terraform variables

types:

• input - as input to the terraform config
• output - get as return from the terraform command
• local - internal variables

there are many ways to define and pass a variable in terraform and each method has a different priority

1. hardcode inside the main.tf file by defining it inside

// define the variable
variable "environment" {
  type = string
  description = "the env type"
  default = "staging"
}
 
 
// create a resource group
resource "azurerm_resource_group" "tf_resource_group" {
  name     = "tf-resources"
  location = "West Europe"
}
 
// create a storage account in the resource group
resource "azurerm_storage_account" "tf_storage_account" {
  name                     = "uxotout7"
  resource_group_name      = azurerm_resource_group.tf_resource_group.name
  location                 = azurerm_resource_group.tf_resource_group.location # implicit dependency
  account_tier             = "Standard"
  account_replication_type = "LRS"
 
  tags = {
    environment = var.environment // access the variable using the dot operator
  }
}

2. pass as argument in the cli (has the highest priority)

terraform plan -var=environment=dev

3. create the variables in a file terraform.tfvars and run tf plan

environment = "demo"

Note: terraform variable precedence - https://developer.hashicorp.com/terraform/enterprise/variables

4. environment variables

we can also set env variables but it should be of the format TF_VAR_name

export TF_VAR_region=us-west-1
export TF_VAR_ami=ami-049d8641
export TF_VAR_alist='[1,2,3]'
export TF_VAR_amap='{ foo = "bar", baz = "qux" }'

5. output variable

we can also print an output variable using terraform, we just need to define the output in the main.tf file

// create a storage account in the resource group
resource "azurerm_storage_account" "tf_storage_account" {
  name                     = "uxotout7"
  resource_group_name      = azurerm_resource_group.tf_resource_group.name
  location                 = azurerm_resource_group.tf_resource_group.location # implicit dependency
  account_tier             = "Standard"
  account_replication_type = "LRS"
 
  tags = {
    environment = var.environment
  }
}
 
output "storage_account_name" {
  value = azurerm_storage_account.tf_storage_account.name
}

once the output is defined just run:

terraform refresh
terraform plan
terraform output

the output variable can be used to pass important Information about the infra once it is created!

6. local variable

• used when these variables are not changed very often

locals{
  common_tags= {
    environment = "dev"
    lob = "abc"
    stage= "123"
  }
}
 
// create a storage account in the resource group
resource "azurerm_storage_account" "tf_storage_account" {
  name                     = "uxotout7"
  resource_group_name      = azurerm_resource_group.tf_resource_group.name
  location                 = azurerm_resource_group.tf_resource_group.location # implicit dependency
  account_tier             = "Standard"
  account_replication_type = "LRS"
 
  tags = {
    environment = local.common_tags.stage
  }
}

~aniket

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