Mastering Terraform Local Variables

Last Updated on August 7, 2025 by Arnav Sharma

Terraform has revolutionized the way DevOps engineers and data scientists manage and provision infrastructure. With its unique Hashicorp Code Language (HCL), Terraform offers a robust coding structure, making it a popular infrastructure tool. Among its myriad features, Terraform Local Values, often termed as “locals,” stand out as a pivotal component. This Saturn Cloud blog aims to provide an in-depth understanding of Terraform Local Values, their declaration, usage, best practices, and practical examples with Azure.

What Exactly is a Terraform Local Value?

In the vast sea of Terraform configurations, a local value is like a beacon. It assigns a name to an expression, allowing users to reference the name multiple times within a module. This eliminates the need to repeat the expression, making the Terraform code more concise and readable. Drawing a parallel with traditional programming languages, Terraform modules can be likened to function definitions:

• Input variables equate to function arguments.
• Output values are analogous to function return values.
• Local values can be compared to a function’s temporary local variables.

For simplicity, local values are often termed as “locals” when the context makes the meaning evident.

Azure-Specific Examples with Terraform Locals

Azure Virtual Network Name Composition: Suppose you have a naming convention for your Azure Virtual Networks that combines the environment, region, and a static string.

locals {
  env      = "prod"
  region   = "westus"
  vnet_name = "${local.env}-${local.region}-vnet"
}

Using the local value in an Azure Virtual Network resource:

resource "azurerm_virtual_network" "example" {
  name                = local.vnet_name
  address_space       = ["10.0.0.0/16"]
  location            = azurerm_resource_group.example.location
  resource_group_name = azurerm_resource_group.example.name
}

Azure Resource Group Naming: Creating a local value for Azure Resource Group name:

locals {
  rg_name = "tf-rg-${local.env}"
}

Using the local value in an Azure Resource Group:

resource "azurerm_resource_group" "example" {
  name     = local.rg_name
  location = "West US"
}

Azure Storage Account Name Composition: Azure storage account names need to be unique across Azure and can only contain lowercase letters and numbers. Using locals can help generate such names.

locals {
  sa_prefix = "tfstg"
  sa_suffix = "001"
  sa_name   = "${local.sa_prefix}${local.sa_suffix}"
}

Using the local value in an Azure Storage Account:  

resource "azurerm_storage_account" "example" {
  name                     = local.sa_name
  resource_group_name      = azurerm_resource_group.example.name
  location                 = azurerm_resource_group.example.location
  account_tier             = "Standard"
  account_replication_type = "LRS"
}

Key Takeaways and Best Practices

Terraform locals are a powerful tool for simplifying Terraform configurations. They enhance code readability and reduce repetition. With the added Azure-specific examples, you can now see how locals can be effectively used in real-world scenarios, making your Terraform configurations more modular and maintainable. As you continue your journey with Terraform, remember to use locals judiciously. Combine them effectively with other Terraform components for optimal results, and always keep an eye on the Terraform state to ensure consistency.

Harnessing the Power of Terraform Locals

The use of local values can be helpful to avoid repeating the same values and expressions multiple times within a Terraform configuration. While they are a powerful tool, if overused, they can also make a configuration hard to read by future maintainers by hiding the actual values used. Therefore, it’s essential to strike a balance. As you delve deeper into the world of IaC and Terraform, locals will undoubtedly become one of your go-to tools to streamline and optimize your configurations.