Capture Groups

There are two types of regex groups:

• Capture groups define the actual text you want to search for. You can have multiple capture groups, and each one must be enclosed in parentheses.
• Non-capturing groups delimit the match but are not counted as part of the match. For example, you could search for the world "apple" surrounded by whitespace so you would not match words like applesauce or grapple. The whitespace is required for the regex expression to be a match, but the whitespace itself is not part of the search pattern. All non-capturing groups must begin with "?:".

For example, the following regex contains a capture group delimited on both sides by a non-capturing group:

(?:\W|^)(apple\d*)(?:\W|$)

The first group — (?:\W|^) — looks for any non-word character (spaces and punctuation) or nothing at the beginning of the string being searched (for example, the beginning of a line). The third group — (?:\W|$) — looks for any non-word character (spaces and punctuation) or the end of the string being searched. Both the first and third group contains the ?: operator, making them non-capturing groups. The regex in non-capturing groups is used to delimit the tag but text matching those groups is not considered part of the tag match.

The second group — (apple\d*) — is the first valid capture group, and this is the group CloudAdvisor uses to determine the matching text. This group looks for the word "apple" followed by an optional sequence of numbers. This regex would match "apple" or "apple1234", but it would not match "Apple", "applesauce", or "grapple".