呵呵,直接写不会,但也有其它方法,like this
exp user/pwd@sid file=d:\%Date:~4,4%%Date:~9,2%%Date:~12,2%.dmp log=d:\back.log buffer=1024000 
rename d:\%Date:~4,4%%Date:~9,2%%Date:~12,2%.dmp newfilename
del d:\????????.dmp
rename newfilename d:\%Date:~4,4%%Date:~9,2%%Date:~12,2%.dmpnewfilename越特殊越好,Good luck