#include <FileConstants.au3>
#include <MsgBoxConstants.au3>
#include <WinAPIFiles.au3>

; filename to read
$file_to_read = "isc480.txt"
; filename to write
$file_to_write = "isc480.new.txt"
; open file to read and store the handle
$handle_read = FileOpen($file_to_read, 0)
; check the handle is valid
If $handle_read = -1 Then
    ; show warning and exit with code 1
    MsgBox(0, @ScriptName, 'failed to open handle to read the file')
    Exit 1
 EndIf

    ; Open the file for writing (append to the end of a file) and store the handle to a variable.
    Local $hFileOpen = FileOpen($file_to_write, $FO_APPEND)
    If $hFileOpen = -1 Then
        MsgBox($MB_SYSTEMMODAL, "", "An error occurred while writing the temporary file.")
        Return False
    EndIf

; loop through each line of the file
While 1
    ; read each line from a file
    $line_read = FileReadLine($handle_read)
    ; exit the loop if end of file
    If @error Then ExitLoop
   ; write to the ini file
   if StringInStr($line_read, "LineDisp_iSC480") = 1 Then
	  MsgBox(0, "Result", "LineDisp_iSC480 was found, no need to append")
	  ; close the file handle for read
	  FileClose($handle_read)

	  ; Close the handle returned by FileOpen.
	  FileClose($hFileOpen)

	  Exit 1
   EndIf
   FileWriteLine($hFileOpen, $line_read)
WEnd

; close the file handle for read
FileClose($handle_read)

; Close the handle returned by FileOpen.
FileClose($hFileOpen)

; Display the contents of the file passing the filepath to FileRead instead of a handle returned by FileOpen.
MsgBox($MB_SYSTEMMODAL, "", "Contents of the file:" & @CRLF & FileRead($file_to_write))