Using mimetype and file to guess content-type

[Jean Louis]

In order to guess the content-type, I am using these functions. It
appears that Perl's `mimetype' works so much better than `file', for
example it will give tell for .gpg file that it is pgp encrypted, but
`file' will tell it is application octet stream.

Overall I am replacing some `mutt' based functions with `mail' and
that works well so far. But `mutt' on the command line in batch mode
does recognize the attached file's content type while `mail' does not.

I understand that `mail' is asking for the content-type to be provided
by user, though question is if some mechanism exists in C libraries
that the content-type gets automatically recognized if not supplied on
the command line?

That would or could liberate the `mail' from external dependencies
such as `file' or `mimetype' where latter works better.

(defun rcd-mime-type (file &optional prefer-mime)
  "Returns mime type of the file"
  (if (rcd-which-list '("file" "mimetype"))
      (let ((file-command (executable-find "file"))
            (mimetype (executable-find "mimetype")))
        ;; TODO:
        ;; There is much work to do here to work on various systems for
        ;; example there may not be same output on BSD and GNU systems.
        ;; Additional problem is file quoting.
        ;; file and mimetype may give different results
        (if (and (not prefer-mime) file-command)
            (string-trim
             (call-process-to-string file-command nil nil "-b" "--mime-type" 
file))
          (if mimetype
              (string-trim
               (call-process-to-string mimetype nil nil "-b" file)))))
    (rcd-warning-message "RCD ERROR: `file' or/and `mimetype' not found in 
$PATH")))


(defun rcd-mailutils-mail-files (files)
  "Return list with \"mail\" program arguments for file attachments."
  (cond ((stringp files) (list "--content-type" (rcd-mime-type files t) "-A" 
files))
        ((listp files) (let (list)
                         (when files
                           (let ((file (pop files)))
                             (push file list)
                             (push "-A" list)
                             (push (rcd-mime-type files t) list)
                             (push "--content-type" list)))
                         list))))


Jean

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