This example creates a read-only file named "DOSFDEL.DAT", then changes its attributes to normal file, and finally uses DosForceDelete to delete the file so that it cannot be restore using UNDELETE.

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

 int main(VOID) {

 UCHAR       uchFileName[]   = "DOSFDEL.DAT";   /* File we want to delete    */
 HFILE       fhDelFile       = 0;               /* File handle from DosOpen  */
 FILESTATUS3 fsts3FileInfo   = {{0}};  /* Information associated with file   */
 ULONG       ulBufferSize    = sizeof(FILESTATUS3); /* File info buffer size */
 ULONG       ulOpenAction    = 0;                 /* Action taken by DosOpen */
 APIRET      rc              = NO_ERROR;          /* Return code             */
 FHLOCK      FHLock          = 0;                 /* File handle lock        */

                 /* Create a read-only file */

  rc = DosProtectOpen(uchFileName, &fhDelFile,
               &ulOpenAction, 10L, FILE_READONLY,
               OPEN_ACTION_CREATE_IF_NEW | OPEN_ACTION_OPEN_IF_EXISTS,
               OPEN_ACCESS_READWRITE | OPEN_SHARE_DENYNONE, 0L, &FHLock);
  if (rc != NO_ERROR) {
     printf("DosProtectOpen error: return code = %u\n", rc);
     return 1;
  }

  rc = DosProtectQueryFileInfo(fhDelFile, FIL_STANDARD,
               &fsts3FileInfo, ulBufferSize, FHLock);   /* Get standard info */
  if (rc != NO_ERROR) {
      printf("DosProtectQueryFileInfo error: return code = %u\n", rc);
      return 1;
  } else { printf("File %s created read-only.\n",uchFileName); }

    /*   Change the file attributes to be "normal"  */

    fsts3FileInfo.attrFile  = FILE_NORMAL;
    rc = DosProtectSetFileInfo(fhDelFile, FIL_STANDARD,
                        &fsts3FileInfo, ulBufferSize, FHLock);
    if (rc != NO_ERROR) {
        printf("DosProtectSetFileInfo error: return code = %u\n", rc);
        return 1;
    }

    rc = DosProtectClose(fhDelFile, FHLock);
    /* Should verify that (rc != NO_ERROR) here... */
           /* Delete the file */

    rc = DosForceDelete(uchFileName);
    if (rc != NO_ERROR) {
        printf("DosForceDelete error: return code = %u\n", rc);
        return 1;
    } else {
        printf("File %s has been deleted.\n",uchFileName);
    }  /* endif */

   return NO_ERROR;
}