The cron job below runs every 4 hours then append the printed logs into a log file called airdrop.log. By calculation, you get 4-5 airdrops a day therefore you get 20-25 test sol in a daily basis.
crontab -e
then enter inside the editor
0 */4 * * * ~/scripts/airdrop.sh >> ~/scripts/airdrop.log 2>&1
then save your changes
cd <path to your scripts directory>
cat airdrop.log