osi-tools/indent

#!/usr/bin/env perl
# Taken from: https://git.parabola.nu/packages/libretools.git/tree/src/chroot-tools/indent
# Relicensed from GPLv3+ to AGPLv3+.
#
# Copyright (C) 2013 Luke Shumaker <lukeshu@parabola.nu>
#
# SPDX-License-Identifier: GPL-3.0-or-later
#
# This file is part of Parabola.
#
# Parabola 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.
#
# Parabola 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 Parabola. If not, see <http://www.gnu.org/licenses/>.

use warnings;
use strict;

use constant BUFFER_SIZE => 40;
binmode(STDIN);
binmode(STDOUT);

exit(1) if ($#ARGV != 0);
my $indent = $ARGV[0];

# 0: no indent has been printed for this line, an indent WILL need to be printed
# 1: an indent needs to be printed for this line IFF there is any more output on it
# 2: no indent (currently) needs to be printed for this line
my $print_indent = 0;

my $buffer;
my $size;
my $c;
while (1) {
	$size = sysread(STDIN, $buffer, BUFFER_SIZE);
	last if ($size < 1);
	for (0..$size-1) {
		$c = substr($buffer, $_, 1);
		if ($c eq "\n") {
			syswrite(STDOUT, $indent) if ($print_indent == 0);
			syswrite(STDOUT, $c, 1);
			$print_indent = 0;
		} elsif ($c eq "\r") {
			syswrite(STDOUT, $c, 1);
			$print_indent = 1 if ($print_indent == 2);
		} else {
			syswrite(STDOUT, $indent) if ($print_indent < 2);
			syswrite(STDOUT, $c, 1);
			$print_indent = 2;
		}
	}
}