How to automatically update tag file in vim?

Question

I use vim C++ tag file for navigation using Ctrl-]. The problem is whenever some file gets modified, the links are no longer valid and I have to re-run ctags and update the tag

Answer 1

http://vim.wikia.com/wiki/Autocmd_to_update_ctags_file

function! DelTagOfFile(file)
  let fullpath = a:file
  let cwd = getcwd()
  let tagfilename = cwd . "/tags"
  let f = substitute(fullpath, cwd . "/", "", "")
  let f = escape(f, './')
  let cmd = 'sed -i "/' . f . '/d" "' . tagfilename . '"'
  let resp = system(cmd)
endfunction

function! UpdateTags()
  let f = expand("%:p")
  let cwd = getcwd()
  let tagfilename = cwd . "/tags"
  let cmd = 'ctags -a -f ' . tagfilename . ' --c++-kinds=+p --fields=+iaS --extra=+q ' . '"' . f . '"'
  call DelTagOfFile(f)
  let resp = system(cmd)
endfunction
autocmd BufWritePost *.cpp,*.h,*.c call UpdateTags()