-caux filename

   Specifies a pathname for the client auxiliary file.  When you give a
   filename, do not give a file extension; the idl compiler appends .c
   to the C source file and .o to the object file.  If you do not use
   the -caux argument, the idl compiler appends _caux.c to the C
   source file and _caux.o to the object file.  If the -lang cxx option
   is used, the source file will have the .cxx extension.