#!/usr/bin/env bash
#
# List open (listened) ports, without the crud that
# usually comes with `lsof -i`
#
# Modified by:     Ismo Vuorinen <https://github.com/ivuorinen> 2020
# Originally from: https://www.commandlinefu.com/commands/view/8951
# Original author: https://www.commandlinefu.com/commands/by/wickedcpj

set -euo pipefail

# Function to print the header
print_header()
{
  echo 'User:           Command:                  PID:     Port:'
  echo '========================================================='
}

# Function to list open ports
list_open_ports()
{
  lsof -i 4 -P -n +c 0 \
    | grep -i 'listen' \
    | awk '{print $3, $1, $2, $9}' \
    | sed 's/ [a-z0-9\.\*]*:/ /' \
    | sort -k 3 -n \
    | xargs printf '%-15s %-25s %-8s %-5s\n' \
    | uniq
}

# Main function
main()
{
  print_header
  list_open_ports
  echo ""
}

main "$@"