# 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](https://iperf.fr/iperf-servers.php).



## 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](perfi.sh)

```bash
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

![gnuplot.png](A screenshot of the gnuplot of an iperf3 test)

## 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