# Terraform Templatefile

> Comprehensive guide and examples for using templatefile() and string templates in Terraform. Use this skill when asked about dynamic file generation, string interpolation, or template syntax in Terraform. Use when this capability is needed.

- Skill: `tomevault-io/terraform-templatefile` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add tomevault-io/terraform-templatefile`
- Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/terraform-templatefile/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: DevOps & Infra
- Author: tomevault-io (https://skillmd.com/u/tomevault-io)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/tomevault-io/terraform-templatefile

---



# Terraform Templatefile Skill

> **Note:** For a comprehensive overview of Terraform HCL syntax—including string interpolation, heredocs, template expressions, directives, and formatting—see the [terraform-syntax skill](/.github/skills/terraform-syntax/SKILL.md). Many syntax rules and best practices for templates are covered there and apply directly to templatefile usage.

## When to Use This Skill

- You want to generate files dynamically in Terraform (e.g., config, scripts, policies)
- You use the `templatefile()` function
- You want to apply string templates, interpolation, or conditional logic in templates
- You are looking for examples of template syntax, directives, or whitespace stripping
- If you want to generate a lot of files in a single directory, you can use the [hashicorp/dir/template](https://registry.terraform.io/modules/hashicorp/dir/template/latest) module with template capabilities.

## Content




### 1. templatefile() function

The [templatefile()](https://developer.hashicorp.com/terraform/language/functions/templatefile) function reads an external file and fills in variables:

```hcl
templatefile(path, vars)
```

- `path`: path to the template file (recommended extension: `.tftpl`)
- `vars`: map of variables used in the template

> **Naming convention:** Use the `.tftpl` extension for Terraform template files. This makes it clear that the file is a Terraform template and improves editor support and discoverability.

**Example:**
```hcl
data "template_file" "example" {
	template = file("${path.module}/example.tftpl")
	vars = {
		name = var.name
		port = var.port
	}
}

# Or with templatefile():
output "rendered" {
	value = templatefile("${path.module}/example.tftpl", {
		name = var.name
		port = var.port
	})
}
```

### 2. String Templates & Interpolation

See [string templates](https://developer.hashicorp.com/terraform/language/expressions/strings#string-templates).

- Variables: `${var.name}`
- Expressions: `${1 + 2}`
- Functions: `${upper(var.env)}`

**Example template.tpl:**
```text
server_name = "${name}"
listen_port = ${port}
env = "${upper(env)}"
```

### 3. Directives

See [directives](https://developer.hashicorp.com/terraform/language/expressions/strings#directives).

- `%{if condition}` ... `%{else}` ... `%{endif}`
- `%{for item in list}` ... `%{endfor}`

**Example:**
```text
%{if enable_tls}
tls_enabled = true
%{else}
tls_enabled = false
%{endif}

servers = [
%{ for s in servers ~}
	"${s}",
%{ endfor ~}
]
```

### 4. Whitespace Stripping


See [whitespace stripping](https://developer.hashicorp.com/terraform/language/expressions/strings#whitespace-stripping).

- Use `~` after `%{` or before `}` to remove whitespace.

**Standard for whitespace trimming:**

- `%{~ for ...}`
- `%{~ if ...}`
- `%{ endif ~}`
- `%{ endfor ~}`

This ensures consistent and minimal whitespace in rendered templates, especially for YAML/JSON output.

**Example:**
```text
%{~ for s in servers ~}
	"${s}",
%{ endfor ~}
```

### 5. Best Practices

- Use clear variable names in your template
- Keep templates as generic as possible
- Test templates with `terraform console` or outputs
- Document which variables are expected

> **Tip:** If you need to generate JSON or YAML output, it is often better to use the built-in `jsonencode()` or `yamlencode()` functions instead of writing JSON/YAML syntax manually in a string template. This avoids formatting errors and ensures valid output.

### 6. Common Pitfalls

- Forgetting to include variables in the vars map
- Syntax errors in directives (`%{if ...}`)
- Whitespace issues in YAML/JSON output

### 7. Extra Examples

**Complex template with for/if:**
```text
users = [
%{ for u in users ~}
	{
		name = "${u.name}"
		admin = %{if u.is_admin}true%{else}false%{endif}
	},
%{ endfor ~}
]
```

**Templatefile in resource:**
```hcl
resource "local_file" "config" {
	content  = templatefile("${path.module}/config.tpl", {
		users = var.users
	})
	filename = "${path.module}/rendered.conf"
}
```

### 8. Using the hashicorp/dir/template Module

The [hashicorp/dir/template](https://registry.terraform.io/modules/hashicorp/dir/template/latest) module allows you to render all template files in a directory using Terraform's string template syntax.

- By default, any file in the base directory whose filename ends in `.tmpl` is interpreted as a template.
- You can override the suffix by setting the variable `template_file_suffix` to any string that starts with a period and is followed by one or more non-period characters (e.g., `.tftpl`).
- Templates use Terraform's string template syntax and can use any built-in function except `templatefile` (which is used internally by the module).
- Files without the template file suffix are treated as static files and their local path is returned.

**Example usage:**
```hcl
module "render_templates" {
	source = "hashicorp/dir/template"
	base_dir = "${path.module}/templates"
	template_file_suffix = ".tftpl" # recommended
	vars = {
		name = var.name
		port = var.port
	}
}
```

> **Tip:** Use `.tftpl` as the template file suffix for consistency with the recommended convention in this skill.

---

## References
- [templatefile() function](https://developer.hashicorp.com/terraform/language/functions/templatefile)
- [String templates](https://developer.hashicorp.com/terraform/language/expressions/strings#string-templates)
- [Directives](https://developer.hashicorp.com/terraform/language/expressions/strings#directives)
- [Whitespace stripping](https://developer.hashicorp.com/terraform/language/expressions/strings#whitespace-stripping)
- [terraform-syntax skill](/.github/skills/terraform-syntax)
- [terraform instructions](/.github/instructions/terraform.instructions.md)

---
> Converted and distributed by [TomeVault](https://tomevault.io/claim/luscii) — claim your Tome and manage your conversions.
<!-- tomevault:4.0:skill_md:2026-04-16 -->