search a file for a pattern

-i     Perform  pattern  matching  in searches without regard to case; see the Base Definitions volume of
       IEEE Std 1003.1-2001, Section 9.2, Regular Expression General Requirements.

-v     Select lines not matching any of the specified patterns.  If  the  -v  option  is  not  specified,
       selected lines shall be those that match any of the specified patterns.