After reading this post from Jeffrey Hicks about  how he found an old script and describes how he would have solved the same task today, I decided to do the same thing with one of my older scripts.

When I had just started learning PowerShell I had a need to map out free space on a large collection of servers, and not wanting to do this manually I of course created a script to help me out. I remember I was immensely proud of my self when I was finished with it, having created a re-usable script with help text and all. Looking back at it now, I see that I manage to break almost all best-practices regarding how to write PowerShell code, but we all have to start some place right?

Here is the original script I created back in 2008:

# ============================ #
# Disk Space Info (dsi) - V1.1 # 
#                              #
# 2008 - Øyvind Kallstad       #
# ============================ #


$wmiQuery = "SELECT SystemName,Caption,VolumeName,Size,Freespace FROM win32_logicaldisk WHERE DriveType=3"
$sortBy = "% Free"
$help = @"

USAGE:
    dsi.ps1 [-? | -help | -list [list.txt] | -remote [machine name] | 
         -sortname | -sort%]

Options:
    [no option]  Lists disk information for local machine
    -list        Lists disk information for all servers in the textfile
    -remote      Lists disk information for the remote machine specified
    -sortname    Sorts the output by the SystemName column
    -sort%       Sorts the output by the % Free column
    -help        This help message
    -?           This help message

"@

if ($args) {
  switch ($args) {
    "-help" {$help}
    "-?" {$help}
    "-list" {$wmi = gwmi -ErrorAction silentlycontinue -ErrorVariable err -query $wmiquery -computer (gc $args[1])}
    "-remote" {$wmi = gwmi -ErrorAction silentlycontinue -ErrorVariable err -query $wmiQuery -computer $args[1]}
    "-sortName" {$sortBy = "SystemName"}
    "-sort%" {$sortBy = "% Free"}
  }

}ELSE{

  $wmi = gwmi -ErrorAction silentlycontinue -ErrorVariable err -query $wmiQuery

}

$wmi | Select-Object SystemName,Caption,VolumeName,@{Name="Size(GB)"; Expression={"{0:N2}" -f ($_.Size/1GB)}},@{Name="Freespace(GB)"; Expression={"{0:N2}" -f ($_.Freespace/1GB)}}, @{n="% Free";e={"{0:P2}" -f ([long]$_.FreeSpace/[long]$_.Size)}} | sort $sortBy | format-table -autosize

if (!$args) {

if ($err) {write-host "There were " $err.count "error(s)"}

}

Looking at it now, I see that I’m almost doing something right, by returning a WMI object, just such a shame I’m ruining it by piping it through Format-Table at the end. I remember I was especially proud of the custom expressions in Select-Object (having googled an example).

So how would I have created this today? Something like this:

function Get-DiskInfo {
    [CmdletBinding()]
    param (
        [Parameter(ValueFromPipeline = $true, ValueFromPipelinebyPropertyName = $true)]
        [string[]] $ComputerName = $env:COMPUTERNAME
    )

    Process {
        foreach ($computer in $ComputerName) {
            try {
                Write-Output (Get-WmiObject -Query 'SELECT SystemName,Caption,VolumeName,Size,Freespace FROM Win32_LogicalDisk WHERE DriveType=3' -ComputerName $ComputerName | Select-Object SystemName,Caption,VolumeName,@{Name="Size(GB)"; Expression={"{0:N2}" -f ($_.Size/1GB)}},@{Name='Freespace(GB)'; Expression={"{0:N2}" -f ($_.Freespace/1GB)}}, @{n='% Free';e={"{0:P2}" -f ([long]$_.FreeSpace/[long]$_.Size)}})
            }
            catch {
                Write-Warning $_.Exception.Message
            }
        }
    }
}

The cool thing about this is that except for the ComputerName parameter, all my “old” parameters are handled by using Get-Help, Get-Content, Sort-Object and Format-Table. All this is possible because I’m outputting an object and handling the pipeline properly. I haven’t implemented comment based help in this example, but doing so would of course make Get-Help even more usable.