asp 截取文件扩展名

我有一个文件名  aaa.bbb.rar或者a.b.c.d.html或者aa.b.dd.shtml
我怎样截取文件的后缀名呀。。。

---

<%
aa="aaa.bbb.rar"
bb=split(aa,".")
response.write bb(ubound(bb))
%>

---

修改一下楼上的代码。
VBScript code:
<%
aa="aaa.bbb.rar"
bb=split(aa,".")
if ubound(bb)=0 then
response.write ""
else
response.write trim(bb(ubound(bb)))
end if
%>

---

s = "F:\aaa\xxx.aaa.txt"
Response.Write("文件名: " & Mid(s, InStrRev(s, "\") + 1, Len(s) - InStrRev(s, "\")))
Response.Write("文件后缀: " & Mid(s, InStrRev(s, ".") + 1, Len(s) - InStrRev(s, ".")))

---

http://www.bhcode.net/article/20080721/1820.html

---

path="aaa.bbb.rar"
kzname=split(path,".")(ubound(split(path,".")))

---

VBScript code:
path="aaa.bbb.rar"
kzname=split(path,".")(ubound(split(path,".")))