/sys$common/syshlp/helplib.hlb CC, Run-time functions, freopen  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  Substitutes the file, named by a file specification, for the open
  file addressed by a file pointer.  The latter file is closed.

  Syntax:

   #include <stdio.h>

   FILE *freopen(const char *file_spec, const char *access_mode,
          FILE *file_pointer,...);

  Where the ...  represents optional file attribute arguments.  The
  file attribute arguments are the same as those used in the creat
  function.