Regular Expressions Syntax

Privilege Management for Windows can control applications at a granular level by using regular expression syntax. Privilege Management for Windows uses the ATL regular expression library CAtlRegExp. Below is a summary of the regular expression syntax used by this library.

Metacharacter

Meaning

Example

Any character except [\^$.|?*+()

All characters except the listed special characters match a single instance of themselves. To match one of these listed characters use a backslash escape character (see below).

abc matches abc

\ (backslash)

Escape character: interpret the next character literally.

a\+b matches a+b

. (dot)

Matches any single character.

a.b matches aab, abb or acb, etc.

[ ]

Indicates a character class. Matches any character inside the brackets (for example, [abc] matches a, b, and c).

[abc] matches a, b, or c

^ (caret)

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).

[^abc] matches all characters except a, b, and c

- (minus character)

In a character class, indicates a range of characters (for example, [0-9] matches any of the digits 0 through 9).

[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).

ab?c matches ac or abc

+

Indicates that the preceding expression matches one or more times (for example, [0-9]+ matches 1, 13, 999, and so on).

ab+c matches abc and abbc, abbbc, etc.

* (asterisk)

Indicates that the preceding expression matches zero or more times

ab*c matches ac and abc, abbc, etc.

| (vertical pipe)

Alternation operator: separates two expressions, exactly one of which matches.

a|b matches a or b

??, +?, *?

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>.

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.

(One)|(Two) matches One or Two

{ }

Indicates a match group. The actual text in the input that matches the expression inside the braces can be retrieved through the CAtlREMatchContext object.

 

\

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>".

Note that in C++ string literals, two backslashes must be used: "\\+", "\\a", "<{.*?}>.*?</\\0>".

<{.*?}>.*?</\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.

[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.

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.

a!b matches a not followed by b