[DJ Mogarych]

Код:

$txt = gc D:\temp\test\Users.txt
[array]$csv = import-csv D:\temp\test\user_list.csv

foreach ($login in $txt) {
    if ($login -notin $csv.samaccountname) {
    $csv += [pscustomobject]@{samaccountname="$login";count="1"}
    }
    else {([double]($csv |? samaccountname -eq "$login").count)++}
}

$csv |export-csv D:\temp\test\user_list.csv -NoTypeInformation