perfi.sh

A script that uses gnuplot to plot iperf3 output in realtime.

iperf3

iperf3  -i $PINTERVAL -R -t $PTIME -f k -c $PERFHOST

-i is the interval in Seconds. Can be a float like 0.1

-f is the ouptut and allows

-k Kbit/s
-m Mbit/s
-K Kbyte/s
-M MByte/s

There exists a list of public iperf servers but though it seemed quite recent as of today, none of the servers I tried did actually work.

stdbuf

iperf3 seems to buffer its stdout. A tool named stdbuf helps achieving realtime output, so the data can be piped into the next tool.

stdbuf -o0 iperf3  -i $PINTERVAL -R -t $PTIME -f k -c $PERFHOST

-o refers to the STDOUT (there is also -i for STDIN and -e for STDERR). 0 will turn buffering off. L would enable Line Buffering.

awk

awk is used to only get the data rate (7th column)

iperf3 example output:

iperf3 -c 192.168.2.70 -f k -t 2
Connecting to host 192.168.2.70, port 5201
[  5] local 192.168.2.199 port 59798 connected to 192.168.2.70 port 5201
[ ID] Interval           Transfer     Bitrate         Retr  Cwnd
[  5]   0.00-1.00   sec  28.3 MBytes  237649 Kbits/sec    0   1.21 MBytes       
[  5]   1.00-2.00   sec  31.2 MBytes  261938 Kbits/sec    0   2.16 MBytes       
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-2.00   sec  59.6 MBytes  249797 Kbits/sec    0             sender
[  5]   0.00-2.02   sec  57.2 MBytes  237330 Kbits/sec                  receiver

iperf Done.

awk '/sec/&&!/receiver/&&!/sender/ {print $7}'

The /sec/ will filter all lines that show a data rate. To filter out the summary at the end, we add &&!/receiver/&&!/sender/. && is logical AND and ! negates the token.

So this would result in

 iperf3 -c 192.168.2.70 -f k -t 2 | awk '/sec/&&!/receiver/&&!/sender/ {print $7}' 
281725
262140

feedgnuplot

feedgnuplot is a wrapper that makes it simpler to feed data to gnuplot in real time.

feedgnuplot --lines --stream --ylabel 'KBytes/sec' --xlabel 'seconds'

--lines tells (feed)gnuplot to connect datapoints by lines (which is easier to read then only points/dots

--stream tells (feed)gnuplot to update its data as it comes in. Per default it will do this once per second.

--ylabel / --xlabel will write a caption. It is not mandatory, but if you want to share the plot later it looks nicer.

Full commandline

(See perfi.sh)

stdbuf -o0 iperf3  -i $PINTERVAL -R -t $PTIME -f k -c $PERFHOST | stdbuf -o0 awk '/sec/&&!/receiver/&&!/sender/ {print $7}' | stdbuf -o0 feedgnuplot --lines --stream $PINTERVAL --ylabel 'Kbit/s' --xlabel  "$PINTERVAL seconds"

Result

Room for improvement

Let user have a commandline switch for the unit (kbit/s vs. mbit/s etc.)
Add checks for dependencies and commandline switches

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