Professorloading163

1. Perl Regex Cheat Sheet Pdf
2. Regex In R Cheat Sheet

Regular expressions are not as difficult as regex haters make them seem. While regex are intimidating, this cheat sheet will help you overcome that. My experience with regex I have always stayed far away from regex. Regular expressions can be made case insensitive using (?i). In backreferences, the strings can be converted to lower or upper case using L or U (e.g. This requires PERL = TRUE. CC BY Ian Kopacka. ian.kopacka@ages.at Regular expressions can conveniently be created using rex::rex. Regex cheat sheet of all shortcuts and commands. Match a single white space character (space, tab, form feed, or line feed).

The tables below are a reference to basic regex. While reading the rest of the site, when in doubt, you can always come back and look here. (It you want a bookmark, here's a direct link to the regex reference tables). I encourage you to print the tables so you have a cheat sheet on your desk for quick reference.
The tables are not exhaustive, for two reasons. First, every regex flavor is different, and I didn't want to crowd the page with overly exotic syntax. For a full reference to the particular regex flavors you'll be using, it's always best to go straight to the source. In fact, for some regex engines (such as Perl, PCRE, Java and .NET) you may want to check once a year, as their creators often introduce new features.

Perl Regex Cheat Sheet Pdf

The other reason the tables are not exhaustive is that I wanted them to serve as a quick introduction to regex. If you are a complete beginner, you should get a firm grasp of basic regex syntax just by reading the examples in the tables. I tried to introduce features in a logical order and to keep out oddities that I've never seen in actual use, such as the 'bell character'. With these tables as a jumping board, you will be able to advance to mastery by exploring the other pages on the site.

How to use the tables

The tables are meant to serve as an accelerated regex course, and they are meant to be read slowly, one line at a time. On each line, in the leftmost column, you will find a new element of regex syntax. The next column, 'Legend', explains what the element means (or encodes) in the regex syntax. The next two columns work hand in hand: the 'Example' column gives a valid regular expression that uses the element, and the 'Sample Match' column presents a text string that could be matched by the regular expression.
You can read the tables online, of course, but if you suffer from even the mildest case of online-ADD (attention deficit disorder), like most of us… Well then, I highly recommend you print them out. You'll be able to study them slowly, and to use them as a cheat sheet later, when you are reading the rest of the site or experimenting with your own regular expressions.
Enjoy!
If you overdose, make sure not to miss the next page, which comes back down to Earth and talks about some really cool stuff: The 1001 ways to use Regex.

Regex Accelerated Course and Cheat Sheet

Regex In R Cheat Sheet

For easy navigation, here are some jumping points to various sections of the page:
✽ Characters
✽ Quantifiers
✽ More Characters
✽ Logic
✽ More White-Space
✽ More Quantifiers
✽ Character Classes
✽ Anchors and Boundaries
✽ POSIX Classes
✽ Inline Modifiers
✽ Lookarounds
✽ Character Class Operations
✽ Other Syntax
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Characters

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

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Quantifiers

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

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More Characters

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	[{()}]	[{()}]

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Logic

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

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More White-Space

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)

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More Quantifiers

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

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Character Classes

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

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Anchors and Boundaries

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

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POSIX Classes

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:]]+	‽,:〽⁆

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Inline Modifiers

None of these are supported in JavaScript. In Ruby, beware of (?s) and (?m).

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

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Lookarounds

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

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Character Class Operations

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

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Other Syntax

Syntax	Legend	Example	Sample Match
K	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
Q…E	Perl, PCRE (C, PHP, R…), Java: treat anything between the delimiters as a literal string. Useful to escape metacharacters.	Q(C++ ?)E	(C++ ?)

The 1001 ways to use Regex










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A regular expression is a pattern that the regular expression engine attempts to match in input text. A pattern consists of one or more character literals, operators, or constructs. For a brief introduction, see .NET Regular Expressions.

Each section in this quick reference lists a particular category of characters, operators, and constructs that you can use to define regular expressions.

We've also provided this information in two formats that you can download and print for easy reference:

Character Escapes

The backslash character () in a regular expression indicates that the character that follows it either is a special character (as shown in the following table), or should be interpreted literally. For more information, see Character Escapes.

Escaped character	Description	Pattern	Matches
a	Matches a bell character, u0007.	a	'u0007' in 'Error!' + 'u0007'
b	In a character class, matches a backspace, u0008.	[b]{3,}	'bbbb' in 'bbbb'
t	Matches a tab, u0009.	(w+)t	'item1t', 'item2t' in 'item1titem2t'
r	Matches a carriage return, u000D. (r is not equivalent to the newline character, n.)	rn(w+)	'rnThese' in 'rnThese arentwo lines.'
v	Matches a vertical tab, u000B.	[v]{2,}	'vvv' in 'vvv'
f	Matches a form feed, u000C.	[f]{2,}	'fff' in 'fff'
n	Matches a new line, u000A.	rn(w+)	'rnThese' in 'rnThese arentwo lines.'
e	Matches an escape, u001B.	e	'x001B' in 'x001B'
nnn	Uses octal representation to specify a character (nnn consists of two or three digits).	w040w	'a b', 'c d' in 'a bc d'
xnn	Uses hexadecimal representation to specify a character (nn consists of exactly two digits).	wx20w	'a b', 'c d' in 'a bc d'
cX cx	Matches the ASCII control character that is specified by X or x, where X or x is the letter of the control character.	cC	'x0003' in 'x0003' (Ctrl-C)
unnnn	Matches a Unicode character by using hexadecimal representation (exactly four digits, as represented by nnnn).	wu0020w	'a b', 'c d' in 'a bc d'
	When followed by a character that is not recognized as an escaped character in this and other tables in this topic, matches that character. For example, * is the same as x2A, and . is the same as x2E. This allows the regular expression engine to disambiguate language elements (such as * or ?) and character literals (represented by * or ?).	d+[+-x*]d+	'2+2' and '3*9' in '(2+2) * 3*9'

Character Classes

A character class matches any one of a set of characters. Character classes include the language elements listed in the following table. For more information, see Character Classes.

Character class	Description	Pattern	Matches
[character_group]	Matches any single character in character_group. By default, the match is case-sensitive.	[ae]	'a' in 'gray' 'a', 'e' in 'lane'
[^character_group]	Negation: Matches any single character that is not in character_group. By default, characters in character_group are case-sensitive.	[^aei]	'r', 'g', 'n' in 'reign'
[first-last]	Character range: Matches any single character in the range from first to last.	[A-Z]	'A', 'B' in 'AB123'
.	Wildcard: Matches any single character except n. To match a literal period character (. or u002E), you must precede it with the escape character (.).	a.e	'ave' in 'nave' 'ate' in 'water'
p{name}	Matches any single character in the Unicode general category or named block specified by name.	p{Lu} p{IsCyrillic}	'C', 'L' in 'City Lights' 'Д', 'Ж' in 'ДЖem'
P{name}	Matches any single character that is not in the Unicode general category or named block specified by name.	P{Lu} P{IsCyrillic}	'i', 't', 'y' in 'City' 'e', 'm' in 'ДЖem'
w	Matches any word character.	w	'I', 'D', 'A', '1', '3' in 'ID A1.3'
W	Matches any non-word character.	W	' ', '.' in 'ID A1.3'
s	Matches any white-space character.	ws	'D ' in 'ID A1.3'
S	Matches any non-white-space character.	sS	' _' in 'int __ctr'
d	Matches any decimal digit.	d	'4' in '4 = IV'
D	Matches any character other than a decimal digit.	D	' ', '=', ' ', 'I', 'V' in '4 = IV'

Anchors

Anchors, or atomic zero-width assertions, cause a match to succeed or fail depending on the current position in the string, but they do not cause the engine to advance through the string or consume characters. The metacharacters listed in the following table are anchors. For more information, see Anchors.

Assertion	Description	Pattern	Matches
^	By default, the match must start at the beginning of the string; in multiline mode, it must start at the beginning of the line.	^d{3}	'901' in '901-333-'
$	By default, the match must occur at the end of the string or before n at the end of the string; in multiline mode, it must occur before the end of the line or before n at the end of the line.	-d{3}$	'-333' in '-901-333'
A	The match must occur at the start of the string.	Ad{3}	'901' in '901-333-'
Z	The match must occur at the end of the string or before n at the end of the string.	-d{3}Z	'-333' in '-901-333'
z	The match must occur at the end of the string.	-d{3}z	'-333' in '-901-333'
G	The match must occur at the point where the previous match ended.	G(d)	'(1)', '(3)', '(5)' in '(1)(3)(5)[7](9)'
b	The match must occur on a boundary between a w (alphanumeric) and a W (nonalphanumeric) character.	bw+sw+b	'them theme', 'them them' in 'them theme them them'
B	The match must not occur on a b boundary.	Bendw*b	'ends', 'ender' in 'end sends endure lender'

Grouping Constructs

Grouping constructs delineate subexpressions of a regular expression and typically capture substrings of an input string. Grouping constructs include the language elements listed in the following table. For more information, see Grouping Constructs.

Grouping construct	Description	Pattern	Matches
(subexpression)	Captures the matched subexpression and assigns it a one-based ordinal number.	(w)1	'ee' in 'deep'
(?<name>subexpression) or (?'name'subexpression)	Captures the matched subexpression into a named group.	(?<double>w)k<double>	'ee' in 'deep'
(?<name1-name2>subexpression) or (?'name1-name2'subexpression)	Defines a balancing group definition. For more information, see the 'Balancing Group Definition' section in Grouping Constructs.	(((?'Open'()[^()]*)+((?'Close-Open'))[^()]*)+)*(?(Open)(?!))$	'((1-3)*(3-1))' in '3+2^((1-3)*(3-1))'
(?:subexpression)	Defines a noncapturing group.	Write(?:Line)?	'WriteLine' in 'Console.WriteLine()' 'Write' in 'Console.Write(value)'
(?imnsx-imnsx:subexpression)	Applies or disables the specified options within subexpression. For more information, see Regular Expression Options.	Ad{2}(?i:w+)b	'A12xl', 'A12XL' in 'A12xl A12XL a12xl'
(?=subexpression)	Zero-width positive lookahead assertion.	bw+b(?=.+and.+)	'cats', 'dogs' in 'cats, dogs and some mice.'
(?!subexpression)	Zero-width negative lookahead assertion.	bw+b(?!.+and.+)	'and', 'some', 'mice' in 'cats, dogs and some mice.'
(?<=subexpression)	Zero-width positive lookbehind assertion.	bw+b(?<=.+and.+) ——————————— bw+b(?<=.+and.*)	'some', 'mice' in 'cats, dogs and some mice.' ———————————— 'and', 'some', 'mice' in 'cats, dogs and some mice.'
(?<!subexpression)	Zero-width negative lookbehind assertion.	bw+b(?<!.+and.+) ——————————— bw+b(?<!.+and.*)	'cats', 'dogs', 'and' in 'cats, dogs and some mice.' ———————————— 'cats', 'dogs' in 'cats, dogs and some mice.'
(?>subexpression)	Atomic group.	(?>a|ab)c	'ac' in'ac' nothing in'abc'

Lookarounds at a glance

When the regular expression engine hits a lookaround expression, it takes a substring reaching from the current position to the start (lookbehind) or end (lookahead) of the original string, and then runsRegex.IsMatch on that substring using the lookaround pattern. Success of this subexpression's result is then determined by whether it's a positive or negative assertion.

Lookaround	Name	Function
(?=check)	Positive Lookahead	Asserts that what immediately follows the current position in the string is 'check'
(?<=check)	Positive Lookbehind	Asserts that what immediately precedes the current position in the string is 'check'
(?!check)	Negative Lookahead	Asserts that what immediately follows the current position in the string is not 'check'
(?<!check)	Negative Lookbehind	Asserts that what immediately precedes the current position in the string is not 'check'

Once they have matched, atomic groups won't be re-evaluated again, even when the remainder of the pattern fails due to the match. This can significantly improve performance when quantifiers occur within the atomic group or the remainder of the pattern.

Quantifiers

A quantifier specifies how many instances of the previous element (which can be a character, a group, or a character class) must be present in the input string for a match to occur. Quantifiers include the language elements listed in the following table. For more information, see Quantifiers.

Quantifier	Description	Pattern	Matches
*	Matches the previous element zero or more times.	d*.d	'.0', '19.9', '219.9'
+	Matches the previous element one or more times.	'be+'	'bee' in 'been', 'be' in 'bent'
?	Matches the previous element zero or one time.	'rai?n'	'ran', 'rain'
{n}	Matches the previous element exactly n times.	',d{3}'	',043' in '1,043.6', ',876', ',543', and ',210' in '9,876,543,210'
{n,}	Matches the previous element at least n times.	'd{2,}'	'166', '29', '1930'
{n,m}	Matches the previous element at least n times, but no more than m times.	'd{3,5}'	'166', '17668' '19302' in '193024'
*?	Matches the previous element zero or more times, but as few times as possible.	d*?.d	'.0', '19.9', '219.9'
+?	Matches the previous element one or more times, but as few times as possible.	'be+?'	'be' in 'been', 'be' in 'bent'
??	Matches the previous element zero or one time, but as few times as possible.	'rai??n'	'ran', 'rain'
{n}?	Matches the preceding element exactly n times.	',d{3}?'	',043' in '1,043.6', ',876', ',543', and ',210' in '9,876,543,210'
{n,}?	Matches the previous element at least n times, but as few times as possible.	'd{2,}?'	'166', '29', '1930'
{n,m}?	Matches the previous element between n and m times, but as few times as possible.	'd{3,5}?'	'166', '17668' '193', '024' in '193024'

Backreference Constructs

A backreference allows a previously matched subexpression to be identified subsequently in the same regular expression. The following table lists the backreference constructs supported by regular expressions in .NET. For more information, see Backreference Constructs.

Backreference construct	Description	Pattern	Matches
number	Backreference. Matches the value of a numbered subexpression.	(w)1	'ee' in 'seek'
k<name>	Named backreference. Matches the value of a named expression.	(?<char>w)k<char>	'ee' in 'seek'

Alternation Constructs

Alternation constructs modify a regular expression to enable either/or matching. These constructs include the language elements listed in the following table. For more information, see Alternation Constructs.

Alternation construct	Description	Pattern	Matches
|	Matches any one element separated by the vertical bar (|) character.	th(e|is|at)	'the', 'this' in 'this is the day.'
(?(expression)yes|no)	Matches yes if the regular expression pattern designated by expression matches; otherwise, matches the optional no part. expression is interpreted as a zero-width assertion.	(?(A)Ad{2}b|bd{3}b)	'A10', '910' in 'A10 C103 910'
(?(name)yes|no)	Matches yes if name, a named or numbered capturing group, has a match; otherwise, matches the optional no.	(?<quoted>')?(?(quoted).+?'|S+s)	'Dogs.jpg ', 'Yiska playing.jpg' in 'Dogs.jpg 'Yiska playing.jpg'

Substitutions

Substitutions are regular expression language elements that are supported in replacement patterns. For more information, see Substitutions. The metacharacters listed in the following table are atomic zero-width assertions.

Character	Description	Pattern	Replacement pattern	Input string	Result string
$number	Substitutes the substring matched by group number.	b(w+)(s)(w+)b	$3$2$1	'one two'	'two one'
${name}	Substitutes the substring matched by the named group name.	b(?<word1>w+)(s)(?<word2>w+)b	${word2} ${word1}	'one two'	'two one'
$$	Substitutes a literal '$'.	b(d+)s?USD	$$$1	'103 USD'	'$103'
$&	Substitutes a copy of the whole match.	$?d*.?d+	**$&**	'$1.30'	'**$1.30**'
$`	Substitutes all the text of the input string before the match.	B+	$`	'AABBCC'	'AAAACC'
$'	Substitutes all the text of the input string after the match.	B+	$'	'AABBCC'	'AACCCC'
$+	Substitutes the last group that was captured.	B+(C+)	$+	'AABBCCDD'	'AACCDD'
$_	Substitutes the entire input string.	B+	$_	'AABBCC'	'AAAABBCCCC'

Regular Expression Options

You can specify options that control how the regular expression engine interprets a regular expression pattern. Many of these options can be specified either inline (in the regular expression pattern) or as one or more RegexOptions constants. This quick reference lists only inline options. For more information about inline and RegexOptions options, see the article Regular Expression Options.

You can specify an inline option in two ways:

• By using the miscellaneous construct(?imnsx-imnsx), where a minus sign (-) before an option or set of options turns those options off. For example, (?i-mn) turns case-insensitive matching (i) on, turns multiline mode (m) off, and turns unnamed group captures (n) off. The option applies to the regular expression pattern from the point at which the option is defined, and is effective either to the end of the pattern or to the point where another construct reverses the option.
• By using the grouping construct(?imnsx-imnsx:subexpression), which defines options for the specified group only.

The .NET regular expression engine supports the following inline options:

Option	Description	Pattern	Matches
i	Use case-insensitive matching.	b(?i)a(?-i)aw+b	'aardvark', 'aaaAuto' in 'aardvark AAAuto aaaAuto Adam breakfast'
m	Use multiline mode. ^ and $ match the beginning and end of a line, instead of the beginning and end of a string.	For an example, see the 'Multiline Mode' section in Regular Expression Options.
n	Do not capture unnamed groups.	For an example, see the 'Explicit Captures Only' section in Regular Expression Options.
s	Use single-line mode.	For an example, see the 'Single-line Mode' section in Regular Expression Options.
x	Ignore unescaped white space in the regular expression pattern.	b(?x) d+ s w+	'1 aardvark', '2 cats' in '1 aardvark 2 cats IV centurions'

Miscellaneous Constructs

Miscellaneous constructs either modify a regular expression pattern or provide information about it. The following table lists the miscellaneous constructs supported by .NET. For more information, see Miscellaneous Constructs.

Construct	Definition	Example
(?imnsx-imnsx)	Sets or disables options such as case insensitivity in the middle of a pattern.For more information, see Regular Expression Options.	bA(?i)bw+b matches 'ABA', 'Able' in 'ABA Able Act'
(?#comment)	Inline comment. The comment ends at the first closing parenthesis.	bA(?#Matches words starting with A)w+b
# [to end of line]	X-mode comment. The comment starts at an unescaped # and continues to the end of the line.	(?x)bAw+b#Matches words starting with A

See also