Raspberry Pi Wifi check / restart script

check_wifi.sh

#!/bin/sh -eu

# Save this to /root/check_wifi.sh then run `sudo crontab -e` and paste the following line:
# * * * * * /root/check_wifi.sh >> /root/check_wifi.log


INTERFACE=wlan0
ROUTER_IP=192.168.0.1

# INTERNET_SITE_A=fake.example.com
# INTERNET_SITE_B=fake.example.com

INTERNET_SITE_A=www.bbc.co.uk
INTERNET_SITE_B=www.twitter.com

UNREACHABLE_FILE=/var/run/internet_unreachable

PATH=$PATH:/sbin:/bin

THIS_SCRIPT=$0

log() {
  echo "$( date --rfc-3339=seconds): $1"
}

wifi_interface_is_down() {
  if ifconfig ${INTERFACE} | grep -q "inet addr:" ; then
    # WiFi is UP, so return nonzero "fail"
    return 1
  else
    # WiFi is DOWN, so return "success" eg "yes, it's down"
    return 0
  fi
}

router_unreachable() {
  if ping_failed ${ROUTER_IP}; then
    return 0
  else
    return 1
  fi
}

internet_unreachable() {
  if ping_failed ${INTERNET_SITE_A}; then
    if ping_failed ${INTERNET_SITE_B}; then
      return 0  # unreachable
    fi
  fi
  return 1
}

ping_failed() {
  if ping -c 1 -W 5 $1 > /dev/null ; then
    return 1
  else
    return 0
  fi
}

create_unreachable_file() {
  if [ ! -f "${UNREACHABLE_FILE}" ]; then
    echo "Created by ${THIS_SCRIPT} at $(date)" > "${UNREACHABLE_FILE}"
  fi
}

remove_unreachable_file() {
  rm -f "${UNREACHABLE_FILE}"
}

attempt_restart_wifi_interface() {
  ifdown --force ${INTERFACE}
  ifup --force ${INTERFACE}
  sleep 10
  if wifi_interface_is_down; then
    log "That didn't seem to work."
  else
    log "That worked!"
  fi
}

reboot_if_unreachable_too_long() {
  if test "$(find ${UNREACHABLE_FILE} -cmin +15)"; then
    log "Internet unreachable for too long, rebooting."
    remove_unreachable_file
    reboot
  fi
}

if wifi_interface_is_down; then
   log "${INTERFACE} appears down, attempting reconnection."
   ifconfig
   attempt_restart_wifi_interface
fi

if router_unreachable; then 
   log "Router is unreachable: ${ROUTER_IP}"
   ifconfig
fi

if internet_unreachable; then
  log "Internet is unreachable."
  echo "${UNREACHABLE_FILE}"
  cat "${UNREACHABLE_FILE}"
  create_unreachable_file
  reboot_if_unreachable_too_long
else
  remove_unreachable_file
fi