main.tf

data "azurerm_subscriptions" "available" {}

output "subscriptions" {
  value = "${data.azurerm_subscriptions.available.subscriptions}"
}

/*
Sample output:
subscriptions = [
    {
        display_name = Subscription One
        subscription_id = ab400b28-6f92-4fb4-a48b-83810ac2f830
    },
    {
        display_name = Subscription Two
        subscription_id = 4e03fb6f-08d7-4793-a863-3e2ac31206df
    }
]
*/
resource "azurerm_role_definition" "custom_role" {
  # assignable_scopes should be a list of all available subscription IDs.
  assignable_scopes = [
    "${data.azurerm_subscriptions.available.subscriptions.*.subscription_id}",
  ]
}