Generating an Atom feed using the rss gem

See Atom feeds for a summary of the Atom specification.

The rss gem is bundled with Ruby. On Debian, it is included in the librubyX.Y package.

Usage example

The README has the following example for generating an Atom feed:

require 'rss'

rss = RSS::Maker.make('atom') do |maker|
  maker.channel.author = 'matz'
  maker.channel.updated = Time.now.to_s
  maker.channel.about = 'http://www.ruby-lang.org/en/feeds/news.rss'
  maker.channel.title = 'Example Feed'

  maker.items.new_item do |item|
    item.link = 'http://www.ruby-lang.org/en/news/2010/12/25/ruby-1-9-2-p136-is-released/'
    item.title = 'Ruby 1.9.2-p136 is released'
    item.updated = Time.now.to_s
  end
end

puts rss

It generates the following output:

<?xml version="1.0" encoding="UTF-8"?>
<feed xmlns="http://www.w3.org/2005/Atom" xmlns:dc="http://purl.org/dc/elements/1.1/">
  <author>
    <name>matz</name>
  </author>
  <id>http://www.ruby-lang.org/en/feeds/news.rss</id>
  <title>Example Feed</title>
  <updated>2025-03-26T08:14:32+02:00</updated>

  <entry>
    <id>http://www.ruby-lang.org/en/news/2010/12/25/ruby-1-9-2-p136-is-released/</id>
    <link href="http://www.ruby-lang.org/en/news/2010/12/25/ruby-1-9-2-p136-is-released/"/>
    <title>Ruby 1.9.2-p136 is released</title>
    <updated>2025-03-26T08:14:32+02:00</updated>
    <dc:date>2025-03-26T08:14:32+02:00</dc:date>
  </entry>

  <dc:date>2025-03-26T08:14:32+02:00</dc:date>

</feed>

Observations

• The /feed/id is set to the value of channel.about.
• The /feed/entry/id is set to the value of items[i].link.
• /feed/dc:date and /feed/entry/dc:date elements are generated for some reason, with the same value as the corresponding updated element.

Decisions

For this blog …

• It should be fine to use Time.now for the channel.updated value, as long as I only run the script when the inputs have changed.

  But use Time.now.utc instead of Time.now.to_s.

• What to put in channel.about??

• Need to pick a fixed value for channel.id in order to not confuse consumers.

• The item.updated field should in theory be set to the date on which the page was last published, but it should be fine if it’s the date on which I updated it locally, even if I don’t publish the update straight away.

  To turn the date into a timestamp, set the time component to 12:00 UTC. There is no need to record the exact hour and minute of publication. In Ruby: Time.new("#{meta['date']} 12:00:00", in: 'Z')