Coyote Point Systems E350GX, Руководство по установке и администрированию

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Equalizer Installation and Administration Guide 273
Appendix D:
Regular Expression Format
Regular Expressions in Match Rules and Responders
Equalizer supports IEEE Std 1003.2 (POSIX.2) extended regular expressions in Match Rules and Responders. There
are many other variants and extensions of regular expressions, including those found in Perl, Java, and various shell
languages; these variants are not supported in Match Rules and Responders.
Regular expressions can be difficult to create and debug, and can use significant system resources to process. We
recommend you use regular expressions only when no other method will provide the functionality you require.
To aid in creating correct and efficient regular expressions, you can use a regular expression evaluator; many of
these are available for download on the internet. Two free online regular expression evaluators are also available at
the following websites:
http://www.rexv.org/ (choose POSIX tab)
http://www.projects.aphexcreations.net/rejax/ (choose PHP POSIX Language)
Terms
The terms in this section describe the components of regular expressions.
• A regular expression (RE) is one or more non-empty branches , separated by pipe symbols (
|)
. An
expression matches anything that matches one of the branches .
• A branch consists of one or more concatenated pieces . A branch matches a match for the first piece ,
followed by a match for the second, and so on.
• A piece is an atom optionally followed by a single *, +, or ?, or by a bound .
• An atom followed by an asterisk (*) matches a sequence of 0 or more matches of the atom.
• An atom followed by a plus sign (+) matches a sequence of 1 or more matches of the atom.
• An atom followed by a question mark (?) matches a sequence of 0 or 1 matches of the atom.
• A bound consists of an open brace ({) followed by an unsigned decimal integer, between 0 and 255
inclusive. You can follow the first unsigned decimal integer with a comma, or a comma and a second
unsigned decimal integer. Close the
bound with a close brace (}). If there are two integers, the value of the
first may not exceed the value of the second.
Learning About Atoms
An atom followed by a bound that contains one integer i and no comma matches a sequence of exactly i matches of
the atom. An atom followed by a bound that contains one integer i and a comma matches a sequence of i or more
matches of the atom. An atom followed by a bound containing two integers i and j matches a sequence of i through j
(inclusive) matches of the atom. An atom can consist of any of the following:
• A regular expression enclosed in parentheses, which matches a match for the regular expression.
• An empty set of parentheses, which matches the null string.