getting information out of the source file and using it in apply tasks

[Graydon Saunders]

Hi --

I'm using ant 1.9.2  via a Fedora rawhide package on Linux.

I have bunch of SGML files (in complex, arbitrary directory structures
which I must preserve) that have different SGML DTDs; these need to be
normalized to XML.

One of the pieces of information required by the program that does the
normalization is the name of the SGML DTD.

That's in the SGML -- and thus effectively text, it can't be treated as raw
XML -- source file as a processing instruction, <?dtd name="oneOfMany"> --
and I'm not seeing how I should get that information out of there and make
it available to the apply task.

As a general structure

<target depends="prepSGML"
    description="normalize SGML input to XML (but not the target XML!)"
name="normalize">
    <mkdir dir="${NORMALIZED}"/>
    <antcall target="copy.only.dir">
      <param name="dest.dir" value="SX"/>
      <param name="source.dir" value="SPrep"/>
    </antcall>
    <mapper from="*" id="normOut" to="SX/*" type="glob"/>
    <apply executable="osx" failonerror="true" logerror="true">
      <env file="${srcfile}" />
      <fileset casesensitive="no" dir="${SPREP}" id="prepSGML">
        <include name="**/*.dat"/>
      </fileset>
      <mapper refid="normOut"/>
      <arg value="--xml-output-option=comment"/>
      <arg value="--catalog=${ENTITIES}/catalog"/>
      <arg value="${SGML_DTD}/prep.dtd"/>
      <srcfile/>
      <redirector>
        <outputmapper refid="normOut"/>
      </redirector>
    </apply>
  </target>

works.

The problem is
 <arg value="${SGML_DTD}/prep.dtd"/>

where I've hard-coded the dtd name.  That obviously won't work in the
general case, even if it convinces me the target works by correctly
normalizing a single sample file.  (I've used ant before, but it's been
awhile.)

I can't shake the sense that this ought to be obvious if I were only
looking at the problem in a suitably ant-like way, but I'm not having much
luck; I've been over the apply documentation and various other things
repeatedly, trying to figure out how to set a property based on individual
files in a fileset, and having no luck.   Which makes me think that's
probably the wrong approach.

Anyone care to suggest how to approach this?  I'd like to stick to core ant
if at all possible.

Thanks!
Graydon