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The Terraform CLI is the primary interface for managing infrastructure as code with Terraform. It provides a consistent command structure across cloud providers and on-premises environments, so the same commands and workflow apply whether you’re deploying to AWS, Azure, GCP, or elsewhere. This predictability helps teams collaborate and automate infrastructure reliably. A typical command pattern is:
Once you learn the CLI conventions, you can apply them across every Terraform project.

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Command structure and examples

Commands are invoked with the base keyword terraform followed by a subcommand and optional flags or parameters:
Example:
  • terraform — invokes the Terraform CLI.
  • plan — subcommand that generates an execution plan.
  • -out=planfile — optional flag that saves the plan for later use with apply.
Use this structure to compose commands for initialization, validation, planning, applying, and destruction.

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Terraform workflow mapped to CLI commands

Terraform’s recommended workflow maps directly to CLI subcommands. Follow these steps to develop, test, and manage infrastructure safely. Canonical sequence of commands:
Note: Running terraform plan before terraform apply is a best practice—it lets you review changes and avoids surprises.
Be careful with terraform destroy. It will remove infrastructure managed by Terraform. Confirm that you really intend to destroy resources before typing yes.

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Core CLI commands — quick reference

Below are the most commonly used Terraform subcommands with a short description and example usage. This list is not exhaustive but covers the commands most teams use daily.
The image lists various Terraform subcommands, with some checked off, such as "apply," "init," "destroy," "validate," and "version." It also notes that this is not an exhaustive list.

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Additional commonly used subcommands

Beyond the core workflow, Terraform includes powerful subcommands for state management, debugging, and advanced operations:
  • terraform state — inspect and manually modify state objects (use carefully).
  • terraform show — display state or plan details in a human-readable format.
  • terraform import — bring existing external resources under Terraform management.
  • terraform fmt and terraform validate — help enforce configuration quality and consistency.

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Environment variables

Environment variables are a secure, convenient way to provide credentials, configure Terraform behavior, and set input variables without embedding secrets in .tf files. Why use environment variables?
  • Avoid committing credentials into version control.
  • Provide defaults or overrides for variables in CI/CD pipelines.
  • Control logging and runtime behavior for debugging.
Common environment variables:
  • TF_LOG — set Terraform logging level (TRACE, DEBUG, INFO, WARN, ERROR). Useful for troubleshooting.
  • TF_VAR_<name> — set Terraform input variables from the environment. For example:
    A configuration referencing var.server_name will pick up this value.
  • Provider-specific variables — many providers support environment-based credentials (for example AWS or Azure environment variables). Terraform checks multiple sources for credentials, including environment variables and credential helpers.
Example combined environment setup:
Use environment variables for credentials and sensitive values instead of hardcoding them into .tf files to reduce the risk of accidentally committing secrets.

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Best practices and tips

  • Always run terraform fmt and terraform validate before committing changes.
  • Use terraform plan -out=planfile and terraform apply planfile to ensure the exact planned changes are applied.
  • Store state securely (remote backends like S3 with locking via DynamoDB, or HashiCorp Consul, are recommended for team workflows).
  • Use workspaces, modules, and variable files to organize environments and reusable components.
  • Limit the use of terraform state commands; prefer importing and re-creating resources through configuration when possible.
Wrapping up You now have a concise, practical overview of the Terraform CLI: its command structure, mapped workflow, useful subcommands, and secure use of environment variables. In later sections you can explore advanced topics like remote state backends, workspaces, custom providers, and automation patterns for CI/CD.

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