Anchors ^ \A $ \Z \b \B \< \> Start of string Start of string End of string End of string Word boundary Not word boundary Start of word End of word
Quantifiers * + ? {3} {3,} {3,5} 0 or more 1 or more 0 or 1 Exactly 3 3 or more 3, 4 or 5
Groups and Ranges . (a|b) (...) (?:...) [abc] [^abc] [a-q] [A-Q] [0-7] \n Any character except new line (\n) a or b Group Passive Group Range (a or b or c) Not a or b or c Letter between a and q Upper case letter between A and Q Digit between 0 and 7 nth group/subpattern Note: Ranges are inclusive. Pattern Modifiers g Global match Case-insensitive Multiple lines Treat string as single line Allow comments and white space in pattern e U Evaluate replacement Ungreedy pattern
Quantifier Modifiers "x" below represents a quantifier x? Ungreedy version of "x"
Character Classes \c \s \S \d \D \w \W \x \O POSIX [:upper:] [:lower:] [:alpha:] [:alnum:] [:digit:] [:xdigit:] [:punct:] [:blank:] [:space:] [:cntrl:] [:graph:] [:print:] [:word:] Upper case letters Lower case letters All letters Digits and letters Digits Hexadecimal digits Punctuation Space and tab Blank characters Control characters Printed characters Printed characters and spaces Digits, letters and underscore Assertions ?= ?! ? . * + ?
i m s x
String Replacement (Backreferences) $n $2 $1 $` $' $+ $& nth non-passive group "xyz" in /^(abc(xyz))$/ "xyz" in /^(?:abc)(xyz)$/ Before matched string After matched string Last matched string Entire matched string
