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Output variables make it easy to expose values from your OpenTofu configuration—such as resource attributes—to users, scripts, or other tools. In this guide, you’ll learn how to define, view, and leverage output variables effectively.

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Table of Contents

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Defining an Output Variable

Use the output block with a unique name and the value argument set to the expression you want to expose. You can also include optional arguments like description and sensitive: 
output "pub_ip" {
  value       = aws_instance.cerberus.public_ip
  description = "The public IPv4 address of the EC2 instance"
}
Output names must be unique within a module. Use descriptive names to make them easy to reference in other modules or scripts.

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Generic Output Syntax

Below is the general form of an output block in OpenTofu: 
output "<NAME>" {
  value       = <EXPRESSION>
  description = "<DESCRIPTION>"      # optional
  sensitive   = true | false        # optional
}
  • NAME: The identifier for this output.
  • EXPRESSION: Any valid expression or reference, such as aws_instance.foo.id.
  • description: A human-readable summary (optional).
  • sensitive: When set to true, the value is omitted from CLI output (optional).

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Output Block Arguments

ArgumentDescriptionRequired
valueExpression or reference whose result you want to expose.Yes
descriptionA short human-readable explanation.No
sensitiveHides the value in CLI output when set to true.No
Mark any output containing secrets or credentials as sensitive = true to prevent leaking them in logs or console output.

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Complete Example

This minimal configuration creates an EC2 instance and then outputs its public IPv4 address: 
resource "aws_instance" "cerberus" {
  ami           = var.ami
  instance_type = var.instance_type
}

output "pub_ip" {
  value       = aws_instance.cerberus.public_ip
  description = "The public IPv4 address of the EC2 instance"
}

variable "ami" {
  default = "ami-06178cf087598769c"
}

variable "instance_type" {
  default = "m5.large"
}

variable "region" {
  default = "eu-west-2"
}

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Viewing Outputs

After running tofu apply, OpenTofu automatically displays all configured outputs: 
$ tofu apply
...
Apply complete! Resources: 1 added, 0 changed, 0 destroyed.

Outputs:
pub_ip = 54.214.145.69
You can also list or fetch outputs at any time: 
# List all outputs
$ tofu output
pub_ip = 54.214.145.69

# Fetch a single output value
$ tofu output pub_ip
54.214.145.69

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Use Cases

  • Quickly inspect provisioned resource attributes on-screen.
  • Pass output values into other IaC tools, ad-hoc scripts, Ansible playbooks, or testing frameworks.
  • Expose dynamic data for remote execution contexts or CI/CD pipelines.

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