# fmt and validate — Terraform

Source: https://www.skillbyai.com/en/terraform/q-fmt

> Fast checks before plan.

## Style and correctness

`terraform fmt` rewrites files to the canonical style; `fmt -check -diff` reports differences without changing files (exit code 3 when changes are needed), ideal for CI. `terraform validate` checks syntax, references and argument names against provider schemas, catching typos like `contents` instead of `content` without touching real infrastructure. Linters such as TFLint and security scanners such as Checkov or Trivy add provider-specific and security rules.

## Consistent, checked, reviewed

Formatting, validation and plan-based reviews keep Terraform changes safe as teams grow.

![Three ideas: fmt and validate, CI workflow, checklist.](assets/figures/terraform/section-8-map.svg) — Figure 8.1 — Quality checks, CI and checklist.

## fmt -check on a messy file, run

I ran this with Terraform 1.16.4 and the hashicorp/local 2.9.1 and hashicorp/random 3.9.1 providers, which manage local files and random values, so no cloud account was needed; each example starts from a fresh directory. fmt shows the diff it would apply (indentation and aligned equals signs) and exits with code 3, which fails a CI check.

```bash
terraform fmt -check -diff -no-color main.tf | tail -6; echo "exit code: ${PIPESTATUS[0]}"
```

Output:

```
 variable "region" {
-type = string
-  default    =   "ap-south-1"
+  type    = string
+  default = "ap-south-1"
 }
exit code: 3
```

## validate catching a typo, run

I ran this with Terraform 1.16.4 and the hashicorp/local 2.9.1 and hashicorp/random 3.9.1 providers, which manage local files and random values, so no cloud account was needed; each example starts from a fresh directory. validate reports that the argument "contents" is not expected and suggests "content".

```bash
terraform validate -no-color 2>&1 | grep -E "Error|contents|not expected"
```

Output:

```
Error: Unsupported argument
  11:   contents = "hello"
An argument named "contents" is not expected here. Did you mean "content"?
```

**Quiz:** What does terraform validate check?

- [x] Syntax, references and arguments against provider schemas, without calling cloud APIs
- [ ] Whether resources exist in the cloud
- [ ] Costs
- [ ] Who wrote the code

*Answer:* Syntax, references and arguments against provider schemas, without calling cloud APIs. Cheap correctness checks.