Search strings

grep -r <directory> -e [expression] -> helps us to find character strings within all the files of the path that we give it, with regular expressions
-r                                  -> make it recursive
-n                                  -> line number where the word is found in the file
-e                                  -> regular expression
-i                                  -> it isn't case sensitive
-v                                  -> shows only the results that do not meet the pattern