Chapter 4 Advanced Expressions: Evaluating Text 67
HTTP.REQ.HEADER("Example").AFTER_REGEX(re/more/)
For more information on regular expressions, see “Matching Text With a
Pattern,” on page 164.
Expression Prefixes for Text
The following sections discuss expression prefixes for strings.

Expression Prefixes for Text in HTTP Requests

and Responses

An HTTP request or response typically contains text, such as in the form of
headers, header values, URLs, and POST body text. You can configure
expressions to operate on one or more of these text-based items in an HTTP
request or response.
The following table describes the expression prefixes that you can configure to
extract text from different parts of an HTTP request or response.
HTTP Expression Prefixes that Return Text
Prefix Description
HTTP.REQ.BODY(integer)Returns the body of an HTTP request as a multiline text
object, up to the character position designated in
integer.
There is no maximum value for the body argument, but
you should use as small a value as is practical. Larger
values can affect performance.
Note: Although it is possible to specify this prefix
without an integer argument, this usage is deprecated.
HTTP.REQ.HOSTNAME Returns the HTTP host name in the first line of the
request, if there is one. Otherwise, this prefix returns the
value in the last occurrence of the HOST header.
Note that there are two similar prefixes that return host
names, as follows:
•http.req.url.hostname only returns the
host name from the URL
•http.req.header("Host") only returns the
value from the Host header. To use this value as a
host name you must typecast this string, as
illustrated in the following example: http.req.
header("host").typecast_http_
hostname_t
For more information on typecasting, see
“Transforming Text and Numbers into Different Data
Types,” on page 169.