VBScript Tutorial

Xah Lee, 2009-06-30

VB is not case sensitive. Set objWMIService = GetObject("winmgmts:") is the same as set objwmiservice = GETOBJECT("winmgmts:") However, strings are of course case sensitive as usual.

' report free disk space

Const CONVERSION_FACTOR = 1048576
Set objWMIService = GetObject("winmgmts:")
Set objLogicalDisk = objWMIService.Get("Win32_LogicalDisk.DeviceID='c:'")
FreeMegaBytes = objLogicalDisk.FreeSpace / CONVERSION_FACTOR
Wscript.Echo Int(FreeMegaBytes)

In VB, a line ending char means end of a statement. To break a long line but not terminate the statement, use “_” as the last char in a line.

Strings

To join strings, use “&”.

' example of getting folder content and file name

Set FSO = CreateObject("Scripting.FileSystemObject")
Set Folder = FSO.GetFolder("C:\Windows")
Set FileList = Folder.Files
For Each File in FileList
    Wscript.Echo File.Name & ", " & File.Size & ", " & File.DateLastModified
Next

' string manipulations

xx = "test 123"
Wscript.Echo len(xx) ' num of chars

Wscript.Echo left(xx, 3) ' get parts of string of 3 chars, starting from left
Wscript.Echo right(xx, 3) ' starting from right

Wscript.Echo mid(xx, 3, 2) ' get parts of string, starting from right

Space(9) ' generates 9 space chars 
Trim(" some ") ' remove leading and ending spaces 
LTrim(" abc ") ' remove spaces from left
RTrim(" def ") ' remove spaces from left

InStr(" something in water", "in") ' find the position of a substr

' lcase() ucase()

to format numbers, use e.g. “FormatNumber(3.142,0)”.

Loops

' example of using loop
Const ForReading = 1
Set objFSO = CreateObject("Scripting.FileSystemObject")
Set objTextFile = objFSO.OpenTextFile _
    ("c:/Users/xah/web/visual_basic/basics.html", ForReading)
Do Until objTextFile.AtEndOfStream
    strNextLine = objTextFile.Readline
    Wscript.Echo strNextLine
Loop

Reading a File

Function

' example of defining a function

Function myFunc(ByVal xx)
myFunc = (xx * (9/5)) + 32
End Function

xx = 20
yy = myFunc(xx)
wscript.Echo yy

Variable needs not be declared. But for writing large scripts, you can force them to needs to be declared. To force, use “Option Explicit”, then for each var, use “Dim”.

' example of forcing declaration for variables

Option Explicit
Dim xx
Dim yy

xx = 11
yy = ff(xx)
Wscript.Echo yy

Function ff(ByVal xx)
        ff = (xx * (9/5)) + 32
End Function

Constants

To declare a var never changes, use “Const”.

Const MY_LOVE = "Jenny"
wscript.echo MY_LOVE

VBS has some built-in constants. e.g.

ConfirmDelete = MsgBox ("Are you sure??", _
 VbYesNo OR VBDefaultButton2, "Delete all files")
If ConfirmDelete = VbNo then
 Wscript.Quit
End If

the following semes to be some common constant: vbcrlf, vbtab.

' example of extracting date parts

Wscript.Echo Now
Wscript.Echo "Year: " & DatePart("yyyy" , Now)
Wscript.Echo "Quarter: " & DatePart("q", Now)
Wscript.Echo "Month: " & DatePart("m" , Now)
Wscript.Echo "Day of Year: " & DatePart("y" , Now)
Wscript.Echo "Day: " & DatePart("d" , Now)
Wscript.Echo "Weekday: " & DatePart("w" , Now)
Wscript.Echo "Week of Year: " & DatePart("ww" , Now)
Wscript.Echo "Hour: " & DatePart("h", Now)
Wscript.Echo "Minute: " & DatePart("n" , Now)
Wscript.Echo "Seconds: " & DatePart("s" , Now)