Dirty but simplest way to get a 95th percentile usage on a network interface

95th_percentile.sh

#!/bin/bash

netdev=eth0
storage=/tmp/95th_percentile_db

:> $storage

while true; do
  rx_bytes_count1=$(awk "/${netdev}/ { print \$2 }" /proc/net/dev)
  tx_bytes_count1=$(awk "/${netdev}/ { print \$10 }" /proc/net/dev)

  sleep 5m

  rx_bytes_count2=$(awk "/${netdev}/ { print \$2 }" /proc/net/dev)
  tx_bytes_count2=$(awk "/${netdev}/ { print \$10 }" /proc/net/dev)

  rx_Bps=$(( (rx_bytes_count2 - rx_bytes_count1) / 300 ))
  tx_Bps=$(( (tx_bytes_count2 - tx_bytes_count1) / 300 ))

  echo $(( rx_Bps + tx_Bps )) >> $storage

  percentile95_index=$(( $(cat $storage | wc -l) * 95 / 100 ))
  [ $percentile95_index -eq 0 ] && continue

  percentile95_bps=$(( $(sort -n $storage | sed -n "${percentile95_index}p") * 8 ))
  echo $percentile95_bps | numfmt --to=iec --suffix bps
done