How To Extract a Farm Solution from SharePoint 2010

I found this useful today.  I need to decompile a solution that was created by someone else and globally deployed to our production farm.  I did not have the original .wsp file, so I had to extract it from SharePoint using these 3 lines of code:

$farm = Get-SPFarm
$file = $farm.Solutions.Item("global.deploy.solution.wsp").SolutionFile
$file.SaveAs("c:\temp\global.deploy.solution.wsp")

Note that in order to run this command, you need to be a member of the Farm Administrators group and have permission to the configuration database.