std::env!

macro_rules! env { ($name:expr) => ({ /* compiler built-in */ }) }

Inspect an environment variable at compile time.

This macro will expand to the value of the named environment variable at compile time, yielding an expression of type &'static str.

If the environment variable is not defined, then a compilation error will be emitted. To not emit a compile error, use the option_env! macro instead.

Example

fn main() { let path: &'static str = env!("PATH"); println!("the $PATH variable at the time of compiling was: {}", path); }

let path: &'static str = env!("PATH");
println!("the $PATH variable at the time of compiling was: {}", path);