42 Citrix NetScaler Policy Configuration and Reference Guide
• The prefix http.req.url designates an HTTP URL in URL-
encoded format.
•SERVER: Identifies an element in the server that is either processing a
request or sending a response.
•SYS: Identifies a characteristic of the NetScaler that is processing the
traffic.
•TARGET:Represents all the strings that result from a search in the target
text. This prefix can be used only in the string expression that specifies
replacement text in a rewrite action. The expression that is used to search
the target text must be a regular expression, and the type of action must be
REPLACE_ALL, INSERT_AFTER_ALL, or INSERT_BEFORE_ALL.
Any operator that is used with the TARGET prefix operates on all the
strings that are found in the target text.
For example, if a search that uses a regular expression finds n occurrences
of the specified string, and if the action type is REPLACE_ALL, the
expression TARGET.TO_UPPER changes the case of all n occurrences of
the string to upper case.
Note: DNS policies support only SYS, CLIENT, and SERVER objects.
In addition, in the Access Gateway, the Clientless VPN function can use the
following types of prefixes:
•TEXT: Identifies any text element in a request or a response.
•TARGET: Identifies the target of a connection.
•URL: Identifies an element in the URL portion of an HTTP request or
response.
As a general rule of thumb, any expression prefix can be a self-contained
expression. For example, the following prefix is a complete expression that
returns the contents of the HTTP header specified in the string argument
(enclosed in quotation marks):
http.res.header.("myheader")
Or you can combine prefixes with simple operations to determine TRUE and
FALSE values. For example, the following returns a value of TRUE or FALSE:
http.res.header.("myheader").exists
You can also use complex operations on individual prefixes and multiple prefixes
within an expression, as in the following example:
http.req.url.length + http.req.cookie.length <= 500