This document provides a quick reference guide for regular expressions (regex). It outlines various regex anchors, literal characters, character groups, counts, comments, conditional subpatterns, recursive patterns, replacements, case foldings and conditional insertions that can be used in regex patterns.

1. Regular Expressions - Quick Reference Guide
Anchors Literal Characters
^
Character group contents
start of line
$ end of line Letters and digits match exactly axB70 x individual chars
b word boundary Some special characters match exactly @-=% x-y character range
B not at word boundary [:class:] posix char class
A start of subject
Escape other specials with backslash . $ [
G first match in subject
[^:class:] negated class
z end of subject Character Groups
Z end of subject Almost any character (usually not newline) . Examples
or before newline at end [a-zA-Z0-9_]
Lists and ranges of characters [ ]
Non-printing characters Any character except those listed [^ ] [[:alnum:]_]
a alarm (BEL, hex 07)
cx "control-x"
e escape (hex 1B) Counts (add ? for non-greedy) Comments
f formfeed (hex 0C) 0 or more ("perhaps some") * (?#comment)
n newline (hex 0A) 0 or 1 ("perhaps a") ?
r carriage return (hex OD)
t 1 or more ("some") + Conditional subpatterns
tab (hex 09)
ddd octal code ddd Between "n" and "m" of {n,m} (?(condition)yes-pattern)
xhh hex code hh Exactly "n", "n" or more {n}, {n,} (?(condition)yes|no-pattern)
x{hhh..} hex code hhh..
Generic character types Alternation Recursive patterns
d decimal digit Either/or | (?n) Numbered
D not a decimal digit (?0) (?R) Entire regex
s whitespace character
S Lookahead and Lookbehind (?&name) Named
not a whitespace char
w "word" character Followed by (?= )
W "non-word" character NOT followed by (?! ) Replacements
POSIX character classes Following (?<= ) $n reference capture
alnum letters and digits NOT following (?<! )
alpha letters Case foldings
ascii character codes 0-127
blank Grouping u upper case next char
space or tab only
cntrl control characters For capture and counts ( ) U upper case following
digit decimal digits Non-capturing (?: ) l lower case next char
graph printing chars -space L lower case following
lower lower case letters
Named captures (?<name> )
print printing chars +space Alternation E end case folding
punct printing chars -alnum Back references
space white space Conditional insertions
upper
Numbered n gn g{n}
upper case letters (?n:insertion)
word "word" characters Relative g{-n}
xdigit hexadecimal digits Named k<name> (?n:insertion:otherwise)
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