Saving lookup meta data values to library using Powershell - SharePoint

When you take an item in a list, the Lookup fields store its value in the following format
id;#string

when programmatically adding meta data to a list's column the lookup value has to be built before assigning to the item field.

In the below example I refer one lookup, get its value/string. Using the string, do a search for the lookup list item id in the lookup list. Then create the new lookup field. Finally update item


  $myLookupItem = [Microsoft.SharePoint.SPFieldLookupValue]($_["FieldOne_InternalName"])
  $newLookupId = GetLookupId $myLookupItem.LookupValue

  $newLookupItem = New-Object Microsoft.SharePoint.SPFieldLookupValue($newLookupId  ,$myLookupItem.LookupValue)

$_["FieldTwo_InternalName"] = $newLookupItem

$_.Update()
$_.File.CheckIn(" FieldTwo value updated", 1)

$_ is explained in an earlier post