colou?r matches color and colour
but what does the following ? do?
(first group)(second group)?(third group)
colou?r matches color and colour but what does the following ? do? (first group)(second
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colou?r matches color and colour
but what does the following ? do?
(first group)(second group)?(third group)
It is a quantifier which means “zero or one”. It applies to the atom preceding it, therefore, here, the
u.It is one of the numerous regex metacharacters, which means, if you want to match a literal question mark, you’ll have to escape it (as in
\?), except in a character class.As to your second example:
it has exactly the same meaning. The grouping operator,
(...), apart from allowing backreferences, also has the nice effect to turn anything into parens into an atom.Which means, here, the text matched by the regex
second groupcan appear 0 or 1 time, similarly to theuinColou?r.http://www.regular-expressions.info/reference.html