VIM putting a line at the top (or bottom) of a tile to set attributes? doesnt work for me

I read in "Vim book OPL.pdf" that you can put a l开发者_如何学Goine at the top of a file, say for instance a .txt file and it would change how that individual file was handled by Vim. for example vim:tw=78

however it doesnt do anything for me and I am wondering if this is still the case for vim7.0 ?

It is called a "modeline" and you can get more information by typing:
:help modeline

From the description in help, I think the correct format should be vim: tw=78

It seems your example is missing white spaces.

Addition from elwoode comment :
Adding the modeline won't reformat automatically existing text. If you want to reformat you have to select an area and use gq. See :help gq

To reformat the whole file according to modeline, use:
gggqG (gg means go to first line, gqapply formating to motion, Ggo to last line)

Be sure that in .vimrc you have formatoptions+=t to take into account formatting according to textwidth. It seems that on my installation t is part of the default formatoptions.

The modeline is often disabled by default due to security reasons (the last of which are abolished in Vim 7.3 as I understand it); it is in Debian, for example. It will be in your case (see :set modeline?).

Add set modeline to your vimrc if you wish to enable modeline support.

You're trying to set a modeline.

Syntax would be:

vim:set textwidth=78:

Just an option, you can use your .vimrc if you want:

autocmd FileType .txt set textwidth=78