/usr/share/vim/vim80/ftplugin/plaintex.vim is in vim-runtime 2:8.0.1453-1ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 | " plain TeX filetype plugin
" Language: plain TeX (ft=plaintex)
" Maintainer: Benji Fisher, Ph.D. <benji@member.AMS.org>
" Version: 1.1
" Last Change: Wed 19 Apr 2006
" Only do this when not done yet for this buffer.
if exists("b:did_ftplugin")
finish
endif
" Start with initex. This will also define b:did_ftplugin and b:undo_ftplugin .
source $VIMRUNTIME/ftplugin/initex.vim
" Avoid problems if running in 'compatible' mode.
let s:save_cpo = &cpo
set cpo&vim
let b:undo_ftplugin .= "| unlet! b:match_ignorecase b:match_skip b:match_words"
" Allow "[d" to be used to find a macro definition:
let &l:define .= '\|\\new\(count\|dimen\|skip\|muskip\|box\|toks\|read\|write'
\ . '\|fam\|insert\)'
" The following lines enable the macros/matchit.vim plugin for
" extended matching with the % key.
" There is no default meaning for \(...\) etc., but many users define one.
if exists("loaded_matchit")
let b:match_ignorecase = 0
\ | let b:match_skip = 'r:\\\@<!\%(\\\\\)*%'
\ | let b:match_words = '(:),\[:],{:},\\(:\\),\\\[:\\],\\{:\\}'
endif " exists("loaded_matchit")
let &cpo = s:save_cpo
unlet s:save_cpo
" vim:sts=2:sw=2:
|