print lines matching a pattern

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

-n, --line-number
       Prefix  each  line of output with the 1-based line number within its input file.  (-n is specified
       by POSIX.)

-w, --word-regexp
       Select  only  those lines containing matches that form whole words.  The test is that the matching
       substring must either be at the beginning of the line,  or  preceded  by  a  non-word  constituent
       character.   Similarly,  it  must  be  either  at  the  end  of the line or followed by a non-word
       constituent character.  Word-constituent characters are letters, digits, and the underscore.

-i, --ignore-case
       Ignore case distinctions in both the PATTERN and the input files.  (-i 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.

Matching Control
    -e PATTERN, --regexp=PATTERN
           Use PATTERN as the pattern.  This can be used to specify multiple search patterns, or to protect a
           pattern beginning with a hyphen (-).  (-e is specified by POSIX.)