Get-LoggedOn.ps1

## /u/omers - reddit /r/PowerShell

<#
    .SYNOPSIS
        List the users that are logged on to a computer or check for a specific user.

    .DESCRIPTION
        This function uses the CMD application query.exe to list the users on the local system, a remote system, or a group of remote systems. It converts the query.exe objects.

        When using the -CheckFor parameter you are able to check for a specific user and the function will return true/false.

    .PARAMETER  Name
        The computer name to be queried.

    .PARAMETER  CheckFor
        A specific username to look for.

    .EXAMPLE
        PS C:\> Get-LoggedOn

        ComputerName Username SessionState SessionType
        ------------ -------- ------------ -----------
        JDOE-Laptop  JohnD    Active       console

        - Description -
        In this example without parameters the command returns locally logged in users.

    .EXAMPLE
        PS C:\> Get-LoggedOn -Name TERMSERV01

        ComputerName Username  SessionState SessionType
        ------------ --------  ------------ -----------
        TERMSERV01   JaneD     Disconnected
        TERMSERV01   JamesR    Disconnected
        TERMSERV01   ToddQ     Active        rdp-tcp
        TERMSERV01   BrianZ    Disconnected

        - Description -
        When a computer name is specific you will se a list of users that are connected to that machine.

    .EXAMPLE
        PS C:\> Get-LoggedOn -Name TERMSERV01 -CheckFor JaneD

        ComputerName IsLoggedOn
        ------------ ----------
        TERMSERV01         True

        - Description -
        CheckFor allows you to check for a specific user on a remote machine.

    .EXAMPLE
        PS C:\> Get-LoggedOn -Name NONEXISTENT -CheckFor JaneD

        ComputerName IsLoggedOn
        ------------ ----------
        NONEXISTENT  [ERROR]

        - Description -
        If query.exe cannot access the compute for any reason it will return [ERROR]

    .EXAMPLE
        PS C:\> Get-ADComputer -Filter 'name -like "TERMSERV*"' | Get-LoggedOn -CheckFor JaneD

        ComputerName   IsLoggedOn
        ------------   ----------
        TERMSERV01          False
        TERMSERV02           True
        TERMSERV03          False

        - Description -
        You can pipe a list of computers to check multiple machines at the same time.

    .INPUTS
        System.String

    .OUTPUTS
        PSCustomObject

#>

function Get-LoggedOn
{
    [CmdletBinding()]
    [Alias('loggedon')]
    [OutputType([PSCustomObject])]

    Param
    (
        # Computer name to check
        [Parameter(ValueFromPipeline = $true,
                   ValueFromPipelineByPropertyName = $true,
                   Position = 0)]
        [Alias('ComputerName')]
        [string]
        $Name = $env:COMPUTERNAME,

        # Username to check against logged in users.
        [parameter()]
        [string]
        $CheckFor
    )

    Process
    {
        function QueryToObject ($Computer)
        {
            $Output = @()
            $Users = query user /server:$Computer 2>&1
            if ($Users -like "*No User exists*")
            {
                $Output += [PSCustomObject]@{
                    ComputerName = $Computer
                    Username = $null
                    SessionState = $null
                    SessionType = "[None Found]"
                }
            }
            elseif ($Users -like "*Error*")
            {
                $Output += [PSCustomObject]@{
                    ComputerName = $Computer
                    Username = $null
                    SessionState = $null
                    SessionType = "[Error]"
                }
            }
            else
            {
                $Users = $Users | ForEach-Object {
                    (($_.trim() -replace ">" -replace "(?m)^([A-Za-z0-9]{3,})\s+(\d{1,2}\s+\w+)", '$1  none  $2' -replace "\s{2,}", "," -replace "none", $null))
                } | ConvertFrom-Csv

                foreach ($User in $Users)
                {
                    $Output += [PSCustomObject]@{
                        ComputerName = $Computer
                        Username = $User.USERNAME
                        SessionState = $User.STATE.Replace("Disc", "Disconnected")
                        SessionType = $($User.SESSIONNAME -Replace '#','' -Replace "[0-9]+","")
                    }

                }
            }
            return $Output | Sort-Object -Property ComputerName
        }

        if ($CheckFor)
        {
            $Usernames = @()
            $Sessions = @()
            $Result = @()
            $Users = QueryToObject -Computer $Name

            foreach ($User in $Users) {
                $Usernames += $User.Username
                $Sessions += $User.SessionType
            }

            if ("[Error]" -in $Sessions)
            {
                $Result += [PSCustomObject]@{
                    ComputerName = $Name
                    IsLoggedOn = "[ERROR]"
                }
            }
            elseif ($CheckFor -in $Usernames -and "[*]" -notin $Sessions)
            {
                $Result += [PSCustomObject]@{
                    ComputerName = $Name
                    IsLoggedOn = $true
                }
            }
            else
            {
                $Result += [PSCustomObject]@{
                    ComputerName = $Name
                    IsLoggedOn = $false
                }
            }
            return $Result | select ComputerName,IsLoggedOn
        }
        elseif (!$CheckFor)
        {
            $Result = QueryToObject -Computer $Name
            return $Result
        }
    }

}