Learning the mechanics and syntax of PowerShell is not that difficult. Anyone can read the documentation for a concept like an IF statement and understand how to use it. What isn’t always apparent is the how and why, the in-between squishy bits of PowerShell. That’s one of the reasons I started this newsletter - to teach people about the PowerShell culture.

Today, I want to discuss managing logic decisions in your PowerShell scripts and functions. Let’s begin with this demonstration script file.

#requires -version 5.1
#requires -runAsAdministrator

#menu1.ps1

$menu = {
    Clear-Host
    $options = @"

    $([char]27)[4;3;92mManagement Menu$([char]27)[0m

  1 - Get uptime
  2 - Get top 20 processes
  3 - Get temp folder size
  4 - Get memory usage
  5 - Get disk usage
  6 - Quit

"@

    Write-Host "$options"
    Read-Host "  $([char]27)[1;38;5;11mSelect a menu option$([char]27)[0m [1-6]"
}

Do {
    <#
    The scriptblocks explicitly pipe to Out-Host to force proper
    formatting. Normally, you would never need to do this.
    #>
    $r = Invoke-Command -ScriptBlock $menu
    if ($r -eq 1) {
        $os = Get-CimInstance -ClassName Win32_OperatingSystem -Property LastBootUpTime
        [PSCustomObject]@{
            LastBoot = $os.LastBootUpTime
            Uptime   = New-TimeSpan -Start $os.LastBootUpTime -End (Get-Date)
        } | Out-Host
        Pause
    }
    elseif ($r -eq 2) {
        Get-Process | Sort-Object WorkingSet64 -Descending | Select-Object -First 20 | Out-Host
        Pause
    }
    elseif ($r -eq 3) {
        $stat = Get-ChildItem -Path $ENV:TEMP -File -Recurse |
        Measure-Object -Property Length -Sum
        [PSCustomObject]@{
            Path  = $ENV:TEMP
            Files = $stat.Count
            SumMB   = $stat.sum/1MB
        } | Out-Host
        Pause
    }
    elseif ($r -eq 4) {
        $os = Get-CimInstance -ClassName Win32_OperatingSystem -Property FreePhysicalMemory,TotalVisibleMemorySize
        $pctFreeMem = [math]::Round(($os.FreePhysicalMemory / $os.TotalVisibleMemorySize) * 100, 2)
        [PSCustomObject]@{
            FreeMemoryKB = $os.FreePhysicalMemory
            PctFree   = $pctFreeMem
        } | Out-Host
        Pause
    }
    elseif ($r -eq 5) {
        #Filter out Google Drive assignments
        $disks = Get-CimInstance -ClassName Win32_LogicalDisk -filter "DriveType=3 AND FileSystem='NTFS'"
        $out = foreach ($disk in $disks) {
            [PSCustomObject]@{
                Drive = $disk.DeviceID
                SizeGB = $disk.Size/1gb -as [Int]
                FreeGB = $disk.FreeSpace/1GB
                PctFree ="{0:p2}" -f ($disk.FreeSpace/$disk.Size)
            }
        }
        $out | Out-Host
        Pause
    }
    elseif ($r -eq 6) {
        #don't do anything except exit
    }
    else {
        Write-Host 'Invalid choice. Please try again.' -ForegroundColor Red
        Pause
    }

} Until ($r -eq 6)

The script presents a menu and prompts the user.