Envflag

A strict, zero-boilerplate environment variable manager with .env support and validation.

envflag enforces a disciplined approach to configuration: you must explicitly initialize the library (which loads .env files via dotenvy), and then query typed values through a validated builder API or simple convenience functions.

Features

• Strict Initialization: All queries panic if init() has not been called — no silent misconfiguration.
• Dotenv Support: Seamlessly loads .env files upon initialization, or from a custom path.
• Prefix Filtering: Keep only environment variables matching configured prefixes (e.g. APP_, SVC_).
• Validated Builder API: Chain .default(), .validate(), and .get() for type-safe, validated lookups that return Result.
• Built-in Validators: is_port, is_integer, is_positive_integer, is_positive_number, is_bool, is_non_empty, is_url, is_integer_in_range, and more.
• Custom Validators: Pass any Fn(&str) -> bool closure as a validator.
• Zero Boilerplate: No built-in logging or printing; you control how to display your config.

Usage Examples

Check the examples directory for runnable code:

• Basic Usage: examples/basic.rs - Initialize and query with convenience API.
• Validation: examples/validation.rs - Chain validators on environment variables.
• Prefix Filtering: examples/prefixes.rs - Filter and scope variables by prefix.
• Custom Init: examples/custom_init.rs - Load from a specific .env file path.

Installation

[dependencies]
envflag = { version = "0.1", features = ["full"] }

Feature Flags

Feature	Description
url	Enables strict URL validation in is_url via the url crate (WHATWG URL Standard).
regex	Enables matches_regex validator via fancy-regex.
tracing	Enables optional tracing::warn on validation failures and parse fallbacks in convenience API.
full	Enables all features above.

License

Released under the MIT License © 2026 Canmi