[Foreigner]

PowerShell:

Код:

$content = get-content 1.txt
$groups = $content -replace '.+\[([^_]+)(\]|_.+\]).*','$1' | get-unique

foreach ($group in $groups) {

    $content -match $group | foreach { $string += $_ }
    $string | add-content 2.txt
    $string = $null

}