Wait for a fix number of process in bash

parallel_wait.sh

for i in {1..10}
do
  {
    c=$((RANDOM % 6 + 1))
    echo "start $c"
    sleep $c
    echo "end $c"
  } &
  if (( (i % 5) == 0 )); then
    wait
  fi
done
wait

parallel_wait2.sh

cnt=1 # Use counter
for i in {1..10}
do
  {
    c=$((RANDOM % 6 + 1))
    echo "start $c"
    sleep $c
    echo "end $c"
  } &
  if (( (cnt++ % 5) == 0 )); then
    wait
  fi
done
wait

$ ./parallel_wait.sh
start 3
start 6
start 6
start 5
start 2
end 2
end 3
end 5
end 6
end 6
start 1
start 1
start 4
start 1
start 5
end 1
end 1
end 1
end 4
end 5