background preloader

Regular Expression Tutorial - Learn How to Use Regular Expressions

Regular Expression Tutorial - Learn How to Use Regular Expressions
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

http://www.regular-expressions.info/tutorial.html

Related:  Regular ExpressionsData Manipulation using REGEX

Regular Expressions Quick Start This quick start gets you up to speed quickly with regular expressions. Obviously, this brief introduction cannot explain everything there is to know about regular expressions. For detailed information, consult the regular expressions tutorial. Each topic in the quick start corresponds with a topic in the tutorial, so you can easily go back and forth between the two. .NET Framework Regular Expressions Regular expressions provide a powerful, flexible, and efficient method for processing text. The extensive pattern-matching notation of regular expressions enables you to quickly parse large amounts of text to find specific character patterns; to validate text to ensure that it matches a predefined pattern (such as an e-mail address); to extract, edit, replace, or delete text substrings; and to add the extracted strings to a collection in order to generate a report. For many applications that deal with strings or that parse large blocks of text, regular expressions are an indispensable tool. The centerpiece of text processing with regular expressions is the regular expression engine, which is represented by the System.Text.RegularExpressions.Regex object in the .NET Framework. At a minimum, processing text using regular expressions requires that the regular expression engine be provided with the following two items of information:

8 Regular Expressions You Should Know Regular expressions are a language of their own. When you learn a new programming language, they're this little sub-language that makes no sense at first glance. Many times you have to read another tutorial, article, or book just to understand the "simple" pattern described. Today, we'll review eight regular expressions that you should know for your next coding project. Regular Expressions - a Simple User Guide A Regular Expression is the term used to describe a codified method of searching invented, or defined, by the American mathematician Stephen Kleene. The syntax (language format) described on this page is compliant with extended regular expressions (EREs) defined in IEEE POSIX 1003.2 (Section 2.8). EREs are now commonly supported by Apache, PERL, PHP4, Javascript 1.3+, MS Visual Studio, most visual editors, vi, emac, the GNU family of tools (including grep, awk and sed) as well as many others.

How lexers (e.g. from LEX) and parsers (e.g. from YACC or JAVACC) work Next: Ambiguous and confusing grammars Up: CS2121: The Implementation and Previous: YACC: Further usage Subsections How lexers and parsers work Lexers - Finite State Automata (FSA)

Popular Tools, Utilities and Programming Languages That Support Regular Expressions These tools and utilities have regular expressions as the core of their functionality. grep - The utility from the UNIX world that first made regular expressions popular PowerGREP - Next generation grep for Microsoft Windows RegexBuddy - Learn, create, understand, test, use and save regular expressions. Learn REGEX - RegExOne LINKS You're done! For now that is... I'm always looking to add more examples and lessons, so please shoot me an email (at regexone@gmail.com) if you have any suggestions or questions! Below are a number of other resources about regular expressions on the web, the most useful of which may be the documentation for whichever language that you use regular expressions in.

VBA For Loop – For Next and For Each In Next The For Loop in VBA is one of the most frequently used loops in VBA. The For loop has two forms: For Next and For Each In Next . The For loop is typically used to move sequentially through a list of items or numbers. To end the for loop at any given point we can use the exit for statement. Let’s take a closer look at each of these loops. VBA For … Next Loop The 30 Minute Regex Tutorial - The Code Project - .NET Expresso 2.1C - 328 Kb Learning .NET Regular Expressions with Expresso Did you ever wonder what Regular Expressions are all about and want to gain a basic understanding quickly? My goal is to get you up and running with a basic understanding of regular expressions within 30 minutes. The reality is that regular expressions aren't as complex as they look. The best way to learn is to start writing and experimenting.

Mini-XML About Mini-XML Mini-XML is a small XML library that you can use to read and write XML and XML-like data files in your application without requiring large non-standard libraries. Mini-XML only requires an ANSI C compatible compiler (GCC works, as do most vendors' ANSI C compilers) and a 'make' program. Mini-XML supports reading of UTF-8 and UTF-16 and writing of UTF-8 encoded XML files and strings. Data is stored in a linked-list tree structure, preserving the XML data hierarchy, and arbitrary element names, attributes, and attribute values are supported with no preset limits, just available memory.

Regular Expression Examples Below, you will find many example patterns that you can use for and adapt to your own purposes. Key techniques used in crafting each regex are explained, with links to the corresponding pages in the tutorial where these concepts and techniques are explained in great detail. If you are new to regular expressions, you can take a look at these examples to see what is possible. Regex Tutorial - Literal Characters and Special Characters The most basic regular expression consists of a single literal character, such as a. It matches the first occurrence of that character in the string. If the string is Jack is a boy, it matches the a after the J. The fact that this a is in the middle of the word does not matter to the regex engine. If it matters to you, you will need to tell that to the regex engine by using word boundaries. We will get to that later.

Related: