《RegularExpressions Succinctly》：简洁掌握正则表达式指南

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《正则表达式精要》(RegularExpressionsSuccinctly)是由Joe Booth所著的一本关于正则表达式的技术书籍。该书特别关注于C# .Net语言环境下的正则表达式应用，旨在帮助读者深入理解并掌握这一强大的文本处理工具。作者通过简洁明了的方式，使复杂的正则表达式概念变得易于理解。本书的前言由Daniel Jebaraj撰写，强调了其作为 Syncfusion Inc.出版的作品，版权信息保护得非常严格。读者需在完成注册后，从官方网站www.syncfusion.com免费下载此书，以确保获取的是合法授权的版本。任何形式的未经许可的复制或分发都是被禁止的，这体现了对作者知识产权的尊重。书中内容涵盖了正则表达式的基础知识，包括元字符、量词、字符集、模式组合、选择与重复以及在C#中的实际应用示例。它不仅适合初学者快速入门，也适合有一定经验的开发者进一步提升他们的正则表达式技能。此外，由于是个人或教育用途专有，它不会涉及商业用途的许可。作者及其版权持有者明确声明，书中提供的所有信息不带有任何保证，且不对因使用本书信息产生的任何损失或责任负责。只有当读者同意书中的条款时，才能合法使用这本书。Syncfusion公司的品牌如SYNCFUSION, Succinctly, Deliver Innovation with Ease, Essential, and .NET Essentials是其商标标识。《RegularExpressions_Succinctly》是一本实用的教程，提供了C# .Net环境下正则表达式的系统学习资料，帮助读者在处理文本数据时更加高效和精准。无论是为了学习编程技巧，还是解决实际项目中的文本匹配问题，这本书都是一份宝贵的资源。

Chapter 1 Text Processing

Computers are very good at dealing with structured data, but cannot come anywhere close (yet)

to how good people are at dealing with text. For example, if the following text were recorded in a

help desk system:

Hi,

I called Jon on Tuesday, March 25th at 7pm and expressed a concern about my

slow times accessing www.cnn.com. He said he would fix it, but I never heard

back. Can someone contact me at Kellie.Booth@if.com ASAP? What does Ctrl-F5

mean, by the way?

Thanks

Kellie

Without much effort, a person can read that text and easily find the person Kellie talked to, the

problem website, the date, and the email address. However, such a simple task for a person is

rather difficult for a computer. What happens if the date was written as Mar-25 instead? Or if the

website didn’t include the “www” prefix? Or if it included “http:” in the address?

Patterns

How do people do it so well? Essentially, we understand patterns and can easily handle missing

information. We know a date may or may not have the day as part of it, and a month name

might be spelled out or might be abbreviated. We know that a website typically is a word or

more (without spaces), followed by a period and a common abbreviation like .com, .net, or .org.

Constructing a regex pattern is a matter of understanding the rules of what some text looks like

and then describing those rules in the regex pattern language. Throughout the rest of this book,

we are going to work with the above example, a help system that contains a date when a

message was received and the text contents of the message. We will explore using regex

patterns to parse these text messages and extract dates, times, URLs, email addresses, etc.

Here is another example message from our help system:

Hey jerks,

I called on Mar 15, spoke to Suzie, and complained about not being able to

access livedates.net after 7:30PM. What the heck is up? Get back to me,

fred@mycollege.edu. Or call me at 619-555-1212. Hopefully, somebody will read

this…

Very upset, Fred!

Chapter 2 Using Regular Expressions in

.NET

The concept of regular expressions first arose in the 1950s when American mathematician

Stephen Kleene designed a simple algebraic system to understand how the brain can produce

complex patterns. In 1968, this pattern algebra was described in the Communications of the

ACM and implemented in several UNIX tools, particularly GREP, a UNIX tool for searching for

files. When the Perl programming language from the late 1980s integrated regular expressions

into the language, adding features to the original algebra, it brought regex parsing into the

mainstream programming community.

Regex processing exists in many languages, so the patterns and rules should work fairly

consistently no matter what tool you are using. There are some subtle differences we will point

out as we explore examples, but most implementations support the language elements the

same way.

Microsoft Regex

For purposes of this book, we are going to use the regex processing engine provided by

Microsoft in the .NET framework. We will use C# as our base language, however, with minor

differences; the code examples will work in VB.NET. The patterns should work in .NET, PHP,

Python, etc.

The Microsoft .NET Framework since version 1.1 has supported regular expressions in the

System.Text.RegularExpressions assembly. This assembly needs to be included in any

application you write in order to take advantage of regular expressions.

Regex Class

The regex class can be used to create an object that will allow you set a pattern and some

options, and then apply this pattern to strings. You can search for strings, split a string to an

array, or even replace strings within a text.

You can use the regex class in two ways. The first is by creating a regex object. You do this by

passing a regex pattern and optionally some regex settings. However, one drawback to using

this approach is that the regex pattern cannot be changed once the object has been

instantiated.

You can also use the regex class as a static class (or shared in Visual Basic). When using this

approach, you will need to pass both the pattern and the search string to the regex call.

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