Write and modify Terrafrom configuration from the CLI

This topic provides an overview of the Terraform CLI commands you can use to programmatically write and modify Terraform configuration code.

Introduction

The Terraform language is Terraform's primary user interface, and all of Terraform's workflows rely on configurations written in the Terraform language.

Workflows

Terraform CLI includes several commands to make Terraform code more convenient to work with. Integrating these commands into your editing workflow can potentially save you time and effort.

The terraform console command starts an interactive shell for evaluating Terraform expressions, which can be a faster way to verify that a particular resource argument results in the value you expect.
The terraform fmt command rewrites Terraform configuration files to a canonical format and style, so you don't have to waste time making minor adjustments for readability and consistency. It works well as a pre-commit hook in your version control system.
The terraform validate command validates the syntax and arguments of the Terraform configuration files in a directory, including argument and attribute names and types for resources and modules. The plan and apply commands automatically validate a configuration before performing any other work, so validate isn't a crucial part of the core workflow, but it can be very useful as a pre-commit hook or as part of a continuous integration pipeline.
The 0.13upgrade command and the 0.12upgrade command can automatically modify the configuration files in a Terraform module to help deal with major syntax changes that occurred in the 0.13 and 0.12 releases of Terraform. Both of these commands are only available in the Terraform version they are associated with, and you are expected to upgrade older code to be compatible with 0.12 before attempting to make it compatible with 0.13. For more detailed information about updating code for new Terraform versions, see the upgrade guides in the Terraform language docs.