Chapter 9 Advanced Expressions: String Sets, String Patterns, and Data Formats 165
http://www.regular-expressions.info/quickstart.html
http://www.silverstones.com/thebat/Regex.html
These sites provide tutorial and reference information on regular expressions.
Note: Processing of regular expressions can be slow, and should only be used if
other expression types do not satisfy your requirements.
Basic Characteristics of Regular Expressions
The following are a few characteristics of a regular expression:
• The string “re” followed by a delimiter indicates the start of a regular
expression within an advanced policy expression.
The expression is ended with a matching delimiter. For example, (re#/#)
extracts information before or after a slash.
• A regular expression cannot exceed 1499 characters.
• To represent a digit, use the string \d (a backslash, followed by d).
• To represent white space, use \s (a backslash, followed by s).
• The regular expression can contain white space. The white space is ignored.
The following are differences between the NetScaler syntax and PCRE syntax:
• The NetScaler does not allow back references.
• You should not use recursive regular expressions.
• The dot meta-character also matches new lines.
• Unicode is not supported.
• The operation SET_TEXT_MODE(IGNORECASE) overrides the (?i)
internal option in the regular expression.
Operations for Regular Expressions
Operations for regular expressions are evaluated somewhat differently, depending
on whether they evaluate text or HTTP headers. Operations that evaluate headers
override any text-based operations for all instances of the current header type.