Creates a bridge between the system network and the local shell session on MAC OS

.bash_network

#!/usr/bin/env bash
#
# Date: 04 2015
# Author: dataday
#
# Support:
# Mac OS 10.6+, or anything with Mac's 'networksetup' tools installed.
# Bash 3.2.48(1)-release
# 
# Links:
# http://www.stunnel.org/
# http://subversion.apache.org/
# https://github.com/philchristensen/svn-color
# https://developer.apple.com/library/mac/#documentation/Darwin/Reference/ManPages/man8/networksetup.8.html
#
# Description: 
# Creates a bridge between the OS network setup and local shell session.
# Detects if the network is BBC / non-BBC and configures the shell as appropriate.
# Any specific network information, eg., HTTP proxy, is exported locally to each 
# shell session created.
#
# Usage: source ~/.bash_network
# stunnel /usr/local/etc/stunnel/stunnel.conf
#

#set -x

shopt -s expand_aliases

# set network by type and setup command
function get_networks () {
  networks=(
    "http -getwebproxy"
    "https -getsecurewebproxy"
    "socks -getsocksfirewallproxy"
    "ftp -getftpproxy"
    "gopher -getgopherproxy"
    "no -getproxybypassdomains"
    "x_host -getwebproxy"
    "x_port -getwebproxy"
  )
}

# get location details, eg., BBC On Network
function get_location () {
  echo "$(networksetup -getcurrentlocation)"
}

# get service details, eg., Thunderbolt Ethernet or Wi-Fi
# http://codesnippets.joyent.com/posts/show/1819
function get_service () {
  local guid
  guid="$(printf "open\nget State:/Network/Global/IPv4\nd.show" | \
      /usr/sbin/scutil | /usr/bin/awk '/PrimaryService/{print $3}')"
  service="$(printf "open\nget Setup:/Network/Service/${guid}\nd.show" | \
      /usr/sbin/scutil | /usr/bin/awk -F': ' '/UserDefinedName/{print $2}')"
  echo "$service"
}

# get network details
function get_network () {
    echo $(networksetup $1 "$2")
}

# get proxy bypass details
function get_proxy_bypass () {
   echo $(echo "$1")
}

# trim a string top and tail
function trim_str () {
    echo $(echo "$1" | sed 's/ *$//g' | sed 's/^ *//g')
}

# toggle set / unset proxy state based on type, eg., http
function set_proxy_state () {
  local cmd="$1"
  local proxy="$2_proxy"
  local proxy_flag="$3"
  local network=$(get_network $proxy_flag "$service")
  local isEnabled=true
  local hasHost=true

  # check network result for enabled and host directives
  [[ $network =~ "Enabled: No Server: Port: 0"* ]] && unset hasHost
  [[ $network =~ "Enabled: No"* ]] && isEnabled=true


  # make sure a network connection can be made to the outside world
  if [ "$(scutil -r duckduckgo.com)" == "Reachable" ]; then

    # if network has a host assigned 
    if [[ $hasHost && $isEnabled ]]; then

      local result
      local port=$(trim_str $(echo $network | cut -f6 -d ' ' ))
      local host=$(trim_str $(echo $network | cut -f4 -d ' ' ))
      local bypass=$(get_proxy_bypass "$network")

      if [ ! -z "$host" -o ! -z "$bypass" ]; then

        case "$proxy" in

        # assign no proxy, 
        no_proxy)
          isEnabled=true
          result="$bypass"
          shift
          ;;

        # assign proxy host
        x_host_proxy)
          result="$host"
          shift
          ;;

        # assign proxy port
        x_port_proxy)
          result="$port"
          shift
          ;;

        # assign proxy host:port by default
        *)
          result="http://$host:$port"
          shift
          ;;
        esac

      fi
    fi


    [[ $cmd == "set" ]] && export "$proxy=$result" || unset $proxy
    [[ $cmd == "set" ]] && echo "$location ($service) - $cmd $proxy=$result" || echo "$location ($service) - $cmd $proxy=$result" 
    #unset result

  else
    echo "$location ($service) - No Internet"
    unset $proxy
  fi

  unset proxy
  unset host
  unset port
}

function update_ssh_config () {
  local ssh_file="$HOME/.ssh/config"
  local ssh_cmd="ProxyCommand nc -x"
  local add_comment="$1"

  # add proxies
  if [ "$add_comment" = true ]; then
    sed -i '' "/$ssh_cmd/ s/[^#]$ssh_cmd/\ #$ssh_cmd/" $ssh_file
  # remove proxies
  else
    sed -i '' "/$ssh_cmd/ s/#$ssh_cmd/$ssh_cmd/" $ssh_file
  fi
}

function init () {
  local cmd
  local service=$(get_service)
  local location=$(get_location)

  [[ $location =~ "BBC On Network" ]] && cmd="set" || cmd="unset"
  [[ $service =~ "Thunderbolt Ethernet" ]] && service="Thunderbolt Ethernet" || service="Wi-Fi"

  get_networks

  for network in "${networks[@]}"
    do 
      :
      #  '--' ignore further options if found in results
      set -- none $network
      shift
      # determine state
      set_proxy_state $cmd $1 $2
  done

  if [[ $x_host_proxy && $x_port_proxy ]]; then

    git config --global http.proxy "${http_proxy}"
    git config --global https.proxy "${https_proxy}"
    git config --global socks.proxy "${socks_proxy}"

    alias svn="/usr/local/bin/svn --config-option servers:global:http-proxy-host=${x_host_proxy} --config-option servers:global:http-proxy-port=${x_port_proxy}"

    update_ssh_config false
  else

    git config --global --unset-all http.proxy
    git config --global --unset-all https.proxy
    git config --global --unset-all socks.proxy

    alias svn="/usr/local/bin/svn"

    update_ssh_config true
  fi

  unset service
  unset networks
  unset location
  unset bypass
  unset cmd
}

init

#set +x