AWS EC2 Inventory script

inventory.rb

#!/usr/bin/ruby

require 'dotenv'
require 'aws'
require 'csv'

# patch instance to return runtime
class AWS::EC2::Instance
  def runtime
    @runtime ||= Time.now - launch_time
  end
end

# load .env into ENV
Dotenv.load

output_file = ARGV[0] || 'output.csv'
puts "Starting inventory, output will be saved to #{output_file}"

# get ec2 client - assumes AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY are in ENV
ec2 = AWS::EC2.new

region_fields = ['name', 'endpoint']
instance_fields = ['availability_zone', 'id', 'ip_address', 'instance_type', 'status', 'runtime', 'launch_time', 'key_name', 'image_id']

headers = region_fields.map {|field| "region_#{field}"}.concat(instance_fields).flatten
rows = []

# go through all regions and instances and store row data
ec2.regions.each do |region|
  puts "Taking inventory of #{region.name}..."
  region_data = region_fields.map {|field| region.send(field) }
  
  ec2.regions["#{region.name}"].instances.each do |i|
    rows << instance_fields.map { |field| i.send(field) }.unshift(region_data).flatten
  end
end

# output to csv
puts "Saving inventory to #{output_file}"
CSV.open(output_file, "w") do |csv|
  csv << headers
  rows.each { |row| csv << row }
end