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# config-rs
[](https://travis-ci.org/mehcode/config-rs)
[](https://crates.io/crates/config)
[](https://docs.rs/config)
> Layered configuration system for Rust applications (with strong support for [12-factor] applications).
[12-factor]: https://12factor.net/config
- Set defaults
- Set explicit values (to programmatically override)
- Read from [JSON], [TOML], and [YAML] 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/chyh1990/yaml-rust
## Install
```toml
[dependencies]
config = "0.2"
```
- `json` - Adds support for reading JSON files
- `yaml` - Adds support for reading YAML files
- `toml` - Adds support for reading TOML files (included by default)
## Usage
Configuration is gathered by building a `Source` and then merging that source into the
current state of the configuration.
```rust
fn main() {
// Add environment variables that begin with RUST_
config::merge(config::Environment::new("RUST"));
// Add 'Settings.json'
config::merge(config::File::new("Settings", config::FileFormat::Json));
// Add 'Settings.$(RUST_ENV).json`
let name = format!("Settings.{}", config::get_str("env").unwrap());
config::merge(config::File::new(&name, config::FileFormat::Json));
}
```
Note that in the above example the calls to `config::merge` could have
been re-ordered to influence the priority as each successive merge
is evaluated on top of the previous.
Configuration values can be retrieved with a call to `config::get` and then
coerced into a type with `as_*`.
```toml
# Settings.toml
debug = 1
```
```rust
fn main() {
// Add 'Settings.toml' (from above)
config::merge(config::File::new("Settings", config::FileFormat::Toml));
// Get 'debug' and coerce to a boolean
assert_eq!(config::get("debug").unwrap().as_bool(), Some(true));
// You can use a type suffix on `config::get` to simplify
assert_eq!(config::get_bool("debug"), Some(true));
assert_eq!(config::get_str("debug"), Some("true"));
}
```
See the [examples](https://github.com/mehcode/config-rs/tree/master/examples) for
more usage information.
## License
config-rs is primarily distributed under the terms of both the MIT license and the Apache License (Version 2.0).
See LICENSE-APACHE and LICENSE-MIT for details.
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