unix - How to correctly use the "grep" command -

i new linux , commands. understand "grep" command.

but not understand following command, do, how type command correctly.

grep -r -e

examples use correctly welcome.

calling grep flags mean search recursively in specified directory , it's children lines match regex.

grep -r -e /p.t/ .

should find lines p , t has single character in between in current directory or of it's children.

-e pattern, --regexp=pattern use pattern pattern; useful protect patterns beginning -.

-r, -r, --recursive read files under each directory, recursively; equiv- alent -d recurse option.

KBPS