get attribute node value

Hi:
I have the following snippet
<plus>
    <addr name ="abc" setup="/jpi/j2re.exe"/>
    <addr name ="def"  setup="/jpi/jre.exe"/>
</plus>

I need to modify the values of the setup attributes to
 setup="http://....../jpi/j2re.exe"
 setup="http://....../jpi/jre.exe"

How should I get the value of the attribute node setup for both the
addr elements?
Thereafter I will modify it  by concatenating the new string to the value.

Thanks.