./test1

seq 0 | dash p1.sh

seq 1 | dash p1.sh
1 

seq 2 | dash p1.sh
1 2

seq 3 | dash p1.sh
1 2
3 

seq 4 | dash p1.sh
1 2
3 4

seq 5 | dash p1.sh
1 2
3 4
5 

seq 6 | dash p1.sh
1 2
3 4
5 6