中国DOS联盟

@echo off
setlocal enabledelayedexpansion
>b.txt type nul
set count=0
for /f "delims=" %%a in (a.txt) do (
  set /a count+=1
  if !count! lss 7 (
    >>b.txt echo %%a
  )
)
move /y b.txt a.txt

@echo off
setlocal enabledelayedexpansion
for /f "delims=" %%a in (1.txt) do (
   set "var=%%a"
   if not "!var:~,3!"==""4"" (echo !var!) else (goto :out)
)
:out
pause

@echo off
more +6 a.txt>b.txt
findstr /b /e /v /g:b.txt a.txt>c.txt
move /y c.txt a.txt
del /q b.txt