regular expression(正则表达式)
2013-06-19正则表达式(regular expression)描述了一种字符串匹配的模式，可以用来检查一个串是否含有某种子串、将匹配的子串做替换或者从某个串中取出符合某个条件的子串等。
随着互联网的迅速发展，几乎所有工具软件和程序语言都支持的正则表达式也变得越来越强大和易于使用。
正则表达式是烦琐的，但是强大的，学会之后的应用会让你除了提高效率外，会给你带来绝对的成就感。
a regular expression (abbreviated regex or regexp) is a sequence of text characters.
a regular expression is a pattern describing a certain amount of text. Their name comes from the mathematical theory on which they are based.
Regular expressions are a language used for parsing and manipulating text. They are often used to perform complex search-and-replace operations, and to validate that text data is well-formed.
Today, regular expressions are included in most programming languages, as well as in many scripting languages, editors, applications, databases, and command-line tools.
Regular expressions are an extremely powerful tool for manipulating text and data. They are now standard features in a wide range of languages and popular tools, including Perl, Python, Ruby, Java, VB.NET and C# (and any language using the .NET Framework), PHP, and MySQL.
http://www.regular-expressions.info/examples.html
http://sed.sourceforge.net/sed1line.txt