Metacharacter What It Matches
x? Matches 0 or 1 occurrences of x
(xyz)? Matches 0 or 1 occurrences of pattern xyz
x* Matches 0 or more occurrences of x
(xyz)* Matches 0 or more occurrences of pattern xyz
x+ Matches 1 or more occurrences of x
(xyz)+ Matches 1 or more occurrences of pattern xyz
x{m,n} Matches at least m occurrences of x and no more than n occurrences of x