- Grouped expressions are automatically captured by default.
- We can also prevent automatic capturing of group expressions.
- Useful for groups which are not used for backreferences.
- Frees up storage for other captures.
- If we have an expression that has a lot of groups, you could potentially end up with more than 9 backreferences.
- If supress capturing the ones we don’t need, we can simplify it.
- May improve the speed of large or complex searches.
- Supported by most regex engines, but not Unix tools.
- Non-capturing was added with PERL Compatible regex.
- To disable capturing for a group, we can perform:
?: –> Disable capturing for this group.
- The
? acts as a modifier for the group.
- The character after the
? indicates the type of modification.
- The
: tells the regex engine not to capture the group.
- An example is “I like pizza.”
- This can be found with
/I (love|like) (.+)\./ captures “like” and “pizza”.
- The first group is using alternation.
- If we do
/I (?:love|like) (.+)\./ captures “pizza”.
- It has become a non-capturing group.
- Another example is:
I like pizza.
I love coffe.
/I (like|love) (.+)\./ matches both of the above./I (?:like|love) (.+)\./makes it a non-capturing group.