config-rs

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

• 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 )

Install

[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.

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_*.

# Settings.toml
debug = 1

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 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.