How can I use an iperf output and only grep Interval and Bandwidth?

Question

I am trying to get the output from the command

iperf -c 10.0.0.1 -t 3600 -i 2  

And only need the Interval and bandwidth fields listed for the entire hour of logging.

I haven't used grep or awk in years upon years.

Help would be awesome!

Sample Output:

------------------------------------------------------------
Client connecting to node2, TCP port 5001
TCP window size:  129 KByte (WARNING: requested  130 KByte)
------------------------------------------------------------
[  3] local <IP Addr node1> port 2530 connected with <IP Addr node2> port 5001
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0-10.0 sec  19.7 MBytes  15.8 Mbits/sec

Desired Output:

0.0-10.0 15.8

Answer 1

Based solely on your posted iperf output, you would simply print fields 3 and 4 from the last line:

| awk 'END{print $3" "$7}'

BUT this question is not simply about awk.

Question: Let's start by explaining what your iperf command does, for the benefit of those who are not familiar with it.

• -c 10.0.0.1 connects to server listening at address 10.0.0.1
• -t 3600 keeps running for 3600 seconds, i.e. 1 hour
• -i 2 prints a report every 2 seconds

During the next hour, a line like this is printed (added) on screen every two seconds:

[  3]  0.0-10.0 sec  19.7 MBytes  15.8 Mbits/sec

What you want is reduce the information printed on screen every two seconds, to lines of the form:

0.0-10.0 15.8

Answer: To obtain this, you pipe the output to awk:

iperf -c 10.0.0.1 -t 3600 -i 2 | awk '/[0-9]]/{sub(/.*]/,"");print $1" "$5}'

You can stop reading here if you employ iperf, i.e. iperf 2.

---

If you use iperf3, you should have found out by now that the piped output gets buffered. This means you do not see a new line printed on screen every two seconds! Instead, a whole bunch of lines gets printed every 50 seconds or so, depending on the system. Note that this does not happen with iperf 2 because it flushes the output after printing each line.

To have a line of the desired form printed on screen at the desired interval, you need --forceflush:

   --forceflush
          force flushing output at every interval.  Used to avoid  buffer-
          ing when sending output to pipe.

Answer:

iperf3 -c 10.0.0.1 -t 3600 -i 2 --forceflush | awk '/[0-9]]/{sub(/.*]/,"");print}'

Note that this option was added to iperf3 version 3.1.5.