Is it possible to add a new element with attributes? I tried this but it didn't work.

xmlstarlet  -s "/CALYPSO/CACHE/MULTIPORT" -t elem -n "LISTEN PORT=\"4000\"" -v "" blah.xml

You missed 'ed'

Example:

$ echo "<x/>" | xml ed --subnode /x -t elem -n new -v val --insert /x/new -t attr -n data -v test -
<?xml version="1.0"?>
<x>
  <new data="test">val</new>
</x>

And your name of the element is not right.

--MG

Thanks for your help.  I have run into another problem.  When the document has a default namespace, the newly added node can't be referred to using the namespace.

[blah.xml]

<?xml version="1.0" encoding='ISO-8859-1'?>
<CALYPSO xmlns="http://www.oracle.com/iAS/EMComponent/webcache">
  <CACHE>
    <MULTIPORT/>
  </CACHE>
</CALYPSO>

[doesn't work]

xmlstarlet ed -N xmlns=http://www.oracle.com/iAS/EMComponent/webcache \ --subnode "/xmlns:CALYPSO/xmlns:CACHE/xmlns:MULTIPORT" -t elem -n "LISTEN" -v "" \ --insert "/xmlns:CALYPSO/xmlns:CACHE/xmlns:MULTIPORT/xmlns:LISTEN" -t attr -n PORT -v 4444 \ blah.xml

$ xml ed -N n=http://www.oracle.com/iAS/EMComponent/webcache --subnode "/n:CALYPSO/n:CACHE/n:MULTIPORT" -t elem -n "LISTEN" -v "" --insert "/n:CALYPSO/n:CA
CHE/n:MULTIPORT/LISTEN" -t attr -n PORT -v 4444 blah.xml

<?xml version="1.0" encoding="ISO-8859-1"?>
<CALYPSO xmlns="http://www.oracle.com/iAS/EMComponent/webcache">
  <CACHE>
    <MULTIPORT>
      <LISTEN PORT="4444"></LISTEN>
    </MULTIPORT>
  </CACHE>
</CALYPSO>

Previous example works and it is actually not quite right.
It should have worked like this

xmlstarlet ed -N xmlns=http://www.oracle.com/iAS/EMComponent/webcache \
--subnode "/xmlns:CALYPSO/xmlns:CACHE/xmlns:MULTIPORT" -t elem -n "xmlns:LISTEN" -v "" \
--insert "/xmlns:CALYPSO/xmlns:CACHE/xmlns:MULTIPORT/xmlns:LISTEN" -t attr -n PORT -v 4444 \
blah.xml

but it seems there is a bug in namespaces handling when adding a new node. It has to be added with its namespace.

Thanks,
--MG