ROS environment with IP from the main network interface

ros_env.sh

#!/bin/bash

NET_IF=`netstat -rn | awk '/^0.0.0.0/ {thif=substr($0,74,10); print thif;} /^default.*UG/ {thif=substr($0,65,10); print thif;}'`
PRIMARY_NET_IF=($NET_IF)
export ROS_IP=`ifconfig ${PRIMARY_NET_IF[0]} | grep -Eo 'inet (addr:)?([0-9]*\.){3}[0-9]*' | grep -Eo '([0-9]*\.){3}[0-9]*' | grep -v '127.0.0.1'`

if [ -z ${ROS_IP} ]
then
    export ROS_IP=127.0.0.1
fi
echo 'ROS_IP='${ROS_IP}

export ROS_HOSTNAME=${ROS_IP}
echo 'ROS_HOSTNAME='${ROS_HOSTNAME}

if [ -z $1 ]
then
    echo 'I am the master!'
    ROS_MASTER_IP=${ROS_IP}
else
    echo 'Setting ROS master IP to '$1
    ROS_MASTER_IP=${1}
fi

export ROS_MASTER_URI=http://${ROS_MASTER_IP}:11311
echo 'ROS_MASTER_URI='${ROS_MASTER_URI}