enable NERDTree only when editing h/c/cpp files

Question

if (&filetype=='c' || &filetype=='cpp' || &filetype=='h')
  autocmd VimEnter * NERDTree
  autocmd VimEnter * wincmd p

  " class outline viewer : F8
  nmap <F8> :TagbarToggle<CR>
endif

I tried this vimrc script, but it is not working.

Answer 1

Not sure but I think VimEnter is called before &filetype is set so that if is never executed. Try:

augroup C
    autocmd!
    autocmd FileType c,cpp NERDTree | wincmd p | nmap <F8> :TagbarToggle<CR>
augroup END

Better to write an filetype plugin (see :h ftplugin). For example I have a file in ~/.config/nvim/after/ftplugin/javascript.vim with this content:

autocmd BufReadPost,BufWritePost <buffer> Accio eslint
autocmd InsertLeave,TextChanged <buffer> call semhl#highlight()
autocmd FileType javascript call semhl#highlight()
nnoremap <buffer> <C-]> :TernDef<cr>

These auto-commands and the mapping are only available for JavaScript files. I don't know how to call an ftplugin for both C and C++, but the content would be something like:

autocmd FileType c,cpp NERDTree | wincmd p
nmap <buffer> <F8> :TagbarToggle<CR>

If you use Vim the location of this file would be ~/.vim/after/ftplugin/c.vim.

Edit

According to this answer you can use symbolic links or source your c.vim ftplugin from your cpp.vim plugin (or vice versa).