How I build Markdown from within Vim

gistfile1.vim

" Written by steven for quick loadup of Markdown text into HTML
function! Mkdp()
  write
  let file   = expand("%")
  let mkd_file = file . ".html"
  let result = system("markdown " . file . " > " . mkd_file)
  let result = system("open " . mkd_file)
endfunction
augroup filetype_markdown
  autocmd!
  au BufNewFile,BufReadPost *.{md,markdown} nnoremap <leader>mm :call Mkdp()<CR>
augroup END