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This is a big advantage over batch files, which are restricted to using shared environment variables, because it eliminates potential conflicts that can occur between scripts.. If you ne

WSH provides the capability for you to create and manipulate variables within your

scripts Unlike batch files, variables are constrained so they are only available within a single script during the execution of the script This is a big advantage over batch files, which are restricted to using shared environment variables, because it eliminates

potential conflicts that can occur between scripts Furthermore, variables within WSH scripts can take any type of value including strings, numbers, and objects In batch files,

If you’ve used batch files before, you might wonder how you can translate

your batch files into their WSH equivalent so that you can take advantage of

the enhanced capabilities of WSH In this section, you’ll take a look at batch

As you go through this section, you’ll notice that some of the WSH

equivalents for batch file functions are much longer in terms of

lines of code That’s one of the few advantages of batch files over

WSH scripts You might find that for certain tasks it’s easier for you

to implement batch files.

First, you’re going to take a look at some of the language constructs that are

used in batch files and the equivalent language constructs in WSH It’s

important to keep in mind that these language constructs are dependent on

If you want to use variables in batch programs, you must use environment

variables Here’s an example that shows how you might use environment

When you’re using scripts with WSH, you don’t need to use environment

variables That’s much safer, and you don’t need to clean up the variables at

the end of your WSH script Here’s a short example that shows how you can

use VBScript to create a variable:

As you can see, the JScript code is actually somewhat shorter than the

VBScript equivalent In any case, like VBScript, you don’t need to clean up







One thing that you can do with variables in WSH scripts is set them to values

that are more than just strings The following example shows how you can

When you use WSH variables, you have very few limitations You also don’t

need to worry about collisions between variables that you use and variables

that exist in other scripts.

to evaluate logical conditions and branch accordingly Here’s a batch file

 IF %MY_VAR%.==.ValueA GOTO WasValueA 

That works okay when you have a simple condition If you have a more

complex condition, batch files quickly become messy The following example

is very similar to the first but includes a more complex condition:

 ’ Create a variable to use to illustrate the use of 

The advantage of the two examples is that the flow of the program is simple

and easy to understand; the flow is certainly simpler and easier than the flow

of the batch file With the second batch file example, you can quickly see

how code turns into spaghetti code that can be very difficult to debug and

maintain Now, take a look at the equivalent of the second batch file in

 Select Case my_var 

That example demonstrates two different ways that you can perform

branching logic in VBScript Now take a look at similar functionality using

You can see that the JScript example is very similar to the VBScript

example; the syntax varies a little Both examples are much better structured

than the batch file example If you need to use complex logic, consider

changing your batch files to WSH scripts so that you can make use of the

In batch files there are two basic types of iteration; you can iterate over a

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vanilla iteration using the GOTO statement The second type of iteration is

similar to the typical iteration that’s used in a program for a while or for

type of loop, but unfortunately it’s much weaker.

Typical batch files use GOTO in conjunction with IF statements to perform

that type of iteration:

The previous example shows a batch file loop that iterates through the

parameters for the batch file If the batch file is run with the command line

gotoloop IterationA IterationB IterationC IterationD, you

see the results in Figure 10.6.





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The batch file iteration techniques are effective but very clunky They make it

easy to iterate over multiple files but difficult to iterate for a specific number

of times or until a complex condition is satisfied.

Some of these batch file restrictions have been eliminated with

Windows NT command extensions For example, the FOR

command is extended to perform iteration for a specific sequence

in Figure 10.7 There are also some additional enhancements with

the command extensions that make it possible to simulate

subroutines using batch files The extensions are very useful;

however, they are still not as flexible or anywhere near as powerful

embedded loops However, this is one situation where the WSH equivalent is

not necessarily as simple or as short as the batch file version Iterating over

a group of files can be more complex but also more flexible using WSH

Here’s an example that uses VBScript to iterate over all the files in the

Windows NT system directory:

That’s not too complex, but it gets worse If you want to iterate over just a

specific type of file, like all the DLLs that begin with the letter e, you need to

implement additional file-checking logic Here’s an example that does the

 Figure 10.8: Iterating over files using VBScript. 









Both of those examples show some of the excellent looping capabilities

provided by WSH, but they also show that sometimes WSH scripts might not

be as easy to implement as batch files Here’s another simple example that

illustrates the use of the while loop:

That’s obviously a very trivial example, but it does demonstrate complex

logic and comparisons that are much better than the capabilities provided by

When a batch file runs a command, the command might return a numeric

DOS error level Typically, an error level of zero represents success,

whereas a nonzero error level is a failure number Here’s an example that

text error and sets the DOS error level That’s more feedback than some

other commands; many set the error level without displaying a descriptive

use it to check for a specific error level; it checks for an error equal to or

greater than the error level that is specified.





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extensions improve the batch file capabilities With the command









WSH scripts, assuming that you’re using VBScript, provide much more

robust error handling than batch files (Unfortunately, the current version of

object that provides properties that include a numeric error code, a

description of the error that occurred, and the source of the error You can

Here’s an example that illustrates the check for an error:

The output of the script is shown in Figure 10.10 The script can easily be

Err.Number <> 0 Then line Because of the capabilities of WSH, you can

create scripts that notify users of problems and then enable them to retry

operations Here’s a sample script that uses retry logic to prompt a user to

enter a different filename if an error occurs:

’ An error occurred when we tried to get the

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doesn’t exist When it fails, it displays a yes/no dialog box, shown in Figure

10.11, that enables the user to retry the operation.

If the user selects yes, he is prompted to enter a new filename The prompt

dialog box is illustrated in Figure 10.12 When he reenters the filename, the



This shows some of the power that is inherent in WSH error handling These

are just basic examples; you can easily extend them to perform additional

In this section, you’re going to examine some common techniques used in

batch files, and you’ll see how you can duplicate the functionality within your

WSH scripts For each section, you’ll follow the pattern that you used in the

previous section; first you’ll see an example for a batch file, and then you’ll

provides a syntax that enables you to perform an action if a file exists Here’s

statement Now, take a look at the equivalent functionality using WSH To

Obviously, because you’re using WSH, it is very easy for you to to

incorporate additional complex logic for the file check For example, you can

check the size of file, or, if the file is a DLL or an executable, you can check

internal file resources such as a version stamp In Day 11, "Administering

User Logins, Program Settings, Folders, and File Shortcuts Using WSH,"

you’ll see additional examples that illustrate how you can use the

FileSystemObject to check for files and perform other file operations.

Batch files can access nine command line parameters simultaneously The

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name of the batch file that was called, and %1 through %9 are the command

parameters You can specify more than nine parameters; to access them,

Accessing command-line parameters is easier using WSH than it is using

batch files With WSH, you can easily access each command-line parameter,

and you can tell from the beginning how many parameters are specified for

the script Here’s a sample script that shows how you can access

If you’re converting a batch file to a WSH script, you can eliminate your

shift statements and just make use of the Wscript.Arguments property

With batch files, you have no choice for how you want to display a message





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You can certainly do the same type of thing with WSH scripts You’ve used

That’s not all that you can do to display messages to the user using WSH

You can use internal functions or objects to display message boxes, or you

can even make use of external custom objects to display your own UI You’ll

see that technique demonstrated later in this book For now, here’s an

There are only two standard options for getting user input with batch files

Press any key to continue and wait for the user to press any

developed to provide more robust support for user input Unfortunately,

Choice was not designed for Windows NT 4.0 You can try to use it; beware

that it is not officially supported The following batch file uses the Choice

is effective for batch files, but it is limited because it only enables the user to

make selections from a canned menu It also shows how weak the structure

of batch files must be because of the lack of good programming constructs

 Figure 10.13: A batch file menu using the Choice command. 









Unfortunately, if you’re using JScript, there is no standard mechanism for

The result of this script is shown in Figure 10.14 The example shows both

strengths and weaknesses of the WSH support for user input The benefit of

InputBox() is that it enables you to capture any type of user input At the

constrain selections or to enable the user to select from a list With VB, Java,

C++, or any other language that enables you to create COM objects, you can

define custom objects that can supplement your WSH scripts with custom

perform drive mapping tasks For now, you’ll do a quick comparison that

that enable you to create or remove drive mappings, among other things

provides all the networking functionality for WSH scripts If you want to find

Object Model." Here’s the equivalent WSH script:



This chapter began with a discussion of the history of batch files on the DOS/Windows platform Batch files were developed as an effective and simple solution for command automation They provide powerful but basic automation capabilities Relative to robust programming languages, batch files are weak and cumbersome However, there are

WSH equivalents for functionality that you might be using in batch files Next, you

examined several standard batch file usage scenarios The batch file scenarios were

In batch files, environment variables are the only place that you can store

temporary values Typically, batch files need to clean up environment

variables that they use before they terminate Do WSH scripts also need to

clean up variables that they use?

No, WSH scripts do not need to clean up variables that they use The internal

variables that are used by a script are only available while that script is executing;

Although batch files provide no debugging utilities, WSH scripts have

excellent debugging tools Name two tools that can be used to debug WSH





 3. What object do you need to use in WSH if you want to check for the existence of a file? 

existing batch files with more robust and complete scripts developed using WSH Now you’re going to put some of those techniques and ideas into action with scripts that will









This chapter shows you how to create WSH login scripts, programmatically create

directory mappings (and check to make sure that directory mappings succeed), check for the existence of files and check file timestamps, administer program Registry

settings, and create shortcuts and directories By the time you are finished with this

chapter, you’ll see how you can use WSH for administration tasks, and you’ll have some

The WindowsScriptingHost is a generalized tool that allows you to perform a multitude

of administrative tasks You can use the objects that are built into WSH, such as the

WshNetwork or WshShell objects, to administer drive mappings or program settings

check files and add folders In this chapter, you'll see code examples that use those

objects and others for user administration.









In this context, user administration means to administer the user's computer, including

the Windows desktop, program settings, files, folders, and so on It does not mean that you will actually be creating or modifying users with WSH scripts That topic is

discussed in Day 18, "Using WSH to Manipulate the Microsoft Active Directory." As Day

administration tool because it can script any ActiveX objects Because many of the

Microsoft technologies expose ActiveX administration objects, they can be administered

no real programming constructs and certainly no capability to leverage COM objects

Now you can replace them with more robust WSH scripts that perform more functions With WSH scripts, you can perform many tasks and check the results much more easily





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Directory mappings are typically done the old way using batch files When you map

drives, you use the net use command with the name of the server and share that you want to map to specified using the Universal Naming Convention (UNC) in the form

\\server\share For example, you may have a batch file that bitmaps to a directory using something like the following syntax:

The problem is that it can be difficult to check whether the directory mapping

succeeded With WSH scripts, you can do the directory mapping using the

WshNetwork object and check the result to ensure that the directory was mapped

With batch files, it’s literally impossible to check file versions There’s no good way,

unless you extend batch files with external programs or utilities, to check file versions

Later in this chapter, you’ll see how you can perform this task using scripts.

One major limitation of batch files is that they don’t provide any capability to change

the Windows Registry Later in this chapter, you use the WSH TextStream objects to

This is one of the few examples where we will use the Microsoft JScript

language Current versions of JScript provide no support for error handling,

so it’s difficult to use them to develop robust scripts This will be fixed in

upcoming versions of JScript, which will support robust error handling using a try catch mechanism similar to the Java language.

To set up login scripts, go into the Windows NT User Manager for domains Select a

user, or multiple users, and press Enter, or select User, Properties from the menu You’ll see the dialog illustrated in Figure 11.2.

Obviously, if Windows NT is installed on a different drive or in a different root directory, your path will be different It’s important to note that the aforementioned directory is also

You may get inconsistent results using the aforementioned method

Sometimes it appears that the user manager has problems resolving the

path to the script Consequently, consider wrapping your scripts in the

following batch file.









That can help you to eliminate any problems with directory dependencies Here’s a

sample batch file that you could use:

Users must have WSH installed locally to run WSH login scripts In the

last chapter of this book, we discuss how you can deploy WSH script

solutions and the files that you need to distribute to end users for them to

user, such as the username You can also use the name with other objects to perform

log in.



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proactive in scripts to give the end user feedback about potential problems, or to alert

whatever is appropriate for your environment Now, let’s run a quick example that shows some of the usage of the object Before running the script, drives in the Explorer look like Figure 11.5.