You read about many different use cases of regular expressions in Chapter 1. Let me repeat some of these use cases:
To test whether a string matches a search expression
To find some characters in a string
To replace substrings in a string matching a regex
To process and format user input
To extract information from server logs, configuration files, and text files
To validate input in web applications and in the terminal
Many of the use cases require that we find a substring of a string and extract it, reorder it, remove it, or replace it.
Regular expressions provide us with some ...
