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Operations for regular expressions

August 20, 2024

Contributed by:

C C S

The following table describes the operators that work with regular expressions. The operation performed by a regular expression operator in a given default syntax expression depends on whether the expression prefix identifies text or HTTP headers. Operations that evaluate headers override any text-based operations for all instances of the specified header type. When you use an operator, replace <text> with the default syntax expression prefix that you want to configure for identifying text.

Regular Expression Operation	Description
`<text>.BEFORE_REGEX(<regular expression>`)	Selects the text that precedes the string that matches the `<regular expression>` argument. If the regular expression does not match any data in the target, the expression returns a text object of length 0. The following expression selects the string “text” from “text/plain”. http.res.header(“content-type”).before_regex(re#/#)
`<text>.AFTER_REGEX(<regular expression>`)	Selects the text that follows the string that matches the `<regular expression>` argument. If the regular expression does not match any text in the target, the expression returns a text object of length 0. The following expression extracts “Example” from “myExample”: http.req.header(“etag”).after_regex(re/my/)
`<text>.REGEX_SELECT(<regular expression>`)	Selects a string that matches the `<regular expression>` argument. If the regular expression does not match the target, a text object of length 0 is returned. The following example extracts the string “NS-CACHE-9.0: 90” from a Via header: http.req.header(“via”).regex_select(re!NS-CACHE-\d.\d:\s*\d{1,3}!)
`<text>.REGEX_MATCH(<regular expression>`)	Returns TRUE if the target matches a `<regular expression>` argument of up to 1499 characters. The regular expression must be of the following format: re`<delimiter>`regular expression`< delimiter>` Both delimiters must be the same. Additionally, the regular expression must conform to the Perl-compatible (PCRE) regular expression library syntax. For more information, go to `<http://www.pcre.org/pcre.txt>`. In particular, see the pcrepattern man page. However, note the following: Back-references are not allowed. Recursive regular expressions are not recommended. The dot metacharacter also matches the newline character. The Unicode character set is not supported. SET_TEXT_MODE(IGNORECASE) overrides the (?i) internal option specified in the regular expression. The following are examples: `http.req.hostname.regex_match(re/[[:alpha:]]+(abc){2,3})` and `http.req.url.set_text_mode(urlencoded).regex_match(re#(ab+c)#)` The following example matches ab and aB: `http.req.url.regex_match(re/a(?i)b)` The following example matches ab, aB, Ab and AB: `http.req.url.set_text_mode(ignorecase).regex_match(re/ab)` The following example performs a case-insensitive, multiline match in which the dot meta-character also matches a newline character: `http.req.body.regex_match(re(?ixm) (^ab (.*) cd$))`

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Operations for regular expressions

August 20, 2024

Contributed by:

C C S

August 20, 2024

Contributed by:

C C S

Operations for regular expressions

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