The Windows Scripting Host - dFPUG-Portal

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Issue Date: FoxTalk January 1999
The Windows Scripting Host
John V. Petersen
Remember batch files? They were easy to program and very
productive in that many tasks could be automated. That's what
Windows has been missing -- the ability to easily create and use
batch files. This gap has been filled by the Windows Scripting Host,
an engine that allows script code to be run by the OS. Not only is the
Windows Scripting Host a powerful engine for running script code, it
also (surprise!) sports a powerful object model as well. This column
will introduce you to the basics of how the scripting host works and
how you can incorporate its features into your VFP applications.
The Windows Scripting Host (WSH) is a language-independent scripting engine. Scripting languages such as VBScript and
JScript can be used to drive many processes. The same language you use to create client-side scripts in Internet Explorer (IE)
or server-side scripts in Internet Information Server (IIS) can now be hosted by the Windows operating system itself.
Prior to the release of the WSH, the only scripting language that existed for Windows was MS-DOS batch files. Although
powerful, batch files lack the control over the Windows operating system that's really desired. The WSH provides this
capability.
What you need to get started
Before I go much further, I should mention that all of the files required to work with the WSH can be downloaded from the
Microsoft Web site at http://msdn.microsoft.com/scripting/. In addition to the core scripting engine, a series of white papers,
code samples, and technical articles can be downloaded as well.
Once you've downloaded the scripting files and run the installer program, you're off to the races!
Scripting files
Unlike scripting in Active Server Pages, where the language can be specified with tags embedded in the file itself, the same
isn't true for script files used by the WSH. Rather, the WSH relies on the file extension to determine which language to use. If
the script file ends in VBS, VBScript is used. If the script file ends in JS, JScript is used.
The following simple "hello world" example points out the differences between VBScript and JScript:
VBSscript:
'hello world.vbs
Dim WSHShell
Set WSHShell = WScript.CreateObject("WScript.Shell")
WSHShell.Popup "Hello World"
JScript:
// hello world.js
var WSHShell = WScript.CreateObject("WScript.Shell");
WSHShell.Popup("Hello World")
The following is a more complex example that uses scripting to open and control Microsoft Excel:
'This VBScript File opens Excel and creates a workbook
Dim objXL,oWorkbook
Set objXL = WScript.CreateObject("Excel.Application")
objXL.Visible = TRUE
Set oWorkbook = objXL.WorkBooks.Add
With objXL
.Cells(1,1) = oWorkbook.Sheets.Count
End With
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Running these script files is a very simple task. In Explorer, you can click the right mouse key over the file, and select Open.
Alternatively, you can double-click the item in Explorer as well. Yet another alternative is to use the Run method of the
Windows Scripting Shell object. This technique will be illustrated when the Shell Object is discussed in detail.
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A quick word about debugging and handling errors
No programming environment is complete without a full-featured debugging environment. The WSH is no exception, as it also
has a full-featured debugger. As far as error handling is concerned, VBScript doesn't have a global error handler. Rather,
errors need to be handled on an in-line basis. The following code demonstrates how to deal with errors on an in-line basis:
On Error Resume Next
dim objxl
Set objXL = WScript.CreateObject("Excel.Application")
objxl.foo ' reference a non-existent Excel Method
If Err.Number > 0 Then
Call ErrorProc
End If
Sub ErrorProc
msgbox err.description
End Sub
If no error trapping exists, you'll be prompted with a dialog box asking if you wish to debug the application. Figure 1 illustrates
how the code will appear in the script debugger.
Figure 1. The Microsoft Script Debugger uses the same IDE as Visual InterDev and Visual J++ 6.0.
The WSH objects
There are two primary objects contained within the WSH. The following code illustrates how these objects can be created:
WSHshell = CreateObject("Wscript.Shell")
WSHNetwork = CreateObject("Wscript.Network")
Both the shell and network objects are hosted by the wshom.ocx ActiveX Control.
Complete documentation for the WSHShell and WSHNetwork Objects can be found by navigating to the following URLs:
http://www.microsoft.com/iis/support/iishelp/iis/htm/asp/wsho7t84.htm for the WSHShell object
http://www.microsoft.com/iis/support/iishelp/iis/htm/asp/wsho20qc.htm for the WSHNetwork object
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Shell object properties and methods
Environment
This property provides access to the environment collection. Information such as number of processors, paths, OS, and so
forth can be determined from this collection.
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oEnv = wshshell.environment
For Each x In oEnv
?oEnv
Next x
The following is a partial listing of some typical environmental variables:
NUMBER_OF_PROCESSORS
OS
PROCESSOR_ARCHITECTURE
PROCESSOR_IDENTIFIER
WINDIR
So, to find out the number of processors:
Numprocessors = oEnv.Item("NUMBER_OF_PROCESSORS")
Like most collections, if you want to find out how many members are contained in the collection, you can refer to the Count
property:
Numitems = oEnv.Count
To be compliant with the Java language, collections in the WSH also support the Length property, which provides the same
functionality as the Count property:
Numitems = oEnv.Length
SpecialFolders
This property provides access to the collection of Windows Shell folders. The following is a listing of folders:
AllUsersDesktop
AllUsersStartMenu
AllUsersPrograms
AllUsersStartup
Desktop
Favorites
Fonts
MyDocuments
NetHood
PrintHood
Programs
Recent
SendTo
StartMenu
Startup
Templates
To find the actual path of the desktop folder, issue this line of code:
DesktopPath = WSHShell.SpecialFolders("Desktop")
CreateShortcut (strPathname)
This method creates and returns a shortcut object. The following block of code illustrates how to create a desktop shortcut:
*/ Read desktop path using WshSpecialFolders object
DesktopPath = WSHShell.SpecialFolders("Desktop")
*/ Create a shortcut object on the desktop
MyShortcut = ;
WSHShell.CreateShortcut(DesktopPath + ;
"\Shortcut to MyFile.lnk")
*/ Set shortcut object properties and save it
FileName = GetFile()
If !Empty(FileName)
FileDir = JustPath(FileName)
With MyShortcut
.TargetPath = Filename
.WorkingDirectory = FileDir
.Save
EndWith
Endif
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The CreateShortcut method returns a WSHShortcut object. This object is only exposed through the CreateShortcut method.
The WSHShortcut object has the following properties:
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Arguments Parameters to a shortcut object
Description A description of a shortcut object
Hotkey The hot key of a shortcut object
IconLocation The icon location of a shortcut object
TargetPath The target path of a shortcut object
WindowStyle The window style of a shortcut object
WorkingDirectory The working directory of a shortcut object
The WSHShortcut object only has one method -- Save() -- which saves the shortcut object to the file system.
ExpandEnvironmentSettings (strString)
This method expands a process environment variable and returns the result. A typical environment variable is WINDIR. The
following code illustrates how this method works:
Fullpath = WSHShell.ExpandEnvironmentStrings ;
("%windir%\notepad.exe, 0")
Popup (strText, [natSecondsToWait], [strTitle], [natType])
This method displays the Window MessageBox. Unlike the existing MessageBox function, the Popup method accepts an
optional argument to clear the dialog box after a specified amount of time. The following line of code illustrates how the Popup
method works:
WSHShell.Popup("Message",1,"Title",64)
Run(strCommand, [intWindowStyle], [blnWaitOnReturn])
The Run method creates a new process that executes a specified command with a specified window style. In addition to being
able to specify the command and the window style, a third parameter can be used to determine whether script execution
should pause until the new process has terminated.
Applications windows can be started in several states. The following outlines the various options available:
SW_HIDE 0
SW_MINIMIZE 6
SW_RESTORE 9
SW_SHOW 5
SW_SHOWMAXIMIZED 3
SW_SHOWMINIMIZED 2
SW_SHOWMINNOACTIVE 7
SW_SHOWNA 8
SW_SHOWNOACTIVATE 4
SW_SHOWNORMAL 1
The following code starts Notepad with a normal window:
WSHshell.Run("notepad",1)
The following code starts Notepad with a maximized window. In addition, the user must close Notepad before control will
return to VFP:
WSHshell.Run("notepad",3,.T.)
Fully qualified paths can be used to denote a file to execute. The following code starts Visio:
WSHshell.Run("D:\VISIO\VISIO32.EXE")
Also, script files can be executed with the Run method as well:
WSHshell.Run("hello world.vbs")
WSHshell.Run("hello world.js")
Network object properties and methods
ComputerName
This property denotes the name of the computer:
ComputerName = WSHNetwork.ComputerName
UserDomain
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This property denotes the domain to which the user belongs:
DomainName = WSHNetwork.UserDomain
UserName
This property denotes the ID of the currently logged-in user:
UserName = WSHNetwork.UserName
AddPrinterConnection(strLocalName, strRemoteName, [bUpdateProfile], [strUser], [strPassword] )
This method maps a network printer to a local resource.
WSHNetwork.AddPrinterConnection("LPT1","\\server\ ;
printer_share",.T.,"UserID","Password")
Of special interest here is the third parameter -- bUpdateProfile. If this parameter is set to .T., the user profile for the local
machine is updated to restore the printer mapping the next time the user logs onto the machine and network.
EnumNetworkDrives
This method returns a collection of drive mappings. The following code loops through the collection of network drive
mappings:
oDrives = WSHNetwork.EnumDriveMappings
item = -1
For Each x In oDrives
item = item + 1
If Mod(item,2) = 0
?"Drive Letter: ",x
Else
?"Network Resource: ",x
Endif
Next x
Like other collections, the drive mapping collection supports both the Count and Length properties as well as the Item()
method.
EnumPrinterConnections
This method works just like the EnumNetworkDrives, with the difference being that the collection returned represents printers,
not drive mappings:
item = -1
For Each x In oPrinters
item = item + 1
If Mod(item,2) = 0
?"Printer Name: ",x
Else
?"Network Resource: ",x
Endif
Next x
MapNetworkDrive(strLocalName, strRemoteName, [bUpdateProfile], [strUser], [strPassword] )
This method works just like the AddPrinterConnection Method, with the exception that a local drive to a network resource is
created:
WSHNetwork.MapNetworkDrive("z:","\\server\ ;
server_share",.T.,"User","Password")
RemoveNetworkDrive(strName, [bForce], [bUpdateProfile] )
This method removes a specified network drive mapping. Optionally, you can force the removal even if the resource is being
used. An optional third parameter specifies whether the user profile should be updated:
WSHNetwork.RemoveNetworkDrive("z:",.T.,.T.)
or
WSHNetwork.RemoveNetworkDrive("\\server\ ;
server_share",.T.,.T.)
RemovePrinterConnection(strName, [bForce], [bUpdateProfile] )
This method works just like the RemoveNetworkDrive method, with the exception that a printer resource is being removed:
WSHNetwork.RemovePrinerConnection("LPT1",.T.,.T.)
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or
WSHNetwork.RemovePrinterConnection("\\server\ ;
printer_share",.T.,.T.)
SetDefaultPrinter(strName)
This method sets the default printer:
WSHNetwork.SetDefaultPrinter("\\server\printer_share")
Conclusion
The ability to work with the Windows Registry, create desktop shortcuts, and map and view network resources all required you
to know how to use extensive Windows API functions, or a third-party DLL. The WSH provides a simple and elegant set of
objects with simple interfaces that allow you to accomplish many tasks. Perhaps your application requires special Registry
entries. Perhaps you've been tasked with developing a utility that modifies the default printer or dynamically maps network
resources. All of these tasks can easily be accomplished with the WSH.
The good news is that the WSH will be a standard part of the operating system beginning with Windows 2000. Until the
release of Windows 2000, you'll need to make sure the WSH is installed on any client workstation that uses your application.
One approach to this problem is to add a method to your application class that tests to see whether the WSH is installed. If it
isn't, prompt the user through the process of both downloading and installing the WSH.
The Windows Scripting Host -- yet another valuable tool to add to your toolbox!
Sidebar: VFP Bug Alert!
While the documentation states that the second argument in the Popup method specifies a timeout interval in which the
MessageBox will be cleared, it doesn't work in VFP. I tested this code in Visual Basic, and the expected behavior occurred.
This behavior has been reported to the VFP team and hopefully will be fixed in the next release.
The WSH Shell object provides three methods for working with the Windows Registry:
RegWrite(strName, anyValue, [strType] )
RegDelete(strName)
RegRead(strName)
With these methods, entries can be created, written, read, and deleted. If you attempt to write to a key that doesn't exist, the
key will be created. The code in Listing 1 illustrates how these three methods work (click on the Listing link for the
code).
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