The dot in regular expressions
One of the most important characters in regular expressions is the
simple dot (strictly the full stop character). The dot
essentially matches any character. For example, the following
expression means "a digit plus any other character":
In fact, the dot is often most useful when combined with another special
character– the asterisk– which we'll look at
properly shortly. But, jumping the gun a little, the sequence .*
means "zero or more instances of any character". We used this sequence in our
introduction to regular expressions when we used
the following expression to mean "contains a sequence of ten or more digits":
Really, this expression means "any number (including zero) of any character, followed by
twn digits, followed by any number of any character".
The asterisk is an example of a repetition operator,
which we look at on the next page.