Verifying the format of a string using regular expressions
Regular expressions are a language intended for performing pattern matching and replacements in texts. C++11 provides support for regular expressions within the standard library through a set of classes, algorithms, and iterators available in the header
<regex>. In this recipe, we will learn how regular expressions can be used to verify that a string matches a pattern (examples can include verifying an email or IP address formats).
Throughout this recipe, we will explain, whenever necessary, the details of the regular expressions that we use. However, you should have at least some basic knowledge of regular expressions in order to use the C++ standard library for regular expressions. A description of regular expressions syntax and standards is beyond the purpose of this book; if you are not familiar with regular expressions, it is recommended that you read more about them before continuing...