output block reference for component configurations

Use the output block in a Stack to expose information about your Stack's infrastructure in the HCP Terraform UI.

Background

Define output blocks in the <NAME>.tfcomponent.hcl file, to expose information about your Stack's infrastructure in the HCP Terraform UI.

If you want to expose a value from a Stack to use another Stack, refer to Pass data from one Stack to another instead. If you are declaring a output block in a traditional Terraform configuration file, ending in .tf, refer to the Terraform configuration output block reference instead.

Configuration model

The output block supports the following arguments:

output "<LABEL>" block
- type type constraint
- value expression
- description string
- sensitive boolean
- ephemeral boolean

Complete configuration

All available arguments are defined in the following output block:

output "<LABEL>" {
  description = "<STRING>"
  type        = <TYPE>
  value       = <EXPRESSION>
  sensitive   = <true|false>
  ephemeral   = <true|false>
}

Specification

In a component configuration file, the output block supports the following configuration.

`output "<LABEL>"`

The label after the output keyword is a name for the output, which must be unique among all outputs in the same component configuration. The name of an output can be any valid identifier.

The following arguments are supported in an output block:

Argument	Description	Type	Required?
`type`	The type constraint for this output value.	Type constraint	Required
`value`	The value Terraform returns for this output.	Expression	Required
`description`	A description of the output's purpose and how to use it.	String	Optional
`sensitive`	Specifies if Terraform hides this value in the UI and logs.	Boolean	Optional
`ephemeral`	Specifies that Terraform must exclude this value from plans and state.	Boolean	Optional

`type`

The type argument specifies the type constraint for the output value. Component configurations require you to explicitly define the type of each output.

output "<LABEL>" {
  type  = <TYPE_CONSTRAINT>
  #...
}

For details about types, constructors, and conversions, refer to Type constraints.

Summary

Data type: Type constraint
Default: None
Required: Yes

`value`

The value argument specifies the expression that Terraform evaluates and exposes to the HCP Terraform UI.

output "<LABEL>" {
  type  = <TYPE_CONSTRAINT>
  value = <EXPRESSION>
}

In component configurations, outputs commonly reference component outputs and other Stack resources, such as component.<COMPONENT_NAME>.<OUTPUT_NAME>.

Summary

Data type: Expression
Default: None
Required: Yes

`description`

The description argument documents the purpose of the output and how consumers should use it.

output "<LABEL>" {
  description = "<DESCRIPTION>"
  type        = <TYPE_CONSTRAINT>
  value       = <EXPRESSION>
}

Write descriptions from the perspective of someone consuming this Stack's outputs to help them understand the output's purpose and usage.

Summary

Data type: String
Default: None
Required: No

`sensitive`

The sensitive argument prevents Terraform from displaying the output value in the HCP Terraform UI and logs.

output "<LABEL>" {
  description = "<DESCRIPTION>"
  type        = <TYPE_CONSTRAINT>
  value       = <EXPRESSION>
  sensitive   = <BOOLEAN>
}

When you set sensitive to true, the HCP Terraform UI displays the output as (sensitive value) instead of showing the actual value. Terraform still records sensitive values in state, so anyone with state access can view these values. For more information about safely storing sensitive data, refer to Manage sensitive data.

Summary

Data type: Boolean
Default: false
Required: No

`ephemeral`

The ephemeral argument excludes the output value from plans and state data, making it available only during runtime.

output "<LABEL>" {
  description = "<DESCRIPTION>"
  type        = <TYPE_CONSTRAINT>
  value       = <EXPRESSION>
  ephemeral   = <BOOLEAN>
}

Ephemeral outputs are useful for temporary values like session tokens or short-lived credentials that you don't want to persist in state.

You can only reference ephemeral variables from specific contexts or Terraform throws an error:

In a managed resource write-only argument
In an ephemeral block
In the locals block
In other variable blocks with the ephemeral argument set to true
In other output blocks with the ephemeral argument set to true
Configuring providers in the provider block
In provisioner and connection blocks

Summary

Data type: Boolean
Default: false
Required: No

Examples

The following examples demonstrate common use cases for output blocks in component configurations.

Fundamental component output

In the following example, the instance_ip output exposes the private_ip value from the web_server component as a string:

output "instance_ip" {
  description = "The private IP address of the web server"
  type        = string
  value       = component.web_server.private_ip
}