If you’ve worked on text parsing projects – or an app that needed it – then you know what regular expressions are. It truly has been a lifesaver for me on many, many occassions. If, however, you haven’t dealt with it before, here’s some background on it:
According to Wikipedia, in computing, a regular expression is a string that is used to describe or match a set of strings, according to certain syntax rules.
For example, to capture the word Perl in the text below, you would use the following expression: .*(Perl).
Regular expressions are used by many text editors and utilities to search and manipulate bodies of text based on certain patterns. Many programming languages support regular expressions for string manipulation. For example, Perl and Tcl have a powerful regular expression engine built directly into their syntax.
How does it work?
- . (dot) means match anything
- * (asterisk) means match the previous character 0 or more times
- (Perl) (open & close parenthesis) mean capture whatever’s in it
A tool that I personally use to learn, construct, and test regular expressions is called: The Regex Coach. This tool offers many views to show how the regex engine parses text, which garners you knowledge on how it works internally, so you can write more advanced expressions.
Here’s what the tool looks like:
To end this post, I highly recommend reading Master Regular Expressions by Jeffrey E. F. Freidl to learn how/when to use it and the text-processing power it offers. This book, in my opinion, reads like a novel and is the best book on regular expressions.Take care! =0)