# Resources and Their Arguments — Terraform

Source: https://www.skillbyai.com/en/terraform/l-resource

> The things Terraform manages.

## type, name, arguments, attributes

A `resource` block has a **type** (from a provider, such as `local_file` or `aws_s3_bucket`) and a local **name**; together they form its address (`local_file.config`). **Arguments** inside the block describe the desired configuration; after creation the resource exposes **attributes** (ids, computed hashes, URLs) that other resources can reference, which also tells Terraform the order to create things in. Each provider's documentation lists the arguments and attributes for every resource type.

## Resources, inputs, values, functions

HCL describes resources and connects them with variables, locals, outputs and expressions.

![Four ideas: resources, variables and validation, locals and outputs, expressions.](assets/figures/terraform/section-2-map.svg) — Figure 2.1 — Resources, variables, outputs and expressions.

## The demo configuration

A variable with validation, locals, one resource and an output.

```hcl
variable "env" {
  type        = string
  description = "Deployment environment"
  default     = "dev"

  validation {
    condition     = contains(["dev", "staging", "prod"], var.env)
    error_message = "env must be dev, staging or prod."
  }
}

locals {
  app_name = "shop"
  settings = "app=${local.app_name}\nenv=${var.env}\n"
}

resource "local_file" "config" {
  filename = "${path.module}/out/${local.app_name}-${var.env}.conf"
  content  = local.settings
}

output "config_path" {
  value = local_file.config.filename
}
```

## Let references define order

Reference attributes (aws_subnet.a.id) instead of using depends_on; Terraform then knows the dependency automatically.

**Quiz:** What is the address of resource "local_file" "config"?

- [ ] config.local_file
- [x] local_file.config
- [ ] local_file/config
- [ ] resource.config

*Answer:* local_file.config. type.name