How to get powershell environment variable value in terraform

Question

Running powershell (7.4.1) and terraform (1.7.5) on Ubuntu (20.04). I have created a powershell profile in which I set some environment variables for terraform to use when executing it.

For example, in 'Microsoft.PowerShell_profile.ps1' I have set.

$env:DA_SUBSCRIPTION_ID="abcd1234"
gci env:DA_*

And when I run pwsh I can see the value printed to console.

Name                           Value
----                           -----
DA_SUBSCRIPTION_ID             abcd1234`

Then I have a terraform file 'providers.tf' (among other tf-files) having content like this.

provider "azurerm" {
  features {}
  subscription_id = "${env.DA_SUBSCRIPTION_ID}"
}

Now, in the powershell console, when I run terraform validate. I get response:

A managed resource "env" "DA_SUBSCRIPTION_ID" has not been declared in the root module.

May be simple, but I am not able to find the correct syntax to use when referring to the environment variables set in the powershell profile.

Could someone give me an advice on how to do this correctly.

Thanks.

Answer 1

First, you have to declare a variable in Terraform.

variable "DA_SUBSCRIPTION_ID" {
  type = string
}

provider "azurerm" {
  features {}
  subscription_id = var.DA_SUBSCRIPTION_ID
}

Then, you can set an environment variable in your shell with the TF_VAR_ prefix. Terraform searches the environment of its own process for environment variables named TF_VAR_ followed by the name of a declared variable.

$env:TF_VAR_DA_SUBSCRIPTION_ID="abcd1234"
terraform plan