search a file for a pattern

-n     Precede  each  output  line by its relative line number in the file, each file starting at line 1.
       The line number counter shall be reset for each file processed.

-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.