unix regex

regex feature	BREs	EREs
dot, ^, $, [ ], [^ ]
"any number" quantifier	*	*
+ and ? quantifiers		+ ?
range quantifier	\{min, max\}	{min, max}
grouping	\( \)	( )
can apply quantifiers to parentheses
backreferences	\1 through \9
alternation

homemahmooz/brain/resources/masteringregularexpressions.pdf

regex table

regex	match	example pattern
[0-9] \d	a single digit
[A-Z]	an upper case letter
[a-z]	a lower case letter
^	start of line
\$	end of line
\b	word boundary
\B	non-word boundary
\D	any non-digit
\w	any alphanumeric/underscore
\W	a non-alphanumeric
\s	whitespace(space,tab)
\S	non-whitespace
*	zero or more occurrences of the previous char or expression
+	one or more occurrences of the previous char or expression
?	exactly zero or one occurrence of the previous char or expression
{n}	occurrences of the previous char or expression
{n,m}	from to occurrences of the previous char or expression
{n,}	at least occurrences of the previous char or expression
{,m}	up to occurrences of the previous char or expression
\*	an asterisk
\.	a period
\?	a question mark
\n	a newline
\t	a tab

[cite:;taken from @nlp_jurafsky_2020 chapter 2 regular expressions, text normalization, edit distance]