Process Synchronization with VBScript

In a few posts we discuss the possibility to use multiple VBScript processes. With the Run command you can start different processes asynchronously. But after the start, you have not really a chance to synchronize the processes. Maybe via a file interface. For the process synchronization and communication offers Windows the IPC interface (Interprocess Communication).

There are different technics to synchronize and to communicate between processes, like

• Events,
• Semaphores,
• FileMaps and
• the ClipBoard
• etc.

To use this possibilities I programmed a COM library which offers this technics. You find it here.

With COMIPC you can easily e.g. synchronize processes, look at the following example:

'-Begin-----------------------------------------------------------------

  '-Directives----------------------------------------------------------
    Option Explicit

  '-Constants-----------------------------------------------------------
    Const INFINITE = -1   

  '-Variables-----------------------------------------------------------
    Dim oIPC, hEvent, wsh, extVBS, rc

  '-Main----------------------------------------------------------------
    Set oIPC = CreateObject("COMIPC")
    If IsObject(oIPC) Then

      hEvent = oIPC.EventCreate("TestEvent", 0, 0)

      If hEvent Then

        extVBS = "Script 2.vbs"
        Set wsh = CreateObject("WScript.Shell")
        If IsObject(wsh) Then
          wsh.Run("wscript.exe " & extVBS)
          Set wsh = Nothing
        End If

        rc = oIPC.EventWait("TestEvent", INFINITE)
        rc = oIPC.EventClose(hEvent)

      End If 
      Set oIPC = Nothing
    End If

    MsgBox "End"     

'-End-------------------------------------------------------------------

We create an event, start a second script and wait until the event is set in the second script.

'-Begin-----------------------------------------------------------------

  '-Directives----------------------------------------------------------
    Option Explicit

  '-Variables-----------------------------------------------------------
    Dim oIPC, rc

  '-Main----------------------------------------------------------------
    Set oIPC = CreateObject("COMIPC")
    If IsObject(oIPC) Then

      MsgBox "Event"

      rc = oIPC.EventSet("TestEvent")
      Set oIPC = Nothing
    End If

'-End-------------------------------------------------------------------

If the event is set, in the second script, the first script will finish.

So it is e.g. possible to start different SAP GUI Scripts and to set different synchronization points. Also you can communicate between different processes via FileMap – File mapping is the association of a file’s contents with a portion of the virtual address space of a process.

Enjoy it.