Regular Expressions (regex) are character-matching patterns that are used to find and/or replace character patterns in strings.With Regular Expression...

A Regular Expression is a pattern of text that consists of ordinary characters (for example, letters a through z) and special characters, known as met...

Ordinary characters consist of all characters that are not explicitly designated as meta characters. This includes:all upper- and lowercase alphabetic charac...

There are a number of meta characters that require special treatment when trying to match them. To match these special characters, you must first escape them...

A number of useful non-printing characters are occasionally used. The table below shows the escape sequences used to represent those non-printing characters:...

Many times it's useful to match specified characters from a list. For example, you may want to search a string for chapter headings that are expressed as Cha...

Sometimes, you don't know how many characters there are to match. In order to accommodate that kind of uncertainty, Regular Expressions support the concept o...

All the examples so far have recognized patterns anywhere in a string. But you may want the patterns to match only if they, for example, appear at the beginn...

Alternation allows use of the | (pipe) character to allow a choice between two or more alternatives, a bit similar to or in Boolean expressions. Expan...

You can store a part of a matched pattern for later reuse. Placing parentheses around a Regular Expression pattern or part of a pattern causes that pa...

CharacterDescription\d Matches a digit character. Equivalent to [0-9]. \D Matches a non-digit character. Equivalent to [^0-9]. \w ...

Character Description \xn Matches n, where n is a hexadecimal escape value. Hexadecimal escape values must be exactly two digits long. For...

Once you have constructed a Regular Expression, it is evaluated much like an arithmetic expression, that is, it is evaluated from left to right and follows a...