std::option_env!

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

Optionally inspect 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.

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

Examples

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

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