omit_trailing_empty_lines

#! /usr/bin/awk -f

# omit_trailing_empty_lines - do not output trailing empty lines
# Copyright (C) 2019  Erik Auerswald <auerswal@unix-ag.uni-kl.de>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

# Delay printing of empty lines until non-empty line is found.
#
# Do not use [:space:] character class for compatibility with ancient mawk
# versions as found in contemporary Debian and Ubuntu distributions, where
# mawk 1.3.3 from 1996 is the default Awk. This is written in 2019. m(
 /^[ \t]*$/{empty_lines=empty_lines $0 "\n"}
!/^[ \t]*$/{print empty_lines $0; empty_lines=""}