Example
Quantifiers allows to specify count of repeated strings.
-
Zero or one:
/a?/ -
Zero or many:
/a*/ -
One or many:
/a+/ -
Exact number:
/a{2,4}/ # Two, three or four /a{2,}/ # Two or more /a{,4}/ # Less than four (including zero)
By default, quantifiers are greedy, which means they take as many characters as they can while still making a match. Normally this is not noticeable:
/(?<site>.*) Stack Exchange/ =~ 'Motor Vehicle Maintenance & Repair Stack Exchange'
The named capture group site will be set to ''Motor Vehicle Maintenance & Repair' as expected. But if 'Stack Exchange' is an optional part of the string (because it could be 'Stack Overflow' instead), the naive solution will not work as expected:
/(?<site>.*)( Stack Exchange)?/
This version will still match, but the named capture will include 'Stack Exchange' since * greedily eats those characters. The solution is to add another question mark to make the * lazy:
/(?<site>.*?)( Stack Exchange)?/
Appending ? to any quantifier will make it lazy.
