Powershell Global Variable usage as parameter to argument - powershell

Question

$global:af_fp = "C:\Path\to\folder\"
Function function-name {
do things …
$global:af_fp = $global:af_fp + $variableFromDo_things + "_AF.csv"
}
function-name | ConvertTo-CSV -NoTypeInformation | Add-Content -Path $($af_fp)
Above is the generalized (and abbreviated) script contents for a powershell script.
Every time I run the script in this way, I get the following error:
Add-Content : Could not find a part of the path 'C:\Users\timeuser\Documents\'.
At C:\Users\timeuser\Documents\get_software.ps1:231 char:51
+ ... ware | ConvertTo-CSV -NoTypeInformation | Add-Content -Path $($af_fp)
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : ObjectNotFound: (C:\Users\timeuser\Documents\:String) [Add-Content], DirectoryNotFoundException
+ FullyQualifiedErrorId : GetContentWriterDirectoryNotFoundError,Microsoft.PowerShell.Commands.AddContentCommand
When I run
Get-Variable -Scope global
after running the script and seeing the error, the variable af_fp contains exactly the information I am seeking for the file name, however, the error shows the variable contents ending in ':String'.
To confuse me even more, if I comment out the lines containing '$global:...' and re-run the same script, IT ACTUALL RUNS AND SAVES THE FILE USING THE LINE
function-name | ConvertTo-CSV -NoTypeInformation | Add-Content -Path $($af_fp)
AS INTENDED. Of course, I had to run the script and watch it error first, then re-run the script with the global variable declaration and update commented out for it to actually work. I want to run the script ONCE and still get the same results.
FYI, I am a complete noob to powershell, but very familiar with the concept of variable scope.....but why is this global not working when initially created and updated, but then work the second time around, when, as far as I can tell, the CONTENT AND SCOPE of the global remains the same...…. any assistance to finding a solution to this small issue would be greatly appreciated; I have tried sooooo may different methods from inquiries through here and on Google...…..
EDIT: not sure why this will matter, because the script ran before as intended when I explicitly typed the parameter for -Path as 'C:\path\to\file'. The ONLY CHANGES MADE to the original, working script (below) were my inclusion of the global variable declaration, the update to the contents of the global variable (near the end of the function), and the attempt to use the global variable as the parameter to -Path, that is why I omitted the script:
'''
$global:af_fp = "C:\Users\timeuser\Documents\"
Function Get-Software {
[OutputType('System.Software.Inventory')]
[Cmdletbinding()]
Param(
[Parameter(ValueFromPipeline = $True, ValueFromPipelineByPropertyName = $True)]
[String[]]$Computername = $env:COMPUTERNAME
)
Begin {
}
Process {
ForEach ($Computer in $Computername) {
If (Test-Connection -ComputerName $Computer -Count 1 -Quiet) {
$Paths = #("SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Uninstall", "SOFTWARE\\Wow6432node\\Microsoft\\Windows\\CurrentVersion\\Uninstall")
ForEach ($Path in $Paths) {
Write-Verbose "Checking Path: $Path"
# Create an instance of the Registry Object and open the HKLM base key
Try {
$reg = [microsoft.win32.registrykey]::OpenRemoteBaseKey('LocalMachine', $Computer, 'Registry64')
}
Catch {
Write-Error $_
Continue
}
# Drill down into the Uninstall key using the OpenSubKey Method
Try {
$regkey = $reg.OpenSubKey($Path)
# Retrieve an array of string that contain all the subkey names
$subkeys = $regkey.GetSubKeyNames()
# Open each Subkey and use GetValue Method to return the required values for each
ForEach ($key in $subkeys) {
Write-Verbose "Key: $Key"
$thisKey = $Path + "\\" + $key
Try {
$thisSubKey = $reg.OpenSubKey($thisKey)
# Prevent Objects with empty DisplayName
$DisplayName = $thisSubKey.getValue("DisplayName")
If ($DisplayName -AND $DisplayName -notmatch '^Update for|rollup|^Security Update|^Service Pack|^HotFix') {
$Date = $thisSubKey.GetValue('InstallDate')
If ($Date) {
Try {
$Date = [datetime]::ParseExact($Date, 'yyyyMMdd', $Null)
}
Catch {
Write-Warning "$($Computer): $_ <$($Date)>"
$Date = $Null
}
}
# Create New Object with empty Properties
$Publisher = Try {
$thisSubKey.GetValue('Publisher').Trim()
}
Catch {
$thisSubKey.GetValue('Publisher')
}
$Version = Try {
#Some weirdness with trailing [char]0 on some strings
$thisSubKey.GetValue('DisplayVersion').TrimEnd(([char[]](32, 0)))
}
Catch {
$thisSubKey.GetValue('DisplayVersion')
}
$UninstallString = Try {
$thisSubKey.GetValue('UninstallString').Trim()
}
Catch {
$thisSubKey.GetValue('UninstallString')
}
$InstallLocation = Try {
$thisSubKey.GetValue('InstallLocation').Trim()
}
Catch {
$thisSubKey.GetValue('InstallLocation')
}
$InstallSource = Try {
$thisSubKey.GetValue('InstallSource').Trim()
}
Catch {
$thisSubKey.GetValue('InstallSource')
}
$HelpLink = Try {
$thisSubKey.GetValue('HelpLink').Trim()
}
Catch {
$thisSubKey.GetValue('HelpLink')
}
$Object = [pscustomobject]#{
#Potential Candidate for AssetID in the TIME system
AssetID = $Computer
#String that contains word or word combinations for the product field of CPE WFN; may also contain the valid values necessary for update, edition, language, sw_edition, target_hw/sw fields as well.
cpeprodinfo = $DisplayName
cpeversion = $Version
InstallDate = $Date
cpevendor = $Publisher
UninstallString = $UninstallString
InstallLocation = $InstallLocation
InstallSource = $InstallSource
HelpLink = $thisSubKey.GetValue('HelpLink')
EstimatedSizeMB = [decimal]([math]::Round(($thisSubKey.GetValue('EstimatedSize') * 1024) / 1MB, 2))
}
$Object.pstypenames.insert(0, 'System.Software.Inventory')
Write-Output $Object
}
}
Catch {
Write-Warning "$Key : $_"
}
}
}
Catch { }
$reg.Close()
}
}
Else {
Write-Error "$($Computer): unable to reach remote system!"
}
$global:af_fp = $global:af_fp + $Computer + "_AF.csv"
}
}
}
Get-Software | ConvertTo-CSV -NoTypeInformation | Add-Content -Path $($af_fp)
'''
IGNORE FORMATTING PLEASE- HAD TROUBLE MAKING INDENTS CORRECTLY FROM COPY-PASTE AND RESTRICTIONS ON SITE FOR CODE BLOCKS.....
NOTE: the ONLY changes I made, that I am asking about, are the global declaration, the global variable update in the function, and the attempt to use the global variable for the -Path parameter....script otherwise runs and will even run WITH THE LAST LINE AS IS if I ran it and errored the first time.....not sure how the addition script will help in any way, shape, or form!

Answer 1

With a little effort, Nasir's solution worked! HOWEVER, I ran across a sample file that had a way of adding to a parameter that inspired me to make a change to my ORIGINAL, that also worked: remove global variable from script entirely and add this code the very end:
$file_suffix = '_AF.csv'
Get-Software | ConvertTo-CSV -NoTypeInformation | Add-Content -Path $env:COMPUTERNAME$file_suffix
In this way, I was able to accomplish exactly what I was setting out to do! Thanks Nasir for your response as well! I was able to also make that work as intended!

Answer 2

Global variables are generally frowned upon, since they often lead to poor scripts, with hard to debug issues.
It seems like your function returns some stuff, which you need to write to a file, the name of which is also generated by the same function. You can try something like this:
function function-name {
param($PathPrefix)
#do things
[pscustomobject]#{"DoThings_data" = $somevariablefromDoThings; "Filename" = "$($PathPrefix)$($variableFromDo_Things)_AF.csv"}
}
function-name -PathPrefix "C:\Path\to\folder\" | Foreach-Object { $_.DoThings_data | Export-Csv -Path $_.Filename -NoTypeInformation }
Or just have your function write the CSV data out and then return the data if you need to further process it outside the function.
Edit: this is just me extrapolating from partial code you have provided. To Lee_Dailey's point, yes, please provide more details.