How to name resources dynamically based on the env they are in?

Question

I'm trying to unify naming of resources, depending on the environment (dev, stage or prod). I will illustrate with an example.

Let's say I want to create an aws iam user resource like:

resource "aws_iam_user" "iam_foo" {
  name = "foo_dev"
}

Here I hard-coded "dev" into the name of the resource. But ideally I would like that to be done dynamically based on the folder it is located in (folder resembles an environment like dev or prod).

The folder structure looks something like:

├── README.md
├── meow-development
│   ├── locals.tf -> ../locals.tf
│   ├── main.tf
│   └── s3.tf
├── meow-production
│   ├── locals.tf -> ../locals.tf
│   ├── main.tf
│   └── s3.tf
├── meow-staging
│   ├── locals.tf -> ../locals.tf
│   ├── main.tf
│   └── s3.tf

So what I am trying to achieve is something like:

resource "aws_iam_user" "iam_foo" {
  name = naming_function(name) # Not intended as actual code
}

The naming function takes a name as input and names it according to the env. So if this resource is created under dev, then naming_function(woof) should return the string "woof_dev"

So my questions are:

1. How can I name things dynamically?
2. Is using a naming convention that includes the environment such as meow_{env_name} correct?

Answer 1

Create a terraform.tfvars inside the meow-development folder with

env_name = "dev"

In the main.tf inside the meow-development folder:

resource "aws_iam_user" "iam_foo" {
  name = "foo_${var.env_name}"
}

Same for other environments. Regarding naming convention, depends on the resource, having env as part of the name is considered a best practice.