std::env
pub fn var_os<K: AsRef<OsStr>>(key: K) -> Option<OsString>
Fetches the environment variable key from the current process, returning None if the variable isn't set.
key
None
use std::env; let key = "HOME"; match env::var_os(key) { Some(val) => println!("{}: {:?}", key, val), None => println!("{} is not defined in the environment.", key) }Run