scroll/up.sh

#!/bin/sh

set -eu
export POSIXLY_CORRECT=1

i=1
while test $i -lt 50; do
	print $i
	i=$((i + 1))
done > tmp.log

(sleep 1; printf "\033[5;2~"; sleep 1; ) \
	| ./ptty ./scroll tail -fn 50 tmp.log > out.log

cmp out.log up.log