AWS SDK for Ruby
Developer Guide

Stopping an Amazon EC2 Instance

The following example stops the instance i-123abc in the us-west-2 region.

require 'aws-sdk-ec2' # v2: require 'aws-sdk' ec2 = 'us-west-2') i = ec2.instance('i-123abc') if i.exists? case i.state.code when 48 # terminated puts "#{id} is terminated, so you cannot stop it" when 64 # stopping puts "#{id} is stopping, so it will be stopped in a bit" when 80 # stopped puts "#{id} is already stopped" else i.stop end end