Write all running processes to a text file in PowerShell - powershell

Question

The purpose of this code is to get a list of all used executables from a specific folder. After a month we will delete any exe's not on this list.
I currently get the correct results using this:
while ($true) {
foreach ($process in Get-Process | where {$_.Path -imatch 'ksv'} | select -Unique) {
$dir = $process | Get-ChildItem;
New-Object -TypeName PSObject -Property #{
'Path' = $process.Path;
} | Out-String | Add-Content -LiteralPath Z:\processList.txt
}
Get-Content Z:\processList.txt | sort | Get-Unique > Z:\uniqueprocesslist.txt
}
I'm going to get rid of the while loop as this will be eventually running as a service.
The problem with this is that it creates a huge list in processlist.txt that I would like to eliminate to save space.
I tried to come up with a better solution that scans the text file to see if the path is written already before adding the new process path. I am not sure what I am doing wrong but nothing is ever written to the text file
while ($true) {
foreach ($process in Get-Process | where {$_.Path -imatch 'ksv'} | select -Unique) {
$dir = $process | Get-ChildItem;
$progPath = New-Object -TypeName PSObject -Property #{
'Path' = $process.Path
}
$file = Get-Content "Z:\processList.txt"
$containsLine = $file | %{$_ -match $progPath}
if ($containsLine -contains $false) {
Add-Content -LiteralPath Z:\processList.txt
}
}
}

Answer 1

If I understand your question correctly you want to build a "recently used" list of executables in a specific directory in a file, and update that (unique) list with each run of your script.
Something like this should do that:
$listfile = 'Z:\processlist.txt'
# Build a dictionary from known paths, so that we can check for already known
# paths with an index lookup instead of a linear search over an array.
$list = #{}
if (Test-Path -LiteralPath $listfile) {
Get-Content $listfile | ForEach-Object {
$list[$_] = $true
}
}
# List processes, expand their path, then check if the path contains the
# string "ksv" and isn't already known. Append the results to the list file.
Get-Process |
Select-Object -Expand Path |
Sort-Object -Unique |
Where-Object {$_ -like '*ksv*' -and -not $list.ContainsKey($_)} |
Add-Content $listfile
Hashtable lookup and wildcard match are used for performance reasons, because they're significantly faster than linear searches in arrays and regular expression matches.

Answer 2

while ($true) {
$file = Get-Content "Z:\processList.txt"
$KSVPaths = Get-Process |
Where-Object {$_.Path -imatch 'ksv'} |
Select-Object -ExpandProperty Path |
Select-Object -Unique
ForEach ($KSVPath in $KSVPaths) {
if ($KSVPath -notin $file) {
Add-Content -Path $file -Value $KSVPath
}
}
}