How to use size of file inside Ant target

Question

I'm currently in the process of replacing my homebrewn build script by an Ant build script.

Now I need to replace various tokens by the size of a specific file. I know how to get the size in bytes via the <length> task and store in in a property, but I need the size in kilobytes and megabytes too.

How can I access the file size in other representations (KB, MB) or compute these values from within the Ant target and store them in a property?

Edit: After I discovered the <script> task, it was fairly easy to calculate the other values using some JavaScript and add a new property to the project using project.setNewProperty("foo", "bar");.

Answer 1

There is a math task at http://ant-contrib.sourceforge.net/ that may be useful

Answer 2

I found a solution that does not require any third-party library or custom tasks using the <script> task that allows for using JavaScript (or any other Apache BSF or JSR 223 supported language) from within an Ant target.

<target name="insert-filesize">
 <length file="${afile}" property="fs.length.bytes" />

 <script language="javascript">
 <![CDATA[
  var length_bytes = project.getProperty("fs.length.bytes");
  var length_kbytes = Math.round((length_bytes / 1024) * Math.pow(10,2)) / Math.pow(10,2);
  var length_mbytes = Math.round((length_kbytes / 1024) * Math.pow(10,2)) / Math.pow(10,2);
  project.setNewProperty("fs.length.kb", length_kbytes);
  project.setNewProperty("fs.length.mb", length_mbytes);
 ]]>
 </script>

 <copy todir="${target.dir}">
  <fileset dir="${source.dir}">
   <include name="**/*" />
   <exclude name="**/*.zip" />
  </fileset>
  <filterset begintoken="$$$$" endtoken="$$$$">
   <filter token="SIZEBYTES" value="${fs.length.bytes}"/>
   <filter token="SIZEKILOBYTES" value="${fs.length.kb}"/>
   <filter token="SIZEMEGABYTES" value="${fs.length.mb}"/>
  </filterset>
 </copy>
</target>