only look for env vars

describe_instances.rs

extern crate rusoto_core;
extern crate rusoto_ec2;

use rusoto_core::{default_tls_client, 
	              EnvironmentProvider,
	              Region};
use rusoto_ec2::{Ec2Client, 
	             DescribeInstancesRequest, 
	             Ec2};

fn main() {
    let dispatcher = default_tls_client().unwrap();
    let provider = EnvironmentProvider;
    let client = Ec2Client::new(dispatcher, provider, Region::UsEast1);
    let req = DescribeInstancesRequest::default();
    let res = client.describe_instances(&req).unwrap();

    match res.reservations {
    	Some(reservations) => for r in &reservations {
    		match r.instances {
    			Some(ref instances) => for i in instances.iter() { 
    				println!("{:?} - {:?}", i.instance_id.as_ref().unwrap(), i.instance_type.as_ref().unwrap());
    			},
    			None => println!("no instances!")
    		}
    	},
    	None => println!("nothing found")
    }
}