Terragrunt Function Overview

As you design your infrastructure with Terragrunt, leveraging its built-in functions can greatly enhance modularity, maintainability, and dynamic configuration. Below, we present a concise overview of core Terragrunt functions, along with practical examples and links to further resources.

Core Terragrunt Functions

Function	Description
`read_terragrunt_config`	Read and parse another Terragrunt configuration file, giving you access to its inputs, dependencies, and locals.
`find_in_parent_folders`	Recursively search parent directories to locate specific files (e.g., `terragrunt.hcl`), enabling shared configs.
`path_relative_to_include`	Compute the relative path from the current file to an included configuration, promoting modular directory layouts.
`get_terragrunt_dir`	Return the full path of the directory containing the current `terragrunt.hcl` file, useful for dynamic file references.
`get_parent_terragrunt_dir`	Retrieve the directory path of the parent Terragrunt configuration, supporting hierarchical inheritance.
`run_cmd`	Execute a shell command directly within Terragrunt, allowing automation of external tools or scripts.

Warning

Use run_cmd with caution. Executing shell commands can expose sensitive information or introduce security risks. Always validate inputs and avoid hardcoding credentials.

The image lists Terragrunt functions in a vertical flowchart format, including functions like `read_terragrunt_config` and `run_cmd`.

Combining Terragrunt with Terraform Functions

Terragrunt functions become even more powerful when combined with Terraform’s native functions. For example, to extract just the directory name of your current Terragrunt configuration, you can use Terraform’s basename together with get_terragrunt_dir:

# Returns the base name of the directory containing this Terragrunt configuration
locals {
  current_module = basename(get_terragrunt_dir())
}

This pattern helps you dynamically name resources or output modules based on directory structure—ideal for large, multi-environment projects.

Links and References

Terragrunt Documentation: https://terragrunt.gruntwork.io/docs/
Terraform Language Functions: https://developer.hashicorp.com/terraform/language/functions
Terragrunt GitHub Repository: https://github.com/gruntwork-io/terragrunt
Best Practices for Infrastructure as Code: https://www.hashicorp.com/resources/series/infrastructure-as-code-guide

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