An object model is a representation of a number of related objects that provide a script or program with the ability to view and interact with each of the objects (files, disks, printers, and so on) represented in the object model.

The Core Object Model

The WSH core object model provides programmatic access to Windows resources. There are 14 objects in the WSH core object model, as depicted in Figure 2.4. Each of these objects provides access to a particular category of Windows resources.

Figure 2.4: The WSH core object model consists of 14 objects, all of which have properties and methods that expose various parts of the Windows operating system.

At the top, or root , of the WSH core object model is the WScript object. It is from this object that all other objects are instantiated. The WScript object is automatically established during the startup of the execution host and can therefore be referenced without first being instantiated within your scripts. For example, let's create a short one-line script called Greeting.vbs.

WScript.Echo "This is an example of the use of WScript object's Echo() method"

To test this script, open your script editor and type in this statement. Now save the script, then run it by double-clicking it. The popup dialog, shown in Figure 2.5, should appear. As this script demonstrates , you can automatically access any of the properties and methods belonging to the WScript object directly from within your scripts.

Figure 2.5: A popup dialog created using the WScript object's Echo() method

The WScript object provides access to a number of very useful methods that you'll see used throughout this book. These methods include

• CreateObject() . Establishes an instance of the specified object.

• DisconnectObject() . Prevents a script from accessing a previously instantiated object.

• Echo() . Displays a text message in the Windows Console or as a popup dialog depending on which execution hosts runs the script.

• Quit() . Terminates a script's execution.

• Sleep() . Pauses the execution of a script for a specified number of seconds.

Instantiation is a term that describes the process of creating a reference to an object. In order to work with an object you must first create, or instantiate, a reference to it within your scripts.

The WScript object is referred to as a public or exposed object. The WSH core object model has three other public objects. These are the WshController , WshShell , and WshNetwork objects. Each of these three objects must be instantiated within your scripts using the WScript object's CreateObject() method. All of the other objects in the WSH core object model can only be instantiated by using properties or methods associated with the WScript , WshController , WshShell , and WshNetwork objects.

Table 2.1 lists the rest of the objects in the WSH core object model, as well as the object properties or methods required to instantiate them.

WSH Objects and Their Properties and Methods

Each object in the WSH core object model provides access to, or exposes, a particular subset of Windows functionality. Table 2.2 lists all 14 of the WSH core objects, provides a high-level description of these objects, and lists all of the properties and methods associated with each object.

The number of properties and methods supported by objects in the WSH core object model is too extensive to include them all in this table; I will cover them separately a little later in this chapter.

Examining Object Properties

By accessing object properties, your scripts can gather all kinds of information when they execute. For example, using the properties associated with the WshNetwork object, your scripts can collect information about the Windows domain that the person who ran the script has logged in to, as well as the computer's name and the user 's name. This information could then be used, for example, to prevent the script from executing on certain domains or computers.

There are over three dozen properties associated with various WSH objects. In many cases, properties may be associated with more than one object. Refer to Table 2.2 to see which properties are associated with which objects.

A complete review of WSH object properties is provided in Table 2.3.

Working with Object Properties

Now let's take a look at an example of a VBScript that demonstrates how to instantiate an instance of the WshNetwork object and access its properties. The script is called NetInfo.vbs and is as follows :

Set WshNtwk = WScript.CreateObject("WScript.Network") PropertyInfo = "User Domain" & vbTab & "= "& WshNtwk.UserDomain & vbCrLf & _ "Computer Name" & vbTab & "= "& WshNtwk.ComputerName & vbCrLf & _ "User Name" & vbTab & "= "& WshNtwk.UserName & vbCrLf MsgBox PropertyInfo, vbOkOnly , "WshNtwk Properties Example"

As you can see, it is not a very big script. It begins by using a Set statement to create an instance of the WshNetwork object, which is associated with a variable name of WshNtwk . Once you have established an instance of the WshNetwork object in this manner, you'll be able to reference the object's properties and methods using its variable name assignment.

The Set statement is used to create a reference to a specified object. Using this reference, you'll be able to refer to the object and its properties and methods over and over again throughout your script.

The next statement is so long, that to improve the script's readability, I decided to break it into three lines and end each of the first two lines with the & and _ characters . The & character is a concatenation character and is used to append two strings together. The _ character is a continuation character and is used to indicate that a statement is continued on the next line. This statement displayed the values of the following WshShell properties:

• WshNetwork.UserDomain . The name of the domain into which the person running the script is logged in.

• WshNetwork.ComputerName . The name of the computer on which the script is being executed.

• WshNetwork.UserName . The username of the person who ran the script.

In order to improve the presentation of the message, I formatted it using the VBScript vbTab and vbCrLf constants. The vbTab constant was used to line up the output at the point of the equals sign. The vbCrLf constant was used to execute a line feed and carriage return at the end of each line of output.

A constant is a VBScript construct that contains information that does not change during the execution of a script. VBScript provides a collection of built-in constants, such as the vbTab and vbCrLf constants, that you can incorporate into your scripts to control the formatting of your script output.

The last thing that the script does is display the message using the following statement:

MsgBox PropertyInfo, vbOkOnly , "WshNetwork Properties Example"

MsgBox() is a built-in VBScript function that displays a text message in a popup dialog. PropertyInfo is a variable that I used to store the output message. VbOkOnly is a VBScript constant that tells the MsgBox() function to only display the OK button in the popup dialog. The last part of the previous statement is a message that will be displayed in the popup dialog's titlebar. If you save and run this script yourself, you should see a popup dialog similar to the one shown in Figure 2.6.

Figure 2.6: A popup dialog displaying properties associated with the WshNetwork object

Examining Object Methods

The WSH also provides a large collection of object methods. By using these methods in your VBScripts, you'll be able to manipulate the Windows resources associated with objects.

For example, using the WshShell object's RegRead() , RegWrite() , and RegDelete() methods, you can create scripts that can access and manipulate the contents of the Windows registry. Using these methods, you can create scripts that can configure just about any Windows resource.

A complete review of WSH object methods is provided in Table 2.4.

Working with Object Methods

To really understand how object methods work you need to work with some examples. Let's take a look at two examples. In the first example, you'll see how to work with the WshShell object's Run() method in order to create a graphical front end to the Windows NET SEND command. In the second example, you'll learn how to use the WshShell object's LogEvent() method to write messages directly to a Windows XP, .NET, 2000, or NT computer's application event log.

The WshShell object provides access to a number of Windows resources, including

• The Windows application log

• The Windows registry

• Any Windows command-line command

Let's look at an example of how to use the WshShell object's Run() method. I've named this VBScript NetMessenger.vbs. NetMessenger.vbs provides a friendly graphical front end to the Windows NET SEND command-line command. The NET SEND command can be used to send text messages over a network to other currently logged-on users by specifying either the user's username or the computer name that the user is using. To use this command from the Windows command line, you might type something like

NET SEND jford Jerry,

please

stop by my office and see me when you have a moment

NET SEND is the command being used. Jford is the username of the person to receive the message, and the rest of the statement is the message text that is to be sent.

Using the NET SEND command is not very complicated. Click on Start, Run, and then type CMD and click OK. This opens the Windows Console. Now type the NET SEND command and press the Enter key. That's it. Within moments, your message should appear on the recipient's screen. Unfortunately, many people are intimidated by the very thought of using the Windows Command Prompt. So let's write a VBScript, shown below, that makes using this command easy.

Set WshShl = WScript.CreateObject("WScript.Shell") Recipient = InputBox("Type the username or computer name "& _ "that the message is to be sent: ") MsgText = InputBox("Type your message: ") WshShl.Run "Net Send "& Recipient & " " & MsgText

The first line of this script instantiates the WshShell object and associates with it a variable called WshShl . The next two lines display a popup dialog asking the user to type a user name or computer name. The information typed in by the user is stored in a variable called Recipient . The next line allows the user to type in a text message and stores it in a variable called MsgText . The last line of this script executes the WshShell object's Run() method, passing it the NET SEND command, the name of the recipient, and the message to be sent.

Open your script editor and type in the script as just shown, then save it as Messenger.vbs. Run it and you'll see a popup dialog, like the one in Figure 2.7, asking for the user name or computer name of the recipient.

Figure 2.7: Type the username or computer name to which you want to send a message.

Type the required information and click OK. The popup dialog shown in Figure 2.8 will appear. Type the message you wish to send and then click OK.

Figure 2.8: Type the message that you wish to send.

Within a few moments your message will appear on the recipient's screen, as shown in Figure 2.9.

Figure 2.9: The recipient of the message will see your message, as well as your computer's name and the date and time of the message.

In the second example, you'll learn how to use the WshShell object's LogEvent() method to write a message to the Windows event log. The Windows event log is accessed differently, depending on which version of Windows you use. For example, on Windows 2000 and Windows XP, you can click Start and then right-click My Computer and select Manage to open the Computer Management console where the Event Viewer utility or snap-in resides. To view the application event log, expand the Event Viewer node and select Application, as shown in Figure 2.10. Then double-click on an event entry in the event log to examine it.

Figure 2.10: Examining the contents of the application event log

The scripting logic to write a message to the Windows application event log is very simple.

Set WshShl = WScript.CreateObject("WScript.Shell") WshShl.LogEvent 0, "EventLogger.vbs - Beginning script execution."

The first line of this script establishes an instance of the WshShell object. The second line uses the WshShell object's LogEvent() method to write a message to the event log.