Hi,

                with the last x86_32 version of sed (windows platform) the
following pattern



sed '\?^$?D'



don’t remove blank line from file if the file is in DOS format. In the
previous version 2.2 this command working.


In attach the demo test files.


*sed --version :*

*sed (GNU sed) 4.4*

*Packaged by Cygwin (4.4-1)*

*Copyright (C) 2017 Free Software Foundation, Inc.*

*License GPLv3+: GNU GPL version 3 or later
<http://gnu.org/licenses/gpl.html <http://gnu.org/licenses/gpl.html>>.*

*This is free software: you are free to change and redistribute it.*

*There is NO WARRANTY, to the extent permitted by law.*


*Written by Jay Fenlason, Tom Lord, Ken Pizzini,*

*and Paolo Bonzini.*

*GNU sed home page: <http://www.gnu.org/software/sed/
<http://www.gnu.org/software/sed/>>.*

*General help using GNU software: <http://www.gnu.org/gethelp/
<http://www.gnu.org/gethelp/>>.*

*E-mail bug reports to: <bug-sed@gnu.org <bug-sed@gnu.org>>.*
-- 

Saluti
Mauro Rigoni