JunOS Regular Expressions for AS Path

I do this exact same thing on my Watchguard.

Here is the regex I use, edited to fit the domains you're working with.

(?i)^([^./]+\.)*(grooveshark\.com|gs-cdn\.net)(?![^/])

I'm not sure if you intended to leave the k off grooveshark at one point in your question or if it was just a typo. If they were to use grooveshar.com sometimes then you would need this:

(?i)^([^./]+\.)*(grooveshark?\.com|gs-cdn\.net)(?![^/])

The ? after the k just makes it not necessary.

I highly recommend The Regex Coach to help you build regex.

I also highly recommend http://www.regular-expressions.info/ as a reference.

There is probably a better way to do this, but here is what I first thought of to accomplish this; this approach uses named capture groups in the regex to make it easier for powershell to sort and group by the base filename and the revision. The final variable $filesToKeep will be an array of FileInfo objects that you can exclude from your delete command. Of course I recommend lots of testing before actually deleting anything.

$filter = [regex] "(?<baseName>[A-Za-z]{3}[0-9]{3})\-(?<revision>[0-9]+)\.p"
$results = ls c:\temp -Recurse | where {$_.Name -match $filter} | foreach-object {
    new-object PSObject -Property @{
        BaseName = $matches.BaseName
        Revision = $matches.Revision
        File = $_
    }
}
$filesToKeep = $results | sort basename, revision  -Descending | group basename | ForEach-Object { $_.group | select -first 1 -ExpandProperty File}