0

I had made a small bash script by which pps from a interface can be calculated. Once the incoming pps reach a desired limit then it executes a command.

I am getting an error while running the script can someone please help me

This is the script

#!/bin/bash

INTERVAL="1"  # update interval in seconds
LIMIT="3000" # Limit in KB/S
URL1="http://1.1.1.1/abcd.php"
IFS=( ens3 ) # Interface names

while true
do
        for i in "${IFS[@]}"
        do
            R1=$(cat /sys/class/net/$i/statistics/rx_packets)
            T1=$(cat /sys/class/net/$i/statistics/tx_packets)
            sleep $INTERVAL
            R2=$(cat /sys/class/net/$i/statistics/rx_packets)
            T2=$(cat /sys/class/net/$i/statistics/tx_packets)
            TBPS=$(expr $T2 - $T1)
            RBPS=$(expr $R2 - $R1)

            echo "Incoming $i: $RKBPS pps || Outgoing $i: $TKBPS pps"
            if (( $RKBPS > $LIMIT )); then
                # Incoming Limit Exceeded
                #bash $URL1
                #sleep 10
                curl $URL1
                sleep 320
            fi
        done
done

Error I am getting as below

Incoming ens3:  pps || Outgoing ens3:  pps
./s.sh: line 22: ((: > 3000 : syntax error: operand expected (error token is "> 3000 ")
Incoming ens3:  pps || Outgoing ens3:  pps
./s.sh: line 22: ((: > 3000 : syntax error: operand expected (error token is "> 3000 ")
Incoming ens3:  pps || Outgoing ens3:  pps
./s.sh: line 22: ((: > 3000 : syntax error: operand expected (error token is "> 3000 ")
Incoming ens3:  pps || Outgoing ens3:  pps
./s.sh: line 22: ((: > 3000 : syntax error: operand expected (error token is "> 3000 ")
Incoming ens3:  pps || Outgoing ens3:  pps
./s.sh: line 22: ((: > 3000 : syntax error: operand expected (error token is "> 3000 ")
Incoming ens3:  pps || Outgoing ens3:  pps
./s.sh: line 22: ((: > 3000 : syntax error: operand expected (error token is "> 3000 ")
Incoming ens3:  pps || Outgoing ens3:  pps
./s.sh: line 22: ((: > 3000 : syntax error: operand expected (error token is "> 3000 ")
Incoming ens3:  pps || Outgoing ens3:  pps
./s.sh: line 22: ((: > 3000 : syntax error: operand expected (error token is "> 3000 ")
Incoming ens3:  pps || Outgoing ens3:  pps
./s.sh: line 22: ((: > 3000 : syntax error: operand expected (error token is "> 3000 ")

can someone please help me. T.I.A

Improve this question
1
  • When you copy from here: xmodulo.com/… read the entire document and copy all! Commented Aug 27, 2022 at 14:52

2 Answers 2

Reset to default
1

You are setting up two variables TBPS and RBPS but then refer to TKBPS and RKBPS instead.

You should also add a brief sleep outside the if statement otherwise it will consume a lot of CPU as it will be in a tight loop when the value is not exceeded.

Improve this answer
1
  • On closer inspection it seems you do have a sleep, I must've glanced over it ¯\_(ツ)_/¯ Commented Aug 27, 2022 at 19:00
1

The if instead of this:

 if (( $RKBPS > $LIMIT )); then

should be:

 if [ "$RKBPS" -gt "$LIMIT" ]; then

And this is quite odd method to shape the traffic. Maybe you can implement some traffic shaper as software.

Also the variables you get from rx_packets is about packets per seconds, not bytes per second. You should use rx_bytes

You forget also to add this before if (to convert bytes in kilobytes):

TKBPS=$(expr $TBPS / 1024)
RKBPS=$(expr $RBPS / 1024)
Improve this answer
4
  • 2
    The if (( $RKBPS > $LIMIT )); then is valid. The problem is the undefined variables Commented Aug 27, 2022 at 14:35
  • @roaima, these )) looks odd for me in if. But there are other issues too. Commented Aug 27, 2022 at 14:51
  • 1
    if (( RKBPS > LIMIT )); then would also be fine and that undefined RKBPS would then be taken as 0 instead of causing the error. That's all from ksh in the mid 80s. expr you would have used in the late 70s or early 80s maybe or when you had to use the Bourne shell or one of its pre-POSIX clones for a reason or another before the mid 90s. Commented Aug 27, 2022 at 17:58
  • @StéphaneChazelas, I just copy the lines from the web page I mention in comment. Seems like OP copy the mix the parts of code. About (( as I said - just feel for me uncomfortable :D Commented Aug 27, 2022 at 18:09

You must log in to answer this question.

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.