Объединение файлов с расширением .R1 согласно содержимого строки

@echo on
set "in=%Userprofile%\Desktop\sin"
for %%i in ("%in%\*") do (
 for /f "delims=" %%j in ('more "%%~i" ^| findstr /irc:"\<L"') do echo %%~j>>"STOCK.txt"
 for /f "delims=" %%j in ('more "%%~i" ^| findstr /irc:"\<U"') do echo %%~j>>"IN.txt"
 for /f "delims=" %%j in ('more "%%~i" ^| findstr /virc:"\<[LU]"') do echo %%~j>>"OUT.txt"
)
pause

@for %%i in (*.R1) do @for %%j in ("\^<L>>"STOCK.txt"" "/v \^<[LU]>>"OUT.txt"" "\^<U>>"IN.txt"") do @type "%%i"| cmd/c findstr %%~j

@echo off
 
set/p "key=Enter the number (1 for L, 2 for P or 3 for U): "
 
for %%i in ("\^<L>>"STOCK.txt"" "\^<P>>"OUT.txt"" "\^<U>>"IN.txt"") do set/a n+=1& (
 cmd/v/c "for %%j in (*.R1) do @if "!n!" equ "%key%" type "%%j"| findstr %%~i")
 
exit/b

@echo off
echo    #include ^<conio.h^>                    >_prompt.c
echo    #include ^<ctype.h^>                    >>_prompt.c
echo    int main(int argc, char **argv) {       >>_prompt.c
echo        int ch;                             >>_prompt.c
echo        _cputs( argv[argc-1]);              >>_prompt.c
echo        ch = _getch();                      >>_prompt.c
echo        exit(ch -'0');                      >>_prompt.c
echo    }                                       >>_prompt.c
 
cl _prompt.c >nul
_prompt "Enter the number (1 for L, 2 for P or 3 for U): "
set answer=%errorlevel%
echo %answer%

@echo off
 
choice/c 123 /n /m "Press the desired key (1 for L, 2 for P or 3 for U)."
 
for %%i in ("\^<L>>"STOCK.txt"" "\^<P>>"OUT.txt"" "\^<U>>"IN.txt"") do set/a n+=1& (
 cmd/v/c "for %%j in (*.R1) do @if "!n!" equ "%errorlevel%" type "%%j"| findstr %%~i")
 
exit/b