Utility for switching between wpa_supplicant wireless connections

wifi_select.sh

#!/bin/bash
#
# NetworkManager is trash for robots (periodic scanning causes
# ~3s latency every 2 minutes). We have disabled Network Manager
# (systemctl disable network-manager) and network interfaces are
# now managed via /etc/network/interfaces, with authenticated
# wireless managed by wpa_supplicant.
#
# Your /etc/network/interfaces probably looks like:
#
#	auto lo
#	iface lo inet loopback
#
#	auto wlp1s0
#	allow-hotplug wlp1s0
#	iface wlp1s0 inet dhcp
#		wpa_conf /etc/wpa_supplicant/wpa_supplicant.conf
#		wireless-power off
#
# Use this script to switch between networks using wpa_supplicant
# and then to force DHCP renewal.
#
# Parker Lusk
# 19 April 2019

# Find the available wireless networks that we can connect to
SSIDs=$(cat /etc/wpa_supplicant/wpa_supplicant.conf | grep ssid | cut -d'"' -f 2)

# What is the max network id that can be requested?
NETID_MAX=$(echo -n "$SSIDs" | grep -c '^')
NETID_MAX=$((NETID_MAX-1))

function usage {
  echo -e ""
  echo -e "./wifi_select.sh NETID"
  echo -e
  echo -e "\tUse this tool to connect to a wireless network that has been configured"
  echo -e "\tin /etc/wpa_supplicant/wpa_supplicant.conf. The \e[1mNETID\e[0m argument"
  echo -e "\tmust be one of the following network IDs listed below:"
  echo -e ""
  # display each one with its connection number (wpa_cli list_networks)
  count=0
  for ssid in $SSIDs
  do
    echo -e "\t  \e[1m$count\e[0m\e[2m: $ssid\e[0m"
    count=$((count+1))
  done
  echo -e ""
  echo -e ""
}

# Make sure a valid network id has been supplied
NETID=$1
if [ -z "$NETID" ] || (( NETID > NETID_MAX )); then
  usage
  exit -1
fi

IFACE=wlp1s0

wpa_cli -i $IFACE sel $NETID
sudo dhclient $IFACE > /dev/null 2>&1

echo -e ""
echo -e "New IP assigned: $(ip a s $IFACE | sed -En -e 's/.*inet ([0-9.]+).*/\1/p')" 
echo -e ""