PowerShell 2.0 – Persisting Command History

update: 2009-09-27 - removed usage of closures - turns out i hadn't tested that modification properly. oops.

Here’s a quick one – in order to sway excessive BASH jealously, I knocked this up to persist the last 100 history items between PowerShell sessions. It hooks the special engine (as opposed to object) event “poweshell.exiting” and runs a script to save history to an XML file using the universally useful Export-CliXML cmdlet. Another trick in there is to use a closure to capture the value of the $historyPath variable. I need to do this because powershell event handlers use their own runspace (and will lose the values of the variables in the current runspace). I also could have passed the value via the –MessageData parameter and done it that way, but I figured I’m already in v2 territory so lets use that feature ;-)

# save last 100 history items on exit
$historyPath = Join-Path (split-path $profile) history.clixml

# hook powershell's exiting event & hide the registration with -supportevent.
Register-EngineEvent -SourceIdentifier powershell.exiting -SupportEvent -Action {
    Get-History -Count 100 | Export-Clixml (Join-Path (split-path $profile) history.clixml) }

# load previous history, if it exists
if ((Test-Path $historyPath)) {
    Import-Clixml $historyPath | ? {$count++;$true} | Add-History
    Write-Host -Fore Green "`nLoaded $count history item(s).`n"

Dump this into your profile and have fun!

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About the author

Irish, PowerShell MVP, .NET/ASP.NET/SharePoint Developer, Budding Architect. Developer. Montrealer. Opinionated. Montreal, Quebec.

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