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Macro std::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);

© 2010 The Rust Project Developers
Licensed under the Apache License, Version 2.0 or the MIT license, at your option.
https://doc.rust-lang.org/std/macro.option_env.html