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Character | Legend | Example | Sample Match |
---|---|---|---|
d | Most engines: one digit from 0 to 9 | file_dd | file_25 |
d | .NET, Python 3: one Unicode digit in any script | file_dd | file_9੩ |
w | Most engines: 'word character': ASCII letter, digit or underscore | w-www | A-b_1 |
w | .Python 3: 'word character': Unicode letter, ideogram, digit, or underscore | w-www | 字-ま_۳ |
w | .NET: 'word character': Unicode letter, ideogram, digit, or connector | w-www | 字-ま‿۳ |
s | Most engines: 'whitespace character': space, tab, newline, carriage return, vertical tab | asbsc | a b c |
s | .NET, Python 3, JavaScript: 'whitespace character': any Unicode separator | asbsc | a b c |
D | One character that is not a digit as defined by your engine's d | DDD | ABC |
W | One character that is not a word character as defined by your engine's w | WWWWW | *-+=) |
S | One character that is not a whitespace character as defined by your engine's s | SSSS | Yoyo |
Quantifier | Legend | Example | Sample Match |
---|---|---|---|
+ | One or more | Version w-w+ | Version A-b1_1 |
{3} | Exactly three times | D{3} | ABC |
{2,4} | Two to four times | d{2,4} | 156 |
{3,} | Three or more times | w{3,} | regex_tutorial |
* | Zero or more times | A*B*C* | AAACC |
? | Once or none | plurals? | plural |
Character | Legend | Example | Sample Match |
---|---|---|---|
. | Any character except line break | a.c | abc |
. | Any character except line break | .* | whatever, man. |
. | A period (special character: needs to be escaped by a ) | a.c | a.c |
Escapes a special character | .*+? $^/ | .*+? $^/ | |
Escapes a special character | [{()}] | [{()}] |
Logic | Legend | Example | Sample Match |
---|---|---|---|
| | Alternation / OR operand | 22|33 | 33 |
( … ) | Capturing group | A(nt|pple) | Apple (captures 'pple') |
1 | Contents of Group 1 | r(w)g1x | regex |
2 | Contents of Group 2 | (dd)+(dd)=2+1 | 12+65=65+12 |
(?: … ) | Non-capturing group | A(?:nt|pple) | Apple |
Character | Legend | Example | Sample Match |
---|---|---|---|
t | Tab | Ttw{2} | T ab |
r | Carriage return character | see below | |
n | Line feed character | see below | |
rn | Line separator on Windows | ABrnCD | AB CD |
N | Perl, PCRE (C, PHP, R…): one character that is not a line break | N+ | ABC |
h | Perl, PCRE (C, PHP, R…), Java: one horizontal whitespace character: tab or Unicode space separator | ||
H | One character that is not a horizontal whitespace | ||
v | .NET, JavaScript, Python, Ruby: vertical tab | ||
v | Perl, PCRE (C, PHP, R…), Java: one vertical whitespace character: line feed, carriage return, vertical tab, form feed, paragraph or line separator | ||
V | Perl, PCRE (C, PHP, R…), Java: any character that is not a vertical whitespace | ||
R | Perl, PCRE (C, PHP, R…), Java: one line break (carriage return + line feed pair, and all the characters matched by v) |
Quantifier | Legend | Example | Sample Match |
---|---|---|---|
+ | The + (one or more) is 'greedy' | d+ | 12345 |
? | Makes quantifiers 'lazy' | d+? | 1 in 12345 |
* | The * (zero or more) is 'greedy' | A* | AAA |
? | Makes quantifiers 'lazy' | A*? | empty in AAA |
{2,4} | Two to four times, 'greedy' | w{2,4} | abcd |
? | Makes quantifiers 'lazy' | w{2,4}? | ab in abcd |
Character | Legend | Example | Sample Match |
---|---|---|---|
[ … ] | One of the characters in the brackets | [AEIOU] | One uppercase vowel |
[ … ] | One of the characters in the brackets | T[ao]p | Tap or Top |
- | Range indicator | [a-z] | One lowercase letter |
[x-y] | One of the characters in the range from x to y | [A-Z]+ | GREAT |
[ … ] | One of the characters in the brackets | [AB1-5w-z] | One of either: A,B,1,2,3,4,5,w,x,y,z |
[x-y] | One of the characters in the range from x to y | [ -~]+ | Characters in the printable section of the ASCII table. |
[^x] | One character that is not x | [^a-z]{3} | A1! |
[^x-y] | One of the characters not in the range from x to y | [^ -~]+ | Characters that are not in the printable section of the ASCII table. |
[dD] | One character that is a digit or a non-digit | [dD]+ | Any characters, inc- luding new lines, which the regular dot doesn't match |
[x41] | Matches the character at hexadecimal position 41 in the ASCII table, i.e. A | [x41-x45]{3} | ABE |
Anchor | Legend | Example | Sample Match |
---|---|---|---|
^ | Start of string or start of line depending on multiline mode. (But when [^inside brackets], it means 'not') | ^abc .* | abc (line start) |
$ | End of string or end of line depending on multiline mode. Many engine-dependent subtleties. | .*? the end$ | this is the end |
A | Beginning of string (all major engines except JS) | Aabc[dD]* | abc (string... ...start) |
z | Very end of the string Not available in Python and JS | the endz | this is...n...the end |
Z | End of string or (except Python) before final line break Not available in JS | the endZ | this is...n...the endn |
G | Beginning of String or End of Previous Match .NET, Java, PCRE (C, PHP, R…), Perl, Ruby | ||
b | Word boundary Most engines: position where one side only is an ASCII letter, digit or underscore | Bob.*bcatb | Bob ate the cat |
b | Word boundary .NET, Java, Python 3, Ruby: position where one side only is a Unicode letter, digit or underscore | Bob.*bкошкаb | Bob ate the кошка |
B | Not a word boundary | c.*BcatB.* | copycats |
Character | Legend | Example | Sample Match |
---|---|---|---|
[:alpha:] | PCRE (C, PHP, R…): ASCII letters A-Z and a-z | [8[:alpha:]]+ | WellDone88 |
[:alpha:] | Ruby 2: Unicode letter or ideogram | [[:alpha:]d]+ | кошка99 |
[:alnum:] | PCRE (C, PHP, R…): ASCII digits and letters A-Z and a-z | [[:alnum:]]{10} | ABCDE12345 |
[:alnum:] | Ruby 2: Unicode digit, letter or ideogram | [[:alnum:]]{10} | кошка90210 |
[:punct:] | PCRE (C, PHP, R…): ASCII punctuation mark | [[:punct:]]+ | ?!.,:; |
[:punct:] | Ruby: Unicode punctuation mark | [[:punct:]]+ | ‽,:〽⁆ |
Modifier | Legend | Example | Sample Match |
---|---|---|---|
(?i) | Case-insensitive mode (except JavaScript) | (?i)Monday | monDAY |
(?s) | DOTALL mode (except JS and Ruby). The dot (.) matches new line characters (rn). Also known as 'single-line mode' because the dot treats the entire input as a single line | (?s)From A.*to Z | From A to Z |
(?m) | Multiline mode (except Ruby and JS) ^ and $ match at the beginning and end of every line | (?m)1rn^2$rn^3$ | 1 2 3 |
(?m) | In Ruby: the same as (?s) in other engines, i.e. DOTALL mode, i.e. dot matches line breaks | (?m)From A.*to Z | From A to Z |
(?x) | Free-Spacing Mode mode (except JavaScript). Also known as comment mode or whitespace mode | (?x) # this is a # comment abc # write on multiple # lines [ ]d # spaces must be # in brackets | abc d |
(?n) | .NET, PCRE 10.30+: named capture only | Turns all (parentheses) into non-capture groups. To capture, use named groups. | |
(?d) | Java: Unix linebreaks only | The dot and the ^ and $ anchors are only affected by n | |
(?^) | PCRE 10.32+: unset modifiers | Unsets ismnx modifiers |
Lookaround | Legend | Example | Sample Match |
---|---|---|---|
(?=…) | Positive lookahead | (?=d{10})d{5} | 01234 in 0123456789 |
(?<=…) | Positive lookbehind | (?<=d)cat | cat in 1cat |
(?!…) | Negative lookahead | (?!theatre)thew+ | theme |
(?<!…) | Negative lookbehind | w{3}(?<!mon)ster | Munster |
Class Operation | Legend | Example | Sample Match |
---|---|---|---|
[…-[…]] | .NET: character class subtraction. One character that is in those on the left, but not in the subtracted class. | [a-z-[aeiou]] | Any lowercase consonant |
[…-[…]] | .NET: character class subtraction. | [p{IsArabic}-[D]] | An Arabic character that is not a non-digit, i.e., an Arabic digit |
[…&&[…]] | Java, Ruby 2+: character class intersection. One character that is both in those on the left and in the && class. | [S&&[D]] | An non-whitespace character that is a non-digit. |
[…&&[…]] | Java, Ruby 2+: character class intersection. | [S&&[D]&&[^a-zA-Z]] | An non-whitespace character that a non-digit and not a letter. |
[…&&[^…]] | Java, Ruby 2+: character class subtraction is obtained by intersecting a class with a negated class | [a-z&&[^aeiou]] | An English lowercase letter that is not a vowel. |
[…&&[^…]] | Java, Ruby 2+: character class subtraction | [p{InArabic}&&[^p{L}p{N}]] | An Arabic character that is not a letter or a number |
Syntax | Legend | Example | Sample Match |
---|---|---|---|
Keep Out Perl, PCRE (C, PHP, R…), Python's alternate regex engine, Ruby 2+: drop everything that was matched so far from the overall match to be returned | prefixKd+ | 12 | |
Perl, PCRE (C, PHP, R…), Java: treat anything between the delimiters as a literal string. Useful to escape metacharacters. | Q(C++ ?)E | (C++ ?) |