Scripting Windows 7 with WSH : Programming the WshShell Object (part 1)

WshShell is a generic name for a powerful object that enables you to query and interact with various aspects of the Windows shell. You can display information to the user, run applications, create shortcuts, work with the Registry, and control Windows environment variables. The next few sections discuss each of those useful tasks.

Referencing the WshShell Object

WshShell refers to the Shell object exposed via the automation interface of WScript. Therefore, you must use CreateObject to return this object:

Set objWshShell = WScript.CreateObject("WScript.Shell")

From here, you can use the objWshShell variable to access the object’s properties and methods.

Displaying Information to the User

You saw earlier that the WScript object’s Echo method is useful for displaying simple text messages to the user. You can gain more control over the displayed message by using the WshShell object’s Popup method. This method is similar to the MsgBox function used in Visual Basic and VBA in that it enables you to control both the dialog box title and the buttons displayed, and to determine which of those buttons the user pressed. Here’s the syntax:

WshShell.Popup(strText [, nSecondsToWait] [, strTitle] [, intType])

For example, the following statements display the dialog box shown in Figure 1:

Set objWshShell = WScript.CreateObject("WScript.Shell")
objWshShell.Popup "Couldn't find Memo.doc!", , "Warning"

WshShell.Popup "First line" & Chr(13) & "Second line"

WshShell.Popup("First line" + "\n" + "Second line");

Setting the Style of the Message

The default Popup dialog box displays only an OK button. You can include other buttons and icons in the dialog box by using different values for the intType parameter. Table 1 lists the available options.

You derive the intType argument in one of two ways:

• By adding the values for each option

• By using the VBScript constants separated by plus signs (+)

The script in Listing 1 shows an example and Figure 2 shows the resulting dialog box.

Listing 1. VBScript Example That Uses the Popup Method to Display the Dialog Box

' First, set up the message
'
strText = "Are you sure you want to copy" & Chr(13)
strText = strText & "the selected files to drive G?"
strTitle = "Copy Files"
intType = vbYesNoCancel + vbQuestion + vbDefaultButton2
'
' Now display it
'
Set objWshShell = WScript.CreateObject("WScript.Shell")
intResult = objWshShell.Popup(strText, ,strTitle, intType)

Here, three variables—strText, strTitle, and intType—store the values for the Popup method’s strText, strTitle, and intType arguments, respectively. In particular, the following statement derives the intType argument:

intType = vbYesNoCancel + vbQuestion + vbDefaultButton2

You also could derive the intType argument by adding up the values that these constants represent (3, 32, and 256, respectively), but the script becomes less readable that way.

Getting Return Values from the Message Dialog Box

A dialog box that displays only an OK button is straightforward. The user either clicks OK or presses Enter to remove the dialog from the screen. The multibutton styles are a little different, however; the user has a choice of buttons to select, and your script should have a way to find out which button the user chose, which enables it to decide what to do next, based on the user’s selection. You do this by storing the Popup method’s return value in a variable. Table 2 lists the seven possible return values.

To process the return value, you can use an If...Then...Else or Select Case structure to test for the appropriate values. For example, the script shown earlier used a variable called intResult to store the return value of the Popup method. Listing 30.5 shows a revised version of the script that uses a VBScript Select Case statement to test for the three possible return values.

Listing 2. Script That Uses a Select Case Statement to Process the Popup Method’s Return Value

' First, set up the message
'
strText = "Are you sure you want to copy" & Chr(13)
strText = strText & "the selected files to drive A?"
strTitle = "Copy Files"
intType = vbYesNoCancel + vbQuestion + vbDefaultButton2
'
' Now display it
'
Set objWshShell = WScript.CreateObject("WScript.Shell")
intResult = objWshShell.Popup(strText, ,strTitle, intType)
'
' Process the result
'
Select Case intResult
    Case vbYes
        WScript.Echo "You clicked ""Yes""!"
    Case vbNo
        WScript.Echo "You clicked ""No""!"
    Case vbCancel
        WScript.Echo "You clicked ""Cancel""!"
End Select

					  

Running Applications

When you need your script to launch another application, use the Run method:

WshShell.Run strCommand [, intWindowStyle] [, bWaitOnReturn]

Here’s an example:

Set objWshShell = WScript.CreateObject("WScript.Shell")
objWshShell.Run "Control.exe Inetcpl.cpl", 1, True

This Run method launches Control Panel’s Internet Properties dialog box.