Function var 

pub fn var<K: AsRef<OsStr>>(key: K) -> Result<String, VarError>

Fetches the environment variable key from the current process.

Errors

Returns VarError::NotPresent if:

• The variable is not set.
• The variable’s name contains an equal sign or NUL ('=' or '\0').

Returns VarError::NotUnicode if the variable’s value is not valid Unicode. If this is not desired, consider using var_os.

Use env! or option_env! instead if you want to check environment variables at compile time.

Examples

use std::env;

let key = "HOME";
match env::var(key) {
    Ok(val) => println!("{key}: {val:?}"),
    Err(e) => println!("couldn't interpret {key}: {e}"),
}