vim function to execute shell command and show output in vim window

gistfile1.vim

function! s:ExecuteInShell(command)
   let command = join(map(split(a:command), 'expand(v:val)'))
   let winnr = bufwinnr('^' . command . '$')
   silent! execute  winnr < 0 ? 'botright new ' . fnameescape(command) : winnr . 'wincmd w'
   setlocal buftype=nowrite bufhidden=wipe nobuflisted noswapfile nowrap number
   echo 'Execute ' . command . '...'
   silent! execute 'silent %!'. command
   silent! execute 'resize ' . line('$')
   silent! redraw
   silent! execute 'au BufUnload <buffer> execute bufwinnr(' . bufnr('#') . ') . ''wincmd w'''
   silent! execute 'nnoremap <silent> <buffer> <LocalLeader>r :call <SID>ExecuteInShell(''' . command . ''')<CR>'
   echo 'Shell command ' . command . ' executed.'
endfunction

command! -complete=shellcmd -nargs=+ Shell call s:ExecuteInShell(<q-args>)