How to delete lines except lines which containing wanted word?

1. Go to Search menu > Find... > Select "Mark" Tab. Enter a Text in Find what search box or Activate regular expressions. Search for ^<Path> (^ is for line start). Don't forget to check "Bookmark lines" and Press "Mark All"
   ==> All Rows you want to keep got a Bookmark
2. Go to Menu "Search - Bookmark - Inverse Bookmark"
   ==> All Line you want to delete are bookmarked.
3. Go to Menu "Search - Bookmark - Remove Bookmarked lines"
   ==> All Bookmarked lines are deleted.