RegEx cheat sheet

.regex_cheat_sheet.md

RegEx cheat sheet

regex_cheat_sheet.md

command	Ragex engine
SEARCH
Matching characters
Character class
\w	.NET: a-z, A-Z, 0-9, _; Vim's regex engine(?)
[[:alpha:]]	BRE, ERE, PCRE: a-z, A-Z
[[:lower:]]	BRE, ERE, PCRE: a-z
[[:upper:]]	BRE, ERE, PCRE: A-Z
[[:alnum:]]	BRE, ERE, PCRE: a-z, A-Z, 0-9
[[:punct:]]	BRE, ERE, PCRE: !,",#,$,%,&,',(,),*,+,,,.,/,:,;,<,=,>,?,@
Not a Word Character
\W	?
Whitespace
\s	.NET (it matches space, tab, newline. Vim's regex engine: it matches only space or tab), PCRE
\n	Vim's regex engine: it matches only a new line)
\s	Vim's regex engine (It matches space, tab, or newline)
Not Whitespace (space, tab, newline)
\S	?
Tab
\t	.NET
Digit (0-9)
\d	.NET, PCRE
[[:digit:]]	BRE, ERE, PCRE
Not a Digit (0-9)
\D	?
Any Character Except New Line
.	BRE, ERE, PCRE, .NET, Vim's regex engine
Boundaries
Word Boundary (begging or end)
\b	BRE, ERE, PCRE, .NET, Vim's regex engine(?)
Not a Word Boundary (begging or end)
\B	BRE, ERE, PCRE, .NET, Vim's regex engine(?)
Beginning of a word
\<	BRE, ERE, Vim's regex engine
End of a word
\>	BRE, ERE, Vim's regex engine
Beginning of the line
^	BRE, ERE, PCRE, .NET, Vim's regex engine
End of the line
$	BRE, ERE, PCRE, .NET, Vim's regex engine(?)
Grouping and Matching in a range
Matches Characters within or in the range
[]	BRE, ERE, PCRE, .NET, Vim's regex engine (matching characters do not work, use range instead)
Matches Characters NOT within or in the range
[^ ]
Either Or
|	ERE, PCRE
\|	BRE
Capturing group
( )	.NET, PCRE
\( \)	BRE(?), Vim's regex engine
match the α-th capturing group again
\α	.NET, PCRE
Noncapturing group
(?:)	.NET
Negative lookahead noncapturing group for the previous character
EX: "q(?!u)" matches "q" that is not followed by "u"
(?!)
Positive lookahead noncapturing group for the previous character
EX: "q(?=u)" matches "q" that is followed by "u"
(?=)
Negative Lookbehind noncapturing group for the next character
EX: (?<!a)b matches a b that is not preceded by an a
(?<!)	.NET
Positive Lookbehind noncapturing group for the next character
EX: (?<=a)b matches a b that is preceded by an a
(?<=)	.NET
Quantifiers (applied to the preceded character)
0 or More (greedy)
*	.NET, Vim's regex engine
0 or More (lazy)
*?	.NET, Vim's regex engine(?)
1 or More (greedy)
\+	BRE(?), Vim's regex engine
+	.NET
1 or More (lazy)
\+?	BRE(?), Vim's regex engine(?)
+?	.NET
0 or One
?	ERE, PCRE, .NET
\?	BRE, Vim's regex engine
Range Number
{i,j}	ERE, PCRE, .NET
\{i,j}	Vim's regex engine
\{i,j\}	BRE
REPLACE
Placeholder, where n is the number order of the placeholder
$n	.NET
\ n	Vim's regex engine
Newline
\ n	.NET
\r	Vim's regex engine
Tab key
\t	.NET
Cause all characters of the next placeholder to be upper case
\U	.NET
Cause the first characters of the first word of the next placeholder to be upper case
\u	.NET
Cause all characters of the next placeholder to be lower case
\L	.NET
Cause the first characters of the first word of the next placeholder to be lower case
\l	.NET
OBS: you can mix them: Ex, you can use \u\L to make the first letter be upper case and the rest of the placeholder lowercase.