shell
[start]
for i in 1 2 3 4; do while : ; do : ; done & done
[stop]
for i in 1 2 3 4; do kill %$i; done
[start]
for i in 1 2 3 4; do while : ; do : ; done & done
[stop]
for i in 1 2 3 4; do kill %$i; done