I am trying to compare two log files, side by side in two emacs buffers. The logfiles are similar in context, but some have extra debug inserted. This makes simple use of pgup/pgdown painful as things get out of alignment between the two buffers.

What I'd like to do is scroll by context, and although I don't expect emacs to know the context, I'd like to find the relevant line in the left and right buffers and then scroll both buffers such that that line appears at the top of the window in both buffers.

Is this achievable?

  • 1
    I don't know a packge which does that. But I'd love to have one. You can easily match-up the lines of the two files by running "diff" on them, so it's only a matter of writing the package which processes diff's output and then uses it in a scroll-hook.
    – Stefan
    Commented Oct 30, 2015 at 13:12
  • 2
    Why don't you use Ediff for this? M-x ediff-buffers.
    – Drew
    Commented Oct 30, 2015 at 18:07

1 Answer 1


You can :

  • go to the right relevant line (with isearch C-s 'pattern') and do C-l (recenter-top-bottom) 2 times.

  • go to the left relevant line (same iseach C-s C-s) and do C-l 2 times.

the two buffers will be align.

The cursor will be at top position if scroll-margin == 0 (default value). if not, add (setq scroll-margin 0) to your .emacs


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