# PowerShell User Audit Script

# Get all local usernames as strings
#! Get-LocalUser returns objects, not just strings.
#! -split $users is incorrect for objects.
$users = Get-LocalUser | Select-Object -ExpandProperty Name

foreach ($username in $users) {
    $badChar = $false

    # Check each character
    foreach ($char in $username.ToCharArray()) {
        if ($char -notmatch "[A-Za-z]") {
            $badChar = $true
            break
        }
    }

    # Check first character
    $firstChar = $username[0]
    $validFirstLetter = $firstChar -match "[A-Za-z]"

    # Flag invalid usernames
    # * Note: -ge 20 includes length 20. If you want max length 20 valid, use -gt 20.
    if ($badChar -or $username.Length -gt 20 -or -not $validFirstLetter) {
        Write-Host "The username '$username' is invalid"
    }
}