Function tracing::stdlib::env::var_os

1.0.0 · source ·
pub fn var_os<K>(key: K) -> Option<OsString>where
    K: AsRef<OsStr>,
Expand description

Fetches the environment variable key from the current process, returning None if the variable isn’t set or if there is another error.

It may return None if the environment variable’s name contains the equal sign character (=) or the NUL character.

Note that this function 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!("{key} is not defined in the environment.")