You can use the Unix redirect and append operator (>>) with w to append all or part of the buffer's contents to an existing file. For example, if you entered:
:1,10w newfile
and then:
:340,$w >>newfile
newfile would contain lines 1-10 and line 340 to the end of the buffer.
--TOR, from Learning the vi Editor (O'Reilly, 1998)
Copyright © 2003 O'Reilly & Associates. All rights reserved.