Find & Replace string using for /f with if statement and variables

I have written a batch file which I want to overwrite key strings with strings from another .txt file.

currently it copies the new File.txt file perfectly but does not replace the strings with the strings from OldFile.txt file.

example of strings in File.txt file:

...

# Password
Pword=

# AccountName
Account=

# TownName
Town=

# Postcode
Postcode=

# LocationChangedDate
LocationChanged=

example of strings in OldFile.txt file I want to replace from:

...

# Password
Pword=ABC

# AccountName
Account=123

# TownName
Town=LDN

# Postcode
Postcode=WS77TP

# LocationChangedDate
LocationChanged=01/01/2015

Can someone please point me in the right direction or explain where I have made a mistake?

@echo off

setlocal disableDelayedExpansion

::Variables
set InputFile=F:\EXCHANGE\3\Machine\File.txt
set OutputFile=F:\EXCHANGE\3\File-New.txt
set CopyFile=F:\EXCHANGE\3\OldMachine\OldFile.txt

set _strFindPword=Pword=.*
for /F "delims=" %%A in ('findstr /x "Pword=.*" %CopyFile%') do set _strInsertPword=%%A

echo.%_strInsertPword%

set _strFindAccount=Account=.*
for /F "delims=" %%B in ('findstr /x "Account=.*" %CopyFile%') do set _strInsertAccount=%%B

echo.%_strInsertAccount%

set _strFindTown=Town=.*
for /F "delims=" %%C in ('findstr /x "Town=.*" %CopyFile%') do set _strInsertTown=%%C

echo.%_strInsertTown%

set _strFindLocationChanged=LocationChanged=.*
for /F "delims=" %%D in ('findstr /x "LocationChanged=.*" %CopyFile%') do set _strInsertLocationChanged=%%D

echo.%_strInsertLocationChanged%

set _strFindPostcode=Postcode=.*
for /F "delims=" %%E in ('findstr /x "Postcode=.*" %CopyFile%') do set _strInsertPostcode=%%E

echo.%_strInsertPostcode%


(
  for /F "delims=" %%L in ('findstr /n "^" "%InputFile%"') do (
    set "line=%%L"
    setlocal EnableDelayedExpansion
    set "line=!line:*:=!"
    if "%%L" equ "_strFindPword" (echo.!_strInsertPword!) else (
       if "%%L" equ "%_strFindAccount%" (echo.!_strInsertAccount!) else (
          if "%%L" equ "%_strFindTown%" (echo.!_strInsertTown!) else (
             if "%%L" equ "%_strFindLocationChanged%" (echo.!_strInsertLocationChanged!) else (
                if "%%L" equ "%_strFindPostcode%" (echo.!_strInsertPostcode!) else (echo.!line!)
             )
          )
       )
    )
    endlocal
  )
) > "%OutputFile%"

del %InputFile% 

ren %OutputFile% File.txt



pause

Solution

I think I finally got it...

What it does:

It goes through the OldFile.txt content, searching for markers, if found they are stored into environment variables to be used in the nest step (e.g. for _PWD marker (variable) which has a value of Pword=, it will create a _PWDCONTENTS variable with the content of Pword=ABC).
It goes through File.txt content, searching for the same markers, if one marker found, the corresponding CONTENTS variable is dumped in the OutFile.txt, else the original line. Because that happens in the inner for loop, I had to add some extra logic (the _WROTE var) to avoid writing the same lines more than once.

Notes:

It is supposed (well, besides doing what it's supposed to) to be "configurable" (the code is complicated, it's heading towards meta :) if you will), meaning that if there are changes between the markers the code shouldn't change (well there would be code changes, but not in the functional part only in variable definitions). Let me detail:
- If you no longer need to replace the Town= string, then all you have to do is removing _TOWN from _ALL: set _ALL=_PWD _ACCT _POST _LOC.
- The reverse: if you want to add some other tag (let's call it Name), you have to create a new environment variable: set _NAME=Name= and add it to _ALL: set _ALL=_PWD _ACCT _TOWN _POST _LOC _NAME.
As an indirect consequence, I didn't focus on performance, so it might run slow. Anyway I tried to keep the disk accesses (which are painfully slow) to a minimum (one example is when having 2 for loops the one that iterates on a file contents - assuming that each iteration takes a disk access; this might not be true, and Win has IO buffering - it's the outer one).
I "commented" out the last line in the file, to avoid overwriting the original file. If that behavior is needed, simply remove the rem at the beginning.

Here's the batch code:

@echo off
setlocal enabledelayedexpansion

set _INFILE="File.txt"
set _OUTFILE="NewFile.txt"
set _OLDFILE="OldFile.txt"


set _PWD=Pword=
set _ACCT=Account=
set _TOWN=Town=
set _POST=Postcode=
set _LOC=LocationChanged=
set _ALL=_PWD _ACCT _TOWN _POST _LOC

echo Parsing old file contents...

for /f "tokens=*" %%f in ('type !_OLDFILE!') do (
    for %%g in (!_ALL!) do (
        echo %%f | findstr /b /c:!%%g! 1>nul
        if "!errorlevel!" equ "0" (
            set %%gCONTENTS=%%f
        )
    )
)

copy nul %_OUTFILE%
echo Merging the old file contents into the new file...
set _WROTE=0

for /f "tokens=*" %%f in ('findstr /n "^^" !_INFILE!') do (
    set _TMPVAR0=%%f
    set _TMPVAR0=!_TMPVAR0:*:=!
    for %%g in (!_ALL!) do (
        echo !_TMPVAR0! | findstr /b /c:!%%g! 1>nul
        if "!errorlevel!" equ "0" (
            echo.!%%gCONTENTS!>>!_OUTFILE!
            set _WROTE=1
        )
    )
    if "!_WROTE!" equ "0" (
        echo.!_TMPVAR0!>>!_OUTFILE!
    ) else (
        set _WROTE=0
    )
)

rem copy /-y %_OUTFILE% %_INFILE%

@EDIT0: Using @StevoStephenson suggestion (as part of the question snippet), I replaced the (2nd) outer for loop to ('findstr /n "^^" !_INFILE!') in order to include the empty lines, so the 3rd remark no longer applies (deleting). Also did some small changes to allow files that contain SPACE s in their paths.