nmap-for-poor-people.sh

#!/usr/bin/env bash

has_wait_p() {
  wait --help | grep -q -- '-p'
}

usage() {
  echo "Usage: $0 [--timeout TIMEOUT] HOST PORT [PORT...]"
}

echo_success() {
  echo -e "🟢 \e[32m${*}\e[0m"
}

echo_error() {
  echo -e "🔴 \e[31m${*}\e[0m"
}

echo_warning() {
  echo -e "⚠️  \e[33m${*}\e[0m"
}

tcp_port_check() {
  local host="$1" port="$2" timeout="$3"
  timeout "$timeout" bash -c "echo > /dev/tcp/${host}/${port}" 2>/dev/null
}

if ! (return 0 2>/dev/null)
then
  RC=0
  PORTS=()
  TIMEOUT=3
  PIDS=()

  while [[ -n "$1" ]]
  do
    case "$1" in
      -h|--help|-\?|help)
        usage
        exit 0
        ;;
      -p|--port)
        PORTS+=("$2")
        shift 2
        ;;
      -t|--timeout)
        TIMEOUT="$2"
        shift 2
        ;;
      *)
        break
        ;;
    esac
  done

  HOST="$1"
  shift

  if [[ -z "${PORTS[*]}" ]]
  then
    PORTS=("$@")
  fi

  if [[ -z "$HOST" ]] || [[ -z "${PORTS[*]}" ]]
  then
    usage >&2
    exit 2
  fi

  for PORT in "${PORTS[@]}"
  do
    (
      MESSAGE="${HOST}:${PORT}"

      if tcp_port_check "$HOST" "$PORT" "$TIMEOUT"
      then
        echo_success "$MESSAGE OPEN"
      else
        echo_error "$MESSAGE CLOSED"
        exit 1
      fi
    ) &
    PIDS[$!]="$!"
  done

  if has_wait_p
  then
    while [[ "${#PIDS[@]}" -gt 0 ]]
    do
      if ! wait -n -p ENDED_PID
      then
        RC=1
      fi
      unset "PIDS[${ENDED_PID}]"
    done
  else
    echo_warning "wait does not support -p, the return code will be wrong" >&2
    wait
    RC="$?"
  fi

  exit $RC
fi