Filtering list of files to those recently edited

Question

Suppose I have a list of files:

(setq files '("/path/to/file1" ...))

Is there a way to reduce this list to only those files which were edited within the past, say, 10 days?

Answer 1

Is there a way to reduce this list to only those files which were edited within the past, say, 10 days?

Something like this? It assumes Emacs 26+, but to support earlier versions you can easily replace (file-attribute-modification-time ...) with (nth 5 ...), seq-filter with other ways of filtering lists, the nil argument to time-subtract with (current-time), etc.

(autoload 'seq-filter "seq")

(defun my-files-since (files days)
  "Return subset of FILES modified within the last DAYS."
  (let ((since (time-subtract nil (days-to-time days))))
    (seq-filter (lambda (file)
                  (let* ((attrs (file-attributes file))
                         (mtime (file-attribute-modification-time attrs)))
                    (time-less-p since mtime)))
                files)))

(my-files-since '("/path/to/foo" "bar" ...) 10)

References:

• (info "(elisp) File Attributes")
• (info "(elisp) Time Calculations")
• (info "(elisp) Sequence Functions")