print lines matching a pattern

Matcher Selection
    -E, --extended-regexp
           Interpret PATTERN as an extended regular expression (ERE, see below).  (-E 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.