Why does PowerShell not want to save my file as a CSV - excel

Question

$Path = 'D:/ETL_Data/TwitchTVData.xlsx'
$csvPath = 'D:/ETL_Data/TwitchTVData2.csv'
# Open the Excel document and pull in the 'Sheet1' worksheet
$Excel = New-Object -Com Excel.Application
$Workbook = $Excel.Workbooks.Open($Path)
$page = 'Sheet1'
$ws = $Workbook.Worksheets | Where-Object {$_.Name -eq $page}
$Excel.Visible = $true
$Excel.DisplayAlerts = $false
# Set variables for the worksheet cells, and for navigation
$cells = $ws.Cells
$row = 1
$col = 4
$formula = #"
=NOW()
"#
# Add the formula to the worksheet
$range = $ws.UsedRange
$rows = $range.Rows.Count
for ($i=0; $i -ne $rows; $i++) {
$cells.Item($row, $col) = $formula
$row++
}
$ws.Columns.Item("A:D").EntireColumn.AutoFit() | Out-Null
$ws.Columns.Range("D1:D$rows").NumberFormat = "yyyy-MM-dd hh:mm"
$Excel.ActiveWorkbook.SaveAs($csvPath)
$Excel.Quit()
[System.GC]::Collect()
[System.GC]::WaitForPendingFinalizers()
[System.Runtime.Interopservices.Marshal]::ReleaseComObject($excel)
https://www.experts-exchange.com/questions/27996530/How-to-convert-and-xlsx-spreadsheet-into-CSV.html#answer38780402-20
I was attempting to follow that, but for some reason for me the SaveAs() doesn't work. It gives me an error
cannot access the file 'D://ETL_Data/E567DF00
What do I have to do to get this to save over to CSV?
Edit:
Exact error without the fileformat parameter 6 as suggested in the comments:
Microsoft Excel cannot access the file 'D:\//ETL_Data/8011FF00'. There are
several possible reasons:
o The file name or path does not exist.
o The file is being used by another program.
o The workbook you are trying to save has the same name as a currently open
workbook.
At D:\PS_Scripts\twitchExcelAddSnapShot.ps1:32 char:1
+ $Excel.ActiveWorkbook.SaveAs($csvPath)
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : OperationStopped: (:) [], COMException
+ FullyQualifiedErrorId : System.Runtime.InteropServices.COMException
Exact error with fileformat parameter 6:
The file could not be accessed. Try one of the following:
o Make sure the specified folder exists.
o Make sure the folder that contains the file is not read-only.
o Make sure the file name does not contain any of the following characters:
< > ? [ ] : | or *
o Make sure the file/path name doesn't contain more than 218 characters.
At D:\PS_Scripts\twitchExcelAddSnapShot.ps1:32 char:1
+ $Excel.ActiveWorkbook.SaveAs($csvPath,6)
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : OperationStopped: (:) [], COMException
+ FullyQualifiedErrorId : System.Runtime.InteropServices.COMException

Answer 1

While PowerShell is pretty forgiving when it comes to path separators, COM+ servers (like Excel.Application) might not be.
Change the $csvPath variable value to use \ instead of /:
$csvPath = 'D:\ETL_Data\TwitchTVData2.csv'

Answer 2

To complement Mathias R. Jessen's helpful answer with background information:
It seems that Excel's application-specific behavior is the cause of your problem, unrelated to the underlying foundational subsystems or APIs used.
(Excel's automation API happens to be a COM server.)
I'm unclear on why Excel acts this way - it also does so in interactive use, though you could argue that at least in programmatic use it should allow / too.
To offer generalized advice:
On Windows, to be safe, use \, especially when dealing with application-level automation APIs, though at the level of system APIs / should work as well - see below.
In cross-platform code, use / (but watch out for the exceptions above; [System.IO.Path]::DirectorySeparatorChar reports the platform-appropriate (primary) character).
Though rarely used, Windows at the API level allows interchangeable use of \ and / (which apparently goes back to the DOS 2.0 days), when support for directories was introduced), and that is also reflected in higher-level subsystems, as the following examples demonstrate.
# PS: OK
# Should output c:\windows\win.ini
(Get-Item c:/windows/win.ini).FullName
# .NET: OK
# Should return the 1st child dir.'s path.
# Note that the child directory names will be appended with "\", not "/"
[System.IO.Directory]::GetDirectories('c:/windows/system32') | Select-Object -First 1
# COM (see Excel exception below): OK
# Should return $true
(New-Object -ComObject Scripting.FileSystemObject).FileExists('c:/windows/win.ini')
# Windows API: OK
# Should return a value such as 32.
(Add-Type -PassThru WinApiHelper -MemberDefinition '[DllImport("kernel32.dll")] public static extern uint GetFileAttributes(string lpFileName);')::GetFileAttributes('c:/windows/win.ini')
# cmd.exe: INCONSISTENTLY SUPPORTED
# Note: *quoting matters* here, so that tokens with / aren't mistaken for options.
# attrib: works
cmd /c 'attrib "c:/windows/win.ini"'
# dir: works with DIRECTORIES, but fails with FILES
cmd /c 'dir /b "c:/windows/system32"' # OK
cmd /c 'dir /b "c:/windows/win.ini"' # FAILS with 'File not found'
cmd /c 'dir /b "c:/windows\win.ini"' # Using \ for the FILE component (only) works.
Here's a minimal example that demonstrates Excel's problem with /:
# Create temporary dir.
$null = mkdir c:\tmp -force
$xl=New-Object -Com Excel.Application
$wb = $xl.Workbooks.Add()
# OK - with "\"
$wb.SaveAs('c:\tmp\t1.xlsx')
# FAILS - with "/":
# "Microsoft Excel cannot access the file 'C:\//tmp/F5D39400'"
$wb.SaveAs('c:/tmp/t2.xlsx')
$xl.Quit()
# Clean up temp. dir.