中国DOS联盟

@echo off
echo 我爱你>>a.txt

@echo off
type nul>c.txt
for /f "delims=" %%a in (b.txt) do (
  if defined _%%a (
    >>c.txt echo.%%a
  )
  set "_%%a=%%a"
)
findstr /g:c.txt b.txt|sort>bb.txt

@echo off
type nul>b.txt
for /f %%a in ('type a.txt^|find /c /v ""') do (
  set "RowNum=%%a"
)
for /f "tokens=1* delims=:" %%a in ('findstr /n .* a.txt') do (
  if %%a lss %RowNum% (
    >>b.txt echo.%%b
  ) else (
    >>b.txt echo.%%b我爱你
  )
)
move /y b.txt a.txt