```
#!/bin/bash

pids=()

thread() {
  local this
  while [ ${#} -gt 6 ]; do
    this=${1}
    wait "$this"
    shift
  done
  pids=($1 $2 $3 $4 $5 $6)
}

for i in 1 2 3 4 5 6 7 8 9 10
do
  <<< COMMAND >>> &
  pids=( ${pids[@]-} $(echo $!) )
  thread ${pids[@]}
done

for pid in ${pids[@]}
do
  wait "$pid"
done
```