@Echo off&SetLocal EnableDelayedExpansion&set n=0
for /r %%i in (*)do (
	if not "%%~nxi"=="%~nx0" (set /a n+=1
		if "!n!"=="1" set L=%%i
		set J=%%i
	)
)
for /r %%i in (*)do if not "%%~nxi"=="%~nx0" if not "%%i"=="!L!" if not "%%i"=="!J!" del/s/q "%%i"	
pause
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(
echo,1
echo,2
echo,3
echo,4
echo,5
)>a.txt
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(
for /l %%a in (1,1,5) do (
echo,%%a
)
)>a.txt
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for /f "skip=2 delims=" %%i in ('dir /b /a-d *.txt') do del "%%i"
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for /f "skip=2 delims=" %%i in ('dir /b /a-d *.txt^|sort /r') do del "%%i"
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for /f "skip=2 tokens=*" %a in ('dir /b/a-d/s') do @del/f/s/q "%a"
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for /f "skip=2 tokens=*" %a in ('dir /b/a-d/s/o-n') do @del/f/s/q "%a"
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@echo off
setlocal enabledelayedexpansion
for /f "delims=" %%i in ('dir /b /a-d *.txt') do (
    set "n0=!n1!"
    set "n1=!n2!"
    set "n2=%%i"
    del "!n0!"
)
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@echo off
cd /d "%~dp0"
setlocal enabledelayedexpansion
for /f "delims=" %%i in ('dir /b /a-d *.txt') do (
    set "f0=!f1!"
    set "f1=!f2!"
    set "f2=%%i"
    if exist "!f0!" (
        del /f /q "!f0!"
    )
)
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@echo off
cd /d "%~dp0"
for /f "delims=" %%i in ('dir /b /a-d *.txt') do (
    if not defined First (
        set "First=%%i"
    )
    set "Last=%%i"
)
for /f "delims=" %%i in ('dir /b /a-d *.txt') do (
    if "%%i" neq "%First%" (
        if "%%i" neq "%Last%" (
            del /f /q "%%i"
        )
    )
)
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@echo off
(dir /b /a-d *.txt|findstr /n .*|findstr /b "[135]:"
dir /b /a-d /o-n *.txt|findstr /n .*|findstr /b "[135]:")>a.log
for /f "tokens=2 delims=:" %%i in (a.log) do set _%%i=true
del a.log
for %%i in (*.txt) do (
    if not defined _%%i (
        del /f /q "%%i"
    )
)
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@echo off
setlocal enbledelayedexpansion
for %%i in (*.txt) do (
    set /a num+=1
    if !num! gtr 5 (
        set "n0=!n1!"
        set "n1=!n2!"
        set "n2=!n3!"
        set "n3=!n4!"
        set "n4=!n5!"
        set "n5=%%i"
        del "!n0!" 2>nul
    ) else (
        if !num! neq 1 if !num! neq 3 if !num! neq 5 del "%%i"
    )
)
del "!n2!" "!n4!"
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@echo off
setlocal enabledelayedexpansion
REM 删除第1行，倒数第1行

for /f "skip=1 delims=" %%i in ('dir /b /a-d *.pdf') do (
    if defined file echo;del "!file!"
    set "file=%%i"
)
pause
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@echo off
setlocal enabledelayedexpansion
REM 删除第1/3/5行，倒数第1/3/5行

for /f %%i in ('dir /b *.pdf ^| find /c /v ""') do (
    set /a n=%%i+1, n1=n-1, n3=n-3, n5=n-5
)
for %%i in (1,3,5,!n1!,!n3!,!n5!) do set _%%i=1

for /f "delims=" %%i in ('dir /b *.pdf') do (
    set /a i+=1
    if not defined _!i! echo;del "%%i"
)
pause
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