🧠 The Concept: Input vs. Output

In the 004 exam, HashiCorp expects you to know how data flows through a Terraform configuration.

  • Input Variables: Like function arguments. They allow users to customize the deployment without touching the main code.
  • Output Values: Like return values. They highlight important information (like an IP address) after an apply.

📋 The Challenge

The goal is to refactor our “Random Pet” lab. Instead of hardcoding the length of the pet name, we will use a variable.

Requirements:

  1. Define a variable for prefix.
  2. Define a variable for separator.
  3. Output the final generated name to the terminal.

🚀 The Solution

View the full code here: Challenge 03 Repo

1. Defining the Input

Instead of hardcoding the prefix “Mrs”, let’s create a variable. This allows other team members to use your code without editing the logic.

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variable "prefix" {
  type = string
  default = "Mrs"
  description = "Prefix of the pet"
}

2. Use the variable

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# main.tf
resource "random_pet" "my-random-pet" {
  prefix = var.prefix
  separator = "."
}

# outputs.tf
output "my-random-pet-name" {
  value = random_pet.my-random-pet
  description = "The full name of the random generated pet"
}

3. The Output Anatomy

When you run terraform plan then you will see:

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my-random-pet-name = {
  "id" = "Mrs.awaited.bullfrog"
  "keepers" = tomap(null) /* of string */
  "length" = 2
  "prefix" = "Mrs"
  "separator" = "."
}

Why does it look like that? You likely used an output that exported the entire resource object. While useful for debugging, it’s “noisy.” In the output above:

  • tomap(null): This is Terraform’s way of saying, “This attribute is a Map type, but it’s currently empty.”

  • /* of string */: This is a hint that if you did provide values, they would need to be strings.

4. Refining the Output

When you run terraform apply then you will see:

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my-random-pet-name = {
  "id" = "Mrs.awaited.bullfrog"
  "keepers" = tomap(null) /* of string */
  "length" = 2
  "prefix" = "Mrs"
  "separator" = "."
}

🧠 Knowledge Check

Test your understanding of Terraform State and Outputs before moving to the next lesson.

⚠️ Quiz data missing.

📚 004 Exam: Official Documentation Reference

To master the variables and outputs section of the Terraform Associate (004) exam, I utilized the following official resources:

1. Variables & Types

  • Input Variables Overview: Covers how to define variables, use default values, and set descriptions.
  • Type Constraints: Crucial for 004. Explains the difference between primitive types (string, number, bool) and complex types (list, map, object).

2. The Data Flow

  • Output Values: Documentation on how to expose information about your infrastructure to the command line or other configurations.
  • Variable Precedence: A favorite 004 exam topic. This page explains which value “wins” when a variable is defined in multiple places (e.g., .tfvars vs environment variables).

3. CLI Interaction

  • Command: output: How to extract specific values from your state file after a successful apply.