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)

License GPLv3+: GNU GPL version 3 or later <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.

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

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