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Regular Expressions are powerful search expressions which can perform advanced pattern recognition and validation.
The following table defines the meta characters of the regular expression language:
|
Character |
Definition |
Pattern |
Sample Matches |
|
^ |
Start of a string. |
^abc |
abc, abcdefg, abc123, ... |
|
$ |
End of a string. |
abc$ |
abc, endsinabc, 123abc, ... |
|
. |
Any character (except \n newline) |
a.c |
abc, aac, acc, adc, aec, ... |
|
| |
Alternation. |
bill|ted |
ted, bill |
|
{...} |
Explicit quantifier notation. |
ab{2}c |
abbc |
|
[...] |
Explicit set of characters to match. |
a[bB]c |
abc, aBc |
|
(...) |
Logical grouping of part of an expression. |
(abc){2} |
abcabc |
|
* |
0 or more of previous expression. |
ab*c |
ac, abc, abbc, abbbc, ... |
|
+ |
1 or more of previous expression. |
ab+c |
abc, abbc, abbbc, ... |
|
? |
0 or 1 of previous expression; also forces minimal matching when an expression might match several strings within a search string. |
ab?c |
ac, abc |
|
\ |
Preceding one of the above, it makes it a literal instead of a special character. Preceding a special matching character, see below. |
a\sc |
a c |
The following table contains the escape sequences used in authoring regular expressions:
|
Character |
Description |
|
ordinary characters |
Characters other than . $ ^ { [ ( | ) ] } * + ? \ match themselves. |
|
\a |
Matches a bell (alarm) \u0007. |
|
\b |
Matches a backspace \u0008 if in a []; otherwise matches a word boundary (between \w and \W characters). |
|
\t |
Matches a tab \u0009. |
|
\r |
Matches a carriage return \u000D. |
|
\v |
Matches a vertical tab \u000B. |
|
\f |
Matches a form feed \u000C. |
|
\n |
Matches a new line \u000A. |
|
\e |
Matches an escape \u001B. |
|
\040 |
Matches an ASCII character as octal (up to three digits); numbers with no leading zero are back-references if they have only one digit or if they correspond to a capturing group number. For example, the character \040 represents a space. |
|
\x20 |
Matches an ASCII character using hexadecimal representation (exactly two digits). |
|
\cC |
Matches an ASCII control character; for example \cC is control-C. |
|
\u0020 |
Matches a Unicode character using a hexadecimal representation (exactly four digits). |
|
\* |
When followed by a character that is not recognized as an escaped character, matches that character. For example, \* is the same as \x2A. |
The following table contains character classes used in regular expressions:
|
Char Class |
Description |
|
. |
Matches any character except \n. If modified by the Single line option, a period character matches any character. For more information, see Regular Expression Options. |
|
[aeiou] |
Matches any single character included in the specified set of characters. |
|
[^aeiou] |
Matches any single character not in the specified set of characters. |
|
[0-9a-fA-F] |
Use of a hyphen (–) allows specification of contiguous character ranges. |
|
\p{name} |
Matches any character in the named character class specified by {name}. Supported names are Unicode groups and block ranges. For example, Ll, Nd, Z, IsGreek, IsBoxDrawing. |
|
\P{name} |
Matches text not included in groups and block ranges specified in {name}. |
|
\w |
Matches any word character. Equivalent to the Unicode character categories [\p{Ll}\p{Lu}\p{Lt}\p{Lo}\p{Nd}\p{Pc}]. If ECMAScript-compliant behavior is specified with the ECMAScript option, \w is equivalent to [a-zA-Z_0-9]. |
|
\W |
Matches any nonword character. Equivalent to the Unicode categories [^\p{Ll}\p{Lu}\p{Lt}\p{Lo}\p{Nd}\p{Pc}]. If ECMAScript-compliant behavior is specified with the ECMAScript option, \W is equivalent to [^a-zA-Z_0-9]. |
|
\s |
Matches any white-space character. Equivalent to the Unicode character categories [\f\n\r\t\v\x85\p{Z}]. If ECMAScript-compliant behavior is specified with the ECMAScript option, \s is equivalent to [ \f\n\r\t\v]. |
|
\S |
Matches any non-white-space character. Equivalent to the Unicode character categories [^\f\n\r\t\v\x85\p{Z}]. If ECMAScript-compliant behavior is specified with the ECMAScript option, \S is equivalent to [^ \f\n\r\t\v]. |
|
\d |
Matches any decimal digit. Equivalent to \p{Nd} for Unicode and [0-9] for non-Unicode, ECMAScript behavior. |
|
\D |
Matches any non-digit. Equivalent to \P{Nd} for Unicode and [^0-9] for non-Unicode, ECMAScript behavior. |
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