;; The C function openp slightly modified would do the trick fine
(defvaralias 'executable-binary-suffixes 'exec-suffixes)
+;;;###autoload
+(defun executable-command-find-posix-p (&optional program)
+ "Check if PROGRAM handles arguments Posix-style.
+If PROGRAM is non-nil, use that instead of "find"."
+ ;; Pick file to search from location we know
+ (let* ((dir (car load-path))
+ (file (find-if
+ (lambda (x)
+ ;; Filter directories . and ..
+ (not (string-match "^\\.\\.?$" x)))
+ (directory-files dir))))
+ (with-temp-buffer
+ (call-process (or program "find")
+ nil
+ (current-buffer)
+ nil
+ dir
+ "-name"
+ file
+ "-maxdepth"
+ "1")
+ (goto-char (point-min))
+ (if (search-forward file nil t)
+ t))))
+
;;;###autoload
(defun executable-find (command)
"Search for COMMAND in `exec-path' and return the absolute file name.