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Provides more information about return values that have been received from other control-program functions.


DosErrClass(code, pClass, pAction, pLocus)


code (ULONG) - input 
A nonzero return value returned by a control-program function.
A nonzero return value indicates that an error has occurred.
pClass (PULONG) - output
A pointer to the ULONG in which the classification for the error is returned.
The following values are possible:
1 ERRCLASS_OUTRES Out of resources
2 ERRCLASS_TEMPSIT Temporary situation
3 ERRCLASS_AUTH Authorization failed
4 ERRCLASS_INTRN Internal error
5 ERRCLASS_HRDFAIL Device hardware failure
6 ERRCLASS_SYSFAIL System failure
7 ERRCLASS_APPERR Probable application error
8 ERRCLASS_NOTFND Item not located
9 ERRCLASS_BADFMT Bad format for function or data
10 ERRCLASS_LOCKED Resource or data locked
11 ERRCLASS_MEDIA Incorrect media, cyclic redundancy check (CRC) error
12 ERRCLASS_ALREADY Action already taken or done, or resource already exists
13 ERRCLASS_UNK Unclassified
14 ERRCLASS_CANT Cannot perform requested action
pAction (PULONG) - output 
A pointer to the ULONG in which the recommended corrective action for the error is returned.
The following values are possible:
1 ERRACT_RETRY Retry immediately
2 ERRACT_DLYRET Delay and retry
3 ERRACT_USER Bad user input - get new values
4 ERRACT_ABORT Terminate in an orderly manner
5 ERRACT_PANIC Terminate immediately
6 ERRACT_IGNORE Ignore error
7 ERRACT_INTRET Retry after user intervention
pLocus (PULONG) - output 
A pointer to the ULONG in which the error origination is returned.
The following values are possible:
1 ERRLOC_UNK Unknown
2 ERRLOC_DISK Random-access device such as a disk
3 ERRLOC_NET Network
4 ERRLOC_SERDEV Serial device

Return Code

ulrc (APIRET) - returns
DosErrClass returns one of the following value:
  • 0 NO_ERROR


DosErrClass receives a non-zero return value from another control-program function as input. It then classifies the return value, tells where in the system the error occurred, and recommends a corrective action.

When called by a family-mode application, DosErrClass can return a valid error classification only for errors that have actually occurred. Also, the classifications of a given return value might not be the same for family-mode and OS/2-mode applications.

Example Code

This example shows how DosError and DosErrClass handle errors. Run this program without a diskette in drive A: so that the DosOpen call fails with a "device not ready" condition, or run it with a disk there for a "file not found" condition.

 #define INCL_DOSFILEMGR   /* File Manager values */
 #define INCL_DOSERRORS    /* DOS error values    */
 #define INCL_DOSMISC      /* DOS miscellaneous   */
 #include <os2.h>
 #include <stdio.h>

 int main(VOID) {
 UCHAR        uchFileName[80] = "A:\\NONEXIST.ZQX"; /* File to fail on      */
 HFILE        hfConfig      = 0;             /* Handle for Config file      */
 ULONG        ulOpenAction  = 0,             /* Action taken by DosOpen     */
              ulErrorClass  = 0,             /* Type of error encountered   */
              ulErrorAction = 0,             /* Action warranted by error   */
              ulErrorLoc    = 0;             /* Where error occurred        */
 APIRET       rc            = NO_ERROR,      /* Return code                 */
              DosOpenRc     = NO_ERROR;      /* Return code from DosOpen    */

  rc = DosError(FERR_DISABLEHARDERR); /* Suppress error window.  If this is
                                         omitted, OS/2 will put up an error
                                         window asking the user to intervene */
  if (rc != NO_ERROR) {
     printf("DosError error: return code = %u\n", rc);
     return 1;
  DosOpenRc = DosOpen(uchFileName,          /* File to open (path and name) */
               &hfConfig,                   /* File handle returned         */
               &ulOpenAction,               /* Action taken by DosOpen      */
               0L,0L,        /* Primary allocation and attributes (ignored) */
               OPEN_ACTION_FAIL_IF_NEW |
               OPEN_ACTION_OPEN_IF_EXISTS,  /* Open an existing file only   */
               OPEN_SHARE_DENYNONE   |
               OPEN_ACCESS_READWRITE,       /* Read and write access        */
               0L);                         /* Extended attributes(ignored) */

    if (DosOpenRc == NO_ERROR) {
        printf("DosOpen successful... but it should have failed.\n");
        return 1;
    } else {
      rc = DosErrClass(DosOpenRc,           /* Return code from failing API */
                       &ulErrorClass,       /* Class of error               */
                       &ulErrorAction,      /* Action to take for error     */
                       &ulErrorLoc);        /* Where did the error occur?   */

      if (rc != NO_ERROR) {
          printf("DosErrClass error: return code = %u\n", rc);
          return 1;
      } else {
          printf("rc= %u  ErrorClass= %u  ErrorLoc= %u\n",
                  DosOpenRc, ulErrorClass, ulErrorLoc);

          printf("ErrorAction= %u means: ", ulErrorAction);
          switch (ulErrorAction) {
           case(ERRACT_RETRY):  printf("Retry immediately");    break;
           case(ERRACT_DLYRET): printf("Retry after a delay");  break;
           case(ERRACT_USER):   printf("Incorrect user input"); break;
           case(ERRACT_ABORT):  printf("Terminate in an orderly fashion");
           case(ERRACT_PANIC):  printf("Terminate NOW");        break;
           case(ERRACT_IGNORE): printf("Ignore this error");    break;
           case(ERRACT_INTRET): printf("Retry after user intervenes");
           default:             printf("Unknown error action"); break;
          } /* switch */
   }  /* DosOpen failure */

  rc = DosError(FERR_ENABLEHARDERR);        /* Re-enable error window */
  if (rc != NO_ERROR) {
     printf("DosError error: return code = %u\n", rc);
     return 1;

  return NO_ERROR;

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