= KEY CONCEPTS =
A regular expression … is a sequence of characters that define a search pattern. Usually such patterns are used by string searching algorithms for "find" or "find and replace" operations on strings, or for input validation.
Reference: https://en.wikipedia.org/wiki/Regular_expression
===Regular Expressions vs. Filename Expansion===
xIn a previous lesson, you learned that �filename expansion symbols allow �the Linux shell to expand filenames as �arguments (referred to as “globbing”) for file management commands.�This is very useful for managing multiple files sharing similar characteristics such as the same file extension. Used for Linux commands such as�ls, rm, mv, cp, cat, less and more. Regular expressions are used to search, edit and manipulate text. This can represent text contained in files or text as a result of issuing Linux commands using a pipeline.�� A regular expression is a combination of two types of characters: literals and special characters. �In combination, these characters define a logical pattern. Strings of text can be compared to this pattern to see if they fit the pattern defined by the expression.�� Reference: https://www.whoishostingthis.com/resources/regex/