Function std::env::var_os

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 or there’s another error.

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.

Errors

This function returns an error if the environment variable isn’t set.

This function may return an error if the environment variable’s name contains the equal sign character (=) or the NUL character.

This function may return an error if the environment variable’s value contains the NUL character.

Examples

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.")
}