Function std::env::var_os1.0.0[][src]

pub fn var_os<K: AsRef<OsStr>>(key: K) -> Option<OsString>
Expand description

Fetches the environment variable key from the current process, returning None if the variable isn’t set.


This function may panic if key is empty, contains an ASCII equals sign '=' or the NUL character '\0', or when the value contains the NUL character.

Note that the method will not check if the environment variable is valid Unicode. If you want to have an error on invalid UTF-8, use the var function instead.


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)