tailieunhanh - Professional Information Technology-Programming Book part 95

Tham khảo tài liệu 'professional information technology-programming book part 95', công nghệ thông tin, kỹ thuật lập trình phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Expression Tester and can be immensely useful in experimenting with regular expressions quickly and easily. Before You Get Started Before you go any further take note of a couple of important points When using regular expressions you will discover that there are almost always multiple solutions to any problem. Some may be simpler some may be faster some may be more portable and some may be more capable. There is rarely a right or wrong solution when writing regular expressions as long as your solution works of course . As already stated differences exist between regex implementations. As much as possible the examples and lessons used in this book apply to all major implementations and differences or incompatibilities are noted as such. As with any language the key to learning regular expressions is practice practice practice. Note I strongly suggest that you try each and every example as you work through this book. Summary Regular expressions are one of the most powerful tools available for text manipulation. The regular expressions language is used to construct regular expressions the actual constructed string is called a regular expression and regular expressions are used to perform both search and replace operations. Lesson 2. Matching Single Characters In this lesson you ll learn how to perform simple character matches of one or more characters. Matching Literal Text Ben is a regular expression. Because it is plain text it may not look like a regular expression but it is. Regular expressions can contain plain text and may even contain only plain text . Admittedly this is a total waste of regular expression processing but it s a good place to start. So here goes Hello my name is Ben. Please visit my website at http . Ben Hello my name is Ben. Please visit my website at http . The regular expression used here is literal text and it matches Ben in the original text. Let s look at another example using the same search text and a .