frozen_string_literal: false

RSS reading and writing

Really Simple Syndication (RSS) is a family of formats that describe 'feeds,' specially constructed XML documents that allow an interested person to subscribe and receive updates from a particular web service. This portion of the standard library provides tooling to read and create these feeds.

The standard library supports RSS 0.91, 1.0, 2.0, and Atom, a related format. Here are some links to the standards documents for these formats:

Consuming RSS

If you'd like to read someone's RSS feed with your Ruby code, you've come to the right place. It's really easy to do this, but we'll need the help of open-uri:

require 'rss'
require 'open-uri'

url = 'http://www.ruby-lang.org/en/feeds/news.rss'
open(url) do |rss|
  feed = RSS::Parser.parse(rss)
  puts "Title: #{feed.channel.title}"
  feed.items.each do |item|
    puts "Item: #{item.title}"
  end
end

As you can see, the workhorse is RSS::Parser#parse, which takes the source of the feed and a parameter that performs validation on the feed. We get back an object that has all of the data from our feed, accessible through methods. This example shows getting the title out of the channel element, and looping through the list of items.

Producing RSS

Producing our own RSS feeds is easy as well. Let's make a very basic 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

As you can see, this is a very Builder-like DSL. This code will spit out an Atom feed with one item. If we needed a second item, we'd make another block with maker.items.new_item and build a second one.

Copyright © 2003-2007 Kouhei Sutou <kou@cozmixng.org>

You can redistribute it and/or modify it under the same terms as Ruby.

There is an additional tutorial by the author of RSS at: www.cozmixng.org/~rwiki/?cmd=view;name=RSS+Parser%3A%3ATutorial.en

frozen_string_literal: false

Namespace
Constants
CONTENT_PREFIX = 'content'
 

The prefix for the Content XML namespace.

CONTENT_URI = "http://purl.org/rss/1.0/modules/content/"
 

The URI of the Content specification.

DC_PREFIX = 'dc'
 

The prefix for the Dublin Core XML namespace.

DC_URI = "http://purl.org/dc/elements/1.1/"
 

The URI of the Dublin Core specification.

DublincoreModel = DublinCoreModel
 

For backward compatibility

IMAGE_PREFIX = 'image'
 

The prefix for the Image XML namespace.

IMAGE_URI = 'http://purl.org/rss/1.0/modules/image/'
 

The URI for the Image specification.

IMAGE_ELEMENTS = []
 

This constant holds strings which contain the names of image elements, with the appropriate prefix.

ITUNES_PREFIX = 'itunes'
 

The prefix for the iTunes XML namespace.

ITUNES_URI = 'http://www.itunes.com/dtds/podcast-1.0.dtd'
 

The URI of the iTunes specification.

AVAILABLE_PARSER_LIBRARIES = [ ["rss/xmlparser", :XMLParserParser], ["rss/xmlscanner", :XMLScanParser], ["rss/rexmlparser", :REXMLParser], ]
 

The list of all available libraries for parsing.

AVAILABLE_PARSERS = []
 

The list of all available parsers, in constant form.

VERSION = "0.2.7"
 

The current version of RSS

URI = "http://purl.org/rss/1.0/"
 

The URI of the RSS 1.0 specification

DEBUG = false
 
NotExceptedTagError = NotExpectedTagError # :nodoc:
 

For backward compatibility :X

UnknownConvertMethod = UnknownConversionMethodError # :nodoc:
 

for backward compatibility

SLASH_PREFIX = 'slash'
 

The prefix for the Slash XML namespace.

SLASH_URI = "http://purl.org/rss/1.0/modules/slash/"
 

The URI of the Slash specification.

SY_PREFIX = 'sy'
 

The prefix for the Syndication XML namespace.

SY_URI = "http://purl.org/rss/1.0/modules/syndication/"
 

The URI of the Syndication specification.

TAXO_PREFIX = "taxo"
 

The prefix for the Taxonomy XML namespace.

TAXO_URI = "http://purl.org/rss/1.0/modules/taxonomy/"
 

The URI for the specification of the Taxonomy XML namespace.

TAXO_ELEMENTS = []
 

The listing of all the taxonomy elements, with the appropriate namespace.