update value in bash script

Question

i have stuck code. i make bash script to send Notification If file Size changed

#!/bin/bash

#File Embeded
test_file=/home/optimus/bot_test/dump.txt
msg_caption=/tmp/telegram_msg_caption.txt

#initialize
initCount=0

#checkLog
#cmd="ls /var/log/snort/* | wc -l"
cmd=$(wc -c "dump.txt" | awk '{print $1}')

#Chat ID and TOKEN Telegram
chat_id="xxxx"
token="xxx"

#Send Alert
function sendAlert
{
        curl -s -F chat_id=$chat_id -F caption="$caption" -F document=@$test_file  https://api.telegram.org/bot$token/sendDocument > /dev/null 2&>1
}

#Monitoring DoS Server
while true
do
    #GetLastCount
    echo "Start Execute"
    lastCount=$cmd
    echo before_last $lastCount #ex 100 #after reset 0
    echo before_init $initCount #ex 0
    echo "--------------------"
    if(($(($lastCount)) > $initCount));
       then
        echo "Running Script..." #debug
        echo -e "Halo Admin\nTerjadi Indikasi Penyerangan DoS!!!" > $msg_caption #set Caption / Pesan
        caption=$(<$msg_caption) #set Caption
        sendAlert #Panggil Fungsi

        #error disini
        initCount=$lastCount
        lastCount=0 #reset

        echo after_last $lastCount
        echo after_Init $initCount
        echo "==================="
        rm -f $msg_caption
        sleep 5 #delay Proses jika ada indikasi
    fi
    sleep 5 #delay proses jika tidak ada indikasi
done

when code first running, send First Notification, and if file size changed , value in code not updated example i use dump.txt to object size changed

how to get Last Size from dump.txt after echo "Start Execute"

conclusion every 5 second, lastCount get last size File updated

Answer 1

The problem in your code is that the cmd=$(wc -c "dump.txt" | awk '{print $1}') line executes only once.

Instead, you should use:

#....
do
#...
   lastCount=$(wc -c "dump.txt" | awk '{print $1}')
#...

Or make the cmd a function or store in a string and evaluate the string. The way you wrote, it is only evaluated in the beginning of your script and you use the same value afterward.