Logon time script | how to overwrite last logon Powershell - powershell

Question

I have a script configured on my GPO that tracks a certain user group their logon times exported to a csv.
Now i've gotten the question, to make it show only the LAST logon time.
At the moment it just writes down every single logon time, but they would like only the last one.
Is there a way to make it overwrite it instead?
Let's say user1 logs in 3 times, i would like to only show it the last one, and that for every user in this group.
The script i have at the moment is a very simple one:
"logon {0} {1} {2:DD-MM-YYYY HH:mm:ss}" -f (Get-Date),$env:username, $env:computername >> \\server\folder\file.csv
Much appreciated if somebody could tell me if it is possible!

Answer 1

First of all, you are appending a line to a text file which is not a CSV file because the values aren't separated by a delimiter character.
Then also, you use the wrong order of values for the -f Format operator: While the template string clearly has the date as the last placeholder in {2:DD-MM-YYYY HH:mm:ss}, you feed that as the first value..
Please also notice that a date format is Case-Sensitive, so you need to change DD-MM-YYYY HH:mm:ss into dd-MM-yyyy HH:mm:ss
I'd advise to change the script you now have to something like:
[PsCustomObject]#{
User = $env:USERNAME
Computer = $env:COMPUTERNAME
LogonDate = '{0:dd-MM-yyyy HH:mm:ss}' -f (Get-Date)
} | Export-Csv -Path '\\server\folder\UserLogon.csv' -NoTypeInformation -Append
Then, when it comes down to reading that file back and preserving only the latest logons, you can do
$data = Import-Csv -Path '\\server\folder\UserLogon.csv' | Group-Object User | ForEach-Object {
$_.Group | Sort-Object {[datetime]::ParseExact($_.LogonDate, 'dd-MM-yyyy HH:mm:ss', $null)} |
Select-Object -Last 1
}
# output on screen
$data
# overwrite the CSV file to keep only the last logons
$data | Export-Csv -Path '\\server\folder\UserLogon.csv' -NoTypeInformation

Answer 2

I think one arrow > should be to overwrite a file.
There is also a command called Out-File with parameters to overwrite a file.
More information on the PowerShell documentation,
https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.utility/out-file?view=powershell-7.1

Answer 3

I must reiterate what others have commented about this not being the best approach to this problem however, given the output file that you have, you could process it like this to get the last record for a given user:
$last = #{} ; Get-Content \\server\folder\file.csv |% { $token = $_ -split ' ' ; $last.$($token[3]) = $_ }
$last
It creates a hash keyed with the username and updates it with the last line from the file. You can also access $last.foo to get the last entry for user foo.
I'd also note that your CSV isn't a CSV which makes it more difficult to process. You'd be better to use Export-CSV or at least putting the commas in. Also, while still not the best approach, you could create a file per user which you could just overwrite each time they login, thus:
new-object PSObject -Property #{ 'date'= (Get-Date); 'username'= $env:username; 'Computer' = $env:computername } | Export-CSV -Path "\\server\folder\$($env:username).csv" -NoTypeInformation
You could import everything for processing by doing:
gci \\server\folder\*.csv |% { import-csv $_ }