ]

YAML

!GetAtt myELB.DNSName

Return multiple attribute values

The following examples return the SourceSecurityGroup.OwnerAlias and SourceSecurityGroup.GroupName of the load balancer with the logical name myELB.

JSON
{
    "AWSTemplateFormatVersion": "2010-09-09",
    "Resources": {
        "myELB": {
            "Type": "AWS::ElasticLoadBalancing::LoadBalancer",
            "Properties": {
                "AvailabilityZones": [
                    "eu-west-1a"
                ],
                "Listeners": [
                    {
                        "LoadBalancerPort": "80",
                        "InstancePort": "80",
                        "Protocol": "HTTP"
                    }
                ]
            }
        },
        "myELBIngressGroup": {
            "Type": "AWS::EC2::SecurityGroup",
            "Properties": {
                "GroupDescription": "ELB ingress group",
                "SecurityGroupIngress": [
                    {
                        "IpProtocol": "tcp",
                        "FromPort": 80,
                        "ToPort": 80,
                        "SourceSecurityGroupOwnerId": {
                            "Fn::GetAtt": [
                                "myELB",
                                "SourceSecurityGroup.OwnerAlias"
                            ]
                        },
                        "SourceSecurityGroupName": {
                            "Fn::GetAtt": [
                                "myELB",
                                "SourceSecurityGroup.GroupName"
                            ]
                        }
                    }
                ]
            }
        }
    }
}
YAML
AWSTemplateFormatVersion: 2010-09-09
Resources:
  myELB:
    Type: AWS::ElasticLoadBalancing::LoadBalancer
    Properties:
      AvailabilityZones:
        - eu-west-1a
      Listeners:
        - LoadBalancerPort: '80'
          InstancePort: '80'
          Protocol: HTTP
  myELBIngressGroup:
    Type: AWS::EC2::SecurityGroup
    Properties:
      GroupDescription: ELB ingress group
      SecurityGroupIngress:
        - IpProtocol: tcp
          FromPort: 80
          ToPort: 80
          SourceSecurityGroupOwnerId: !GetAtt myELB.SourceSecurityGroup.OwnerAlias
          SourceSecurityGroupName: !GetAtt myELB.SourceSecurityGroup.GroupName

Use Fn::Sub inside Fn::GetAtt function

Note

When you use the AWS::LanguageExtensions transform, you can use Fn::GetAtt in combination with other intrinsic functions. For supported functions, see Supported functions.

The following examples show how to use Fn::GetAtt with Fn::Sub, in conjuction with Fn::ForEach, in the Outputs section of a template to reduce the template length and verbosity. The use of Fn::Sub within Fn::GetAtt allows the template to contain one intrinsic function that can reference a different bucket at every iteration of the Fn::ForEach call.

JSON
{
    "AWSTemplateFormatVersion": "2010-09-09",
    "Transform": "AWS::LanguageExtensions",
    "Mappings": {
        "Buckets": {
            "Properties": {
                "Identifiers": ["A", "B", "C"]
            }
        }
    },
    "Resources": {
        "Fn::ForEach::Buckets": [
            "Identifier",
            {"Fn::FindInMap": ["Buckets", "Properties", "Identifiers"]},
            {
                "S3Bucket${Identifier}": {
                    "Type": "AWS::S3::Bucket",
                    "Properties": {
                        "AccessControl": "PublicRead",
                        "MetricsConfigurations": [
                            {
                                "Id": {"Fn::Sub": "EntireBucket${Identifier}"}
                            }
                        ],
                        "WebsiteConfiguration": {
                            "IndexDocument": "index.html",
                            "ErrorDocument": "error.html",
                            "RoutingRules": [
                                {
                                    "RoutingRuleCondition": {
                                        "HttpErrorCodeReturnedEquals": "404",
                                        "KeyPrefixEquals": "out1/"
                                    },
                                    "RedirectRule": {
                                        "HostName": "ec2-11-22-333-44.compute-1.amazonaws.com",
                                        "ReplaceKeyPrefixWith": "report-404/"
                                    }
                                }
                            ]
                        }
                    },
                    "DeletionPolicy": "Retain",
                    "UpdateReplacePolicy": "Retain"
                }
            }
        ]
    },
    "Outputs": {
        "Fn::ForEach::BucketOutputs": [
            "Identifier",
            {"Fn::FindInMap": ["Buckets", "Properties", "Identifiers"]},
            {
                "Fn::ForEach::GetAttLoop": [
                    "Property",
                    ["Arn", "DomainName", "WebsiteURL"],
                    {
                        "S3Bucket${Identifier}${Property}": {
                            "Value": {
                                "Fn::GetAtt": [{"Fn::Sub": "S3Bucket${Identifier}"}, {"Ref": "Property"}]
                            }
                        }
                    }
                ]
            }
        ]
    }
}
YAML
AWSTemplateFormatVersion: 2010-09-09
Transform: AWS::LanguageExtensions
Mappings:
  Buckets:
    Properties:
      Identifiers:
        - A
        - B
        - C
Resources:
  'Fn::ForEach::Buckets':
    - Identifier
    - Fn::FindInMap: 
      - Buckets
      - Properties
      - Identifiers
    - 'S3Bucket${Identifier}':
        Type: 'AWS::S3::Bucket'
        Properties:
          AccessControl: PublicRead
          MetricsConfigurations:
            - Id: 
                Fn::Sub: 'EntireBucket${Identifier}'
          WebsiteConfiguration:
            IndexDocument: index.html
            ErrorDocument: error.html
            RoutingRules:
              - RoutingRuleCondition:
                  HttpErrorCodeReturnedEquals: '404'
                  KeyPrefixEquals: out1/
                RedirectRule:
                  HostName: ec2-11-22-333-44.compute-1.amazonaws.com
                  ReplaceKeyPrefixWith: report-404/
        DeletionPolicy: Retain
        UpdateReplacePolicy: Retain
Outputs:
  'Fn::ForEach::BucketOutputs':
    - Identifier
    - Fn::FindInMap:
      - Buckets
      - Properties
      - Identifiers
    - 'Fn::ForEach::GetAttLoop':
        - Property
        - - Arn
          - DomainName
          - WebsiteURL
        - 'S3Bucket${Identifier}${Property}':
            Value: !GetAtt 
              - !Sub 'S3Bucket${Identifier}'
              - !Ref Property

Supported functions

When you use the AWS::LanguageExtensions transform, you can use the following functions within the Fn::GetAtt function. This is true with either the Fn::GetAtt logical resource name or the Fn::GetAtt attribute name.

When the AWS::LanguageExtensions transform is not used:

  • The Fn::GetAtt attribute name can only use the Ref function.

  • The Fn::GetAtt logical resource name can't use functions. You must specify a string that's a resource's logical ID.