Skipping computers with error - vbscript

Question

I'm having an issue with a VBScript that looks for printers on computers from a list on an Excel sheet and then finds them through WMI. It matches them through the IP address name and then writes a batch file that I can install them from. My issue is that when I have a computer that is turned off I get a 462 error which is then cleared but then the printers for the previous computer are written again. I'm quite new at this so I'm not sure if I'm just missing something really basic here.
Batch = "printerOutput.txt"
Const ForWriting = 2 'Set to 8 for appending data
Set objFSO = CreateObject("Scripting.FileSystemObject")
Set objFile = objFSO.OpenTextFile(Batch, ForWriting)
On Error Resume Next
Dim printerDictionary 'Create Printer dictionary of names and IP addresses
Set printerDictionary = CreateObject("Scripting.Dictionary")
printerDictionary.Add "Printer","xxx.xxx.xxx.xxx"
Set objExcel_1 = CreateObject("Excel.Application")
' Statement will open the Excel Workbook needed.
Set objWorkbook = objExcel_1.Workbooks.Open _
("x\p.xls")
If Err.Number <> 0 Then
MsgBox "File not Found"
Wscript.Quit
End If
'Checks for errors
f = 1 'Sets variable that will loop through Excel column
Do
' Msgbox f,, "Begining of Do Loop"
strComputer = objExcel_1.Cells(f, 1).Value
Set objWMIService = GetObject("winmgmts:\\" & strComputer & "\root\cimv2")
Set colPrinters = objWMIService.ExecQuery("Select * From Win32_Printer")
For Each objPrinter in colPrinters 'For ever objPrinter found in the computers WMIService
If Err.Number = 0 Then
objFile.WriteLine Err.Number
If InStr(ObjPrinter.PortName,".") = 4 then 'If the printers IP port name is written like 128.xxx.xxx.xxx
'MsgBox ObjPrinter.Name & " " & ObjPrinter.PortName,, "IfStatement"
PrtDict ObjPrinter.PortName, StrComputer
ElseIf InStr(ObjPrinter.PortName,"_") = 3 Then 'If the printers IP port name is written like IP_128.xxx.xxx.xxx
cleanIP = GetIPAddress(objPrinter.PortName) 'Clean IP
PrtDict cleanIP, StrComputer
End If
Else
objFile.WriteLine "REM " & strComputer & " - Error: " & err.number
Err.Clear
End If
Next
f = f + 1
Loop Until objExcel_1.Cells(f, 1).Value = ""
objExcel_1.ActiveWorkbook.Close
ObjExcel_1.Quit
Function PrtDict(PrtMn, CMP) 'Loops through the dictionary to find a match from the IP address found
For Each x in printerDictionary
'MsgBox PrtMn & "=" & printerDictionary.Item(x),,"InPtrDict"
If printerDictionary.Item(x) = PrtMn Then
objFile.WriteLine "psexec -u \%1 -p %2 " & CMP & " path\" & x & ".bat"
End If
Next
End Function
'100
Function GetIPAddress(Address) 'For cleaning up IP address with names like IP_128.xxx.xxx.xxx
IPtext = InStr(Address,"_")
IPaddress = len(Address) - IPtext
GetIPAddress = Right(Address,IPaddress)
End Function

Answer 1

What happens is this:
On Error Resume Next
This enables error-handling (or rather error suppression) for the rest of the script, since it's never disabled.
Set objWMIService = GetObject("winmgmts:\\" & strComputer & "\root\cimv2")
This command fails, because strComputer is not reachable. Because of the error the variable Err is set and objWMIService retains its previous value.
Set colPrinters = objWMIService.ExecQuery("Select * From Win32_Printer")
This command succeeds and re-reads the printer list from the previous computer, because objWMIService still refers to that computer.
For Each objPrinter in colPrinters
The script enters the loop, because colPrinters got populated with the printers from the previous computer (again), …
If Err.Number = 0 Then ... Else ... End If
… but because Err is still set, the script goes into the Else branch, where the error is reported and cleared:
objFile.WriteLine "REM " & strComputer & " - Error: " & err.number
Err.Clear
Then the script goes into the next iteration of the loop. Err is now cleared, so the rest of the printers in colPrinters is being processed normally.
Global On Error Resume Next is the root of all evil. Don't do this. EVER.
If you absolutely must use On Error Resume Next, enable error-handling locally, put some actual error handling code in place, and disable error-handling right afterwards. In your case one might implement it like this:
...
Do
strComputer = objExcel_1.Cells(f, 1).Value
On Error Resume Next
Set objWMIService = GetObject("winmgmts:\\" & strComputer & "\root\cimv2")
If Err Then
objFile.WriteLine "REM " & strComputer & " - Error: " & err.number
Set objWMIService = Nothing
End If
On Error Goto 0
If Not objWMIService Is Nothing Then
Set colPrinters = objWMIService.ExecQuery("Select * From Win32_Printer")
For Each objPrinter in colPrinters
...
Next
f = f + 1
End If
Loop Until objExcel_1.Cells(f, 1).Value = ""
...