In traditional string matching, as used by the ColdFusion Find and Replace functions, you provide the string pattern to search for and the string to search. The following example searches a string for the pattern " BIG " and returns a string index if found. The string index is the location in the search string where the string pattern begins.

You must provide the exact string pattern to match. If the exact pattern is not found, Find returns an index of 0. Because you must specify the exact string pattern to match, matches for dynamic data can be difficult, if not impossible, to construct.

The next example uses a regular expression to perform the same search. This example searches for the first occurrence in the search string of any string pattern that consists entirely of uppercase letters enclosed by spaces:

ColdFusion supplies four functions that work with regular expressions:

REFind and REFindNoCase use a regular expression to search a string for a pattern and return the string index where it finds the pattern. For example, the following function returns the index of the first instance of the string " BIG ":

The simplest regular expression contains only literal characters. The literal characters must match exactly the text being searched. For example, you can use the regular expression function REFind to find the string pattern " BIG ", just as you can with the Find function:

In this example, REFind must match the exact string pattern " BIG ".

To use the full power of regular expressions, combine literal characters with character sets and special characters, as in the following example:

The literal characters of the regular expression consist of the space characters at the beginning and end of the regular expression. The character set consists of that part of the regular expression in brackets. This character set specifies to find a single uppercase letter from A to Z, inclusive. The plus sign  after the brackets is a special character specifying to find one or more occurrences of the character set. If you removed the + from the regular expression in the previous example, " A-Z " matches a literal space, followed by any single uppercase letter, followed by a single space. This regular expression matches " B " but not " BIG ". The REFind function returns 0 for the regular expression, meaning that it did not find a match.  You can construct complicated regular expressions containing literal characters, character sets, and special characters. Like any programming language, the more you work with regular expressions, the more you can accomplish with them. The examples here are fairly basic. For more examples, see Regular expression examples.

In the ColdFusion Administrator, in Server Settings > Settings, you can change the Regex engine at the server level for your ColdFusion applications.

Enable or disable the option Use Java as Regex Engine to specify whether or not Java must be used as the fefault Regex engine for your ColdFusion applications.