What is the function of 'grep -i' command?

The command 'grep -i' is used to perform a case-insensitive search through the input text. This means that when using this option, the 'grep' command will return lines that match the specified pattern regardless of the case of the letters. For example, if you were searching for the term "linux" with the '-i' flag, it would match occurrences of "Linux", "LINUX", and any other case variations as well.

This capability is particularly useful when the casing of the text being searched is not consistent, enabling users to retrieve all relevant results without needing to specify every possible case combination. The other options either imply a function that does not relate to the '-i' flag or do not accurately capture the primary purpose of this command.