The following tables provide the constructs for regular expressions:
Table E-2 Characters
Construct |
Matches |
---|---|
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. |
Table E-3 Character Classes
Construct |
Matches |
---|---|
[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). |
Table E-4 Predefined Character Classes
Construct |
Matches |
---|---|
Any character (could match line terminators). |
|
\d |
A digit: [0–9] |
\D |
A nondigit: [^0–9] |
\s |
A whitespace character: [ \t\n\x0B\f\r] |
\S |
A nonwhitespace character: [^\s] |
\w |
A word character: [a‑zA‑Z_0‑9] |
\W |
A nonword character: [^\w] |
Table E-5 POSIX character classes (US‑ASCII only)
Construct |
Matches |
---|---|
\p{Lower} |
A lowercase alphabetic character: [a‑z] |
\p{Upper} |
An uppercase 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}\x20] |
\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] |
Table E-6 Classes for Unicode Blocks and Categories
Construct |
Matches |
---|---|
\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). |
Table E-7 Boundary Matchers
Construct |
Matches |
---|---|
^ |
The beginning of a line. |
$ |
The end of a line. |
\b |
A word boundary. |
\B |
A nonword 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. |
Table E-8 Greedy quantifiers
Construct |
Matches |
---|---|
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. |
Table E-9 Reluctant quantifiers
Construct |
Matches |
---|---|
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. |
Table E-10 Possessive quantifiers
Construct |
Matches |
---|---|
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. |
Table E-11 Logical operators
Construct |
Matches |
---|---|
XY |
X followed by Y. |
X|Y |
Either X or Y. |
(X) |
X, as a capturing group. |
Table E-12 Back references
Construct |
Matches |
---|---|
\n |
Whatever the nth capturing group matched. |
Table E-13 Quotation
Construct |
Matches |
---|---|
\ |
Nothing, but quotes the following character. |
\Q |
Nothing, but quotes all characters until \E. |
\E |
Nothing, but ends quoting started by \Q. |