Add Check If A URL Resolves To 200 as a Ruby TIL

README.md

@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
 For a steady stream of TILs, [sign up for my newsletter](https://crafty-builder-6996.ck.page/e169c61186).
 
-_1293 TILs and counting..._
+_1294 TILs and counting..._
 
 ---
 
@@ -1013,6 +1013,7 @@ _1293 TILs and counting..._
 - [Build HTTP And HTTPS URLs](ruby/build-http-and-https-urls.md)
 - [Chaining Multiple RSpec Change Matchers](ruby/chaining-multiple-rspec-change-matchers.md)
 - [Check For Any Overlaps In List Of Ranges](ruby/check-for-any-overlaps-in-list-of-ranges.md)
+- [Check If A URL Resolves To 200](ruby/check-if-a-url-resolves-to-200.md)
 - [Check If An Object Includes A Module](ruby/check-if-an-object-includes-a-module.md)
 - [Check Return Status Of Running A Shell Command](ruby/check-return-status-of-running-a-shell-command.md)
 - [Click On Text With Capybara](ruby/click-on-text-with-capybara.md)

ruby/check-if-a-url-resolves-to-200.md

@@ -0,0 +1,29 @@
+# Check If A URL Resolves To 200
+
+Ruby's built-in [`Net::HTTP`
+library](https://ruby-doc.org/stdlib-2.7.0/libdoc/net/http/rdoc/Net/HTTP.html)
+allows us to make different kinds of HTTP requests. We can use it to make a
+`HEAD` request which will request the status of a URL without actually fetching
+its contents.
+
+We can work directly with `Net::HTTP` using strings, but I find it is easier
+and less error-prone to get help from the `URI` class.
+
+To make a `#head` request, we first need to establish a connection to the host
+with [the `#start`
+method](https://ruby-doc.org/stdlib-2.7.0/libdoc/net/http/rdoc/Net/HTTP.html#method-i-start).
+Then we can initiate our request from that connection object.
+
+```ruby
+url = 'https://my.app.com/path/to/video.mp4'
+uri = URI(url)
+conn = Net::HTTP.start(uri.host, uri.port, use_ssl: true)
+resp = conn.head(uri.path)
+
+resp.code
+#=> "200"
+```
+
+We initiate the connection with the host and port of our URL. Then request the
+`HEAD` response for the path of our URL. If we are working with an `https` URL,
+we need to indicate that with `use_ssl: true` in the `#start` method options.