Copy one S3 bucket's contents to another bucket; supports file > 5gb. Also copies over Access Control List options and encryption options. Won't overwrite files that already exist on the bucket you're copying to.

s3_copy.rb

require 'aws-sdk'

class S3Copy
  attr_reader :from_bucket, :to_bucket

  def initialize(from_bucket, to_bucket)
    access_key = ENV['AWS_ACCESS_KEY_ID']
    secret_key = ENV['AWS_SECRET_ACCESS_KEY']

    s3_instance = AWS::S3.new(access_key_id: access_key, secret_access_key: secret_key)

    @from_bucket = s3_instance.buckets[from_bucket]
    @to_bucket = s3_instance.buckets[to_bucket]
  end

  def perform_copy
    from_bucket.objects.each do |f_obj|
      t_obj = to_bucket.objects[f_obj.key]
      options = {}
      
      next if t_obj.exists?

      options.merge!({ use_multipart_copy: true }) if f_obj.content_length > 5368709120
      options.merge!({ server_side_encryption: f_obj.server_side_encryption }) if f_obj.server_side_encryption?

      t_obj.copy_from(f_obj, options)
      t_obj.acl = f_obj.acl
    end
  end
end