# Function std::env::var_os

1.0.0 · source ·

    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 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.

## 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.")
    }

Run