Recursive grep

grep (case-insensitive, recursive) grep doesn't offer any possibility to recursively descent down the directory tree. The following command searches e.g. just thru all the files in the current directory:

grep bacteria *

To make the search case-insensitive, one can use the i flag:

grep -i bacteria *

But if you want to do a recursive search you have to use a quite complicated construction of UNIX commands to achieve this goal:

find ~/Mail -type f -exec grep 'bacteria' {} \; -print

This command searches recursively thru the Mail directory of the current user and prints all the lines that contain the word bacteria.