# Function std::env::var_os 1.0.0[−][src]

    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.

# Panics

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.

# Examples

    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