Hide all (not)matching lines in Vim

Question

Is it possible to show/hide all matching lines in vi or Vim? Not highlight but just show only those lines.

For example I have a text with word the word ERROR

Answer 1

Some hackish dirty way to do this:

:w (save)
ggdG (deletes everything)
:.!grep something % (replace current line with grep output)

Answer 2

The best way to do this is->

:vimgrep /something/g % | copen

This will open the list of matches for your keyword and also will show only the matched lines in quickfix window.

Replace % with path to file if not considering the current file.