获取对象列表

def list_objects(client, bucket_name, max_keys = 50)
  if max_keys < 1 || max_keys > 1000
    puts 'Maximum number of objects to request must be between 1 and 1,000.'
    return
  end

  resp = client.list_objects(
    bucket: bucket_name,
    max_keys: max_keys
  )
  objects = resp.contents

  if objects.count.zero?
    puts "No objects in bucket '#{bucket_name}'."
    return
  else
    if resp.is_truncated
      puts "First #{objects.count} objects in bucket '#{bucket_name}':"
    else
      puts "Objects in bucket '#{bucket_name}':"
    end
    objects.each do |object|
      puts object.key
    end
  end
rescue StandardError => e
  puts "Error accessing bucket '#{bucket_name}' " \
    "or listing its objects: #{e.message}"
end