regular expression cheatsheet

1Regular Expression FUll Cheatsheet (For quick look) :)
2note: for downloading visit https://buggyprogrammer.com/regular-expression-cheatsheet/
3------x-------------------x----------------x------------x----------------x-------------
4
5# -------------- Anchors --------------
6^   →  Start of string, or start of line in multiline pattern
7\A  →  Start of string
8$   →  End of string, or end of line in multi-line pattern
9\Z  →  End of string
10\b  →  Word boundary
11\B  →  Not word boundary
12\<  →  Start of word
13\>  →  End of word
14
15
16# ---------- Character Classes --------
17\c  →  Control character
18\s  →  White space
19\S  →  Not white space
20\d  →  Digit
21\D  →  Not digit
22\w  →  Word
23\W  →  Not word
24\x  →  Hexadecimal digit
25\O  →  Octal digit
26
27
28# --------- Quantifiers -----------------
29*     →    0 or more 
30{3}   →    Exactly 3
31+     →    1 or more 
32{3,}  →    3 or more
33?     →    0 or 1 
34{3,5} →    3, 4 or 5
35Add a ? to a quantifier to make it ungreedy.
36
37
38# ------- Special Characters -------------
39\n   →  New line
40\r   →  Carriage return
41\t   →  Tab
42\v   →  Vertical tab
43\f   →  Form feed
44\xxx →  Octal character xxx
45\xhh →  Hex character hh
46
47
48# --------- Groups and Ranges -------------
49.       →  Any character except new line (\n)
50(a|b)   →  a or b
51(...)   →  Group
52(?:...) →  Passive (non-capturing) group
53[abc]   →  Range (a or b or c)
54[^abc]  →  Not (a or b or c)
55[a-q]   →  Lower case letter from a to q
56[A-Q]   →  Upper case letter from A to Q
57[0-7]   →  Digit from 0 to 7
58\x      →  Group/subpattern number "x"
59Ranges are inclusive.
60
61
62# ----------- Assertions ---------------
63?=         →  Lookahead assertion
64?!         →  Negative lookahead
65?<=        →  Lookbehind assertion
66?!= or ?<! →  Negative lookbehind
67?>         →  Once-only Subexpression
68?()        →  Condition [if then]
69?()|       →  Condition [if then else]
70?#         →  Comment
71
72
73# ------ Pattern Modifiers --------
74g   →  Global match
75i*  →  Case-insensitive
76m*  →  Multiple lines
77s*  →  Treat string as single line
78x*  →  Allow comments and whitespace in pattern
79e*  →  Evaluate replacement
80U*  →  Ungreedy pattern
81*   →  PCRE modifier
82
83
84# ------ String Replacement ------
85$n  →  nth non-passive group
86$2  →  "xyz" in /^(abc(xyz))$/
87$1  →  "xyz" in /^(?:abc)(xyz)$/
88$`  →  Before matched string
89$'  →  After matched string
90$+  →  Last matched string
91$&  →  Entire matched string
92Some regex implementations use \ instead of $
93
94
95# ---------- Escape Sequences ------------
96\ Escape following character
97\Q Begin literal sequence
98\E End literal sequence
99
100"Escaping" is a way of treating characters which have a special meaning in regular
101expressions literally, rather than as special characters.
102
103
104# --------- Common Metacharacters ---------
105^ 
106[
107.
108$
109{
110*
111(
112\
113+
114)
115|
116<
117>
118The escape character is usually \
119
120
121# ------------ POSIX ----------------
122[:upper:]  →  Upper case letters
123[:lower:]  →  Lower case letters
124[:alpha:]  →  All letters
125[:alnum:]  →  Digits and letters
126[:digit:]  →  Digits
127[:xdigit:] →  Hexadecimal digits
128[:punct:]  →  Punctuation
129[:blank:]  →  Space and tab
130[:space:]  →  Blank characters
131[:cntrl:]  →  Control characters
132[:graph:]  →  Printed characters
133[:print:]  →  Printed characters and spaces
134[:word:]   →  Digits, letters and underscore

1/* shorthand character classes */
2regex = /d/; // matches any digit, short for [0-9]
3regex = /D/; // matches non-digits, short for [^0-9]
4regex = /S/; // matches non-white space character
5regex = /s/; // matches any white space character
6regex = /w/; // matches character, short for [a-zA-Z_0-9]
7regex = /W/; // matches non-word character [^w]
8regex = /b/; // Matches a word boundary where a word character is [a-zA-Z0-9_]