| Characters |
|---|
| Character | Description | Example |
|---|
| Any character except [\^$.|?*+() |
All characters except the special characters on the left match a single instance of themselves. { and } are literal characters, unless they're part of a valid regular expression token (e.g. the {n} quantifier). |
a
matches a |
| \ (backslash) followed by any of [\^$.|?*+(){} |
Escapes character to suppress the immediate following special character′ meaning. |
\+
matches + |
| \Q...\E |
Matches the characters between \Q and \E literally, suppressing the meaning of special characters. |
\Q+-*/\E
matches +-*/ |
| \xHH where HH are 2 hexadecimal digits |
Matches HEX ASCII code of a character. |
\x21
matches ! |
| \n, \r and \t |
Match LineFeed, Carrige Return and tab character respectively. |
\r\n matches a DOS CRLF. |
| \a, \e, \f and \v |
Match printer/keyboard special characters: bell character (\x07), escape character (\x1B), form feed (\x0C) and vertical tab (\x0B) respectively. Can be found in ASCII code page. |
|
| \cA through \cZ |
Match keyboard code Control+A through Control+Z, equivalent to ASCII code\x01 through \x1A. |
\cS\cQ matches a stop and go on keyboard. |
| Character Sets [abc] |
|---|
| Character | Description | Example |
|---|
[
(opening square bracket) |
Starts a character set. A character set contains all character within the range. |
|
| Any character except ^-]\ can belongs to the character set. |
All characters except the special characters on the left. |
[abc]
matches a, b or c |
\
(backslash) |
A escapes special characters to suppress the special meaning ofi ^-]\. |
[\^\]]
matches ^ or ] |
-
Hyphen |
Specifies a range of characters if placed between characters and numbers.
(represent a hyphen in the set, if placed immediately after [.) |
[a-z0-9]
matches any lower case letter or digit |
^
Caret |
Negates the character set if placed immediately after [, if placed anywhere except after the opening [, represent the
caret belongs to the set |
[^A-C]
matches any character except A, B, or C) |
| Dot |
|---|
| Character | Description | Example |
|---|
.
Dot |
The most important shorthand character, matches any single character except line break characters \r and \n. |
.
Matches any ONE character |
| Anchors |
|---|
| Character | Description | Example |
|---|
| ^ |
Matches at the beginning of the string. |
|
| $ |
Matches the end of the string. |
|
| \A |
Start the regular expression match from the beginning of the string. |
|
| \Z |
Position the regular expression match to the end of the string. |
|
| Word Boundaries |
|---|
| Character | Description | Example |
|---|
| \b |
This is a zero-width assertion that matches only at the beginning or end of a word. |
\bgreat\b
matches only "great" is a compelete word exist |
| \B |
Another zero-width assertion that is opposite the above. |
\Bhello\B success if there is no "hello" exist |
| \w |
Matches any alphanumeric character or string, including "_". |
|
| \W |
Matches any non-alphanumeric character or string. |
|
| Alternation |
|---|
| Character | Description | Example |
|---|
| | |
Match possible correct answers. |
a (2|two)-year-old girl
matches ether 2 or two, both are correct |
| Quantifiers |
|---|
| Character | Description | Example |
|---|
| ? |
Lazy quantifier. Matches the preceding pattern element zero or one times. |
xyz? matches xy or xyz |
| * |
Matches the preceding pattern element zero or more times. Can not be placed at the first position
as match pattern, since it can not repeat nothing. |
".*"
default WebMux match pattern to match anything in anylength |
| + |
Matches the preceding pattern element one or more times. |
"l+"
If the URL contains "hello", it will be matched. |
+?
None Greedy Match |
Modify the "+" regular expression to match as few time as possible. |
|
{n}
An integer in curly brackets |
Repeats the preceeding character n times. |
t{3} return true if ttt exist |
| {M,N} |
Denotes the minimum M and the maximum N match count. M,N must be > 0. |
l{1,2} matches Hello, World but not here |
