(cond ((numberp fd)
(case direction
((:input :output :io)
+ ;; For O_APPEND opened files, lseek returns 0 until first write.
+ ;; So we jump ahead here.
+ (when (eq if-exists :append)
+ (sb!unix:unix-lseek fd 0 sb!unix:l_xtnd))
(make-fd-stream fd
:input input
:output output