Last time we started looking at creating a basic PowerShell function. The function is a command written in PowerShell’s scripting language that accomplishes a given task. The task can be described using a Verb-Noun naming convention. This will become the function’s name. To re-iterate key points, a PowerShell function does one thing and writes one type of object to the pipeline. Ideally, the output is a structured object that other PowerShell commands, like Select-Object and ConvertTo-Json can consume.

At the end of the previous article, I had completed this basic function.

function Get-ComputerUptime {
    Param($ComputerName = $env:computername)
    $os = Get-CimInstance -ClassName Win32_OperatingSystem -ComputerName $ComputerName
    $up = New-TimeSpan -Start $os.LastBootUpTime -End (Get-Date)
    [PSCustomObject]@{
        ComputerName = $os.CSName
        LastBoot     = $os.LastBootUpTime
        Uptime       = $up
    }
}

When this function is loaded into my PowerShell session, I have an easy-to-use tool that writes a rich object to the pipeline.