Regular Expression Syntax
Use Basic Regular Expression (BRE) syntax for settings that take regular expressions. This syntax is summarized in the following table.
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", "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]+) |
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