@echo off
del big.one 2> NUL
for %%f in (*.mf) do (
if not exist big.one (
copy "%%f" big.one
) else (
for /F "usebackq skip=1 delims=" %%a in ("%%f") do (
echo %%a>> big.one
)
)
)
set /P fileDate=< big.one
ren big.one filename_%fileDate:~0,-1%.mf
This solution does not preserve empty lines from second file on; this may be fixed, if needed.