Basic Regular Expression Rules

This section describes the basic rules for creating regular expressions (REs), including single-character regular expressions.

The following are the basic rules for regular expressions:

Special characters are: + * ? . [ ^ $ ( ) { | \
Any character that is not a special character matches itself.
A backslash (\) followed by any special character matches the literal character itself, that is, the backslash escapes the special character.
A period (.) matches any character, including newline. To match any character except a newline, use [^#chr(13)##chr(10)#], which excludes the ASCII carriage return and line feed codes. The corresponding escape codes are \r and \n.
A set of characters enclosed in brackets ([]) is a one-character RE that matches any of the characters in that set. For example, "[akm]" matches an "a", "k", or "m". A dash in a set of characters inside braces indicates a range of characters; for example, [a-z] matches any lowercase letter.
If the first character of a character set is the caret (^), the RE matches any character except those in the set. It does not match the empty string; for example: [^akm] matches any character except "a", "k", or "m". The caret loses its special meaning if it is not the first character of the set.
To make a regular expression case insensitive, substitute individual characters with character sets; for example, [Nn][Ii][Cc][Kk].

If you want to include ] (closing square bracket) in square brackets it must be the first character. Otherwise, it does not work even if you use \]. The following example illustrates this:

<!--- Want to replace closing square bracket and all a's with * --->

<cfset strSearch = "[Test message]">

<!--- Next line does not work since ] is not the FIRST character

      within [] --->

<cfset re = "[a\]]">

<cfoutput>REReplace(#strSearch#,#re#,"*","ALL") -

    #REReplace(strSearch,re,"*","ALL")#<br>

    Neither ']' nor 'a' was replaced because we searched for 'a'

    followed by ']'<br>

</cfoutput>

<!--- Next line works since ] is the FIRST character within [] --->

<cfset re = "[]a]">

<cfoutput>REReplace(#strSearch#,#re#,"*","ALL") -

    #REReplace(strSearch,re,"*","ALL")#<br>

    Both 'a' and ']' were Replaced with *<br></cfoutput>

Character classes

In ColdFusion regular expressions, you can specify a character using one of the POSIX character classes. You enclose the character class name inside two square brackets, as in this example:

REReplace ("Macromedia Web Site","[[:space:]]","*","ALL")

This code replaces all the spaces with *, producing this string:

Macromedia*Web*Site

The following table shows the POSIX character classes that ColdFusion supports:

Character Class

Matches

alpha
Matches any letter. Same as [A-Za-z].

upper
Matches any uppercase letter. Same as [A-Z].

lower
Matches any lowercase letter. Same as [a-z].

digit
Matches any digit. Same as [0-9].

alnum
Matches any alphanumeric character. Same as [A-Za-z0-9].

xdigit
Matches any hexadecimal digit. Same as [0-9A-Fa-f].

space
Matches a tab, new line, vertical tab, form feed, carriage return, or space.

print
Matches any printable character.

punct
Matches any punctuation character, that is, one of ! ' # S % & ` ( ) * + , - . / : ; < = > ? @ [ / ] ^ _ { | } ~

graph
Matches any of the characters defined as a printable character except those defined as part of the space character class.

cntrl
Matches any character not part of the character classes [:upper:], [:lower:], [:alpha:], [:digit:], [:punct:], [:graph:], [:print:], or [:xdigit:].

Developing ColdFusion Applications
Using Regular Expressions in Functions

Character Class	Matches
alpha	Matches any letter. Same as [A-Za-z].
upper	Matches any uppercase letter. Same as [A-Z].
lower	Matches any lowercase letter. Same as [a-z].
digit	Matches any digit. Same as [0-9].
alnum	Matches any alphanumeric character. Same as [A-Za-z0-9].
xdigit	Matches any hexadecimal digit. Same as [0-9A-Fa-f].
space	Matches a tab, new line, vertical tab, form feed, carriage return, or space.
print	Matches any printable character.
punct	Matches any punctuation character, that is, one of ! ' # S % & ` ( ) * + , - . / : ; < = > ? @ [ / ] ^ _ { \| } ~
graph	Matches any of the characters defined as a printable character except those defined as part of the space character class.
cntrl	Matches any character not part of the character classes [:upper:], [:lower:], [:alpha:], [:digit:], [:punct:], [:graph:], [:print:], or [:xdigit:].