5

I'm trying to develop a git hook that warns me if any files that belong to a repo are unsaved in the editor. For that I need a list of open files/buffers and their state, so basically a non-interactive version of (list-buffers).

I run Emacs in server mode so I know I can do emacsclient -e '(command)', but how do I dump the list of current buffers?

6

The function buffer-list returns a list of buffers. Call buffer-modified-p to test if a buffer has been modified and buffer-file-name to test if a buffer is visiting a file.

The following snippet from the code of save-buffers-kill-emacs tests if there are any unsaved open files.

(memq t (mapcar (function
                  (lambda (buf) (and (buffer-file-name buf)
                                     (buffer-modified-p buf))))
                (buffer-list)))

Rather than enumerate all buffers, you may be better off testing only the buffers that are visiting files that are about to be committed. You can call find-buffer-visiting to get the buffer visiting a particular file, if any. Thus, given a list of file names in filenames:

(let ((unsaved 0))
  (mapc (lambda (filename)
          (let ((buffer (find-buffer-visiting filename)))
            (when filename
              (setq unsaved (1+ unsaved))
              (princ (concat "File not saved: " filename "\n")))))
        filenames)
  (when (> unsaved 0)
    (printc "There were unsaved files, aborting\n")))

In Emacs 24, it's possible to make emacsclient exit with a nonzero status, but this doesn't look easy: you have to send the die command to the appropriate client of which there can be many. Anyway emacsclient could also fail because there's no running Emacs, which is a success condition for you. So I suggest to check whether emacsclient emits output on stdout.

files=
for x; do
  files="$files \"`absolute_path "$x" | sed 's/[\\\\\\\"]/\\\\&/g'`\""
done
unsaved=$(emacsclient -e '(let ((filenames ('"$files"'))) …)' 2>/dev/null)
if [ -n "$unsaved" ]; then
  echo "$unsaved"
  exit 1
fi

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