Script Tips

Recycling: It's Good for the Script

Modularize your VBScripts with subs and functions.

This is the second column in which I'll continue to look at several confusing core techniques in VBScript. This time, I'll focus on VBScript Subs and Functions, which are a great way to modularize your code. But, keep in mind that there are some rules about how to use them. Here's a perfect example:

Function TestPing(sName)
Dim cPingResults, oPingResult
Set cPingResults = _
  GetObject("winmgmts://./root/cimv2").ExecQuery(_
  "SELECT * FROM Win32_PingStatus WHERE Address = '"_
  & sName & "'")
On Error Resume Next
For Each oPingResult In cPingResults
  If oPingResult Is Null Then
   TestPing = False
  ElseIf oPingResult.StatusCode = 0 Then
   TestPing = True
  Else
   TestPing = False
  End If
Next
End Function

Here what this function does:

  • It declares an argument, strComputer, which will hold the function's input. The function doesn't rely on any data apart from this argument, thus making the function entirely self-contained.
  • The function returns a result, either True or False, by setting the function's name equal to whatever value is to be returned.
  • The function doesn't reference any variables apart from those declared within the function itself.
  • The strComputer argument works like a variable, but doesn't need to be declared using the Dim keyword-it's declared as a part of the function itself.

By the way, this will only run on WinXP and Win2003 boxes, and it'll give you a True or False if the computer you specify that it's pingable or not. Use this function like this:

If TestPing("server1") Then
  'is available
Else
  'is not pingable
End If

By keeping the TestPing() function self-contained, it can be easily pasted into any script where you need to use it. That's the real goal of Subs and Functions: to modularize and encapsulate code so that it can be more easily reused. Reusing code saves time, so it's a good habit to practice.

About the Author

Don Jones is a multiple-year recipient of Microsoft’s MVP Award, and is an Author/Evangelist for video training company Pluralsight. Don is also a co-founder and President of PowerShell.org, a community dedicated to Microsoft’s Windows PowerShell technology. Don has more than two decades of experience in the IT industry, and specializes in the Microsoft business technology platform. He’s the author of more than 50 technology books, an accomplished IT journalist, and a sought-after speaker and instructor at conferences worldwide. Reach Don on Twitter at @concentratedDon, or on Facebook at Facebook.com/ConcentratedDon.

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