»Local Values

Local values assign a name to an expression, that can then be used multiple times within a folder.

If variables are analogous to function arguments then local values are comparable to a function's local variables.

Input variable and local variable usage are introduced in the Variables Guide.


Local values are defined in locals blocks:

# Ids for multiple sets of EC2 instances, merged together
locals {
  instance_ids = "${concat(aws_instance.blue.*.id, aws_instance.green.*.id)}"

# A computed default name prefix
locals {
  default_name_prefix = "${var.project_name}-web"
  name_prefix         = "${var.name_prefix != "" ? var.name_prefix : local.default_name_prefix}"

# Local values can be interpolated elsewhere using the "local." prefix.
source "virtualbox-iso" "example" {
  output = "${local.name_prefix}-files"
  # ...

Named local maps can be merged with local maps to implement common or default values:

# Define the common tags for all resources
locals {
  common_tags = {
    Component   = "awesome-app"
    Environment = "production"

# Create a resource that blends the common tags with instance-specific tags.
source "amazon-ebs" "server" {
  source_ami    = "ami-123456"
  instance_type = "t2.micro"

  tags = "${merge(
      "Name", "awesome-app-server",
      "Role", "server"
  # ...


The locals block defines one or more local variables within a folder.

The names given for the items in the locals block must be unique throughout a folder. The given value can be any expression that is valid within the current folder.

The expression of a local value can refer to other locals, but reference cycles are not allowed. That is, a local cannot refer to itself or to a variable that refers (directly or indirectly) back to it.

It's recommended to group together logically-related local values into a single block, particularly if they depend on each other. This will help the reader understand the relationships between variables. Conversely, prefer to define unrelated local values in separate blocks, and consider annotating each block with a comment describing any context common to all of the enclosed locals.