3 Terraform Variable

---

⭐ Input Variables (variable)

Used to pass values into Terraform.

variable "environment" {
  default     = "dev"
  type        = string  (optional)
  description = "name of the environment" (optional)
}

Use them as:

var.environment

Warning

If No default value provided then we have to enter value in Interactive Mode

---

⭐ Local Variables (locals)

Used for internal calculation, concatenation, and reusable values.

locals {
  bucket_name = "${var.project}-bucket-${var.environment}"
}

Use as:

local.bucket_name

---

Types of Variables (Based on Value / Type Constraints)

• Primitive Types — string, number, bool
• Complex Types — list(), set(), map(), object(), tuple()
• Special Types — any, null

---

How to Set Variable Values (Precedence Order)

Method	Example	Notes
1️⃣ Default value in variable block	default = "dev"	Used when no other value is provided
2️⃣ Environment variable	export TF_VAR_environment=stage	Overrides default value
3️⃣ .tfvars / .auto.tfvars files	environment = "preprod"	Overrides defaults & env vars
4️⃣ -var / -var-file CLI flag	terraform plan -var="environment=prod"	Overrides everything

Dependency in terraform

Implicit dependency

explicit dependency

resource "local_file" "whale" {
  filename = "/root/whale"
  content = "whale"
  depends_on = [ local_file.krill ]  # explicit
}
 
resource "local_file" "krill" {
  filename = "/root/krill"
  content = "krill"
}