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Regular Expression Syntax

Use Basic Regular Expression (BRE) syntax for settings that take regular expressions. This syntax is summarized in the following table.

Character

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", "456", 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 that match as much as possible (for 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 (for example, "1" or "1,23,456").

\

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 the following table).

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 (for 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 (for example, a!b matches "a" not followed by "b").

 

The following abbreviations are also supported.

Abbreviation

Matches

\a

Any alphanumeric character: ([a-zA-Z0-9])

\b

White space (blank): ([ \\t])

\c

Any alphabetic character: ([a-zA-Z])

\d

Any decimal digit: ([0-9])

\h

Any hexadecimal digit: ([0-9a-fA-F])

\n

Newline: (\r|(\r?\n))

\q

A quoted string: (\"[^\"]*\")|(\'[^\']*\')

\w

A simple word: ([a-zA-Z]+)

\z

An integer ([0-9]+)