This Ruby gem builds RSS 2.0 feeds from a feed config.
With the feed config containing the URL to scrape and CSS selectors for information extraction (like title, URL, ...) your RSS builds. Extractors and chain-able post processors make information extraction, processing and sanitizing a breeze. Scraping JSON responses and setting HTTP request headers is supported, too.
Searching for a ready to use app which serves generated feeds via HTTP?
Head over to html2rss-web!
To support the development, feel free to sponsor this project on Github. Thank you! 💓
| Install | gem install html2rss |
|---|---|
| Usage | html2rss help |
You can also install it as a dependency in your Ruby project:
| 🤩 Like it? | Star it! ⭐️ |
|---|---|
Add this line to your Gemfile: |
gem 'html2rss' |
| Then execute: | bundle |
| In your code: | require 'html2rss' |
Create a file called my_config_file.yml with this example content:
channel:
url: https://stackoverflow.com/questions
selectors:
items:
selector: "#hot-network-questions > ul > li"
title:
selector: a
link:
selector: a
extractor: hrefBuild the RSS with: html2rss feed ./my_config_file.yml.
Here's a minimal working example within Ruby:
require 'html2rss'
rss =
Html2rss.feed(
channel: { url: 'https://stackoverflow.com/questions' },
selectors: {
items: { selector: '#hot-network-questions > ul > li' },
title: { selector: 'a' },
link: { selector: 'a', extractor: 'href' }
}
)
puts rssA feed config consists of a channel and a selectors Hash.
The contents of both hashes are explained in the chapters below.
Good to know:
- You'll find extensive example feed configs at
spec/*.test.yml. - See
html2rss-configsfor ready-made feed configs! - If you've already created feed configs, you're invited to send a PR to
html2rss-configsto make your config available to the general public.
Alright, let's move on.
| attribute | type | default | remark | |
|---|---|---|---|---|
url |
required | String | ||
title |
optional | String | auto-generated | |
description |
optional | String | auto-generated | |
ttl |
optional | Integer | 360 |
TTL in minutes |
time_zone |
optional | String | 'UTC' |
TimeZone name |
language |
optional | String | 'en' |
Language code |
author |
optional | String | Format: email (Name) |
|
headers |
optional | Hash | {} |
Set HTTP request headers. See notes below. |
json |
optional | Boolean | false |
Handle JSON response. See notes below. |
Sometimes there are structurally equal pages with different URLs. In such a case you can add dynamic parameters to the channel's attributes.
Example of a dynamic id parameter in the channel URLs:
channel:
url: "http://domainname.tld/whatever/%<id>s.html"Command line usage example:
bundle exec html2rss feed the_feed_config.yml id=42See a Ruby example
config = Html2rss::Config.new({ channel: { url: 'http://domainname.tld/whatever/%<id>s.html' } }, {}, { id: 42 })
Html2rss.feed(config)See the more complex formatting of the sprintf method for formatting options.
First, you must give an items selector hash which contains a CSS selector. The selector selects a collection of HTML tags from which the RSS feed items are build.
Except the items selector, all other keys are scoped to each item of the collection.
Then, to build a
valid RSS 2.0 item,
you need to have at least a title or a description. You can have both.
Having an items and a title selector is already enough to build a simple feed.
Your selectors Hash can contain arbitrary named selectors, but only a few will make it into the RSS feed (This due to the RSS 2.0 specification):
| RSS 2.0 tag | name in html2rss |
remark |
|---|---|---|
title |
title |
|
description |
description |
Supports HTML. |
link |
link |
A URL. |
author |
author |
|
category |
categories |
See notes below. |
guid |
guid |
Default title/description. See notes below. |
enclosure |
enclosure |
See notes below. |
pubDate |
updated |
An instance of Time. |
comments |
comments |
A URL. |
source |
Not yet supported. |
Every named selector in your selectors hash can have these attributes:
| name | value |
|---|---|
selector |
The CSS selector to select the tag with the information. |
extractor |
Name of the extractor. See notes below. |
post_process |
A hash or array of hashes. See notes below. |
Extractors help with extracting the information from the selected HTML tag.
- The default extractor is
text, which returns the tag's inner text. - The
htmlextractor returns the tag's outer HTML. - The
hrefextractor returns a URL from the tag'shrefattribute and corrects relative ones to absolute ones. - The
attributeextractor returns the value of that tag's attribute. - The
staticextractor returns the configured static value (it doesn't extract anything). - See file list of extractors.
Extractors might need extra attributes on the selector hash. 👉 Read their docs for usage examples.
See a Ruby example
Html2rss.feed(
channel: {}, selectors: { link: { selector: 'a', extractor: 'href' } }
)See a YAML feed config example
channel:
# ... omitted
selectors:
# ... omitted
link:
selector: 'a'
extractor: 'href'Extracted information can be further manipulated with post processors.
| name | |
|---|---|
gsub |
Allows global substitution operations on Strings (Regexp or simple pattern). |
html_to_markdown |
HTML to Markdown, using reverse_markdown. |
markdown_to_html |
converts Markdown to HTML, using kramdown. |
parse_time |
Parses a String containing a time in a time zone. |
parse_uri |
Parses a String as URL. |
sanitize_html |
Strips unsafe and uneeded HTML and adds security related attributes. |
substring |
Cuts a part off of a String, starting at a position. |
template |
Based on a template, it creates a new String filled with other selectors values. |
sanitize_html post processor for HTML content. Never trust the internet!
👉 Read their docs for usage examples.
See a Ruby example
Html2rss.feed(
channel: {},
selectors: {
description: {
selector: '.content', post_process: { name: 'sanitize_html' }
}
}
)See a YAML feed config example
channel:
# ... omitted
selectors:
# ... omitted
description:
selector: '.content'
post_process:
- name: sanitize_htmlPass an array to post_process to chain the post processors.
YAML example: build the description from a template String (in Markdown) and convert that Markdown to HTML
channel:
# ... omitted
selectors:
# ... omitted
price:
selector: '.price'
description:
selector: '.section'
post_process:
- name: template
string: |
# %{self}
Price: %{price}
- name: markdown_to_htmlNote the use of | for a multi-line String in YAML.
The categories selector takes an array of selector names. Each value of those
selectors will become a <category> on the RSS item.
See a Ruby example
Html2rss.feed(
channel: {},
selectors: {
genre: {
# ... omitted
selector: '.genre'
},
branch: { selector: '.branch' },
categories: %i[genre branch]
}
)See a YAML feed config example
channel:
# ... omitted
selectors:
# ... omitted
genre:
selector: ".genre"
branch:
selector: ".branch"
categories:
- genre
- branchBy default, html2rss generates a GUID from the title or description.
If this does not work well, you can choose other attributes from which the GUID is build. The principle is the same as for the categories: pass an array of selectors names.
In all cases, the GUID is a SHA1-encoded string.
See a Ruby example
Html2rss.feed(
channel: {},
selectors: {
title: {
# ... omitted
selector: 'h1'
},
link: { selector: 'a', extractor: 'href' },
guid: %i[link]
}
)See a YAML feed config example
channel:
# ... omitted
selectors:
# ... omitted
title:
selector: "h1"
link:
selector: "a"
extractor: "href"
guid:
- linkAn enclosure can be any file, e.g. a image, audio or video.
The enclosure selector needs to return a URL of the content to enclose. If the extracted URL is relative, it will be converted to an absolute one using the channel's URL as base.
Since html2rss does no further inspection of the enclosure, its support comes with trade-offs:
- The content-type is guessed from the file extension of the URL.
- If the content-type guessing fails, it will default to
application/octet-stream. - The content-length will always be undetermined and therefore stated as
0bytes.
Read the RSS 2.0 spec for further information on enclosing content.
See a Ruby example
Html2rss.feed(
channel: {},
selectors: {
enclosure: { selector: 'img', extractor: 'attribute', attribute: 'src' }
}
)See a YAML feed config example
channel:
# ... omitted
selectors:
# ... omitted
enclosure:
selector: "img"
extractor: "attribute"
attribute: "src"Although this gem's name is html2rss, it's possible to scrape and process JSON.
Adding json: true to the channel config will convert the JSON response to XML.
See a Ruby example
Html2rss.feed(
channel: {
url: 'https://example.com', json: true
},
selectors: {} # ... omitted
)See a YAML feed config example
channel:
url: https://example.com
json: true
selectors:
# ... omittedSee example of a converted JSON object
This JSON object:
{
"data": [{ "title": "Headline", "url": "https://example.com" }]
}converts to:
<object>
<data>
<array>
<object>
<title>Headline</title>
<url>https://example.com</url>
</object>
</array>
</data>
</object>Your items selector would be array > object, the item's link selector would be url.
See example of a converted JSON array
This JSON array:
[{ "title": "Headline", "url": "https://example.com" }]converts to:
<array>
<object>
<title>Headline</title>
<url>https://example.com</url>
</object>
</array>Your items selector would be array > object, the item's link selector would be url.
You can add any HTTP headers to the request to the channel URL. Use this to e.g. have Cookie or Authorization information sent or to spoof the User-Agent.
See a Ruby example
Html2rss.feed(
channel: {
url: 'https://example.com',
headers: {
'User-Agent': 'html2rss-request',
'X-Something': 'Foobar',
Authorization: 'Token deadbea7',
Cookie: 'monster=MeWantCookie'
}
},
selectors: {}
)See a YAML feed config example
channel:
url: https://example.com
headers:
"User-Agent": "html2rss-request"
"X-Something": "Foobar"
"Authorization": "Token deadbea7"
"Cookie": "monster=MeWantCookie"
selectors:
# ...The headers provided by the channel are merged into the global headers.
By default, html2rss keeps the order of the collection returned from the items selector. The items selector hash can optionally contain an order attribute.
If its value is reverse, the order of items in the RSS will reverse.
See a YAML feed config example
channel:
# ... omitted
selectors:
items:
selector: 'ul > li'
order: 'reverse'
# ... omittedNote that the order of items, according to the RSS 2.0 spec, should not matter to the feed-consuming client.
This step is not required to work with this gem. If you're using
html2rss-web
and want to create your private feed configs, keep on reading!
First, create a YAML file, e.g. feeds.yml. This file will contain your global config and multiple feed configs under the key feeds.
Example:
headers:
"User-Agent": "Mozilla/5.0 (iPhone; CPU iPhone OS 10_3_1 like Mac OS X) AppleWebKit/603.1.30 (KHTML, like Gecko) Version/10.0 Mobile/14E304 Safari/602.1"
feeds:
myfeed:
channel:
selectors:
myotherfeed:
channel:
selectors:Your feed configs go below feeds. Everything else is part of the global config.
Find a full example of a feeds.yml at spec/feeds.test.yml.
Now you can build your feeds like this:
Build feeds in Ruby
require 'html2rss'
myfeed = Html2rss.feed_from_yaml_config('feeds.yml', 'myfeed')
myotherfeed = Html2rss.feed_from_yaml_config('feeds.yml', 'myotherfeed')Build feeds on the command line
$ html2rss feed feeds.yml myfeed
$ html2rss feed feeds.yml myotherfeedTo display RSS feeds nicely in a web browser, you can:
- add a plain old CSS stylesheet, or
- use XSLT (eXtensible Stylesheet Language Transformations).
A web browser will apply these stylesheets and show the contents as described.
In a CSS stylesheet, you'd use element selectors to apply styles.
If you want to do more, then you need to create a XSLT. XSLT allows you to use a HTML template and to freely design the information of the RSS, including using JavaScript and external resources.
You can add as many stylesheets and types as you like. Just add them to your global configuration.
Ruby: a stylesheet config example
config = Html2rss::Config.new(
{ channel: {}, selectors: {} }, # omitted
{
stylesheets: [
{
href: '/relative/base/path/to/style.xls',
media: :all,
type: 'text/xsl'
},
{
href: 'http://example.com/rss.css',
media: :all,
type: 'text/css'
}
]
}
)
Html2rss.feed(config)YAML: a stylesheet config example
stylesheets:
- href: "/relative/base/path/to/style.xls"
media: "all"
type: "text/xsl"
- href: "http://example.com/rss.css"
media: "all"
type: "text/css"
feeds:
# ... omittedRecommended further readings:
- How to format RSS with CSS on lifewire.com
- XSLT: Extensible Stylesheet Language Transformations on MDN
- The XSLT used by html2rss-web
- Check that the channel URL does not redirect to a mobile page with a different markup structure.
- Do not rely on your web browser's developer console.
html2rssdoes not execute JavaScript. - Fiddling with
curlandpupto find the selectors seems efficient (curl URL | pup). - CSS selectors are versatile. Here's an overview.
- Check out the repository:
git clone ... && cd html2rss - Install Ruby >=3.3, if you haven't already.
- Run
bin/setupto install dependencies. - Run the test suite
bundle exec rspec.- To generate Test Coverage, run
COVERAGE=true bundle exec rspecand opencoverage/index.html.
- To generate Test Coverage, run
- For an interactive prompt You can also run
bin/console.
Releasing a new version
git pull- increase version in
lib/html2rss/version.rb bundlegit add Gemfile.lock lib/html2rss/version.rbVERSION=$(ruby -e 'require "./lib/html2rss/version.rb"; puts Html2rss::VERSION')git commit -m "chore: release $VERSION"git tag v$VERSIONstandard-changelog -fgit add CHANGELOG.md && git commit --amendgit tag v$VERSION -fgit push && git push --tags
Bug reports and pull requests are welcome on GitHub at https://github.com/html2rss/html2rss.
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