#define NOCCARGC
#include stdio.h
/*
** Close previously opened fd and reopen it.
** Entry: fn  = Null-terminated CP/M file name.
**              May be prefixed with letter of drive.
**              May be just CON:, RDR:, PUN:, or LST:
**        mode =  "a"   -append
**                "r"   -read
**                "w"   -write
**                "a+"  -append update
**                "r+"  -read update
**                "w+"  -write update
** Returns the original fd on success, else NULL.
*/
freopen(fn, mode, fd) char *fn, *mode; int fd; {
  if(fclose(fd)) return (NULL);
  if(_open(fn, mode, fd)==ERR) return (NULL);
  return (fd);
  }