Quick Scripting Tips

Let's review a few general tips for scripting in VBScript. Future columns will include more specific tips that apply to the topic I discuss in the column, but these general tips will always apply.

• Keep the lines in your scripts short. Short lines are easier to read. VBScript lets you use underscores to break lines, and statements such as If ...Then ... Else let you list conditions instead of crowding everything on one line.
• Comment liberally. You know now what the statement you typed means. But will you remember what it means 6 months from now? Will someone else reviewing your code understand it? Make sure by spelling out what the pieces of the script do.
• Mix case in your code. The mixed-case oDiskSpace is easier to read than lowercase odiskspace or uppercase ODISKSPACE. VBScript is case insensitive for most purposes (one exception is when you're computing the ASCII character values for letters: Uppercase letters have ASCII values different from lowercase letters).
• When using Windows Script Host (WSH), use the command-line environment. WSH has two execution environments: a command-line one and a graphical one (the default). In the command-line environment, output appears in a command window unless you specifically send it to a dialog box. In the graphical environment, all output goes to message boxes. You'll want to use the command-line environment most of the time. Some operations won't work in a graphical environment, and if your script produces several lines of output, each line will have its own message box that will halt the script's execution until you click OK. To execute scripts in the command-line environment, you have two options: Preface each command you run with cscript, for example

cscript getfree.vbs

or make the command line the default execution environment by typing

wscript //h:cscript //s

Name variables according to the kind of data they represent (e.g., give strings names that begin with the letter s and objects names that begin with o). This practice makes debugging code easier. Some expressions won't work or will work differently with data of an unexpected data type. And if you know what data type you intended to feed a script, unraveling type-mismatch errors is easier.

Explicitly define variables up front. Although you can implicitly define variables by just assigning them values in the body of the script, use an Option Explicit statement at the beginning of the script to announce that only explicitly declared variables are permissible, then declare with a Dim statement each variable you'll be using. Disallowing the use of undefined variables helps you catch bugs introduced by mistyping variable names.

Write scripts in a text editor. Don't write them in a word processor, then copy them to a text editor for saving. Scripts use a lot of quotation marks. If your word processor converts straight quotes to smart quotes, when you copy the script to the text editor, junk characters will replace the quotes and the script won't work.