Find the ARN/AWS Account ID (whoami) for a given credential set via AWS Ruby SDK

get_aws_account_id.rb

require 'aws-sdk'

def get_aws_account_id(access_key_id, secret_access_key)
  begin
    iam = AWS::IAM.new(:access_key_id => access_key_id,
                       :secret_access_key => secret_access_key)
    iam = iam.client.get_user
    id, user = iam[:user][:arn].match('^arn:aws:iam::([0-9]{12}):(.*)$').captures
  rescue AWS::IAM::Errors::AccessDenied
      result = $!
      id, user = result.to_s.match('^User: arn:aws:iam::([0-9]{12}):(.*) is not auth.*$').captures
  end
  raise 'incorrect account id' unless id.match(/^[0-9]{12}$/)
  [id, user]
end