core::option_env - Rust
Description: API documentation for the Rust `option_env` macro in crate `core`.
Keywords: rust, rustlang, rust-lang, option_env

# 1.0.0[−][src]Macro core::option_env

    macro_rules! option_env {
        ($name:expr) => { ... };
        ($name:expr,) => { ... };
    }

Optionally inspects an environment variable at compile time.

If the named environment variable is present at compile time, this will expand into an expression of type `Option<&'static str>` whose value is `Some` of the value of the environment variable. If the environment variable is not present, then this will expand to `None`. See `Option<T>` for more information on this type.

A compile time error is never emitted when using this macro regardless of whether the environment variable is present or not.

# Examples

    let key: Option<&'static str> = option_env!("SECRET_KEY");
    println!("the secret key might be: {:?}", key);Run

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