Regular Expression Tutorial - Learn How to Use Regular Expressio. This tutorial teaches you all you need to know to be able to craft powerful time-saving regular expressions. It starts with the most basic concepts, so that you can follow this tutorial even if you know nothing at all about regular expressions yet. The tutorial doesn't stop there. It also explains how a regular expression engine works on the inside, and alert you at the consequences. This helps you to quickly understand why a particular regex does not do what you initially expected.
It will save you lots of guesswork and head scratching when you need to write more complex regexes. What Regular Expressions Are Exactly - Terminology Basically, a regular expression is a pattern describing a certain amount of text. This first example is actually a perfectly valid regex. \b[A-Z0-9._%+-]+@[A-Z0-9.-]+\.
With the above regular expression pattern, you can search through a text file to find email addresses, or verify if a given string looks like an email address. Different Regular Expression Engines. Country Code List: ISO 3166-1993 (E) DataPortability.org - Share and remix data using open standards. WURFL.