dosexterr()             Get DOS Extended Error Values

 #include   <dos.h>

 int              dosexterr(buffr);
 struct DOSERROR  *buffr;

    dosexterr() sets the fields of 'buffr' to the values returned by the
    MS-DOS system call 0x59.  Setting 'buffr' to the NULL pointer causes
    the function to return the value of AX, without filling in the fields
    of 'buffr'.

       Returns:     The value in the AX register, (which is also set in
                    the 'exterror' field of 'buffr').

         Notes:     dosexterr() is only valid for MS-DOS version 3.0 or
                    later.

                    The structure type DOSERROR is defined (in <dos.h>
                    as:

                    struct DOSERROR {
                            int exterror;
                            char class;
                            char action;
                            char locus;
                            };

   Portability:     MS-DOS 3.0 and later only.

   -------------------------------- Example ---------------------------------

    The following statements try to open the file "testfile.dat". If this
    fails, and the MS-DOS version is 3.0 or later, the program prints
    extended error information.

           #include <dos.h>       /* for dosexterr() and struct DOSERROR */
           #include <fcntl.h>     /* for open() and O_RDWR */
           #include <stdio.h>     /* for printf() */
           #include <stdlib.h>    /* for _osmajor */

           struct DOSERR   doser;
           int fd;

           main()
           {
               if ((fd = open("testfile.dat", O_RDWR)) == -1) /* if error */
                  if (_osmajor >= 3) {  /* if DOS 3.0 or later... */
                        dosexterr(&doser);
                        printf("error=%d, class=%d, action=%d, locus=%d\n",
                                doser.exterror, doser.class,
                                doser.action, doser.locus);
                  }
           }