<exec> kicking my butt with something very simple

All,
I've tried all I can figure out to try on a simple unix command in redhat.  I can run the command line and it works fine, but ant can't run it to save its life:
<exec executable="sort" dir=".">
  <arg value="-u"/>
  <arg value="existingFile"/>
  <arg value=">"/>
  <arg value="newFile"/>
</exec>
I've tried putting all the args together, putting some of the args together...  If I run it like this, I get "sort: stat failed: >: No such file or directory.  If I put the "existingFile > newFile" in the same arg, I get "sort: stat failed existingFile > newFile: No such file or directory.  If I make the executable "bash" and use "sort" as the first argument, I get:  [exec] /bin/sort: /bin/sort: cannot execute binary file.  If I run it as bash and put all the arguments into a single arg value, I get: [exec] bash: sort -u existingFile > newFile: No such file or directory.

This has got to be simple, please help!

Thanks,
Erc