Tuesday, 25 January 2011

Several days ago I faced with a simple task - I had to execute program (automated QTP test in my case) on several remote computers.
My goal was simple - if I can execute scripts on my computer, then why don't we execute them on remote computers?


I think, this task is very interesting and practical, isn't it? :)

There was one condition. I tried to use "native" Windows solutions, which do not require additional installed software or libraries. I didn't want to use external soft, files, etc.

As a result, I found two solutions. Both of them use WMI:

  1. Win32_Process Class
  2. Win32_ScheduledJob Class
I will describe both of them.
Running ahead, I will say that I decided in favour of second solution (Win32_ScheduledJob class).


Let's explore these solutions, and compare them.
For clarity, I will show how to execute simple application (notepad.exe) on remote computer.

  1. Execute program on remote computer with Win32_Process сlass
    To create and start new process, I used Create method of the Win32_Process class.
    VBScript code is simple enough:

    1. strComputer = "."
    2. strCommand = "notepad.exe"

    3. Set objWMIService = GetObject("winmgmts:" & "{impersonationLevel=impersonate}!\\" & strComputer &"\root\cimv2")
    4. Set objProcess objWMIService.Get("Win32_Process")

    5. errReturn = objProcess.Create(strCommandnullnullintProcessID)

    6. If errReturn 0 Then
    7. Wscript.Echo "notepad.exe was started with a process ID: " & intProcessID
    8. Else
    9. Wscript.Echo "notepad.exe could not be started due to error: " & errReturn
    10. End If

    String strComputer = "." means "local computer".
    So, the result of notepad starting on my local computer was:
    And notepad started on my computer! Great!

    Then I tried execute my script on remote computer (I set strComputer = "servername"). The result was:
    Script said, that the process was created.
    Indeed, process was created. It was shown in Task Manager on remote computer:
    But I didn't see it on a desktop of remote computer!
    Further investigations shown, that:
    For security reasons the Win32_Process.Create method cannot be used to start an interactive process remotely.

    Win32_Process class is very useful to create and execute batch tasks on remote computer. But it can be applicable for interactive processes.

    That's why I preferred the second way. I mean Win32_ScheduledJob сlass.

  2. Execute program on remote computer with Win32_ScheduledJob сlass
    By analogy, to create and start new process, I used Create method of the Win32_ScheduledJob class.
    VBScript code is :

    1. strComputer = "."
    2. strCommand = "notepad.exe"

    3. Const INTERVAL "n"
    4. Const MINUTES = 1

    5. Set objWMIService = GetObject("winmgmts:\\" & strComputer & "\root\cimv2")
    6. Set objScheduledJob objWMIService.Get("Win32_ScheduledJob")
    7. Set objSWbemDateTime = CreateObject("WbemScripting.SWbemDateTime")

    8. objSWbemDateTime.SetVarDate(DateAdd(INTERVAL, MINUTES, Now()))
    9. errReturn objScheduledJob.Create(strCommand, objSWbemDateTime.ValueFalse, 0, 0, True, intJobID)

    10. If errReturn = 0 Then
    11. Wscript.Echo "notepad.exe was started with a process ID: " & intJobID
    12. Else
    13. Wscript.Echo "notepad.exe could not be started due to error: " & errReturn
    14. End If

    Create method of Win32_ScheduledJob сlass creates new scheduled job on computer. (Hm... Have I said a tautology? :) ) In script I specified the time when scheduled job should be executed - in one minute from now. For that i used standard VBScript function - DateAdd.

    Hint: Some time ago I wrote an article abount time/date functions in VBScript. Read it.

    The result of execution was excellent! It created 
    scheduled jobs both on local and remote computer.
    This is result for remote computer is:

    In one minute, the notepad was started and shown on desktop of remote computer!
    I was happy :))


I hope, these two methods of remote application execution will be very helpful for you. Computer should calculate, human should think :)

So, I shown how to force your computers to work.
Do you have any ideas on how to force a human to think? :)

Summary:
If you have to run batch tasks, I think first method (Win32_Process Class) is simpler.
If you have to run interactive programs, use Win32_ScheduledJob Class.

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