RPi3 Auto reconnect to wifi when lost connect

Create script file

Use touch /home/pi/wifi-reconnect.sh to create shell script file, with following content:

#!/bin/bash 

SSID=$(/sbin/iwgetid --raw) 

if [ -z "$SSID" ] 
then 
    echo "`date -Is` WiFi interface is down, trying to reconnect" >> /home/pi/wifi-log.txt
    sudo ifconfig wlan0 down
    sleep 30
    sudo ifconfig wlan0 up 
fi 

echo "WiFi check finished"

Or you can also use sudo wget https://raw.github.com/carry0987/Raspberry-Pi-Repo/master/Auto-WiFi-Reconnect/wifi-reconnect.sh to download the script

Make new file executable

sudo chmod +x /home/pi/wifi-reconnect.sh

Install cron

sudo apt-get install cron

Edit crontab

Use sudo vim /etc/crontab to edit crontab

By putting following content at end of file:

* * * * * root /home/pi/wifi-reconnect.sh

Test it by disconnecting from WiFi:

sudo ifconfig wlan0 down

Script should reestablish connection within 1 minute.

Check log file

After the RPi reestablish connection, reconnect RPi and check log file:
cat /home/pi/wifi-log.txt

Auto Reconnect WiFi