Highlighting the 70th character of a current line in Vim

Question

I like to keep a strict 70 character margin whenever possible. To help with this, I want to configure vim so that the 70th character of the current line is highlighted. I understand that

set cursorline

can be used to highlight the current line. I, however, would like just the very end of the line (the 70th character) to be highlighted. How would I go about accomplishing this?

Edit: cursorcolumn isn't what I'm looking for. I just want a single character (the 70th one on the current line).

Edit 2: perhaps a picture will help.

Answer 1

You can use colorcolumn to set a "right margin" bar.

This did not exist before Vim 7.3, so it is wisest to only enable it if the feature is available.

if exists('&colorcolumn')
    set colorcolumn=70
endif

I prefer that this only be shown in insert mode, so I use this:

if exists('&colorcolumn')
    autocmd InsertEnter * set colorcolumn=80
    autocmd InsertLeave * set colorcolumn=""
endif

That will set the option when you switch to insert mode, and turn it off when you leave insert mode.