que3.sh

#!/bin/bash
show_welcome_screen() {
  clear
  echo "**** Welcome to My shellATM ****"
  echo "**** Press any key to continue ****"
  read -n 1
  authenticate_user
}

authenticate_user() {
  while true; do
    echo -n "Enter your Card Number: "
    read card_number
    echo -n "Enter your Password: "
    read -s password
    echo
  
    if grep -q "^$card_number, $password$" Credentials.txt; then
      echo "Authentication done!"
      list "$card_number"
      break
    else
      echo "Invalid Card Number or Password. Please try again."
    fi
  done
}

list() {
  card_number=$1
  while true; do
    echo "1. Withdraw cash"
    echo "2. Deposit cash"
    echo "3. Settings"
    echo "4. Exit"
    echo -n "Choose an option: "
    read option
    case $option in
      1) withdraw_cash "$card_number";;
      2) deposit_cash "$card_number";;
      3) settings "$card_number";;
      4) exit 0;;
      *) echo "Invalid option. Please try again.";;
    esac
  done
}
get_balance() {
  card_number=$1
  grep "$card_number" Account.txt | awk -F', ' '{print $4}'
}
update_balance() {
  card_number=$1
  new_balance=$2
  sed -i "/$card_number/ s/\(.*,\)\(.*\)$/\1 $new_balance/" Account.txt
}
withdraw_cash() {
  card_number=$1
  current_balance=$(get_balance "$card_number")
  echo "Current Balance: $current_balance"
  echo -n "Enter the amount to withdraw: "
  read withdraw_amount

  if [[ "$withdraw_amount" =~ ^[0-9]+$ ]]; then
    if [ "$withdraw_amount" -le "$current_balance" ]; then
      new_balance=$((current_balance - withdraw_amount))
      update_balance "$card_number" "$new_balance"
      echo "Withdrawal successful! New Balance: $new_balance"
    else
      echo "Insufficient balance."
    fi
  else
    echo "Invalid amount. Please enter a non-negative number."
  fi
}
deposit_cash() {
  card_number=$1
  current_balance=$(get_balance "$card_number")
  echo "Current Balance: $current_balance"
  echo -n "Enter the amount to deposit: "
  read deposit_amount

  if [[ "$deposit_amount" =~ ^[0-9]+$ ]]; then
    new_balance=$((current_balance + deposit_amount))
    update_balance "$card_number" "$new_balance"
    echo "Deposit successful! New Balance: $new_balance"
  else
    echo "Invalid amount."
  fi
}
settings() {
  card_number=$1
  current_email=$(grep "$card_number" Account.txt | awk -F', ' '{print $3}')
  echo "Current Email ID: $current_email"
  echo -n "Enter new Email ID: "
  read new_email
  
  if [[ "$new_email" =~ ^[a-zA-Z][a-zA-Z0-9]*@[a-z]+\.[a-z]+\.[a-z]+$ ]]; then
    sed -i "/$card_number/ s/\(.*,\)\(.*\),\(.*\)$/\1\2, $new_email, \4/" Account.txt
    echo "Email ID updated successfully!"
  else
    echo "Invalid Email ID format. Try again."
  fi
}
show_welcome_screen