Construct |
Matches |
---|---|
Characters |
|
x |
The character x |
\\ |
The backslash character |
\0n |
The character with octal value 0n (0 <= n <= 7) |
\0nn |
The character with octal value 0nn (0 <= n <= 7) |
\0mnn |
The character with octal value 0mnn (0 <= m <= 3, 0 <= n <= 7) |
\xhh |
The character with hexadecimal value 0xhh |
\uhhhh |
The character with hexadecimal value 0xhhhh |
\t |
The tab character ('\u0009') |
\n |
The newline (line feed) character ('\u000A') |
\r |
The carriage-return character ('\u000D') |
\f |
The form-feed character ('\u000C') |
\a |
The alert (bell) character ('\u0007') |
\e |
The escape character ('\u001B') |
\cx |
The control character corresponding to x |
|
|
Character classes |
|
[abc] |
a, b, or c (simple class) |
[^abc] |
Any character except a, b, or c (negation) |
[a-zA-Z] |
a through z or A through Z, inclusive (range) |
[a-d[m-p]] |
a through d, or m through p: [a-dm-p] (union) |
[a-z&&[def]] |
d, e, or f (intersection) |
[a-z&&[^bc]] |
a through z, except for b and c: [ad-z] (subtraction) |
[a-z&&[^m-p]] |
a through z, and not m through p: [a-lq-z](subtraction) |
|
|
Predefined character classes |
|
. |
Any character (may or may not match line terminators) |
\d |
A digit: [0-9] |
\D |
A non-digit: [^0-9] |
\s |
A whitespace character: [ \t\n\x0B\f\r] |
\S |
A non-whitespace character: [^\s] |
\w |
A word character: [a-zA-Z_0-9] |
\W |
A non-word character: [^\w] |
|
|
POSIX character classes (US-ASCII only) |
|
\p{Lower} |
A lower-case alphabetic character: [a-z] |
\p{Upper} |
An upper-case alphabetic character:[A-Z] |
\p{ASCII} |
All ASCII:[\x00-\x7F] |
\p{Alpha} |
An alphabetic character:[\p{Lower}\p{Upper}] |
\p{Digit} |
A decimal digit: [0-9] |
\p{Alnum} |
An alphanumeric character:[\p{Alpha}\p{Digit}] |
\p{Punct} |
Punctuation: One of !"#$%&'()*+,-./:;<=>?@[\]^_`{|}~ |
\p{Graph} |
A visible character: [\p{Alnum}\p{Punct}] |
\p{Print} |
A printable character: [\p{Graph}] |
\p{Blank} |
A space or a tab: [ \t] |
\p{Cntrl} |
A control character: [\x00-\x1F\x7F] |
\p{XDigit} |
A hexadecimal digit: [0-9a-fA-F] |
\p{Space} |
A whitespace character: [ \t\n\x0B\f\r] |
|
|
Classes for Unicode blocks and categories |
|
\p{InGreek} |
A character in the Greek block (simple block) |
\p{Lu} |
An uppercase letter (simple category) |
\p{Sc} |
A currency symbol |
\P{InGreek} |
Any character except one in the Greek block (negation) |
[\p{L}&&[^\p{Lu}]] |
Any letter except an uppercase letter (subtraction) |
|
|
Boundary matchers |
|
^ |
The beginning of a line |
$ |
The end of a line |
\b |
A word boundary |
\B |
A non-word boundary |
\A |
The beginning of the input |
\G |
The end of the previous match |
\Z |
The end of the input but for the final terminator, if any |
\z |
The end of the input |
|
|
Greedy quantifiers |
|
X? |
X, once or not at all |
X* |
X, zero or more times |
X+ |
X, one or more times |
X{n} |
X, exactly n times |
X(n,} |
X, at least n times |
X{n,m} |
X, at least n but not more than m times |
|
|
Reluctant quantifiers |
|
X?? |
X, once or not at all |
X*? |
X, zero or more times |
X+? |
X, one or more times |
X{n}? |
X, exactly n times |
X(n,}? |
X, at least n times |
X{n,m}? |
X, at least n but not more than m times |
|
|
Possessive quantifiers |
|
X?+ |
X, once or not at all |
X*+ |
X, zero or more times |
X++ |
X, one or more times |
X{n}+ |
X, exactly n times |
X(n,}+ |
X, at least n times |
X{n,m}+ |
X, at least n but not more than m times |
|
|
Logical operators |
|
XY |
X followed by Y |
X|Y |
Either X or Y |
(X) |
X, as a capturing group |
|
|
Back references |
|
\n |
Whatever the nth capturing group matched |
|
|
Quotation |
|
\ |
Nothing, but quotes the following character |
\Q |
Nothing, but quotes all characters until \E |
\E |
Nothing, but ends quoting started by \Q |
|
|
Special constructs (non-capturing) |
|
(?:X) |
X, as a non-capturing group |
(?idmsux-idmsux) |
Nothing, but turns match flags on - off |
(?idmsux-idmsux:X) |
X, as a non-capturing group with the given flags on - off |
(?=X) |
X, via zero-width positive lookahead |
(?!X) |
X, via zero-width negative lookahead |
(?<=X) |
X, via zero-width positive lookbehind |
(?<!X) |
X, via zero-width negative lookbehind |
(?>X) |
X, as an independent, non-capturing group |
The backslash character ('\') serves to introduce escaped constructs, as defined in the table above, as well as to quote characters that otherwise would be interpreted as unescaped constructs. Thus the expression \\ matches a single backslash and \{ matches a left brace.
It is an error to use a backslash prior to any alphabetic character that does not denote an escaped construct; these are reserved for future extensions to the regular-expression language. A backslash may be used prior to a non-alphabetic character regardless of whether that character is part of an unescaped construct.
A line terminator is a one- or two-character sequence that marks the end of a line of the input character sequence. The following are recognized as line terminators:
A newline (line feed) character ('\n'),
A carriage-return character followed immediately by a newline character ("\r\n"),
A standalone carriage-return character ('\r'),
A next-line character ('\u0085'),
A line-separator character ('\u2028'), or
A paragraph-separator character ('\u2029).
The regular expression . matches any character except a line terminator.