Gather info through several foreach and then export-csv at the end of script

Question

I have a script that scans all my servers in my domains and outputs to two separate CSV files - one simple and one extensive.

I write one line at the time to my csv.. This results in thousands of file-open and file-close.. I've lurked around and understand that I should first gather all the info and write it all in one sweep at the end of the script. But how do I do this with export-csv (preferably using a function)?

And is there a way I can use the same function for short and long list?

The script performs numerous tasks on each domain/server, but I've trimmed it down to this for your viewing pleasure:

$domains = "no","se","dk"

# Loop through specified forests
foreach ($domain in $domains) {

    # List all servers
    $servers = Get-QADComputer 

    # Looping through the servers
    foreach ($server in $servers) {

        # GENERATE LONGLIST #
        # Ping server
        if (Test-Connection -ComputerName $server.name -count 1 -Quiet )
        {
            $Reachable = "Yes"

            # Fetch IP address
            $ipaddress = [System.Net.Dns]::GetHostAddresses($Server.name)|select-object IPAddressToString -expandproperty IPAddressToString

            # Formatting output and export all info to CSV
            New-Object -TypeName PSObject -Property @{
                SystemName = ($server.name).ToLower()
                Reachable = $Reachable
                Domain = $server.domain
                IPAddress = $IPAddress
                } | Select-Object SystemName,Domain,IPAddress| Export-Csv -Path "longexport.csv" -append    
        } 
        else # Can't reach server
        {
            $reachable = "No"
            $IPAddress = "Unknown"

            # Formatting output and export all info to CSV
            New-Object -TypeName PSObject -Property @{
                SystemName = ($server.name).ToLower()
                Reachable = $Reachable
                Domain = $server.domain
                } | Select-Object SystemName,Domain,IPAddress| Export-Csv -Path "shortexport.csv" -append
        }
    }
}

(and let me just say that I know that I cannot do -append with export-csv, but I am using a function that let's me do this..)

Answer 1

You are exporting the same amount of properties to each file so I'm not sure I understand why one of them is considered long and one short. Anyway, I suggest the following, don't assign all computers to a variable, it can take up a lot of RAM, instead use a streaming way (one object at a time) and use foreach-object. Also, since I find no difference in the files I output to the file at the end of each domain operation (one per domain). And with another twick you could write only once to the file.

$domains = "no","se","dk"

foreach ($domain in $domains) {

    Get-QADComputer -Service $domain -SizeLimit 0 | Foreach-Object {

        $reachable = Test-Connection -ComputerName $_.Name -count 1 -Quiet

        if($reachable)
        {
            $IPAddress = [System.Net.Dns]::GetHostAddresses($_.Name)|select-object IPAddressToString -expandproperty IPAddressToString
        }
        else
        {
            $IPAddress = $null
        }


        New-Object -TypeName PSObject -Property @{
                SystemName = $_.Name.ToLower()
                Reachable = $reachable 
                Domain = $_.Domain
                IPAddress = $IPAddress
        } | Select-Object SystemName,Domain,IPAddress 

    } | Export-Csv -Path export.csv -Append  
}

Answer 2

You'll need to keep data in memory to prevent multiple file open/closes.

You can do this by adding your data to an array like this:

$myData = @()
$myData += New-Object -TypeName PSObject -Property @{
                SystemName = ($server.name).ToLower()
                Reachable = $Reachable
                Domain = $server.domain
                } | Select-Object SystemName,Domain,IPAddress

Then at the end of processing convert the array to CSV using $myData | ConvertTo-CSV | Out-File C:\Data.csv or just $myData | Export-Csv C:\Data.csv.