How to do it...

1. In the bin folder, create a file called env_vars.rs

2. Add the following code and run it with cargo run --bin env_vars:

1   use std::env;
2
3   fn main() {
4     // We can iterate over all the env vars for the current
      process
5     println!("Listing all env vars:");
6     for (key, val) in env::vars() {
7       println!("{}: {}", key, val);
8     }
9
10    let key = "PORT";
11    println!("Setting env var {}", key);
12    // Setting an env var for the current process
13    env::set_var(key, "8080");
14
15    print_env_var(key);
16
17    // Removing an env var for the current process
18    println!("Removing env var {}", key);
19    env::remove_var(key);
20
21    print_env_var(key);
22  }
23
24  fn print_env_var(key: &str) {
25    // Accessing an env var
26    match env::var(key) {
27      Ok(val) => println!("{}: {}", key, val),
28      Err(e) => println!("Couldn't print env var {}: {}", key, e),
29    }
30  }