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AWS CloudFormation
User Guide (API Version 2010-05-15)

AWS Documentation » AWS CloudFormation » User Guide » Template Reference » Intrinsic Function Reference » Fn::ImportValue

Fn::ImportValue

The intrinsic function Fn::ImportValue returns the value of an output exported by another stack. You typically use this function to create cross-stack references. In the following example template snippets, Stack A exports VPC security group values and Stack B imports them.

Note

The following restrictions apply to cross-stack references:

  • For each AWS account, Export names must be unique within a region.

  • You can't create cross-stack references across regions. You can use the intrinsic function Fn::ImportValue to import only values that have been exported within the same region.

  • For outputs, the value of the Name property of an Export can't use Ref or GetAtt functions that depend on a resource.

    Similarly, the ImportValue function can't include Ref or GetAtt functions that depend on a resource.

  • You can't delete a stack if another stack references one of its outputs.

  • You can't modify or remove an output value that is referenced by another stack.

Stack A Export

"Outputs" : {
  "PublicSubnet" : {
    "Description" : "The subnet ID to use for public web servers",
    "Value" :  { "Ref" : "PublicSubnet" },
    "Export" : { "Name" : {"Fn::Sub": "${AWS::StackName}-SubnetID" }}
  },
  "WebServerSecurityGroup" : {
    "Description" : "The security group ID to use for public web servers",
    "Value" :  { "Fn::GetAtt" : ["WebServerSecurityGroup", "GroupId"] },
    "Export" : { "Name" : {"Fn::Sub": "${AWS::StackName}-SecurityGroupID" }}
  }
}

Stack B Import

"Resources" : {
  "WebServerInstance" : {
    "Type" : "AWS::EC2::Instance",
    "Properties" : {
      "InstanceType" : "t2.micro",
      "ImageId" : "ami-a1b23456",
      "NetworkInterfaces" : [{
        "GroupSet" : [{"Fn::ImportValue" : {"Fn::Sub" : "${NetworkStackNameParameter}-SecurityGroupID"}}],
        "AssociatePublicIpAddress" : "true",
        "DeviceIndex" : "0",
        "DeleteOnTermination" : "true",
        "SubnetId" : {"Fn::ImportValue" : {"Fn::Sub" : "${NetworkStackNameParameter}-SubnetID"}}
      }]
    }
  }
}

Declaration

JSON

{ "Fn::ImportValue" : sharedValueToImport }

YAML

You can use the full function name: 

Fn::ImportValue: sharedValueToImport

Alternatively, you can use the short form: 

!ImportValue sharedValueToImport

Important

You can't use the short form of !ImportValue when it contains a !Sub. The following example is valid for AWS CloudFormation, but not valid for YAML: 

!ImportValue
  !Sub "${NetworkStack}-SubnetID"

Instead, you must use the full function name, for example: 

Fn::ImportValue:
  !Sub "${NetworkStack}-SubnetID"

Parameters

sharedValueToImport

The stack output value that you want to import.

Return Value

The stack output value.

Example

JSON

{ "Fn::ImportValue" : {"Fn::Sub": "${NetworkStackNameParameter}-SubnetID" } }

YAML

Fn::ImportValue:
  !Sub "${NetworkStackName}-SecurityGroupID"

Supported Functions

You can use the following functions in the Fn::ImportValue function. The value of these functions can't depend on a resource.

  • Fn::Base64

  • Fn::FindInMap

  • Fn::If

  • Fn::Join

  • Fn::Select

  • Fn::Split

  • Fn::Sub

  • Ref