Regular Expressions Syntax
This table lists the metacharacters understood by ClearBox
Server and which may be used in matching RADIUS attributes or in
user name rewriting rules.
| Metacharacter |
Meaning |
| . |
Matches any single character. |
| [ ] |
Indicates a character class. Matches any
character inside the brackets (for example, [abc] matches "a", "b", and "c"). |
| ^ |
If this metacharacter occurs at the start of a
character class, it negates the character class. A negated
character class matches any character except those inside the
brackets (for example, [^abc] matches all
characters except "a", "b", and "c").
If ^ is at the beginning of the regular
expression, it matches the beginning of the input (for example,
^[abc] will only match input that begins
with "a", "b", or "c"). |
| - |
In a character class, indicates a range of
characters (for example, [0-9] matches any
of the digits "0" through "9"). |
| ? |
Indicates that the preceding expression is
optional: it matches once or not at all (for example, [0-9][0-9]? matches "2" and "12"). |
| + |
Indicates that the preceding expression matches
one or more times (for example, [0-9]+
matches "1", "13", "789", and so on). |
| * |
Indicates that the preceding expression matches
zero or more times. |
| ??, +?, *? |
Non-greedy versions of ?,
+, and *. These
match as little as possible, unlike the greedy versions which match
as much as possible. Example: given the input
"<abc><def>", <.*?>
matches "<abc>" while <.*>
matches "<abc><def>". |
| ( ) |
Grouping operator. Example: (\d+,)*\d+ matches a list of numbers separated by
commas (such as "1" or "1,23,456"). |
| { } |
Indicates a match group. The actual text in the
input that matches the expression inside the braces is placed in
the ouput, i.e. in the rewritten user name. |
| \ |
Escape character: interpret the next character
literally (for example, [0-9]+ matches one
or more digits, but [0-9]\+ matches a digit
followed by a plus character). Also used for abbreviations (such as
\a for any alphanumeric character; see
table below).
If \ is followed by a number n,
it matches the nth match group (starting from 0). Example:
<{.*?}>.*?</\0> matches
"<head>Contents</head>". |
| $ |
At the end of a regular expression, this
character matches the end of the input. Example: [0-9]$ matches a digit at the end of the input. |
| | |
Alternation operator: separates two expressions,
exactly one of which matches (for example, T|the matches "The" or "the"). |
| ! |
Negation operator: the expression following
! does not match the input. Example:
a!b matches "a" not followed by "b". |
Abbreviations
ClearBox can handle abbreviations, such as \d instead of [0-9].
The following abbreviations are supported:
| Metacharacter |
Meaning |
| .\a |
Any alphanumeric character. |
| \b |
White space (blank). |
| \c |
Any alphabetic character. |
| \d |
Any decimal digit. |
| \h |
Any hexadecimal digit. |
| \n |
Newline. |
| \q |
A quoted string. |
| \w |
A simple word. |
| \z |
An integer. |
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