Citrix Systems 9.2 Benutzerhandbuch

Which expression prefixes you can specify depends on the NetScaler feature. The 
following table describes the expression prefixes that are of interest on a per-
feature basis.

For details on the permitted expression prefixes in a feature, see the 

documentation for that feature.

The simplest type of advanced expression contains a single element. This element 
can be one of the following:

•

true

. An advanced expression can consist simply of the value true. This 

type of expression always returns a value of TRUE. It is useful for chaining 
policy actions and triggering Goto expressions.

•

false

. An advanced expression can consist simply of the value false. 

This type of expression always returns a value of FALSE.

•

A prefix for a compound expression. For example, the prefix 

HTTP.REQ.HOSTNAME 

is a complete expression that returns a host name, and 

HTTP.REQ.URL

 is a complete expression that returns a URL. The prefix 

could also be used in conjuction with operations and additional prefixes to 
form a compound expression.

In most expressions, you specify an operation on the data that the prefix 
identifies. For example, suppose that you specify the following prefix:

http.req.url

DNS

SYS, CLIENT, SERVER

Responder in Protection 
Features

HTTP, SYS, CLIENT

Content Switching

HTTP, SYS, CLIENT

Rewrite

HTTP, SYS, CLIENT, SERVER, URL, TEXT, 
TARGET, VPN

Integrated Caching

HTTP, SYS, CLIENT, SERVER

Access Gateway, 
Clientless Access

HTTP, SYS, CLIENT, SERVER, URL, TEXT, 
TARGET, VPN