Fusionner plusieurs fichiers

Lignes de commandes dos / window$ :
for /r "D:\logs\" %%i in (*.txt) do for /f "delims=" %%j in ('type "%%i"') do echo %%j>> resultat.txt
for /r "D:\logs\" %%i in (*.html) do for /f "delims=" %%j in ('type "%%i"') do echo %%j>> resultat.html