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

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

CodePudding user response：

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

CodePudding user response：

Using the shell to do arithmetic with a while/read loop is slow and clunky. You could simply do:

ifconfig | awk '/RX packets/{ s  = $5 } END {print s}'

(This assumes a particular format for the output of ifconfig, so this will likely fail if you use it on a different platform.)

CodePudding user response：

Alternatively, with sed and bash:

bytes=$(ifconfig | sed -n 's/.*RX packets.*bytes \([0-9]*\).*/\1/p')
echo $(( ${bytes//$'\n'/ } ))