Folder Hash

Overview

This module calculates a SHA256 hash of all files in a source directory. It’s designed for change detection in Terraform workflows, particularly useful for determining when source code has changed and rebuilds are needed.

Features

• Cross-platform compatibility - Automatically detects and uses sha256sum (Linux) or shasum (macOS)

• Optional debug output - Enable detailed logging for troubleshooting (disabled by default)

• File filtering - Exclude common directories/files (.git, node_modules, etc.)

• Error handling - Gracefully handles missing directories

• Consistent hashing - Uses absolute paths and sorted file lists for reproducible results

• Performance optimized - Excludes build artifacts and dependency directories by default

Usage

Basic Usage

module "folder_hash" {
  source = "./modules/utils/folder_hash"
  source_dir = "/path/to/your/source/directory"
}

# Use the hash in other modules
output "source_hash" {
  value = module.folder_hash.folder_hash
}

Advanced Usage with Custom Exclusions

module "folder_hash" {
  source = "./modules/utils/folder_hash"
  source_dir = "/path/to/your/source/directory"

  # Enable debug output
  debug = true

  # Custom exclude patterns
  exclude_patterns = [
    ".git",
    "node_modules",
    "dist",
    "*.log",
    ".terraform",
    ".venv",
  ]
}

Inputs

Name	Description	Type	Default	Required
source_dir	The source directory to calculate hash for	string	n/a	Yes
debug	Enable debug output to stderr	bool	false	No
exclude_patterns	List of glob patterns to exclude from hash calculation	list(string)	[“.git”, “.terraform”, “node_modules”, “.DS_Store”]	No

Outputs

Name	Description
folder_hash	The calculated SHA256 hash of the source directory

How It Works

1. Path Resolution: Converts the source directory to an absolute path

2. File Discovery: Finds all files in the directory recursively

3. Hash Calculation: Calculates SHA256 of each file, sorts the results, and creates a final hash

4. Debug Output: Provides detailed logging for troubleshooting

Example Debug Output

When debug = true:

Debug: Source directory is: /path/to/source
Debug: Current working directory is: /current/dir
Debug: Exclude patterns: .git .terraform node_modules .DS_Store
Debug: Using hash command: sha256sum
Debug: Absolute source directory is: /absolute/path/to/source
Debug: Directory exists, calculating hash...
Debug: Changed to directory: /absolute/path/to/source
Debug: Find command: find . -type f ! -path '*/.git/*' ! -name '.git' ...
Debug: Files found:
./file1.py
./file2.py
./subdir/file3.py
Debug: Calculated hash: a1b2c3d4e5f6...

Platform Support

• Linux - Uses sha256sum

• macOS - Uses shasum -a 256

• Windows - Requires bash (WSL, Git Bash, or Cygwin)

Dependencies

• bash shell

• find command

• sha256sum (Linux) or shasum (macOS)

Notes

• The hash is calculated based on file content, not file names or timestamps

• Empty directories are ignored

• Hidden files (starting with .) are included unless explicitly excluded

• The hash is deterministic and will be the same for identical directory contents

• Exclusion patterns use standard shell glob syntax (* matches any characters, ? matches single character)

• Debug output is sent to stderr and won’t affect Terraform output when disabled