The optional Outputs section declares output values for the stack. These output values can be used in various ways:
Capture important details about your resources â An output is a convenient way to capture important information about your resources. For example, you can output the S3 bucket name for a stack to make the bucket easier to find. You can view output values in the Outputs tab of the CloudFormation console or by using the describe-stacks CLI command.
Cross-stack references â You can import output values into other stacks to create references between stacks. This is helpful when you need to share resources or configurations across multiple stacks.
CloudFormation doesn't redact or obfuscate any information you include in the Outputs section. We strongly recommend you don't use this section to output sensitive information, such as passwords or secrets.
Output values are available after the stack operation is complete. Stack output values aren't available when a stack status is in any of the IN_PROGRESS statuses. We don't recommend establishing dependencies between a service runtime and the stack output value because output values might not be available at all times.
The Outputs section consists of the key name Outputs. You can declare a maximum of 200 outputs in a template.
The following example demonstrates the structure of the Outputs section.
Use braces to enclose all output declarations. Delimit multiple outputs with commas.
"Outputs" : {
"OutputLogicalID" : {
"Description" : "Information about the value",
"Value" : "Value to return",
"Export" : {
"Name" : "Name of resource to export"
}
}
}Outputs:
OutputLogicalID:
Description: Information about the value
Value: Value to return
Export:
Name: Name of resource to exportThe Outputs section can include the following fields.
An identifier for the current output. The logical ID must be alphanumeric (aâz, AâZ, 0â9) and unique within the template.
Description (optional)
A String type that describes the output value. The value for the description declaration must be a literal string that's between 0 and 1024 bytes in length. You can't use a parameter or function to specify the description.
Value (required)
The value of the property returned by the describe-stacks command. The value of an output can include literals, parameter references, pseudo parameters, a mapping value, or intrinsic functions.
Export (optional)
The name of the resource output to be exported for a cross-stack reference.
You can use intrinsic functions to customize the Name value of an export.
For more information, see Get exported outputs from a deployed CloudFormation stack.
To associate a condition with an output, define the condition in the Conditions section of the template.
ExamplesThe following examples illustrate how stack output works.
Stack outputIn the following example, the output named BackupLoadBalancerDNSName returns the DNS name for the resource with the logical ID BackupLoadBalancer only when the CreateProdResources condition is true. The output named InstanceID returns the ID of the EC2 instance with the logical ID EC2Instance.
"Outputs" : {
"BackupLoadBalancerDNSName" : {
"Description": "The DNSName of the backup load balancer",
"Value" : { "Fn::GetAtt" : [ "BackupLoadBalancer", "DNSName" ]},
"Condition" : "CreateProdResources"
},
"InstanceID" : {
"Description": "The Instance ID",
"Value" : { "Ref" : "EC2Instance" }
}
}Outputs:
BackupLoadBalancerDNSName:
Description: The DNSName of the backup load balancer
Value: !GetAtt BackupLoadBalancer.DNSName
Condition: CreateProdResources
InstanceID:
Description: The Instance ID
Value: !Ref EC2InstanceFn::Sub
In the following examples, the output named StackVPC returns the ID of a VPC, and then exports the value for cross-stack referencing with the name VPCID appended to the stack's name.
"Outputs" : {
"StackVPC" : {
"Description" : "The ID of the VPC",
"Value" : { "Ref" : "MyVPC" },
"Export" : {
"Name" : {"Fn::Sub": "${AWS::StackName}-VPCID" }
}
}
}Outputs:
StackVPC:
Description: The ID of the VPC
Value: !Ref MyVPC
Export:
Name: !Sub "${AWS::StackName}-VPCID"For more information about the Fn::Sub function, see Fn::Sub.
Fn::Join
You can also use the Fn::Join function to construct values based on parameters, resource attributes, and other strings.
The following examples use the Fn::Join function to customize the export name instead of the Fn::Sub function. The example Fn::Join function concatenates the stack name with the name VPCID using a colon as a separator.
"Outputs" : {
"StackVPC" : {
"Description" : "The ID of the VPC",
"Value" : { "Ref" : "MyVPC" },
"Export" : {
"Name" : { "Fn::Join" : [ ":", [ { "Ref" : "AWS::StackName" }, "VPCID" ] ] }
}
}
}Outputs:
StackVPC:
Description: The ID of the VPC
Value: !Ref MyVPC
Export:
Name: !Join [ ":", [ !Ref "AWS::StackName", VPCID ] ]For more information about the Fn::Join function, see Fn::Join.
Fn::Join
In the following example for a template that creates a WordPress site, InstallURL is the string returned by a Fn::Join function call that concatenates http://, the DNS name of the resource ElasticLoadBalancer, and /wp-admin/install.php. The output value would be similar to the following:
http://mywptests-elasticl-1gb51l6sl8y5v-206169572.aws-region.elb.amazonaws.com/wp-admin/install.php JSON
{
"Outputs": {
"InstallURL": {
"Value": {
"Fn::Join": [
"",
[
"http://",
{
"Fn::GetAtt": [
"ElasticLoadBalancer",
"DNSName"
]
},
"/wp-admin/install.php"
]
]
},
"Description": "Installation URL of the WordPress website"
}
}
}Outputs:
InstallURL:
Value: !Join
- ''
- - 'http://'
- !GetAtt
- ElasticLoadBalancer
- DNSName
- /wp-admin/install.php
Description: Installation URL of the WordPress websiteFor more information about the Fn::Join function, see Fn::Join.
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