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Transit : Bandwidth Usage Breakdown
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Last Month Usage Breakdown:

       From: Tue Jan  1 00:00:00 CST 2013
         To: Fri Feb  1 00:00:00 CST 2013

  GBytes     IN =   184.661
  GBytes    OUT =   944.873
          -----------------
          TOTAL =  1129.534

  95th Percentile:  9.866 Mbps

--------------------------------
Month-To-Date Usage Breakdown:

       From: Fri Feb  1 00:00:00 CST 2013
         To: Mon Feb 11 07:33:37 CST 2013

  GBytes     IN =    60.902
  GBytes    OUT =   287.265
          -----------------
          TOTAL =   348.168

  95th Percentile:  9.906 Mbps

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Current Month Projection Usage Breakdown:

       From: Fri Feb  1 00:00:00 CST 2013
         To: Fri Mar  1 00:00:00 CST 2013

  GBytes     IN =    60.902
  GBytes    OUT =   287.265
          -----------------
          TOTAL =   348.168

  95th Percentile:  9.412 Mbps

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#!/bin/bash

IFACE=${1-eth0}
INTERVAL=${2-10}
# Generate environment vars RX1,RX2 and TX1,TX2 which are 10 seconds apart:
eval $(
    ifconfig  $IFACE | grep '[RT]X packets' | awk '{print $1" "$5}' | sed 's/ /1=/'
    sleep $INTERVAL
    ifconfig  $IFACE | grep '[RT]X packets' | awk '{print $1" "$5}' | sed 's/ /2=/')

# Convert to kbit/sec:
let "RX=($RX2-$RX1)*8/$INTERVAL / 1000"
let "TX=($TX2-$TX1)*8/$INTERVAL / 1000"

# BX is the max of both:
let "BX = $TX > RX ? $TX : $RX"

echo $BX RX=$RX TX=$TX BX=$BX $(date '+%F %H:%M:%S')

*/5  *  *  *  * root /usr/local/bin/95th.sh eth0 >> /var/log/95th-percent.log

DATE=2019-06
PERCENTILE=95
grep $DATE /var/log/95th-percent.log | sort -nr | head -n $(( $( grep -c $DATE /var/log/95th-percent.log ) * (100-$PERCENTILE) / 100 )) | tail -1