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Running WinBatch.exe from NT AT Scheduler

Keywords: NT AT Scheduler 

The AT command schedules commands and programs to run on a computer at a specified time and date. There are several things to keep in mind when using the AT command to launch a script.

The "AT" command, that allows scheduled program-run. Be careful, it uses a system account (not administrator !!!)

Winbatch scripts running under the AT command have several problems.

  1. The AT command problem is that WinBatch is running then as a service and with a DIFFERENT userid (some low-level default) unless you add special command line options to run it as someone else. So, for example, if you're having problems creating a directory via the NT AT command, that means that apparently the default user does not have permissions to create directories.

  2. Getting userid during netlogon problems: Sometimes you can check environment variables with the Environment function, but I think it does not work since you are not completely logged in yet. Although the environment variables %USERNAME% and %USERDOMAIN% variables are present as soon as the dosbox opens for a logon script.

  3. They are run without any reasonable default environment variables, temp directories, security clearances, etc., etc., so you cannot make any assumptions about paths and stuff.

  4. They are run sort of as a "guest" user where the process running has no network privileges higher than guest. It can't really log into network servers etc etc unless its uses the guest account or something like that. So it is real difficult to access stuff on network servers...

By default, the AT scheduler runs under the security context of the NT System account which doesn't have network access. There are two ways to get around your problem.

  1. Using the Control Panel Services applet, change the service account that the scheduler uses to an account that has access to the UNC you are trying to access. Make sure you enter the right password.

  2. Define the UNC on the target system as a "Null Session Share" and then reboot the target system. When it comes up again, it will accept connection requests to that share point from the System account on other machines. I don't recall the exact path to the registry key but you can use regedit to search for "nullsessionshares". When adding your share to the MULTISZ field be carefull not to delete what is already there.
The NT AT command can run when no-one is logged on within certain contraints:
  1. Hard code everything.
  2. No network connections allowed.
  3. You cannot send keystrokes to anything UNLESS the AT command is set to be interactive AND there is a logged in user AND the workstation is not locked ... only then *maybe* you can send keystrokes..
Note that you can also make a primitive scheduler with the TimeWait function.

Getting the NT AT command to work with WinBatch may be tricky. The command requires that the user who is logged into the NT system has the appropriate permissions to be able to run the scheduled job. When run via the AT command, WinBatch runs more or less as a service and cannot send keystrokes to anything (unless you adhere to the restrictions above). You might look into the WinBatch TimeWait function to avoid the AT command altogether.

HINTS:

  1. Use the /interactive parameter, which allows the job to interact with the desktop of the user who is logged on at the time the job runs. Below is an example of how to use the /interactive parameter in the command line:
    
          at \\server 23:59 /interactive "C:\MYDIR\MYWINBATCH.EXE"   
           
    
  2. Make sure you specify only the server name (not the server name plus sharename).

  3. The quotes around the path to the app you want to run works only in NT3.5X. In NT 4.0 and above, you have to remove the quotes otherwise the command is not executed. There's a new registry value coming with 6a (or maybe 2000) to toggle this behaviour - see MS Knowledge Base.

    When the command in quotes requires a path as an argument, use the absolute path (the entire pathname beginning with the drive letter).

  4. If your compiled WinBatch EXE is on a remote computer, specify the server and sharename UNC, rather than a remote drive letter. You can use quotation marks around the command, whether you are using "at" in the command line or in a batch file. If the command includes switches used by both the command and "at", you *must* enclose the WinBatch command in quotation marks. So, since we're using the "/interactive" parameter, then you must enclose the WinBatch command script in quotes.

  5. If you are launching an uncompiled .WBT, you must precede the .WBT filename with the path and filename of the WINBATCH.EXE interpreter program.

Connecting to Network Drives

When the AT command is used across network drives, the scheduler does not recognize your normal login mappings. So, even though you may be mapped to W:, the AT command will not recognize this mapping. You must use UNC names as suggested below. "UNC" refers to the "Universal Naming Convention" path, which is the standard way to access a networked drive without having to map it to a drive letter. You also have the option to re-map the drive with the NetAddDrive command, as described in the Win32 Network Extender Help file in your WinBatch directory.

From the NT documentation regarding the AT command:


Scheduled jobs that access the network should not use redirected drives made by the user. The Schedule service may not be able to access these drives and they may not be present if a different user is logged on at the time the scheduled job runs. Instead, scheduled jobs should use UNC paths.


For example, use the next command line:

 
        at \\server\share 23:59 /interactive "\\server\sharename\MYDIR\MYWINBATCH.EXE"
**not:**
        
        at x: 23:59 /interactive "X:\MYDIR\MYWINBATCH.EXE"

Additional Tech Notes:

IF the AT command is set to be interactive AND there is a logged in user AND the workstation is not locked then *maybe* you can send keystrokes.

If you're using the NT AT command with the RAS connection, you might be able to bypass this way of doing things altogether by using our WinSock extender. Take a look at the WinSock DUNConnect function to dial for you, along with the TimeWait (or you could TimeDelay(3600) to wait an hour) as alternatives to the AT and RAS phone stuff.

The NT AT scheduler runs tasks in the background. If you want to run them in the foreground, a Winbatch user reported that a product called LaunchPad in conjunction with Winbatch has worked well for them on NT4.

Tip on MSIE5 and the AT Scheduler:

FYI for all you winbatch users that launch your programs from the AT scheduler.

If you install MSIE 5 it'll replace your scheduler with the TASK SCHEDULER. If you look in START/SETTINGS/CONTROL PANEL/SERVICES you'll notice the SCHEDULER is now the TASK SCHEDULER.

You'll also notice you can no longer specify a username/password to the account, through this interface.

Solution: click on MY COMPUTER, double-click on SCHEDULED TASKS. Then you can reset all your AT programs with the correct params.


Article ID:   W13655
Filename:   The NT AT command .txt