@echo off
for /f "delims=" %%i in ('type a.txt') do (set "str=%%i"&call :s)
pause&exit
:s
set str=%str:~12%
echo.%str%>>a2.txt
没考虑特殊字符的情况。
setlocal enabledelayedexpansion
for /f "tokens=*" %%i in ('type a.txt') do (
set str=%%i
echo !str:~12!>>1.txt
)