$ grep -i "\.mkv" list2.txt list1.txt
list2.txt:Human.Planet.S01E05.720p.BluRay.x264-SHORTBREHD.mkv
list2.txt:Human.Planet.S01E02.720p.BluRay.x264-SHORTBREHD.mkv
list2.txt:Human.Planet.S01E06.720p.BluRay.x264-SHORTBREHD.mkv
list2.txt:Human.Planet.S01E03.720p.BluRay.x264-SHORTBREHD.mkv
list2.txt:Human.Planet.S01E04.720p.BluRay.x264-SHORTBREHD.mkv
list2.txt:Human.Planet.S01E01.720p.BluRay.x264-SHORTBREHD.mkv
list2.txt:Human.Planet.S01E07.720p.BluRay.x264-SHORTBREHD.mkv
