online

#!/bin/sh
ip -o addr \
  | awk '
$2 ~ /:$/ {
  i=$2;
  sub(/:$/,"",i);
  status[i]=$9
}

$3 == "inet" {
  ipv4_address[$2]=$4
}

END {
  general_status=0

  for(interface in status) {
    if(status[interface] == "UP") {
      general_status++;
      print interface;
    }
  }

  exit(! general_status);
}'