iperf - iPerf コマンドの stdout にタイムスタンプを毎秒更新する方法

Question

2 つの端末間で iperf を実行しており、次のように出力を取得できます。

2017-01-09 16:43:03: Connecting to host 192.168.234.2, port 5201
2017-01-09 16:43:03: [  4] local 192.168.234.1 port 36544 connected to 192.168.234.2 port 5201
2017-01-09 16:43:03: [ ID] Interval           Transfer     Bandwidth       Retr  Cwnd
2017-01-09 16:43:03: [  4]   0.00-1.00   sec   553 KBytes  4.53 Mbits/sec    1   29.7 KBytes
2017-01-09 16:43:03: [  4]   1.00-2.00   sec   499 KBytes  4.09 Mbits/sec    1   26.9 KBytes
2017-01-09 16:43:03: [  4]   2.00-3.00   sec   515 KBytes  4.22 Mbits/sec    0   32.5 KBytes
2017-01-09 16:43:03: [  4]   3.00-4.00   sec   508 KBytes  4.16 Mbits/sec    1   31.1 KBytes
2017-01-09 16:43:03: [  4]   4.00-5.00   sec   496 KBytes  4.07 Mbits/sec    1   26.9 KBytes
2017-01-09 16:43:03: [  4]   5.00-6.00   sec   515 KBytes  4.22 Mbits/sec    0   33.9 KBytes
2017-01-09 16:43:03: [  4]   6.00-7.00   sec   513 KBytes  4.21 Mbits/sec    1   31.1 KBytes
2017-01-09 16:43:03: [  4]   7.00-8.00   sec   495 KBytes  4.05 Mbits/sec    1   28.3 KBytes
2017-01-09 16:43:03: [  4]   8.00-9.00   sec   501 KBytes  4.10 Mbits/sec    1   32.5 KBytes
2017-01-09 16:43:03: [  4]   9.00-10.00  sec   513 KBytes  4.20 Mbits/sec    0   32.5 KBytes
2017-01-09 16:43:03: - - - - - - - - - - - - - - - - - - - - - - - - -
2017-01-09 16:43:03: [ ID] Interval           Transfer     Bandwidth       Retr
2017-01-09 16:43:03: [  4]   0.00-10.00  sec  4.99 MBytes  4.18 Mbits/sec    7             sender
2017-01-09 16:43:03: [  4]   0.00-10.00  sec  4.97 MBytes  4.17 Mbits/sec                  receiver
2017-01-09 16:43:03: iperf Done.

問題は、タイムスタンプが最後まで同じままであることです。タイムスタンプを毎秒更新する方法を教えてもらえますか?