print lines matching a pattern

-R, -r, --recursive
       Read all files under each directory, recursively; this is equivalent to the -d recurse option.

-H, --with-filename
       Print  the  file  name  for  each  match.  This is the default when there is more than one file to
       search.

-l, --files-with-matches
       Suppress normal output; instead print the name of each input file from which output would normally
       have been printed.  The scanning will stop on the first match.  (-l is specified by POSIX.)

grep searches the named input FILEs (or standard input if no files are named, or if a single hyphen-minus
(-) is given as file name) for lines containing a match to the given PATTERN.  By  default,  grep  prints
the matching lines.