# config-rs

> Layered configuration system for Rust applications (with strong support for [12-factor] applications).

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[12-factor]: https://12factor.net/config

 - Set defaults
 - Set explicit values (to programmatically override)
 - Read from [JSON], [TOML], [YAML], [INI], [RON], [JSON5], [CORN] files
 - Read from environment
 - Loosely typed — Configuration values may be read in any supported type, as long as there exists a reasonable conversion
 - Access nested fields using a formatted path — Uses a subset of JSONPath; currently supports the child ( `redis.port` ) and subscript operators ( `databases[0].name` )

[JSON]: https://github.com/serde-rs/json
[TOML]: https://github.com/toml-lang/toml
[YAML]: https://github.com/Ethiraric/yaml-rust2
[INI]: https://github.com/zonyitoo/rust-ini
[RON]: https://github.com/ron-rs/ron
[JSON5]: https://github.com/callum-oakley/json5-rs
[CORN]: https://cornlang.dev/

Please note that this library can not be used to write changed configuration
values back to the configuration file(s)!

## Usage

### Feature flags

 - `ini` - Adds support for reading INI files
 - `json` - Adds support for reading JSON files
 - `yaml` - Adds support for reading YAML files
 - `toml` - Adds support for reading TOML files
 - `ron` - Adds support for reading RON files
 - `json5` - Adds support for reading JSON5 files
 - `corn` - Adds support for reading Corn files

### Support for custom formats

Library provides out of the box support for most renowned data formats such as JSON or Yaml. Nonetheless, it contains an extensibility point - a `Format` trait that, once implemented, allows seamless integration with library's APIs using custom, less popular or proprietary data formats.

See [custom_file_format](https://github.com/rust-cli/config-rs/tree/main/examples/custom_file_format) example for more information.

### More

See the [documentation](https://docs.rs/config) or [examples](https://github.com/rust-cli/config-rs/tree/main/examples) for
more usage information.

## License

Licensed under either of

* Apache License, Version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or <https://www.apache.org/licenses/LICENSE-2.0>)
* MIT license ([LICENSE-MIT](LICENSE-MIT) or <https://opensource.org/license/mit>)

at your option.
