1.0.0[−][src]Macro std::env
Inspects 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.
Examples
let path: &'static str = env!("PATH"); println!("the $PATH variable at the time of compiling was: {}", path);Run
You can customize the error message by passing a string as the second parameter:
ⓘThis example deliberately fails to compile
let doc: &'static str = env!("documentation", "what's that?!");Run
If the documentation
environment variable is not defined, you'll get
the following error:
error: what's that?!