How to add an output to the result in a while loop Bash

August 30, 2022

I’m trying to sum all bytes in "RX packets" lines of an ifconfig | grep "RX packets" output.

How do I do that?

Here’s my code

#!/usr/lib/env bash

clear

result=0

while read i; do

    line=${i##*'bytes'} | awk '{print $1;}' 
    
    (( "$result"+="$line" ))

    echo "$result"

done <<< "$(ifconfig | grep "RX packets")"

Also: How should I extract those lines of bytes in a better way, doing "$(ifconfig | grep "RX packets")" and then line=${i##*'bytes'} | awk '{print $1;}' seems so ugly and complicated

if config | grep "RX packets" my output:

        RX packets 7817232  bytes 9337993347 (9.3 GB)
        RX packets 1240058  bytes 83114376 (83.1 MB)
        RX packets 0  bytes 0 (0.0 B)
        RX packets 188707  bytes 27682805 (27.6 MB)

Desired result – sum of all bytes:

9337993347 + 83114376 + 27682805

>Solution :

When assigning to a variable, even inside an arithmetic expression, use the variable name without the dollar sign.

When reading from a command list, use process substitution rather than a here string.

Also, you don’t need awk, you can remove the substring similarly to how you removed the other part.

#! /bin/bash
result=0

while read line; do

    line=${line##*bytes}  # Remove everything up to bytes.
    line=${line%(*}       # Remove everything starting from (.
    
    (( result+="$line" ))
done < <(ifconfig | grep "RX packets")
echo $result