@if(0)==(0) echo off
cscript //nologo //e:jscript "%~f0" < a.txt > b.txt
pause & exit
@end

var map = [];
while( !WSH.StdIn.AtEndOfStream ){
    var s = WSH.StdIn.ReadLine();
    map[s] = map[s] ? map[s]+1 : 1;
}
for( s in map ){ if( map[s] > 1 ) WSH.Echo(s); }
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gawk "{a[$0]++}END{for(i in a)if(a[i]>1)print i}" a.txt > b.txt
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PowerShell "$a=@{};forEach($s In (gc a.txt -ReadCount 0)){$a[$s]++};$b=forEach($s In $a.Keys){if($a[$s]-1){$s}};sc b.txt $b"
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@echo off
pushd "%~dp0"
set "infile=A.txt"
set "outfile=B.txt"
Powershell -NoProfile -Command "Get-Content \"%infile%\" | Group-Object | Where-Object {$_.Count -gt 1} | ForEach-Object { $_.Name } | Out-File -FilePath \"%outfile%\""
pause
exit /b
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type a.txt | cscript //nologo //e:jscript "%~f0" > b.txt
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@echo off
setlocal enabledelayedexpansion
for /f %%i in ( 'type a.txt ^| sort' ) do (
    if /i "%%i" == "!s!" (
        if not defined flag (set "flag=1" & echo;!s!)
    ) else (
        if defined flag set "flag="
    )
    set "s=%%i"
)
pause
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