amazon_s3.yml

development:
  access_key_id: YOUR-KEY-ID
  secret_access_key: YOUR-SECRET-KEY

test:
  access_key_id:
  secret_access_key:

production:
  access_key_id: YOUR-KEY-ID
  secret_access_key: YOUR-SECRET-KEY

copy_buckets.rb

require 'aws/s3'

CONFIG = YAML.load_file("config/amazon_s3.yml")
CONFIG.symbolize_keys!
CONFIG.each_pair{|x,y| y.symbolize_keys! }

AWS::S3::Base.establish_connection! CONFIG[:production]

AWS::S3::S3Object.class_eval do
  def copy_to_bucket(copy_name, target_bucket, options = {})
    self.class.copy_to_bucket(key, copy_name, bucket.name, target_bucket, options)
  end
  
  def self.copy_to_bucket(key, copy_key, bucket = nil, to_bucket = nil, options = {})
    
    bucket          = bucket_name(bucket)
    source_key      = path!(bucket, key)
    default_options = {'x-amz-copy-source' => source_key, 'x-amz-metadata-directive' => "COPY"}
    target_key      = path!(to_bucket || bucket, copy_key)
    returning put(target_key, default_options) do
      acl(copy_key, to_bucket || bucket, acl(key, bucket)) if options[:copy_acl]
    end
  end
end

source_bucket = "bucket-name"
target_bucket = "target-bucket-name"

AWS::S3::Bucket.objects(source_bucket).each do |x|
  if AWS::S3::S3Object.exists? x.key, source_bucket
    puts "Skipping #{x.key}, file exists in #{target_bucket}"
    next
  end
  
  x.copy_to_bucket(x.key, target_bucket)
  puts "Copied #{x.key} to #{target_bucket}"
end