How can I determine what the current stable version of Ruby is? - ruby

Question

I want to write a Ruby method that does two things:
Determine what the current stable version of Ruby is. My first thought is to get the response from https://www.ruby-lang.org/en/downloads/ and use RegEx to isolate the phrase The current stable version is [x]. Is there is an API I'm not aware of?
Get the URL to download the .tar.gz of that release. For this I was thinking the same thing, get it from the output of the site URL.
I'm looking for advice about the best way to go about it, or direction if there's something in place I might use to determine my desired results.

Answer 1

Ruby code to fetch the download page, then parse the current version and the link URL:
html = Net::HTTP.get(URI("https://www.ruby-lang.org/en/downloads/"))
vers = html[/http.*ruby-(.*).tar.gz/,1]
link = html[/http.*ruby-.*.tar.gz/]
GitHub code: ruby-stable-version.rb
Shell code:
ruby-stable-version

Answer 2

If you are using rbenv you can use ruby-build to get a list of ruby versions and then grep against that.
ruby-build --definitions | tail -r | grep -x -G -m 1 '[0-9]\.[0-9].[0-9]\-*[p0-9*]*'
You can then use that within your code like so:
version = `ruby-build --definitions | tail -r | grep -x -G -m 1 '[0-9]\.[0-9].[0-9]\-*[p0-9*]*'`.strip
You can then use this value to get the download URL.
url = "http://cache.ruby-lang.org/pub/ruby/#{version[0..2]}/ruby-#{version}.tar.gz"
And then download the file:
require 'open-uri'
open("ruby-#{version}.tar.gz", 'wb') do |file|
file << open(url).read
end
Learn more about rbenv here and ruby-build here.

Answer 3

Another possibility would be to use the Ruby source repository. Check version.h in every branch, filter by RUBY_PATCHLEVEL > -1 (-1 is used for -dev versions), sort by RUBY_VERSION and take the latest one.

Answer 4

You can use:
Ruby's built-in OpenURI, and Nokogiri, to read a page, parse it, search for certain tags, extract a parameter such as a "src" or "href".
OpenURI to read the URL, or curl or wget at the command-line to retrieve the file.
Nokogiri's tutorials including showing how to use OpenURI to retrieve the page and hand it off to Nokogiri.
OpenURI's docs show how to "open" URLs and retrieve their content using read. Once you've done that, the data will be easy to save to disk using something like this for text files:
File.write('some_file', open('http://www.example.com/').read)
or for binary:
File.open('some_file', 'wb') { |fo| fo.write(open('http://www.example.com/').read) }
There are examples of using both Nokogiri and OpenURI for this all over Stack Overflow.