DECC$FILENAME_UNIX_REPORT

   With DECC$FILENAME_UNIX_REPORT enabled, all filenames are
   reported in UNIX style unless the caller specifically selects
   OpenVMS style. This applies to getpwnam, getpwuid, argv[0],
   getname, fgetname, and tempnam.

   With DECC$FILENAME_UNIX_REPORT disabled, unless specified in the
   function call, filenames are reported in OpenVMS style.