列举当前登陆的用户

int main(argc, argv)  int argc;  char *argv[];{  LPWKSTA_USER_INFO_0    /*     * This structure contains the name of the user on a specified workstation.     */    buffer = NULL,    tempbuffer = NULL;  NET_API_STATUS    /*     * Return code            Description     * NERR_SUCCESS           The function call successfull.     * ERROR_ACCESS_DENIED    The user does not have access to the requested information.     * ERROR_MORE_DATA        More totalentries are available. Specify a large enough     *                        buffer to receive all totalentries.     * ERROR_INVALID_LEVEL    The level parameter is invalid.     */    status;  char    /*     * Pointer to a string that specifies the DNS or NetBIOS name of the remote server on     * which the function is to execute. If this parameter is NULL, the local computer is used.     */    *server = NULL,    username[MAX_PATH],    servername[MAX_PATH * 2];  DWORD    /*     * Value    Meaning     * 0        Return the names of users currently logged on to the workstation.     *          The bufptr parameter points to an array of WKSTA_USER_INFO_0 structures.     * 1        Return the names of the current users and the domains accessed by the workstation.     *          The bufptr parameter points to an array of WKSTA_USER_INFO_1 structures.     */    level = 0,    /*     * Specifies the preferred maximum length of returned data, in bytes.     * If you specify MAX_PREFERRED_LENGTH, the function allocates the amount of memory     * required for the data. If you specify another value in this parameter,     * it can restrict the number of bytes that the function returns.     * If the buffer size is insufficient to hold all entries,     * the function returns ERROR_MORE_DATA. For more information     */    prefmaxlen = MAX_PREFERRED_LENGTH,    /*     * Pointer to a value that receives the count of elements actually enumerated.     */    entriesread = 0,    /*     * Pointer to a value that receives the total number of entries that could have been     * enumerated from the current resume position. Note that applications should consider     * this value only as a hint.     */    totalentries = 0,    /*     * Pointer to a value that contains a resume handle which is used to continue an     * existing search. The handle should be zero on the first call and left unchanged     * for subsequent calls. If this parameter is NULL, no resume handle is stored.     */    resumehandles = 0,    usercount = 0,    i, j;  if (argc > 2)  {    fprintf(stderr, "Usage: %s [\\\\ServerName]\n", argv[0]);    return 1;  }  fprintf(stdout, "\nLogged users on ");  /*   * The server is not default of local computer.   */  if (argc != 2)  {    server = NULL;    fprintf(stdout, "localhost:\n");  }  else  {    // The first parameter of the NetWkstaUserEnum function must be unicode format.    MultiByteToWideChar(      0, 0,      argv[1],      lstrlen(argv[1]),      (LPWSTR)servername,      MAX_PATH);    server = servername;    fprintf(stdout, "%s:\n", argv[1]);  }  do  {   /*    * Call the NetWkstaUserEnum function, specifying level 0.    *    * If the function succeeds, the return value is NERR_SUCCESS.    * If the function fails, the return value can be one of the following error codes.    */    status = NetWkstaUserEnum(      (LPWSTR)server,      level,      (LPBYTE*)&buffer,      prefmaxlen,      &entriesread,      &totalentries,      &resumehandles);    // If an error has occurred,    if (status != NERR_SUCCESS)      if (status != ERROR_MORE_DATA)      {        fprintf(stderr, "A system error has occurred: %d\n", status);        break;      }    // If the call succeeds,    if ((tempbuffer = buffer) != NULL)    {      for (i = 0; i < entriesread; i++)      {        if (tempbuffer == NULL)        {          /*           * Only members of the Administrators local group           *  can successfully execute NetWkstaUserEnum           *  locally and on a remote server.           */          fprintf(stderr, "An access violation has occurred\n");          break;        }        for (j = 0; ; j++)          if (!tempbuffer->wkui0_username[j])            break;        // Emptying the username.        RtlZeroMemory(username, MAX_PATH);        WideCharToMultiByte(          0, 0,          tempbuffer->wkui0_username,          j + 1,          username,          MAX_PATH,          0, 0);        // Print the user logged on to the workstation.        fprintf(stdout, " %d -- %s\n", usercount + 1, username);        tempbuffer++;        usercount++;      }      // Free the allocated memory.      NetApiBufferFree(buffer);      buffer = NULL;    }  }  /*   * Continue to call NetWkstaUserEnum while   *  there are more totalentries.   */  while (status == ERROR_MORE_DATA); // end do  fprintf(stdout, "\n\tTotal %lu users.\n", usercount);  // Check again for allocated memory.  if (buffer != NULL)    NetApiBufferFree(buffer);  return 0;}