Regexps
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This document provides a summary of regular expression anchors, quantifiers, character classes, escape characters, modifiers, replacements, assertions and sample patterns. It defines common regex tokens like ^, $, *, +, ?, {}, [], \b, \B, etc and explains what characters and patterns they can be used to match. Examples are given for matching dates, images, hex colors, passwords, emails and HTML tags.
![Anchors Quantifiers Groups and Ranges
^ Start of string * 0 or more . Any character except
A Start of string + 1 or more new line (n)
$ End of string ? 0 or 1 (a|b) a or b
Z End of string {3} Exactly 3 (...) Group
b Word boundary {3,} 3 or more (?:...) Passive Group
B Not word boundary {3,5} 3, 4 or 5 [abc] Range (a or b or c)
< Start of word [^abc] Not a or b or c
> End of word [a-q] Letter between a and q
Quantifier Modifiers
[A-Q] Upper case letter
"x" below represents a quantifier between A and Q
Character Classes
x? [0-7] Digit between 0 and 7
Ungreedy version of "x"
n nth group/subpattern
c Control character
Note: Ranges are inclusive.
s White space Escape Character
S Not white space
d Digit Pattern Modifiers
Escape Character
D Not digit
w g Global match
Word
W Metacharacters (must be escaped) i Case-insensitive
Not word
x m Multiple lines
Hexadecimal digit
^ [ . s Treat string as single line
O Octal digit
$ { * x Allow comments and
( + white space in pattern
POSIX
) | ? e Evaluate replacement
< > U Ungreedy pattern
[:upper:] Upper case letters
[:lower:] Lower case letters
[:alpha:] All letters Special Characters String Replacement (Backreferences)
[:alnum:] Digits and letters
[:digit:] Digits n New line $n nth non-passive group
[:xdigit:] Hexadecimal digits r Carriage return $2 "xyz" in /^(abc(xyz))$/
[:punct:] Punctuation t Tab $1 "xyz" in /^(?:abc)(xyz)$/
[:blank:] Space and tab v Vertical tab $` Before matched string
[:space:] Blank characters f Form feed $' After matched string
[:cntrl:] Control characters xxx Octal character xxx $+ Last matched string
[:graph:] Printed characters xhh Hex character hh $& Entire matched string
[:print:] Printed characters and
spaces Sample Patterns
[:word:] Digits, letters and
underscore Pattern Will Match
([A-Za-z0-9-]+) Letters, numbers and hyphens
(d{1,2}/d{1,2}/d{4}) Date (e.g. 21/3/2006)
Assertions
([^s]+(?=.(jpg|gif|png)).2) jpg, gif or png image
?= Lookahead assertion (^[1-9]{1}$|^[1-4]{1}[0-9]{1}$|^50$) Any number from 1 to 50 inclusive
?! Negative lookahead (#?([A-Fa-f0-9]){3}(([A-Fa-f0-9]){3})?) Valid hexadecimal colour code
?<= Lookbehind assertion ((?=.*d)(?=.*[a-z])(?=.*[A-Z]).{8,15}) String with at least one upper case
?!= or ?<! Negative lookbehind letter, one lower case letter, and one
?> Once-only Subexpression digit (useful for passwords).
?() Condition [if then] (w+@[a-zA-Z_]+?.[a-zA-Z]{2,6}) Email addresses
?()| Condition [if then else] (<(/?[^>]+)>) HTML Tags
?# Comment
Note: These patterns are intended for reference purposes and have not been
extensively tested. Please use with caution and test thoroughly before use.
Available free from
www.ILoveJackDaniels.com](https://image.slidesharecdn.com/regexp-110625142106-phpapp02/85/Regexps-1-320.jpg)
Regexps
- 1. Anchors Quantifiers Groups and Ranges ^ Start of string * 0 or more . Any character except A Start of string + 1 or more new line (n) $ End of string ? 0 or 1 (a|b) a or b Z End of string {3} Exactly 3 (...) Group b Word boundary {3,} 3 or more (?:...) Passive Group B Not word boundary {3,5} 3, 4 or 5 [abc] Range (a or b or c) < Start of word [^abc] Not a or b or c > End of word [a-q] Letter between a and q Quantifier Modifiers [A-Q] Upper case letter "x" below represents a quantifier between A and Q Character Classes x? [0-7] Digit between 0 and 7 Ungreedy version of "x" n nth group/subpattern c Control character Note: Ranges are inclusive. s White space Escape Character S Not white space d Digit Pattern Modifiers Escape Character D Not digit w g Global match Word W Metacharacters (must be escaped) i Case-insensitive Not word x m Multiple lines Hexadecimal digit ^ [ . s Treat string as single line O Octal digit $ { * x Allow comments and ( + white space in pattern POSIX ) | ? e Evaluate replacement < > U Ungreedy pattern [:upper:] Upper case letters [:lower:] Lower case letters [:alpha:] All letters Special Characters String Replacement (Backreferences) [:alnum:] Digits and letters [:digit:] Digits n New line $n nth non-passive group [:xdigit:] Hexadecimal digits r Carriage return $2 "xyz" in /^(abc(xyz))$/ [:punct:] Punctuation t Tab $1 "xyz" in /^(?:abc)(xyz)$/ [:blank:] Space and tab v Vertical tab $` Before matched string [:space:] Blank characters f Form feed $' After matched string [:cntrl:] Control characters xxx Octal character xxx $+ Last matched string [:graph:] Printed characters xhh Hex character hh $& Entire matched string [:print:] Printed characters and spaces Sample Patterns [:word:] Digits, letters and underscore Pattern Will Match ([A-Za-z0-9-]+) Letters, numbers and hyphens (d{1,2}/d{1,2}/d{4}) Date (e.g. 21/3/2006) Assertions ([^s]+(?=.(jpg|gif|png)).2) jpg, gif or png image ?= Lookahead assertion (^[1-9]{1}$|^[1-4]{1}[0-9]{1}$|^50$) Any number from 1 to 50 inclusive ?! Negative lookahead (#?([A-Fa-f0-9]){3}(([A-Fa-f0-9]){3})?) Valid hexadecimal colour code ?<= Lookbehind assertion ((?=.*d)(?=.*[a-z])(?=.*[A-Z]).{8,15}) String with at least one upper case ?!= or ?<! Negative lookbehind letter, one lower case letter, and one ?> Once-only Subexpression digit (useful for passwords). ?() Condition [if then] (w+@[a-zA-Z_]+?.[a-zA-Z]{2,6}) Email addresses ?()| Condition [if then else] (<(/?[^>]+)>) HTML Tags ?# Comment Note: These patterns are intended for reference purposes and have not been extensively tested. Please use with caution and test thoroughly before use. Available free from www.ILoveJackDaniels.com