Send all writable buffers to external command?

Question

How can I send all writable buffers to an external command? For example,

:wa ! wc -l

does not work (gives trailing characters error). (Also, wa will not work anyway because it does not write unchanged buffers).

It needs to be writable buffers because I may have buffers like help open that are not writable that I do not want to include.

BTW, bufdo does not work, both because it includes read only buffers and because it executes the commands separately and therefore hangs the interface.

Answer 1

This is not easily doable. You need to script a little bit. Something like this should do it:

func! CollectContent()
  let l=[]
  for i in range(1,bufnr('$'))
    if bufexists(i) && getbufvar(i, '&modifiable')
        let l += getbufline(i, 1, '$')
    endif
  endfor
  return l
endfu

func! GetOutput()
  let cnt=CollectContent()
  let cmd='wc -l'
  let out=system(cmd, join(cnt, "\n")."\n")
  echo out
endfu

Error management left as excercise to the reader.