#!/usr/bin/env bash
set -o errexit
set -o nounset
set -o pipefail

if [[ "${1-}" =~ ^-*h(elp)?$ ]]; then
    echo 'Usage: ./script.sh arg-one arg-two
This is an awesome bash script to make your life better.
'
    exit
fi

if [[ "${TRACE-0}" == "1" ]]; then
    set -o xtrace
fi

cd "$(dirname "$0")"

main() {
  # no connection
  state=0

  # test each interfaces for connectivity
  for iface in $(ls /sys/class/net/ | grep -v lo); do
    if [[ $(cat /sys/class/net/$iface/carrier 2>/dev/null) = 1 ]]; then
      echo -e "$iface \e[32mconnected\e[0m"
      state=1
    else
      echo -e "$iface \e[31mno_connection\e[0m"
    fi
  done

  # check summary
  if [[ $state -eq 0 ]]; then
    echo -e " \n\e[31mno connection\e[0m" > /dev/stderr;
    exit -1;
  else
    echo -e "\n\e[32mconnected\e[0m" > /dev/stdout;
    exit 0;
  fi
}

main "[email protected]"