I have very large files (more than 10Gb). I need only some lines from the top of the file. Is it possible (in vim) to delete the rest of the file (from current line to the end of file)?
dG will delete from the current line to the end of file
dCtrl+End will delete from the cursor to the end of the file
But if this file is as large as you say, you may be better off reading the first few lines with head
rather than editing and saving the file.
head hugefile > firstlines
(If you are on Windows you can use the Win32 port of head
)