HCL and Configuration

HashiCorp Configuration Language (HCL) is the language used to write Terraform configuration files. This lesson covers HCL syntax, block structure, arguments, expressions, functions, and comments.

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HCL Basics

HCL files use the .tf extension. The language is designed to be:

• Human-readable — easy to write and review
• Machine-friendly — parseable and generatable
• Declarative — describes the desired end state

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Block Structure

HCL is built around blocks. Every block has a type, optional labels, and a body:

block_type "label_1" "label_2" {
  argument = value
}

Common Block Types

Block Type	Labels	Purpose
terraform	none	Terraform settings (providers, backend)
provider	provider name	Provider configuration
resource	type, name	Infrastructure resource
data	type, name	Data source (read-only)
variable	name	Input variable
output	name	Output value
locals	none	Local values
module	name	Module call

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Arguments and Attributes

Arguments assign values inside blocks: