#include <AutoItConstants.au3>
#include<array.au3>

$sCommands = "ipconfig /all"

$iPID = Run(@ComSpec & " /c " & $sCommands, "", @SW_HIDE , $stdout_child)

$sOutput = ""

 While 1
        $sOutput &= StdoutRead($iPID)
        If @error Then
            ExitLoop
        EndIf
 WEnd

 msgbox(0, '' , $sOutput)
 $aOutput = stringsplit($sOutput , @CR , 2)
 _ArrayDisplay($aOutput)
$destinationfile = "c:\test\2.txt"

 for $i = 0 to ubound($aOutput) - 1

    If stringinstr($aOutput[$i] , "target string") Then Filewrite($destinationfile , $aOutput[$i])

next