I am trying to find (in Vim script) if the 2 files open using vimdiff are same or different? Is there a way to do that? (a variable like &diff perhaps?)

  • 1
    If the files are identical, there is one closed fold displayed on each side. Perhaps you could check for that.
    – Ralf
    Mar 29, 2019 at 13:17

2 Answers 2


The easiest option is not to make vim do any work at all: diff -q reports if files are different, and diff -s if they are the same. According to this answer if you don’t need output, cmp -s works.

So in vimscript you might do

let l:files = [ get_file_names() ] " left as an exercise
call system('cmp -s ' . join(l:files, ' '))
" do something with v:shell_error
  • Thanks for the reply. I am looking for any sort of native solution. Don't want to depend on external programs for better portability. If nothing comes up, will use this :)
    – Ankit Jain
    Mar 29, 2019 at 13:04
  • 1
    @AnkitJain, I think you should depend on external dependencies in this case, because vimdiff is supposed to be used for resolving merge conflicts and such, not calculation stuff. I skimmed through the help docs for vimdiff, and found nothing related to what you want. As I said, it is supposed to be interactive. But if you have constraints to fulfill, then you should be able to build up a vimscript function that ultimately checks itself if contents of two files are same or not. But I doubt you can do it with vimdiff itself.
    – 3N4N
    Mar 29, 2019 at 13:46
  • @klaus you may be able to use the fact that vimdiff folds sections of the file that are the same, but as I learned creating auto-origami this kind of fold detection is hard
    – D. Ben Knoble
    Mar 29, 2019 at 13:50
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    @D.BenKnoble, one answer using that approach is provided.
    – 3N4N
    Mar 29, 2019 at 14:04
  • 1
    @klaus I guess I will accept this answer since there is nothing that can be done by Vim itself.
    – Ankit Jain
    Mar 29, 2019 at 15:17

Okay, this is a very hacky approach. You really should check the result of diff using e.g. a custom diffexpr. But you asked for it, so here we go:

let a=win_getid()|exe "windo let g:diff=(get(g:, 'diff', 1) && foldclosed(1) && foldclosedend(1)==line('$'))"|if g:diff |echomsg 'no differences found' |else |echomsg 'there are some differences!' |endif|call win_gotoid(a)

(one line).

This assumes, that all windows are in diff mode and basically checks, whether each window contains only a single folded line.

  • As you said this is a hacky. Let me check it out nonetheless and see if this can work. Thank you.
    – Ankit Jain
    Mar 29, 2019 at 15:19
  • 1
    Well, you asked for it... Mar 29, 2019 at 17:00

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