Parse strings with Regular Expressions

Regular Expressions (commonly abbreviated as regex) are commonly used for lexical analysis and pattern-matching on streams of text. They are common in Unix text-processing utilities, such as grep, awk, and sed, and are an integral part of the Perl language. There are a few common variations in the syntax. A POSIX standard was approved in 1992, while other common variations include Perl and ECMAScript (JavaScript) dialects. The C++ regex library defaults to the ECMAScript dialect.

The regex library was first introduced to the STL with C++11. It can be very useful for finding patterns in text files.

To learn more about Regular Expression syntax and usage, I recommend the book, Mastering Regular Expressions by Jeffrey Friedl.

How to do it…

For this recipe, we will extract hyperlinks from an HTML file. A hyperlink is coded in HTML like this:

<a href="http://example.com/file.html">Text goes here</a>

We...