converts fractional seconds to HH:MM:SS.sss

seconds2codes() (
  local seconds=$1
  local hh=$(bc <<< "scale=0; $seconds / 3600")
  local remainder=$(bc <<< "$seconds % 3600")
  local mm=$(bc <<< "scale=0; $remainder / 60")
  local ss=$(bc <<< "$remainder % 60")
  printf "%02d:%02d:%06.3f" "$hh" "$mm" "$ss"
)