[autoit]
#include <File.au3>
$password = InputBox("", "")
$file = @ScriptDir & "\test.txt"
For $i = 1 To _FileCountLines($file)
If $password = FileReadLine($file, $i) Then
MsgBox(0, 0, "Passwort existiert bereits")
Exit
EndIf
Next
MsgBox(0, 0, "Passwort wird in Datei geschrieben")
$hFile = FileOpen($file, 1)
FileWriteLine($hFile, $password)
FileClose($hFile)