Persisting a Hash Table

I was on a chat earlier today with one of our users.  I’m not sure why, but he  wanted to find a way to persist a Hash Table between PowerShell sessions.  I was pretty sure the both Ed Wilson and Jeffery Hicks had addressed similar problems in the past, so I gave him links to their sites, but I figured there was probably a pretty easy way to do this.  Here’s what I came up with as a basic premise:

PS C:\Users\jhofer> $myHash = @{“foo”=1;”ack”=2}
PS C:\Users\jhofer> $myHash

Name                           Value
——                           ——-
foo                            1
ack                            2

PS C:\Users\jhofer> $myHash | Export-Clixml c:\myhash.xml
PS C:\Users\jhofer> $newHash = Import-Clixml C:\myhash.xml
PS C:\Users\jhofer> $newHash

Name                           Value
——                           ——-
ack                            2
foo                            1

PS C:\Users\jhofer> $newHash.Keys
ack
foo

So basically, it looks like he could add a line like $myHash = Import-Clixml C:\myhash.xml to his profile so that it would load his hash each time he starts up PowerShell.  He could then add a PowerShell function to that would add or update values in his hash table and then overwrite the xml file.  Here’s the final version of what I would add to the profile to accomplish this:

$global:persistentHash = @{}
$global:persistentHash = import-Clixml c:\Public\persistentHash.xml

function update-PersistentHash($key, $value)
{
    if($global:persistentHash.Contains($key))
    {
        $global:persistentHash.Remove($key)
    }

    $global:persistentHash.Add($key,$value)
    $global:persistentHash | export-Clixml c:\Public\persistentHash.xml -Force
   
}

• #powershell
• #how to