List all the devices in the local network and their local IPs

network-detect.zsh

#!/usr/bin/env zsh

set -e

# --- CONFIG ---
NMAP_BIN=""
BREW_BIN=""

# --- FUNCTIONS ---
function find_nmap() {
  if command -v nmap >/dev/null 2>&1; then
    NMAP_BIN=$(command -v nmap)
    return
  fi

  echo "nmap not found. Attempting installation..."

  if command -v brew >/dev/null 2>&1; then
    BREW_BIN=$(command -v brew)
  else
    echo "Homebrew not found. Installing Homebrew..."
    /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"

    if [[ -x /opt/homebrew/bin/brew ]]; then
      BREW_BIN="/opt/homebrew/bin/brew"
    elif [[ -x /usr/local/bin/brew ]]; then
      BREW_BIN="/usr/local/bin/brew"
    else
      echo "Homebrew installation failed. Exiting."
      exit 1
    fi
  fi

  echo "Installing nmap..."
  $BREW_BIN install nmap

  if command -v nmap >/dev/null 2>&1; then
    NMAP_BIN=$(command -v nmap)
  else
    echo "nmap installation failed. Exiting."
    exit 1
  fi
}

function get_active_interface() {
  local iface
  iface=$(route get default 2>/dev/null | awk '/interface:/{print $2}')
  if [[ -z "$iface" ]]; then
    echo "Unable to determine active network interface."
    exit 1
  fi
  echo "$iface"
}

function get_ip() {
  local iface=$1
  ipconfig getifaddr "$iface" 2>/dev/null
}

function get_subnet() {
  local ip=$1
  if [[ -z "$ip" ]]; then
    echo "Unable to determine IP address."
    exit 1
  fi

  # Assume /24 if netmask parsing is unavailable
  echo "${ip%.*}.0/24"
}

# --- MAIN ---
echo "Detecting network..."

find_nmap

INTERFACE=$(get_active_interface)
echo "Active interface: $INTERFACE"

IP_ADDR=$(get_ip "$INTERFACE")
echo "Local IP: $IP_ADDR"

SUBNET=$(get_subnet "$IP_ADDR")
echo "Using subnet: $SUBNET"

echo "Running scan (requires sudo)..."
echo

sudo "$NMAP_BIN" -sn -PR "$SUBNET"