[Xml-coreutils-discuss] Where to start?

[Douglas H. <do...@do...>]

I need some help getting my thinking in the xml-coreutils world.

I have some prepared data in the format:
<response>
  <listing>
    <foo>foo</foo>
    <bar>bar</bar>
    <floor_plan>http://example.com/123456</floor_plan>
    <listing_id>1</listing_id>
  </listing>
  <listing>
    <listing_id>2</listing_id>
    <foo>foo</foo>
    <bar>bar</bar>
  </listing>
</response>

Each /response/listing element has a //listing_id and some, but not all
listings have a floor_plan element.

Goal:
I would like to extract only listings with floor plans, and only the
selected elements I am interested in, into a new document as:
<listings>
 <listing>
   <listing_id>1</listing_id>
   <floor_plan>http://example.com/123456</floor_plan>
 </listing>
<listings>

I have tried commands such as:
# Create the target file
xml-echo -e "[listings@updated=20150210]" >listings.xml
# Copy selected elements into target
xml-cp page1.xml :/response/listing/listing_id[/response/listing/floor_plan
!= null]  listings.xml :/listings/

I have read all the man pages and experimented with many different of the
xml-* commands. Very seldom do they work as I am hoping.

The workflow I would expect, based on the coreutils workflows I normally
use, would be:
cat source.xml | while read element; do
   if echo $element | grep -q floor_plan ; then
     echo $element >> target.xml
   fi
done

It would be nice if I could use a complement of the above technologies for
processing the XML.  The below are imaginary pseudo-commands:

xml-cat source.xml :/response/listing | while xml-read listing; do
 # $listing is now an xml fragment of one listing element's full content
   if echo $listing | xml-grep -q ://floor_plan; then
     cat $element | xml-egrep
"://listing|://listing/listing_id|://listing/floor_plan" | xml-insert
target.xml :/listings/
   fi
done

Perhaps by following my pseudo-logic, you can explain how I can carry out
these operations with xml-coreutils.

I have attached one of my source files.

Regards,
Doug
-- 
Douglas Held
do...@do...
+447775733093