I just needed to know how long it was since my box was last rebooted.  Windows Vista has a nice feature where this is now a property of the Performance tab in Task Manager.  But alas, there's no such nice functionality in Windows 2K3.  Usually I end up in PerfMon to get the number of seconds the box has been up and then in calculator to convert this into real time.

Enter PowerShell to the rescue:

function GLOBAL:Get-SystemBootupTime([String]$computer="localhost") { 
      $wmiOsInformation = Get-WmiObject -computer $computer -class Win32_OperatingSystem 
      $wmiOsInformation.ConvertToDateTime($wmiOsInformation.LastBootUpTime)
} 
 
function GLOBAL:Get-SystemUptime([String]$computer="localhost") { 
      $wmiPerfOsSystem = Get-WmiObject -computer $computer -class Win32_PerfFormattedData_PerfOS_System 
      $wmiPerfOsSystem.SystemUpTIme
} 
 
# Get System Bootup time
PS C:\> Get-SystemBootupTime
21 December 2006 17:16:02 
 
# Get system uptime in seconds
PS C:\> Get-SystemUptime
1016328

Not bad, I can now see the system uptime in seconds, but I want the result formatted

function GLOBAL:Get-SystemUptimeFormatted([String]$computer="localhost") { 
      $wmiPerfOsSystem = Get-WmiObject -computer $computer -class Win32_PerfFormattedData_PerfOS_System 
      [TimeSpan] $systemUptime = New-TimeSpan -seconds $wmiPerfOsSystem.SystemUpTIme 
      [String]::Format("{0:G}", $systemUptime)
} 
 
PS C:\> Get-SystemUptimeFormatted
11.18:53:16

Job done! As a developer, I tend towards using .NET all over, so I've probably missed some rather subtle ways of achieving the formatting with PowerShell.

You can get a lot of other useful information from the WMI classes that could be the focus of other functions:

PS C:\> $computer = "localhost"
PS C:\> $wmiOsInformation = Get-WmiObject -computer $computer -class Win32_OperatingSystem
PS C:\> $wmiOsInformation 

SystemDirectory : C:\WINDOWS\system32
Organization    : My Org 
BuildNumber     : 3790
RegisteredUser  : Me
SerialNumber    : xxxxx-xxx-xxxxxxx-xxxxx
Version         : 5.2.3790

To ensure that this handy set of functions is always there when needed, I've added them to my profile:

PS C:\> Notepad $profile