$(for n in $(seq 0 5 100); do
printf '<button class="%s" type="submit" name="vol" value="%s"> </button>' "$([ "$volume" = "$n" ] && printf selected)" "$n"
done)
$(for n in $(seq 0 5 100); do
printf '<button class="%s" type="submit" name="vol" value="%s"> </button>' "$([ "$volume" = "$n" ] && printf selected)" "$n"
done)