grep(1) -vP '^((\s+|)(\/\/|#)|$)'
print lines matching a pattern
-v, --invert-match
       Invert the sense of matching, to select non-matching lines.  (-v is specified by POSIX.)
-P, --perl-regexp
       Interpret PATTERN as a Perl regular expression (PCRE, see below).  This is highly experimental and
       grep -P may warn of unimplemented features.
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.
source manpages: grep