VBScript MapNetworkDrive Error Handling - vbscript

Question

I am attempting to write a small script in VBScript just purely for my home use, which is run prior to a scheduled backup in Macrium Reflect.
I am stuck on one seemingly small issue and that is error handling when the Network Drive is physically disconnected, i.e. the cable is not attached.
At the moment the script check to see if the Drive is already attached, if the drive is not attached then a message is displayed telling the user to connect the cable and press YES.
Now, all things being well the user would have connected the cable as asked and then pressed the YES button but I want to catch the times when YES was pressed before attaching the drive's cable.
Within the code there's an 'On Error Resume Next' which masks this eventuality, so I comment out this line & indeed I get an Error 'The Network Path Was Not Found' on line 40:
objNetwork.MapNetworkDrive strDriveLetter, strRemotePath, _
I want to use this caught error to display an alert to the user that the drive has not yet been connected, please connect and retry & KEEP RETRYING until the drive is actually connected.
My problem is I cannot seem to find where to add any error handling code to display this message.
Here's my code:
Option Explicit
Dim strDriveLetter, strRemotePath, strUser, strPassword, strProfile, strName, objNetwork, objShell, CheckDrive, AlreadyConnected, intDrive
' The section sets the variables.
strDriveLetter = "X:"
strRemotePath = "\\192.168.1.1\shared"
strUser = "user"
strPassword = "password"
strProfile = "true"
strName = "Backup Drive"
' This sections creates two objects:
' objShell and objNetwork and counts the drives
Set objShell = CreateObject("WScript.Shell")
Set objNetwork = CreateObject("WScript.Network")
Set CheckDrive = objNetwork.EnumNetworkDrives()
' This section deals with a For ... Next loop
' See how it compares the enumerated drive letters
' with strDriveLetter
On Error Resume Next
AlreadyConnected = False
For intDrive = 0 To CheckDrive.Count - 1 Step 2
If CheckDrive.Item(intDrive) =strDriveLetter _
Then AlreadyConnected = True
Next
If AlreadyConnected = False Then
Dim result
result = MsgBox("A Backup Is Now Due But The Drive Is Not Connected." & vbNewLine & vbNewLine & "Please Connect The Drive & Press YES To Continue." & vbNewLine & vbNewLine & "If You Wish To Postpone Backup Then Press NO Now.", 4 + 32, "BACKUP DRIVE NOT CONNECTED")
If result = 7 Then
WScript.Quit
Else
Call MapDRV
End If
Sub MapDRV()
Set objNetwork = WScript.CreateObject("WScript.Network")
objNetwork.MapNetworkDrive strDriveLetter, strRemotePath, _
strProfile, strUser, strPassword
Set objShell = CreateObject("Shell.Application")
objShell.NameSpace(strDriveLetter).Self.Name = strName
End Sub
WScript.Quit
The error handling code is something along these lines:
If Err.Number <> 0 Then
'error handling:
'ALERT USER HERE
Err.Clear
End If
Any help would be appreciated

Answer 1

Err Object (VBScript) reference does not give useful guide. You need to trap an error or success separate for every run-time error prone action.
Common rule (best practice): keep error handling disabled via On Error GoTo 0 and enable it only for suspected actions.
For instance, there could me more than one reason why MapNetworkDrive method could fail (server off-line, user blocked, wrong/changed password etc.):
Sub MapDRV
Dim errResult
Set objNetwork = WScript.CreateObject("WScript.Network")
errResult = ""
On Error Resume Next
objNetwork.MapNetworkDrive strDriveLetter, strRemotePath _
, strProfile, strUser, strPassword
If Err.Number = 0 Then
On Error GoTo 0
Set objShell = CreateObject("Shell.Application")
objShell.NameSpace(strDriveLetter).Self.Name = strName
Else
errResult = Err.Number & " 0x" & Hex(Err.Number) & " " & Err.Source
errResult = errResult & vbNewLine & Err.Description
On Error GoTo 0
MsgBox errResult, vbOKOnly + vbCritical, "Error occurred"
End If
End Sub
The whole script then could look as follows:
Option Explicit
On Error GoTo 0
Dim strResult: strResult = Wscript.ScriptName
Dim strDriveLetter, strRemotePath, strUser, strPassword, strProfile , strName _
, objNetwork, objShell, CheckDrive, AlreadyConnected, intDrive
' The section sets the variables.
strDriveLetter = "X:"
strRemotePath = "\\192.168.1.1\shared"
strUser = "user"
strPassword = "password"
strProfile = "true"
strName = "Backup Drive"
' This sections creates two objects:
' objShell and objNetwork and counts the drives
Set objShell = CreateObject("WScript.Shell")
Set objNetwork = CreateObject("WScript.Network")
' This section deals with a For ... Next loop
' See how it compares the enumerated drive letters with strDriveLetter
Dim result, toShare
AlreadyConnected = False
Do While AlreadyConnected = False
strResult = strResult & vbNewLine & "--- new check"
AlreadyConnected = False
Set CheckDrive = objNetwork.EnumNetworkDrives()
For intDrive = 0 To CheckDrive.Count - 1 Step 2
If CheckDrive.Item(intDrive) = strDriveLetter Then
AlreadyConnected = True
toShare = CheckDrive.Item(intDrive + 1)
End If
strResult = strResult & vbNewLine & CheckDrive.Item(intDrive)
strResult = strResult & vbTab & CheckDrive.Item(intDrive + 1)
Next
If AlreadyConnected Then Exit Do
result = MsgBox("A Backup Is Now Due But The Drive Is Not Connected." _
& vbNewLine & vbNewLine & "If you wish to ..." _
& vbNewLine & vbTab & "... postpone backup then press ABORT." _
& vbNewLine & vbTab & "... backup to " & strRemotePath & " then press RETRY." _
& vbNewLine & "Otherwise, please connect the drive & press IGNORE to continue." _
, vbAbortRetryIgnore + vbQuestion, "BACKUP DRIVE NOT CONNECTED")
Select Case result
Case vbAbort
Call scriptQuit
Case vbRetry
Call MapDRV
Case Else
' The Case Else clause is not required
End Select
Loop
strResult = strResult & vbNewLine & "copy here to " & toShare
Sub MapDRV
' no need to redefine: WshNetwork Object is already defined
' Set objNetwork = WScript.CreateObject("WScript.Network")
Dim errResult
On Error Resume Next
objNetwork.MapNetworkDrive strDriveLetter, strRemotePath _
, strProfile, strUser, strPassword
If Err.Number = 0 Then
On Error GoTo 0
Set objShell = CreateObject("Shell.Application")
objShell.NameSpace(strDriveLetter).Self.Name = strName
Else
errResult = Err.Number & " 0x" & Hex(Err.Number) & " " & Err.Source
errResult = errResult & vbNewLine & Err.Description
On Error GoTo 0
MsgBox errResult, vbOKOnly + vbCritical, "Error occurred"
strResult = strResult & vbNewLine & vbNewLine & errResult
End If
End Sub
Call scriptQuit
Sub scriptQuit
Wscript.Echo strResult
Wscript.Quit
End Sub
Please note that strResult variable is there merely for debugging purposes to see next output:
==> cscript D:\VB_scripts\SO\37776762.vbs
37776762.vbs
--- new check
Y: \\S-PC\VB_scripts_help
-2147024843 0x80070035 WSHNetwork.MapNetworkDrive
The network path was not found.
--- new check
Y: \\S-PC\VB_scripts_help
--- new check
Y: \\S-PC\VB_scripts_help
X: \\S-PC\test
copy here to \\S-PC\test
==>
Above output corresponds to next actions:
run script
1st --- new check found Y: mapped disk; then invoked Retry action failed (network path was not found);
2nd --- new check found Y: mapped disk again; then mapped disk X: manually and then invoked Ignore action;
3rd --- new check found Y: and X: mapped disks;
Do While loop exited and script continues to next action.
For completeness, following output shows invoked Abort action:
==> net use x: /delete
x: was deleted successfully.
==> cscript D:\VB_scripts\SO\37776762.vbs
37776762.vbs
--- new check
Y: \\S-PC\VB_scripts_help
==>