Final answer:
Regex can be found in Splunk documentation, online forums and communities, and books and tutorials; all of these resources provide valuable information for learning and using regex.
Step-by-step explanation:
You can find regular expressions, or regex, in multiple sources. The correct answer to where you can find regex is 4) All of the above. First, the Splunk documentation is a great place to start as it will offer precise information on how regex is implemented within Splunk itself. Second, online forums and communities are beneficial resources where experienced users share their regex patterns and solutions to common problems. Third, books and tutorials dedicated to regex can provide in-depth explanations and a structured approach to learning. Each of these resources has its unique advantages, and when used together, they can significantly enhance your understanding and ability to use regex effectively.