Ruby - Regex Non-Greedy Operator (?)- Using Ruby to easily scrape/search/spider a web page for "things" - Part 2

Hello again,

This is part 2 of the "Using Ruby to easily scrape/search/spider a web page for "things"" multi-part post.

In this post I will explain the use of the non-greedy regex operator. In the spider example used in part 1, I scraped for all uses of the html heading element. The html heading element includes h1, h2, h3, etc. More specifically, I was looking for all matches of the regex: <h[0-9]>(.*?)</h[0-9]>

The following breaks down and explains the above regex:
<h[0-9]> → Find <h followed by one digit ([0-9]) followed by >
.*? → Find any character (.) zero or more times (*) non-greedily (?)
</h[0-9]> → Find </h followed by one digit ([0-9]) followed by >

The parentheses (), mark what I want to capture from my regex match. In this case, it is the actual heading, I don't want to capture the <h[0-9]> or the </h[0-9]>.

The non-greedy operator (?) means that the regex should not be greedy; it should look-ahead to see if it can break what it is currently looking at. In the above example, the non-greedy operator was used to prevent the .* from matching everything and thus never allowing the regex to match </h[0-9]>. The following examples demonstrate greedy vs non-greedy:

Example 1: Greedy:
Regex: <h[0-9]>.*</h[0-9]>
Input: <h3>My Title</h3>
<h[0-9]> matches: <h3>
.* matches: My Title</h3>

Example 2: Non-Greedy:
Regex: <h[0-9]>.*?</h[0-9]>
Input: <h3>My Title</h3>
<h[0-9]> matches: <h3>
.*? matches: My Title
</h[0-9]> matches: </h3>

Further Reading:
Ruby regex, quick reference guide
Ruby-doc, user's guide to regex
Ruby API: Regexp
Rubular: A Ruby regular expression editor (Interactive)