[SOLVED] Isolate last non 0 digit from IP address

Isolate last non 0 digit from IP address

I have to read an IP from def.cfg file that is set in a line named TERMINAL_IP (TERMINAL_IP = "192.168.0.140"), then do an append to the end of the def.cfg file with the last digit read that is not a 0 number, in this example have a 0 in the last digit so the value to show must be 4 and if the last number is .100 the value to show will be 1 but if the last number is .145 the value to show must be 5.

I'm using the following script to do that:

#!/bin/bash

CONFIG_FILE="def.cfg"

TERMINAL_IP=$(grep -oP '(?<=TERMINAL_IP = ).*' "$CONFIG_FILE")

if [[ -z "$TERMINAL_IP" ]]; then
  echo "TERMINAL_IP not found in the configuration file."
  exit 1
fi

LAST_DIGIT=$(echo "$TERMINAL_IP" | grep -oE '[0-9]+' | tail -n 1)

if [[ "$LAST_DIGIT" == "0" ]]; then
  # If the last digit is 0, take the second-to-last digit
  LAST_DIGIT=$(echo "$TERMINAL_IP" | grep -oE '[0-9]+' | tail -n 2 | head -n 1)
fi

echo "LSTD = \"${LAST_DIGIT}\"" >> "$CONFIG_FILE"

The problem is that instead append the number 4, it is appending the number 140, for some reason it does not isolate the number 4.

Any ideas to solve this?

Solution

I found the solution as follows:

TERMINAL_IP=$(awk -F'=' '/TERMINAL_IP/ {gsub(/ /, "", $2); print $2}' "$CONFIG_FILE" | tail -1)
TERMINAL_IP_LAST_DIGIT=""
for (( i=${#TERMINAL_IP}-1; i>=0; i-- )); do
  DIGIT="${TERMINAL_IP:$i:1}"
  if [[ "$DIGIT" =~ [0-9] && "$DIGIT" -ne 0 ]]; then
    TERMINAL_IP_LAST_DIGIT="$DIGIT"
    break
  fi
done

Thanks all.